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Group Title: Bulletin of the Florida State Museum
Title: The pine woods snake, Rhadinaea flavilata (Cope)
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Permanent Link: http://ufdc.ufl.edu/UF00001538/00001
 Material Information
Title: The pine woods snake, Rhadinaea flavilata (Cope)
Series Title: Bulletin of the Florida State Museum
Physical Description: 48-97 p. : illus., maps. ; 23 cm.
Language: English
Creator: Myers, Charles W
Publisher: University of Florida
Place of Publication: Gainesville
Publication Date: 1967
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Subject: Rhadinaea flavilata   ( lcsh )
Genre: bibliography   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
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Bibliography: "Literature cited": p. 92-97.
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Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
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alephbibnum - 000443514
oclc - 05069203
lccn - a 67007281

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Full Text





BULLETIN

OF THE

FLORIDA STATE MUSEUM


BIOLOGICAL SCIENCES


Volume II


Number 2


THE PINE WOODS SNAKE, RHADINAEA FLAVILATA
(COPE)

Charles W. Myers


UNIVERSITY


OF FLORIDA


Gainesville
1967


51~YblL~










Numbers of the BULLETIN OF THE FLORIDA STATE MUSEUM are pub-
lished at irregular intervals. Volumes contain about 300 pages and are not nec-
essarily completed in any one calendar year.


WALTER AUFFENBERG, Managing Editor
OLIVER L. AUSTIN, JR., Editor


Consultant for this issue:
Charles W. Myers



















Communications concerning purchase or exchange of the publication and all
manuscripts should be addressed to the Managing Editor of the Bulletin, Florida,
State Museum, Seagle Building, Gainesville, Florida. 32601


Published February 3, 1967


P'ric~e for this issue $.90










THE PINE WOODS SNAKE, RHADINAEA FLAVILATA (COPE)

CHARLES W. MYERS 1

SYNOPSIS: Rhadinaea flavilata (Cope, 1871) is a small colubrid snake inhabiting
a narrow coastal range in the southeastern United States. Its distribution closely
approximates that of the low pine flatwoods, which constitute its principal habitat.
A few individuals have been found in other situations, especially in Florida ham-
mocks and on coastal islands. The species is most commonly encountered in
pine logs and stumps during March and April; with the approach of warmer
weather and drier conditions in May and June, Rhadinaea and other small snakes
become more difficult to find. R. flavilata feeds on small amphibians, lizards,
and perhaps snakes; literature records referring to predation on insects are ques-
tioned. The pine woods snake kills or incapacitates some of its prey with a
venom introduced into wounds made by enlarged rear maxillary teeth. Other
snakes are likely its main predators and food competitors. R. flavilata lays two
to four elongate eggs; the period of egg deposition is speculated to extend from
May into August, although it probably is not so extensive in any given season;
the natural nest is unknown. There is slight statistical evidence of unbalanced
sex ratios in some populations.
Structural variation was observed in many characters, and for discussion is
classified as intrapopulational variation (including ontogenetic, sexual, and un-
correlated or "individual" variation) and interpopulational (geographic) variation,
the latter being compounded from the former. No geographic races are recog-
nized in this species.
Structurally the pine woods snake is a rather generalized Rhadinaea. Its
closest living relative is R. laureate of the highlands of western Mexico. Fossils
show that R. flavilata, or a genetic predecessor, had arrived in the southeastern
United States at least by the third (Illinoian) glacial stage of the Pleistocene.
The lack of marked geographic variation in this species can be explained by the
relatively recent (postglacial) dispersal of a homogeneous Floridian stock through-
out a relatively uniform pine-flatwoods habitat. Environment, nonselective gen-
etic mechanisms, and natural selection are considered briefly in terms of the
evolution of geographic variation." A seemingly primitive color pattern is re-
tained at the northern limits of the range; the southern populations are charac-
terized by loss of pattern -and'by increased variability (often anomalous) in
scutellation. It is inferred that southern populations, being most influenced by a
warming post-glacial climate, are evolving faster than northern populations.

1The study- reported on in this paper was initiated when the author was an
undergraduate student at the' Tniversity of Florida and a research assistant in
the Florida State Museum (1958-1960). The paper was completed at the Co-
operative Wildlife Research Laboratory, Southern Illinois University, where it
was accepted as a thesis in partial fulfillment Qf the requirements for the Master
of Arts degree (1962). The author is currently a visiting scientist at Gorgas Me-
morial Laboratory, Panama City, Panama, and research associate of the Museum
of Natural History, University of I4ansas. An earlier contribution to this Bulle-
tin deals with the biology of the r neck snake in Florida. Manuscript received
1 December 1965.-ED. -.

Myers, Charles W. 1967. The Piiue Woods Snake, Rhadinaea flavilata '(Cope).
Bull. Florida State Museum, vol. 11, no. 2, pp. 47-97.




5< 7 o. /



48 BULLETIN FLOR1IDA STATE MUSEUM Vol. 11



TABLE OF CONTENTS
INTRODUCTION -- ----------------- 48 VARIATION ------------- 68
TAXONOMY ---------- --- -51 Ontogenetic variation -------70
DISTIBUTION -----------------54 Sexual dimorphism --- 70
ECOLOGY ------------------57 Uncorrelated variation ------ 75
Habitats --- ---------- 57 Geographic variation --------78
Animal associates -- -------61 AFFINITIES ------ 88
Habitats and behavior---- 63 EVOLUTION -- 88
Sex ratios ---------- 67 LITERATURE CITED -- 92



INTRODUCTION
Rhadinaea flavilata (Cope, 1871) is a small snake of the extensive
pine flatwoods on the coastal plain of southeastern United States. As
with many small and secretive animals, especially those of limited
distribution, knowledge of this species is slight. In this paper I have
attempted to provide a more complete account of R. flavilata than
heretofore available. The principal aim was to determine its struc-
tural variation, distribution, affinities, and ecological relationships. On
the data assembled is based a hypothetical history of the species' evo-
lution.
The written history of Rhadinaea flavilata is not extensive. Post-
surgeon H. C. Yarrow found the type specimen near Fort Macon on
Bogue Banks, North Carolina, in November 1871 (Coues and Yarrow,
1878). The novelty was forwarded alive to E. D. Cope, who prompt-
ly named it Dromicus flavilatus, believing it to have affinities with D.
callilaemus of Jamaica, and a possible origin in the United States via
floating drift in the Gulf Stream (Cope, 1871). Specimens next be-
came available from Florida (Cope, 1877, 1878, 1888), and after an
examination of the hemipenis Cope (1894, 1895) decided that flavila-
tus was most closely allied with the species of Rhadinaea, a genus he
had described in 1863 from the tropical mainland. Boulenger (1894)
concurrently placed the species in Liophis, a designation no other
worker followed, and Boulenger is said (Malnate, 1939) to have re-
alized his error later. Steneger and "arbour (1917) allocated flavila-
tus to Leimadophis, and Amaral (19) placed the remaining species
of Rhadinaea in Liophis. Dunn res re'eted the genus Rhadinaea in
1932, and since that time the affinities of Rhadinaea flavilata have not
been questioned. Here ignored are 'suggestions (Dunn 1944, 1957;







1967 MYERS: THE PINE WOODS SNAKE 49

Rozel:1958, 1959) that Urotheca Bibron, 1843 is the proper generic
namelfor species currently placed in Rhadinaea Cope, 1863. I have
examined the holotype of Calamaria dumerilli, type species of Uro-
thead, and intend to take up this strictly nomenclatorial problem else-
where.
Rhadinaea flavilata has remained scarce in collections, although
Brown (1901) early extended its known range to include the eastern
Gulf Coast. Malnate (1939) made the first substantial contribution
to a knowledge of this snake; he summarized previous literature, gave
original observations on habits and habitats, and analyzed variation
on the basis of 55 specimens. E. Ross Allen (1939) found the species
abundant at Burbank, Florida, and cited a catch nearly twice as large
as Malnate's sample from the entire range. Other'interesting contri-
butions were the discoveries that R. flavilata possesses a weak venom
(Neill, 1954a), and that fossil vertebrae from the Florida Pleistocene
can be assigned to it (Auffenberg, 1963; Holman, 1958, 1959). Several
other writers cited at appropriate places in the text have supplied
additional information.
PROCEDURE OF STUDY. Much of this paper is based on data from
museum specimens. My field experience with the pine woods snake
is limited to northern Florida. Available for this study were 192 pre-
served specimens and a small series of skeletons in the following col-
lections: American Museum of Natural History (AMNH); Academy
of Natural Sciences of Philadelphia (ANSP); collection of Barry Man-
sell (BM); Chicago Academy of Sciences (CAS); Carnegie Museum
(CM); Chicago Natural History Museum (CNHM); Cornell Univer-
sity, (CU); collection of the writer (CWM); Duke University (DU);
Illinois Natural History Survey (INHS); collection of J. Alan Holman
(JAH); collection of Jpseph Pylka (JP); Louisiana State University
Museum of Zoology 'LSU); Loyola University, New Orleans (LU);
Museum of Comparative Zoology (MCZ); Museum of Vertebrate
Zoology (MVZ); collection of Sam R. Telford (SRT); Texas Coopera-
tive Wildlife Museum (TCWM); Tulane University (TU); University
of Florida (UF); University of Illinois Museum of Natural History
(UIMNH); University of Kansas Museum of Natural History (KU);
University of Michigan Museum of Zoology (UMMZ); United States
National Museum (USNM); collection of W. E. Brode (WEB); col-
lection of'William L. Erels (WLE).
Data on scutellatioieolpr pattern, size, and sex were recorded
when possible (some specimens were poorly preserved or mutilated);
observations on certain aspects of the internal anatomy were made
from selected specimens. All measurements and ratios were based on







50 BULLETIN FLORIDA STATE MUSEUM Vol. 11

preserved specimens. Tooth counts were obtained from the skeleton-
ized specimens; no attempt was made to record detailed osteological
descriptions.
The terminology used to describe the hemipenis is that of Dow-
ling and Savage (1960). Ventral plates were counted in the manner
suggested by Dowling (1951); neither the anal plate nor terminal
caudal spine were included in the ventral or subcaudal counts. The
first ventral plate videe Dowling, 1951, fig. 1) was used as the ref-
erence point for the first dorsal scale count; this count started with
the dorsal scale bordering the posterior corer of the first ventral,
and ended at the starting place for the next count (approximately a
head's length behind the head). Other dorsal scale counts were made
at midbody and immediately anterior to the anal plate.
The temporals of Rhadinaea flavilata are defined as those plates
lying in vertical rows between the parietals and supralabials. (A
row of scales bordering the posterior margins of the parietals and
labials has been considered temporals by some authors.)
Numbers on the left and right sides of a slant line (/) show varia-
tion in counts made on the left and right sides of the body, respec-
tively (e.g. 9/10 infralabials). Numbers above and below a horizontal
line show that a vertical division has occurred in one or more plates
2
of a vertical row. Thus, the temporal formula 1 + means that
1
2
the top plate in the second row is divided; the formula 1 + shows
2
that both plates are divided in the second row. The + sign indicates
that counts have been made in vertically arranged rows, rather than
horizontal ones.
Statistics found useful are range and standard deviation as meas-
ures of absolute dispersion, arithmetic mean as a measure of central
tendency, standard errors of means and chi-square (x2) as clues to
the probability of difference between samples, coefficient of diver-
gence (Klauber, 1940, 1943) as a relative measure of difference be-
tween characters, and tail length divided by total length as a meas-
ure qf proportion. Except where sex ratios are tested, chi-square
was obtained by use of a 2 x 2 table and a formula that contains a
Yates' correction factor for small numbers (Croxton, 1959, p. 276)..
Botanical names used are thosi given by Small (1933), except for
the species of Pinus, where the nomenclature is that of Critchfield
and Little (1966).








MYERS: THE PINE WOODS SNAKE


ACKNOWLEDGMENTS. For making available facilities at the Flor-
ida State Museum where this study was initiated, and for much en-
couragement, I am grateful to William J. Riemer. The manuscript
was prepared at Southern Illinois University, where it was improved
by comments and helpful criticisms given by W. D. Klimstra and
Richard E. Blackwelder. The paper also profited from a reading by
William E. Duellman, University of Kansas. For field notes and
other information I am indebted to Charles M. Bogert, William L.
Engels, Sam R. Telford, and Wilfred T. Neill. Isabelle Hunt Conant
photographed the pine woods snake in fig. 1 and Robert McFarlane
took the photographs in figs. 3, 4, and 10 for me. For typing the man-
uscript and other favors, I am especially grateful to my wife, Joan
W. Myers.
TAXONOMY
Rhadinaea flavilata (Cope, 1871)
1871. Drmoicus flavilatus Cope, Proc. Acad. Nat. Sci. Philadelphia, vol. 23,
pp. 222-223.
1894. Liophis flavilatus (Cope). Boulenger, Cat. Snakes British Mus. (Nat.
Hist.), vol. 2, p. 143.
1894. Rhadinaea flavilata (Cope). Cope, Proc. Acad. Nat. Sci. Philadelphia, vol.
46, p. 428.
1901. Rhadinea flavilata (Cope). Brown, Proc. Acad. Nat. Sci. Philadelphia, vol.
53, p. 88. [Probably an intended emendation as this generic spelling was
used elsewhere by Garman (1884, p. 29) and Brown (1904, p. 467; 1908,
p. 123). Several recent authors, apparently following Schmidt's check-
list (1953), have used this spelling, but I have been unable to find a valid
basis for it.]
1917. Leimadophis.-favilatus (Cope). Stejneger and Barbour, Check List N.
Amer. Amphibians and Reptiles, 1st. ed., p. 86.
1958. Urotheca [fiavilata (Cope) included by inference]. Roze, Breviora, Mus.
Comp. Zool., no. 88, p. 5. [Followed in this usage by Neill (1963, p. 205;
1964, pp. 287-288).]
HOLOTYPE. ANSP 5583, collected by Dr. H. C. Yarrow, in No-
vember, 1871. Now lost (Malnate, 1939; James E. Bohlke, in litt.).
TYPE LOCALITY. Approximately 8 miles westward from Fort Ma-
con, on Bogue Banks, Carteret County, North Carolina.
In the original description, Cope (1871) says that the type speci-
men came from "nea.Fort Macon, on the coast of North Carolina."
Coues and Yarrow (1878j relate that it was found "on Bogue Banks
some eight miles south of Fort Macon, near marshy ground." Rob-
ertson and Tyson (1950), however, point out that the last is an un-
likely locality (being in the Atlantic Ocean), and that Coues and
Yarrow probably intended 8 miles west or southwest of Fort Macon.
.. 1


1967








BULLETIN FLORIDA STATE MUSEUM


ETYMOLOGY. The name Rhadinaea flavilata is presumably de-
rived from the Greek rhadinos (slender or lithe) and the Latin flavus
(gold colored, or yellow) + latus (broad or extensive, full or rich).
It seems probable, at least, that the specific epithet was intended to
refer to the rich (or extensive) golden-brown coloring of the body.
Latus is also the past participle of the verb fero, and so flavilata
conceivably could mean "golden borne," but this seems less likely.
Latus is furthermore a noun meaning side or flank, but it is unlikely
that the name is based on this. Cope added the feminine ending "a"
when he transferred flavilatus from Dromicus to Rhadinaea, and so
apparently did not intend a noun in apposition; and had "golden
sided" been meant the name should have been "flavilateralis."
There seem to be no true vernacular names for this species, as
humans living within the range of R. flavilata are usually unaware
of its existence. The common name in current usage, yellow-lipped
snake (A.I.S.H., 1956), is not suitable for most populations; it was
apparently coined by Ditmars (1907), who described the upper lip as
"bright yellow." The name "brown-headed snake" has been used,
but is equally applicable to any of several other small snakes in the
eastern United States. "Yarrow's Dromicus" is the only other com-
mon name that has been used in print. I suggest "pine woods snake"
for those in need of an English name. The species is partial to the
pine flatwoods, probably even more so than the pine woods treefrog,
Hyla femoralis.











f
Figure 1. A pine woods snake, Rhadinaea flavilata, from Burbank, Marion
County, Florida. Isabelle Hunt Conant

DESCRIPTION. A moderately slender snake with head slightly
wider than neck. Largest specimen examined 387 mm. Tail/total
length ratio 27.0-35.9 percent.


Vol. 11







1967 MYERS: THE PINE WOODS SNAKE 53

Color above golden brown, lightest on first two scale rows. Mid-
dorsal stripe of diffused chromatophores sometimes present on verte-
bral scale row, with the pigment often confined to apexes of the
vertebral scales. Diffused lateral stripe usually present on scale rows
1-4, mainly on 2-3 anteriorly and on 3 posteriorly (sometimes not evi-
dent until the stratum corneum falls away in preservative): Some-
times a yellowish occipital spot on each side of neck behind head.
Top of head usually darker than body and often marked with pale
vermiculations. A brown stripe, light-bordered above and dark-
bordered below, extends from the snout through the eye and to the
angle of the jaws. Labials white to pale yellowish, variably spotted
with black, and sometimes with faint splotches of brown. Underside
of head and neck white; rest of venter white or pale yellowish
green.
Dorsal scales smooth, except for anal ridges on some specimens,
and without apical pits; in 17 rows except immediately behind the
head, where the count is usually 18 but occasionally 17 or 19. Ven-
trals 112-139; anal plate divided; subcaudals in 59-83 pairs; tail with
terminal spine. Supralabials normally 7, with third and fourth en-
tering orbit and the sixth the largest; occasionally 8, with fourth and
fifth entering the orbit and the seventh the largest. Infralabials
usually 9, with the first five bordering the genials and the fifth the
largest; infralabials sometimes 7, 8, or 10, often with corresponding
changes in position of the largest plate and the number bordering
the genials. Posterior genials slightly longer than anterior ones;
first pair of infralabials meet behind mental. Temporals typically
1 + 2, but these plates, especially in row 2, are frequently divided
or fused. One preocular, two postoculars; pseudo-oculars some-
times present as the result of transverse labial divisions. Loreal as
high or higher than long, rarely absent.' Nasal single, but grooved
and may appear divided on casual examination. Rostral about twice
as wide as high and barely visible from above. Internasals nearly
quadrate; prefrontals nearly as long as wide; supraoculars narrow,
longer than wide; frontal about one and one-half to two times longer
than wide, pentagonal with apex caudlad; parietals elongate, truncate
or slightly pointed posterioly.
Everted hemipenis a s gle, clavate organ, extending to between
the sixth and ninth subcdls. Basal part smooth; middle part
spinose with greatest enlargement of spines towards surface opposite
sulcus spermaticus; distal end capitate and calyculate calycess papillate
apically and spinulate basally). Sulcus spermaticus bifdrcate, di-
viding on the capitate portion of the organ at abdut the 5th or 6th








BULLETIN FLORIDA STATE MUSEUM


subcaudal level and not extending to the apex. The m. retractor
penis magnus originates at the level of the 21st to 24th subcaudal.
Anal sac extending to between the 9th and 14th subcaudals.
Anterior maxillary teeth 14-15, slightly increasing in length from
front to rear, followed by a short diastema and two enlarged, un-
grooved teeth. Palatine teeth 11-13; pterygoid teeth 19-23; dentary
teeth 19-22. The middle, precaudal vertebrae are described by Auf-
fenberg (1963).

DISTRIBUTION
Rhadinaea flavilata occupies a narrow coastal range (fig. 2) from
the vicinity of Cape Hatteras, North Carolina (Carteret County), south


Figure 2. Geographic distribution of Rhadinaea flavilata. Only one sym-
bol is plotted per county (or parish) but, with few exceptions, this covers all
known localities within the county. Open symbols indicate literature records.


Vol. 11







1967 MYERS: THE PINE WOODS SNAKE 55

through the northern four-fifths of the Florida peninsula (to Palm
Beach County), and west to extreme eastern Louisiana (Livingston
Parish).
Most localities are less than 100 feet above sea level, although
specimens have been found at approximately 180 feet in Gainesville,
Florida. At no place has the species been found more than about 70
miles from the coast.
The present-day range of Rhadinaea flavilata appears to lie en-
tirely east of the Mississippi River. A Texas record (Netting, 1936),
based on a specimen (CM 8937) reputedly from the vicinity of Clif-
ton, in Bosque County, is almost certainly erroneous. Rhadinaea
flavilata is a coastal form, whereas the Clifton area lies farther inland
(by about 175 miles) and at a higher elevation (by over 400 feet) than
other known localities for the species. Correlated with this are con-
spicuous differences in habitat. Rhadinaea flavilata is found mainly
in low, poorly drained pine woods, whereas Clifton is in a region of
cedar-covered ridges and limestone outcroppings. I visited this
area in April 1961 with Sam R. Telford and Robert Mount; we col-
lected or observed such animals as the plains narrow-mouthed toad
(Gastrophryne olivacea), spiny lizard (Sceloporous olivaceus), blind
snake (Leptotyphlops dulcis), ground snake (Sonora episcopa), and
flat-headed snake (Tantilla gracilis). These species occupy habitats
more arid than the coastal pine flatwoods, and are members of a
faunal unit different from that associated with R. flavilata. Grobman
(1941, 1944, 1950) advised caution in the acceptance of this and cer-
tain other records based on specimens not individually tagged and
for which the place of shipment may be given as the collecting
locality.
SPECIMENS EXAMINED.-ALABAMA: Baldwin County-10 mi. S Foley (CM
9879). Mobile County-no other locality data (CU 1739; USNM 51888, 56445-
56446); Mobile (CAS 12130-12131). FLORIDA: No other locality data (ANSP
10800, 26075; CNHM 38022-48023). Alachua County-Air Base (UIMNH
25700); Gainesville (CWM 1855; TCWM 10418; UF 460, 620, 2740, 2977, 7087,
7278, 8021, 8860); near Gainesville (AMNH 36589); approximately 6 mi. NE
Gainesville (CWM 1863); 7.1 mi. NNE Gainesvile (UF 10023); 7 mi. E Gaines-
ville) % mi. W Hatchet Creek (SRT 628); 7 mi. E, 2% mi. N Gainesville (qWM
1560, 1580-1582, 1800, 1860-1862, 1864); 2 mi. E Paradise (UIMNH 25701-
25706). Brevard County-Georgiana JSNM 11989, 13642, 13649, 13661, 18708).
Duval County-Jacksonville (BM [3 fYacksonville, north section along St. Johns
River (UF 8271). Glades County-Injian Prairie Canal, 18 mi. SW Okeechobee
(town) (UF 8864). Hamilton Countb-15 mi. NNE, 7 mi. W White Springs
(town) (KU 68940). Indian River County-Sebastian (MCZ 12792; UMMZ
56987). Levy County--4 mi. S, 1 mi. W Otter Creek (town) (UF 14904). Marion
County-no other locality data (CNHM 48287, 95341 [2]); Burbank (CNHM








56 BULLETIN FLORIDA STATE MUSEUM Vol. 11

48288-48296; MVZ 53907; TCWM 10416-10417; UF 2714, 2750 [2], 7504);
Burbank, 7 mi. N Silver Springs (CNHM 48297-48306); 4 mi. NE Burbank (UF
10026); Ft. McCoy (UF 10028); near Silver Springs (CM 9636-9646); 10 mi.
from Silver Springs (CU 2211 [2]). Okeechobee County-Opal, NE of Okee-
chobee (AMNH 63891-63892); near Opal, N of Okeechobee (AMNH t6491); S
of Okeechobee (AMNH 63364, 63436-63438). Orange County-Orlando (MCZ
6978). Palm Beach County-Palm Beach (UMMZ 85110). Polk County-5 mi.
N Lakeland (JAH [skeleton only]); - mi.'SE Pasco-Polk County line, on U.S.
Highway 98 (JP 58-20); Winter Haven, Lake Shipp (SRT 49); 7 mi. SW Winter
Haven, Lake Hancock (SRT 119, 1136). Putnam County-Univ. Florida Con-
servation Reserve, Welaka Mud Springs (CM 21439). St. Johns County--An-
astasia Island, near St. Augustine (AMNH 63362-63363, 63434-63435); Anastasia
Island, 5 mi. SE St. Augustine (CU 4980). Seminole County--4 mi. E Sanford
(UF 10024). Taylor County-7% mi. 315 from Perry (UF 14903). Volusia
County-Daytona Beach (UF 10030); 3 mi. N DeLand (UF 10029); 7 mi. E
DeLand (UF 10027). "Warren" [Walton ?] County-no other locality data
(ANSP 11730). GEORGIA: Charlton County-Okefenokee Swamp, Chesser's
Island (CM 19869). LOUISIANA: Livingston Parish-5 mi. NW Springfield (LSU
7433,7435). St. Tammany Parish-Bayou Lacombe (TU 11849); Covington (TU
3237-3238); Mandeville (TU 3235); Oaklawn (TU 3239); Pearl River (town) (TU
369, 3889); 5 mi. W Slidell (TU 7031, 14991, 15044, 15073); Sun (CAS 12132);
0.3 mi. N Talisheek (TU 16098). MIssIssIPPI: No other locality data (USNM
56443-56444). Jackson, Hancock, Harrison, and Pearl River counties. [The tags
on the following specimens were attached by slip-knots and came loose during
shipment.]-(WEB 31a-31b, 37, 52, 68, 78, 87, 91, 109, 111-113, 115). Hancock
County-Bay St. Louis (ANSP 12061-12062; LU 456 [2]; USNM 24452-24454);
10 mi. W Bay St. Louis (TU 13770 [2]); 4 mi. NE Logtown (TU 14264); Pearling-
ton (LU 295 [3]); 7.5 mi. NNW Pearlington, just W of Westonia (TU 17618);
5 mi. N, 3 mi. W Pearlington (TU 17351-17352); 4 mi. W Waveland on U. S.
Highway 90 (UF 10025 [2]). Harrison County-Biloxi (CNHM 21533; CU 1867
[2]; UMMZ 76827; USNM 125546); near Biloxi (AMNH 46745; CM 5240); 3 mi.
N Biloxi (CNHM 12000); 6 mi. N Biloxi (INHS 6336); 13 mi. NW Biloxi on
State Highway 55 (TU 17353); Gulfport, AAF (UMMZ 93998); 4 mi. N d'Iber-
ville (UIMNH 29110). NORTH CAROLINA: Bladen County-North River, Cam-
den Pt., Councils ["Council" on recent maps] (CU 1342). Carteret County-
6 mi. E Beaufort, on Highway 70 (DU [1]); Harkers Island (WLE 1142-1143);
24 mi. SW Morehead City, 3 mi. from Swansboro (DU [1]); Shackleford Banks
[an island] (WLE 778); South end of Shackleford Banks (UIMNH 5233). SOUTH
CAROLINA: Berkeley County-Alvin (CM 21791); 2.1 mi. N, 0.3 mi. E Cainhoy
(UMMZ 109235); 7 mi. W Moncks Corer (CM 25190-25191); 8 mi. W Moncks
Corner (CM 28892-28893). Charleston County-Mt. Pleasant (CNHM 4076).
Horry County-St. Park [presumably Myrtle Beach State Park] (UMMZ 94166).
TEXAS: \Bosque County-Clifton (CM 8937). [Locality data not acceptable;
see text.]
LITERATURE RECORDS. Specimens w4re not available from the following
counties, indicated on the distributioi- map (fig. 2) by unshaded symbols.
FLORIDA: Sarasota County (Allen, 1939'. MIssIssIPPI: Forest Courty (Cli-
burn, 1959). NORTH CAROLINA: BrunMwick County-near Shallotte (White,
1960); New Hanover County (Funderberg, 1958).







MYERS: THE PINE WOODS SNAKE


ECOLOGY
The pine woods snake is too secretive and difficult to find to be
studied easily in the field, but the study of specimens, habitats, and
distribution provides information of ecological import, and observa-
tions on a dozen or so individuals in captivity give additional clues
to the species' nature.

HABITATS
PINE FLATWOODS. Several types of flat pine forests comprise the
high flatwoods of the upper coastal plain and the low flatwoods of
the lower coastal plain. The pine flatwoods are vegetational associ-
ations distinct from the pine or pine-oak forests of the hills and ridges,
nor are they to be confused with the New Jersey pine barrens, which
are of different origin and greater antiquity videe Harshberger, 1916).
A generalized profile of coastal plain pine forests is given by Wahlen-
berg (1946, fig. 14).


Figure 3.' Low pine flatwoods near Hatchet Creek, Alachua County, Florida.
Robert McFarlane

The low flatwoods (figs. 3 and 4) seem to be the main habitat of
Rhadinaea flavilata. These woods are probably confined entirely to
nearly level Pleistocene terrace deposits of the lower coastal plain.


1967







BULLETIN FLORIDA STATE MUSEUM


"Low pine barrens" and "pine savannas" are among the older names
for this association, but the term used here is more descriptive and
is the one most frequently used in recent literature.


Figure 4. A cutover section of low pine flatwoods near Hatchet Creek,
Alachua County, Florida. The pine woods snake and other small reptiles and
amphibians frequent pine logs with loose bark. Robert McFarlane

The low flatwoods are characterized by flat, poorly drained to-
pography on which slash pine (Pinus elliottii) or longleaf pine (Pinus
palustris) is usually the dominant tree. Characteristic plants include
wire-grasses (Aristida spp.), gallberry (Ilex glabra), saw-palmetto (Ser-
enoa repens), pitcher plants (Sarracenia spp.), St. John's-worts (Hyper-
icum spp.), huckleberries (Vacciniaceae), Sabbatia spp., polygalas
(Pilostaxis spp.), butterworts (Pinguicula spp.), Lobelia spp., ground
orchids (Ibidium and Limodorum spp.), Easter-lilies (Atamosco spp.),
and Sphagnum spp. Cypress ponds and their associated flora are
often a conspicuous element of the low flatwoods. Frequently pres-
ent is a hardpan which allows water to stand for long periods in wet
weather (fig. 4) and prevents the rise of capillary water during dry
spells; consequently many flatwoods are seasonally subjected to the
extremes of flooding and drought. Occasional fires are conducive to
the preservation of the flatwoods; without fire, plant succession would
probably proceed to a broad-leaved forest videe Laessle, 1942).


Vol. 11







MYERS: THE PINE WOODS SNAKE


The distribution of Rhadinaea flavilata closely approximates that
of the low pine flatwoods. The western extent of the snake's range
in eastern Louisiana corresponds to the western limits of the slash
pine flatwoods, and it is not found south of the flatwoods in Florida
(fig. 5). To the north and east its known distribution nearly corre-
sponds to that of the "Campulosus-Sarracenia association," which
Wells (1924) states lies south of a line drawn through Cape Hatteras,
North Carolina; this association appears to be nothing more than a
cut-over flatwoods in which longleaf pine was the dominant tree
videe Wells, 1924). I do not know the exact northern limits of the low
flatwoods, but they probably do not extend much beyond southeastern
Virginia. The narrow coastal range of R. flavilata seems to agree
with the inland distribution of the low flatwoods.


Figure 5. Distribution of Rhadinaea flavilata and the pine flatwoods in
Florida. Drawn from a Generalized Vegetation Map of Florida (Florida Agri.
Exp. Station, University of Florida, 1938).


1967







BULLETIN FLORIDA STATE MUSEUM


The close association between R. flavilata localities and the flat-
woods in Florida can be seen in fig. 5. That the same general habi-
tat is occupied in other parts of the range is indicated by the following
references. Use of the words "low," "flooded," and "cypress" indi-
cates that flatwoods are being discussed, and not the pine-oak associ-
ations that grow on sandy, rolling terrain. ALABAMA: Allen (1932)
found two specimens in Harrison County, under the bark of pine
stumps. In Mobile County, Loding (1922) reported the species to
be "not uncommon in low cut-over pine lands under logs in early
spring." MISSISSiPPI: Malnate (1939) quoted Stewart Springer as
having found flavilata near Biloxi, in "a pine woods flat with occa-
sional gum- and cypress-surrounded ponds, and the entire area is
flooded once in two years." In the panhandle counties, Brode and
Allison (1958) found it to be a common inhabitant of pine stumps, in
communities designated as "cypress-bay" and "pine and live oak ..
on or near a stream." NORTH CAROLINA: Schmidt (1916) found a
specimen under a pine log (in flatwoods?) near Councils, in Bladen
County. White (1960) collected two specimens from pine stumps in
a "pine plantation" in Brunswick County (the associated fauna indi-
cates this to be a flatwoods; table 1). SOUTH CAROLINA: Malnate
(1939), in Berkely County, found a few specimens under leaves and
soil, in "rather open pine woods. . flooded with each rain .... "
HAMMOCKS. A few pine woods snakes have been found in Flor-
ida's hardwood forests at places not far removed from flatwoods.
Walter Auffenberg found a specimen (UF 10030) under a piece of
paper in a hammock at Daytona Beach, Volusia County, and Goin
and Goin (1953) record the species from a hammock in Alachua
County. Several have been found in yards in Gainesville, Alachua
County. Carr (1940) found two under a board in a Gainesville saw-
mill, and I have heard of another Gainesville specimen that was taken
from a woodpile. A specimen (UF 3271) from Jacksonville, Duval
County (not a hammock area), was found in a lumber yard. These
records suggest the possibility that individuals occasionally are trans-
ported from the flatwoods in shipments of pine (the main timber tree
of the Southeast). Nevertheless, I have no doubt that flavilata does
enter hammocks of its own accord.
COASTAL ISLANDS. Rhadinaea flavilata has been found on several
islands off the coasts of North Carolina and Florida. It was found
"near marshy ground" at the type locality on Bogue Banks, N. C.
(Coues and Yarrow, 1878); specimens also have been taken on nearby
Shackleford Banks (Robertson and Tyson, 1950; Engels, 1952) and
Harkers Island (Engels, 1952). These islands support dry woodlands


Vol. 11







MYERS: THE PINE WOODS SNAKE


and marsh, but, so far as I know, nothing resembling a flatwoods.
Bogue Banks and Shackleford Banks are off-shore bars of submarine
origin. Rhadinaea probably reached these islands in partly decayed
logs carried by flood waters, as Engels (1952) suggested.
C. M. Bogert (in litt.) reports that the specimens from Anastasia
Island in St. Johns County, Florida, were found on an old railway
bed under ties partly covered by sand. Possibly, Anastasia Island
was connected at one time to the mainland, from which it is not far
removed; Neill (1954b) assumes a former land connection to explain
the existence of the fresh-water Siren lacertina on nearby Merritt
Island.
OTHER HABITATS. Funderberg (1958) reports that Rhadinaea was
found in an area of upland bogs and longleaf pine-oak vegetation (a
sandhills association) in New Hanover County, North Carolina. Camp-
bell and Stickel (1939) quote a letter from H. K. Gloyd saying that a
Louisiana specimen (probably CAS 12132) was found "among loose
bark, leaves, and other debris on one of the alluvial ridges between
the swamps." Smith and List (1955) found three specimens in drift-
wood on a floodplain 6 miles north of Biloxi, Harrison County, Mis-
sissippi (near flatwoods?).
MICROHABITATS. Literature references and notes with museum
specimens show that Rhadinaea flavilata occurs in various microhabi-
tats. Individuals have been found under logs, leaves, pieces of paper,
in woodpiles, and buried in loose soil. Wilfred T. Neill (pers. comm.)
has found the species in crayfish burrows during dry weather. Most
specimens have been found under the loose bark or in the decaying
interiors of pine logs and stumps (fig. 4).

ANIMAL ASSOCIATES
FREE-LIVING ASSOCIATES. Small frogs, lizards, and snakes seem to
be the only vertebrates that regularly share the flatwoods pine log
and stump microhabitat of Rhadinaea flavilata (table 1). Frogs and
lizards (and snakes?) serve as the food of flavilata, whereas other
snakes are likely the main predators and food competitors. Perhaps
the single most important associate in many flatwoods is the ringneck
snake, Diadophis punctatus, (Myers, 1965). Diadophis is nearly the
same size as Rhadinaea and occupies the same flatwoods microhabi-
tats, but is more generalized, as indicated by its considerably wider
geographic and ecological distribution and by its more varied food
habits. Diadophis is regarded as an important food competitor, prob-
ably a competitor for space, and possibly a predator on young pine


1967








BULLETIN FLORIDA STATE MUSEUM


woods snakes. It is worth noting that in Marion County, Florida,
the only flatwoods area in which the pine woods snake has been
found really plentiful (Allen, 1989), Diadophis is uncommon (W. T.
Neill, personal communication).

TABLE 1. SOME MICROHABITAT ASSOCIATES OF Rhadinaea flavilata
IN PINE FLATWOOD REGIONS.*

Species N. C. S. C. Fla. Miss.


AMPHIBIANS
Bufo terrestris
Hyla femoralis
Hyla squirella
Gastrophryne carolinensis
REPTILES
Eumeces inexpectatus
Lygosoma laterale
Ophisaurus ventralis
Thamnophis sauritus
Thamnophis sirtalis
Virginia striatula
Virginia valeriae
Storeria occipitomaculata
Storeria dekayi
Diadophis punctatus
Lampropeltis doliata
Lampropeltis getulus
Cemophora coccinea
Coluber constrictor
Elaphe guttata
Tantilla coronata
Micrurus fulvius


X


X
X

x


X
X X
x x

X


X


X
x
x


x
X



X


x


x


X
X X
X X

X
X X
X X


X
X


X X


*Sources: North Carolina-White (1960); South Carolina-Malnate (1939);
Florida-personal observation; Mississippi-Allen (1932), Brode and Allison (1958),
Malnate (1939).

The most conspicuous invertebrates found in logs and stumps in
north Florida flatwoods are earthworms, centipedes, roaches, ter-
mites, and ants. The vertebrate fauna seems to avoid those logs and
stumps with the heaviest concentrations of ants; the vacated tunnels
of termites and ants, however, provide additional places of conceal-
ment.
Timbering practices of man help provide microhabitat space in
some places (fig. 4); Rhadinaea and other log dwellers are at least
easier to find in cut-over areas. Semi-feral pigs roam many flatwoods


62


Vol. 11







MYERS: THE PINE WOODS SNAKE


and probably prey on any small creature that they uncover while
rooting.
Little is known of flavilata's associates in habitats other than the
pine flatwoods. Engels (1952) surveyed the fauna of a North Caro-
lina coastal island where Rhadinaea has been found; Goin and Goin
(1953) list the herpetofauna, including R. flavilata, of a small ham-
mock area in northern Florida. One specimen (UF 7278) was dug
up with a worm lizard (Rhineura floridana) in a yard in Gainesville,
Florida.
PARASITES. Telford (1961) found Monocercomonas colubrorum
Hammerschmidt and Hypotrichomonas acosta Moskowitz, two wide-
spread polymastiginid flagellates of snakes and lizards, in a pine
woods snake from Alachua County, Florida. The same culture (Tel-
ford, in litt.) later produced Acanthamoeba sp. (a normally free-living
soil amoeba) and Entamoeba sp. A second specimen Telford ex-
amined was seemingly free of intestinal protozoans.

HABITATS AND BEHAVIOR

DAILY ACTIVITY. Like many snakes, R. flavilata probably does
not have a set daily cycle, but most likely adjusts its daily activities
to season and to such variables as temperature and hunger. Captive
individuals are mostly nocturnal in their prowling; one specimen
(TU 17353) was found crossing a highway the night of 4 July 1959.
SEASONAL OCCURRENCE. The term seasonal occurrence is a some-
what subjective index to cyclic variations in microhabitat selection.
More than twice as many pine woods snakes have been captured in
April as in any other month (fig. 6); there is a sharp decline in May
and numbers remain small until March, when an increase is noted.
March and April are apparently the most favorable months for R.
flavilata to occupy the pine log and stump environment, where it
is easily collected. This reflects more than the seasonal activity of
collectors for, in the Florida flatwoods, small snakes (Diadophis,
Virginia, Rhadinaea) of the rotting logs become progressively more
difficult to find with the approach of warmer weather and drier con-
ditions in May and June. Winter collecting in my experience, while
better than during the hot summer months, yields fewer small snakes
than early spring.
Few dates of collection from the Carolinas were available for in-
clusion in fig 6. Because of temperature lag, the peak of activity
in this region might be expected to occur in May, rather than April.
Brimley (1925) found May the peak month for Diadophis punctatus


1967








BULLETIN FLORIDA STATE MUSEUM


near Raleigh, North Carolina, but in Florida (Myers, 1965) Diadophis
occurs at the same seasons Rhadinaea does.


50o


45


U)
Z 40
w



30

S25
0 25


w

Z


20

15

10


J


F M A M J J A S


o N 0


MONTH OF COLLECTION

Figure 6. Months of collection for 123 specimens of Rhadinaea flavilata.

FOODS AND FEEDING BEHAVIOR. The diet of this species probably
consists mainly, if not entirely, of small amphibians and reptiles.
Malnate (1939) found the remains of small frogs (Hyla?) and the
tail of a ground skink (Lygosoma laterale) in flavilata stomachs. In
four stomachs containing food I found the following items: unidenti-
fied frog (Gastrophryne?, Rana?), tree frog (Hyla sp.), cricket frog
(Acris gryllus), and the tail of a ground skink (Lygosoma laterale).
Conant (1958) says that snakes are included in the diet, but his un-
elaborated statement needs confirmation. Brode and Allison (1958)
state that "Some were taken from rain ponds, feeding on Acris
gryllus."
Malnate (1939) doubts Haltom's (1931) statement that flavilata
feeds "on small insects." I likewise question the assertion of Brode
and Allison (1958) that "In the drier stumps Rhadinaea, Storeria and
Lampropeltis fed on roaches and other insects." Such undocumented


64


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MYERS: THE PINE WOODS SNAKE


statements have long clouded our knowledge of dietary patterns; it
is difficult to judge whether they are based on fact or fancy-for
instance none of the specimens Mr. Brode kindly loaned me had the
stomach opened. Even when arthropods are found in the stomach,
most recent writers (e.g. Neill and Allen, 1956) demand more con-
clusive proof that these are primary foods. I found the intestine of
one flavilata crammed with ants, but suspect that these were secon-
darily ingested, perhaps with the frog Gastrophryne carolinensis,
which lives in the same habitats with Rhadinaea and whose fond-
ness for ants Anderson (1954) has documented.
In captivity R. flavilata has accepted a variety of salamanders,
frogs, and lizards, but has refused invertebrates, baby mice, a small
snake, and a few species of salamanders and lizards (table 2). It
seems odd that several individuals refused small Eumeces (inexpec-
tatus and egregius) but fed readily on Lygosoma.

TABLE 2. FOOD PREFERENCES OF Rhadinaea flavilata IN CAPTIVITY.


Food accepted


Food rejected


AMPHIBIA: CAUDATA
Desmognathus fuscus conanti 1
Plethodon glutinosus
Manculus quadridigitatus

AMPHIBIA: SALIENTIA
Bufo quercicus 2
Bufo t. terrestris 1
Acris gryllus 1.2,4,6
Hyla crucifer 1,
Hyla ocularis
Hyla squirella 1
Eleutherodactylus ricordi
Gastrophryne carolinensis 1,3
Rana catesbeiana 5

REPTILIA: SAURIA
Hemidactylus turcicus 1
Anolis carolinensis ,5
Lygosoma laterale 1


ANNELIDA
Earthworms 1,5
INSECTA
"small insects" 5
wood roaches 1
AMPHIBIA: CAUDATA
"salamanders" 5
REPTILIA: SAURIA
Ophisauris ventralis 1
hatchlingg)
Eumeces inexpectatus 1
Eumeces egregious 1

REPTILIA: SERPENTES
Diadophis punctatus 1

MAMMALIA
baby mice 5


Sources: personal observation; 'Allen (1939); 'Campbell and Stickel (1939);
'Funderberg (1958); "Malnate (1939); 'Neill (1954a).


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BULLETIN FLORIDA STATE MUSEUM


The feeding behavior of R. flavilata led Neill (1954a: 59-60) to be-
lieve that it kills prey with a mild venom it introduces into wounds
made by its enlarged rear maxillary teeth:
"The method of feeding was unusual. The snake would seize a frog or lizard,
chew until the back teeth were imbedded, and then remain motionless. Seldom
was any prey held for less than 45 minutes. Usually a frog would be held for
about 70 or 80 minutes. A large, active frog or lizard was often retained for
2 or even 3 hours, until it had become quiescent. Apparently the yellow-lipped
snake imbeds its posterior teeth and then waits until a mild venom has numbed
the prey. These feeding habits were independently observed by Walter Auffen-
berg, of the University of Florida. Malnate (1939, Zoologica, (24): 364) observed
this snake eating an Anolis in captivity. The snake seized the anole, held it
until it ceased struggling, and then worked its jaws along the lizard's body to
the head and immediately commenced swallowing operations. However, the
entire process from the time the lizard was seized until it was completely swal-
lowed took only 25 minutes."
Funderberg (1958) states that his specimen seemed to use no venom
on cricket frogs (Acris gryllus) but swallowed them at once. My
own observations showed that small food items often are swallowed
alive, but that larger items are first killed, or at least rendered inac-
tive, as Neill described. I have never observed any feeding that
lasted over one hour; several times I have watched captives kill and
swallow ground skinks (Lygosoma laterale) within 15 minutes.
Rhadinaea flavilata feeds well in captivity, especially if isolated
with the prey in a small container. I regularly placed both snake
and prey in a 1/2 x 4-inch vial and left it in a darkened part of the
laboratory; usually the prey animal had disappeared within an hour.
Prey is usually swallowed head-first, but small frogs and lizards some-
times are taken from the rear or side.
DEFENSE. The pine woods snake exudes the amber-colored con-
tents of its anal glands when handled, but does not attempt to bite.
Whether the'anal glands of snakes afford protection against some pred-
ators is not known, but seems likely.
The slender tail of R. flavilata breaks readily and probably helps
some snakes escape predation, as 29.4 percent of all specimens ex-
amined had stub tails. Some of'this breakage, however, may be due
to the ophidian disease that Neill (1960) calls "tail-rot."
REPRODUCTION. Examination of the reproductive tracts of eight
adult females collected in different years in Florida, Louisiana, and
Mississippi gave the following results:
February (1 specimen): Largest ovarian eggs 4 mm in diameter.
Late April (3 specimens): One had three ovarian eggs, 12 x 4,
13 x 4, and 15 x 4 mm; another had three ovarian eggs, 6 x 4, 15 x 5,


Vol. 11


66







MYERS: THE PINE WOODS SNAKE


and 16 x 5 mm; the third had two eggs in the oviducts, 26 x 6
and 28 x 6 mm.
May (3 specimens): Position of the eggs in two poorly preserved
specimens collected May 13 could not be determined; one from each
measured 18 x 6 and 28 x 7 mm. The third specimen collected May
25 had three oviductal eggs, 25 x 7, 27 x 7, and 27 x 7 mm.
July (1 specimen): collected July 4 had two ova (probably ovarian)
measuring 14 x 4 and 16 x 5 mm.
The above observations of egg size and placement suggest a long
egg deposition season, which is further indicated by a few records of
captive layings. Funderberg (1958) reports a specimen from North
Carolina that on 4 June 1958 laid four eggs which measured only 13 x
5 mm. Telford (1952 and pers. comm.) records a female 207 mm in
total length that deposited four eggs averaging 20 x 4 mm. in Polk
County, Florida, 19 July 1946; and a specimen collected in Polk
County in June 1947 that measured 381 mm and laid four eggs aver-
aging 18 x 5 mm on 6 July. Allen (1939) mentions a Marion County,
Florida individual that laid three eggs averaging 23 x 8 mm 19 Au-
gust 1937; these hatched in September. The season of egg laying
seems similar to that of Diadophis punctatus in Florida (Myers, 1965),
which is thought to lay from May or June into August, although egg
laying in any one year and locality probably does not extend over
so great a period.
Funderberg (1958) states that the eggs of a North Carolina speci-
men were white; the leathery surface was granular to the naked eye,
but under magnification irregular, wavy, longitudinal ridges were
visible. Curiously, these eggs were smaller than some of the ovarian
ova mentioned above. Telford (pers. comm.) noted that the eggs
in a clutch from Polk County, Florida were bright yellow. The
natural nest has not been reported.

SEX RATIOS
The total sample breaks down nicely into a 1:1 sex ratio, but devia-
tions from this occur in a series from Florida and in the western part
of the range. In the combined sample from Alachua and Marion
counties, Florida, the ratio is 37 per cent males to 63 per cent females;
the exact reverse occurs in the Louisiana-Mississippi sample (table 3).
If the deviations from a theoretical 1:1 ratio in these two samples
reflect more than chance collecting, I am unable to account for them;
there are no conspicuous differences in number of juveniles present
or in times of collection.


1967







BULLETIN FLORIDA STATE MUSEUM


TABLE 3. SEX RATIOS OF Rhadinaea falilata. THE LARGEST SAMPLES ARE
TESTED BY CH-SQUARE FOR STATISTICAL DEVIATION FROM A
THEORETICAL 1:1 RATIO.

Number Number
%Males: of of
Series %Females males females 2 P

ALABAMA 43:57 3 4
FLORIDA (total) 44:56 47 59 1.358 <0.25> 0.20
Alachua Co. 36:64 9 16
Marion Co. 37:63 16 27
Alachua-Marion Co.
(combined) 37:63 25 43 4.764 <0.05> 0.025
All other counties 58:42 22 16
GEORGIA 0 1
LOUISIANA 62:38 8 5
MISSISSIPPI 63:37 27 16
LOUISIANA-
MISSISSIPPI (combined) 63:37 35 21 3.500 <0.10> 0.05
NORTH CAROLINA 57:43 4 3
SOUTH CAROLINA 50:50 4 4

ALL STATES COMBINED 50:50 93 92


VARIATION

All observed structural variations are treated in this section.
Most variation in this and other species of snakes presumably has
a genetic basis, but studies by Fox (1948) and Fox et al (1961) show
that environment may have major morphological influence in some
cases. Until such problems can be studied and discussed in more
detail, it seems best to classify variations of snake species without
regard to possible genetic or environmental causes. The following
scheme seems useful.
A) Intrapopulational variation
1) Ontogenetic variation
2) Sexual dimorphism
3) Uncorrelated variation

B) Interpopulational variation
4) Geographic variation

Overlap is frequent between classes 1 and 2. Class 3, uncorre-
lated variation, is equivalent to the "individual variation" of most


Vol. 11







MYERS: THE PINE WOODS SNAKE


authors, which seems to me a poor term because all variation relates
ultimately to the individual. Uncorrelated variation is that which is
not basically related to age or sex, although differential mortality
rates may sometimes superimpose an age or sex correlation.
Interpopulational, or geographic variation can be variously sub-
divided, but, as R. flavilata provides few good examples, this is not
attempted here. The study of geographic variation is essentially
the study of shifting frequencies of a character or attribute between
populations. Whatever pattern such shifting involves, be it mosaic
or smooth or stepped dines, it must be remembered that geographic
variation is not something completely apart, but rather is compounded
from any or all of the three classes of intrapopulational variation.
The only exception is the relatively rare intraspecific situation (absent
in R. flavilata) where a geographically variable character shows no
intrapopulational variation, its frequency being either 0 or 100. In
the pine woods snake geographic variation is compounded mainly
from uncorrelated variation, partly from sexual variation, and, so
far as known, not at all from ontogenetic variation.
Table 4 lists the variable characters determined for Rhadinaea
flavilata and the classes of variation to which they are assigned.
TABLE 4. CLASSIFICATION OF OBSERVED VARIATION IN Rhadinaea flavilata.

Type of variation
Character studied Ontogenetic Sexual Uncorrelated Geographic
Color brightness and pattern X
Anal ridges X X
Sexual segments of kidney X X
Tail length X X
Total and body lengths X
Anal sacs X
Tail breakage X
Number of subcaudals X
Number of ventrals X X
Colgr pattern X X
Labials X X
Temporals X X
Dorsal scales on neok X X
Labial and ventral color X
Loreals X
Oculars X
Divided or half-ventrals X
Fused subcaudals X
Number of teeth X


1967







BULLETIN FLORIDA STATE MUSEUM


Characters that vary in more than one way are so indicated in the
text. In the following accounts, individuals with total lengths (pre-
served) over 250 mm are considered adult, and those under 200 mm
juvenile, as explained in the discussion of anal ridges.
ONTOGENETIC VARIATION
COLOR AND PATTERN. Most snakes probably undergo some onto-
genetic changes in color brightness (= value or brilliance) and satu-
ration. Young R. flavilata seem somewhat brighter than adults. Mal-
nate (1939) mentions that some individuals have an indistinct light
yellow patch on each side of the neck. The prominence of these
occipital spots seems determined partly by age, as they were conspic-
uous on three juveniles from Okeechobee County, Florida and on
one juvenile from Berkely County, South Carolina,. but absent or
faint on other juveniles and adults.
ANAL RImGE. These structures are discussed more fully on pages
72-73. Anal ridges are absent on most juveniles, but present on some
adult females and most adult males (fig. 9).
KIDNEYS. The kidney in juvenile males is similar to that in fe-
males lacking noticeably enlarged "sexual segments" of the urinary
tubules. For more details see below.
TAIL LENGTH. This is also a sexually dimorphic feature (fig. 8);
tails average proportionally shorter in juveniles of both sexes than
in adults. Nine juvenile males have a mean tail/total length ratio
of 30.0 per cent (range 28.7-30.7), whereas 47 adult males have a mean
of 32.6 per cent (range 30.2-35.9). Corresponding percentages for
nine juvenile females and 42 adult females are 28.6 (27.0-30.6), and
29.8 (27.5-32.0), respectively.
SEXUAL DIMORPHISM
Aside from differences in the reproductive organs, the sexes of
Rhadinaea flavilata were found to vary in the following ways.
KIDNEYS. The adult male kidney is relatively larger than that
of the female, and is white with a convoluted surface caused by 'en-
larged segments ("sexual segments") of the urinary tubules. The
juvenile and female kidneys'are smoother in texture and darker in
color. Kidney texture in Rhadinaea flavilata is similar in general ap-
pearance to that in Diadophis punctatus (see Myers, 1965). The func-
tion of this dimorphism in the kidneys of some snakes and lizards
is unknown.
ANAL SACS. The anal sacs (also called musk or scent glands) of
snakes are paired structures lying in the base of the tail and opening


Vol. -11







MYERS: THE PINE WOODS SNAKE


into the cloaca. In the males the sacs lie dorsad from the hemipenes,
and for this reason occupy a lesser circumference than in females.
The function of these structures is not known with certainty, but as
the contents are discharged when R. flavilata and most other snakes
are handled, they may have some protective value. The sacs are
well developed in juveniles.
The length of the anal sacs was determined in only 26 specimens,
but the data suggest that the sacs tend to extend more caudad in
males than in females (table 5). This is perhaps a compensation
for the smaller diameter of the sacs in males.

TABLE 5. LENGTH OF THE LEFT ANAL SAC IN Rhadinaea flavilata.

Number of subcaudals spanned
Sex 9 10 11 12 13 14 No. Mean

Males 0 1 7 4 3 1 16 11.8
Females 2 3 2 2 1 0 10 10.7
Both sexes 2 4 9 6 4 1 26 11.3


SIZE AND PROPORTIONS. Females attain greater total length than
do males (fig. 7). The seven largest specimens (365-387 mm total
length) are females. Assuming individuals over 250 mm total length
to be adults, 46 adult males with complete tails average 301.88 4.15
mm in total length, and 45 adult females 325.40 5.20 mm. These
differences are due to the greater body (snout-vent) length attained
by females (fig. 9), as males usually have longer tails than do females
of equivalent length (fig. 8). The largest male (St. Johns County,
Florida) is 363 mm in total length and has a tail length of 125 mm;


6
S2
z


62 MALES


***** U E E Il rlhhll~lll


O 140 160 10 200 220 240 260 210 300 320 340 360 380 400
SL. 2


60 FEMALES
TOTAL LENGTH (mm.)
Figure 7. Observed frequency of total lengths in Rhadinaea flavilata. In-
dividuals with incomplete tails are excluded.


1967








BULLETIN FLORIDA STATE MUSEUM


in contrast, the largest female (Alachua County, Florida) is 387 mm
in total length but has a tail measurement of only 114 mm. Mean
proportional tail to total length for 60 males is 32.0 per cent (range
28.7-35.9), and for 57 females is 29.5 per cent (range 27.0-32.0).
The presence of the hemipenes and associated muscles is un-
doubtedly the basis for longer tails in male snakes generally, while
the value of additional space for egg or embryo development is logi-
cally the selective agent responsible for larger body size in the fe-
males. Because of the hemipenes, the base of the tail in male
R. flavilata is noticeably wider than in females.


*
Ito MALES *
10 0 0
o o
10o F*tU o **S o0 Oo
*o. ao o o
4 0
t0o 0 Wo C o 0
o
o0 o o

so .

so 0.
5 .B

t0


go


40 0 120 1S0 200o 240 2o0 t20 300
TOTAL LENGTH (mm.)


Figure 8. Tail length to total length relationships in
Individuals with incomplete tails are excluded.


Rhadinaea flavilata.


ANAL RDGES. This term was coined by Blanchard (1931) for the
keel-like ridges on dorsal scales in the anal region of certain other-
wise smooth-scaled snakes, including Rhadinaea flavilata. In snakes
of the genera Carphophis and Diadophis Blanchard found such struc-
tures characteristic of males over certain lengths, and seldom present
in females and young males. Blanchard and other workers have
logically assumed that the ridges indicate the approximate size at
.which sexual maturity is reached. This belief has been objectively
documented for Diadophis punctatus in Florida (Myers, 1965), but
the function of the structures remains uncertain.


Vol. 11







MYERS: THE PINE WOODS SNAKE


In Rhadinaea flavilata, anal ridges are present on all male speci-
mens over 164 mm snout-vent length (fig. 9) or 243 mm total length.
Therefore all specimens over 250 mm total length are arbitrarily
considered to be adults, and all specimens under 200 mm to be juve-
niles. Malnate (1939) mentioned two males of 275 mm and 305 mm
total length that lacked anal ridges. Possibly Malnate overlooked
poorly developed ridges on these specimens because of poor magni-
fication or lighting. Nevertheless occasional large Diadophis males
lack anal ridges (Blanchard, 1931, 1942; Myers, 1965), and so might
some large Rhadinaea males. Malnate (1939) also said that anal
ridges were not present on any females examined, but they appear
on 34 of 87 females I examined (fig. 9).


SNOUT-VENT LENGTH (mm.)
Figure 9. Distribution of anal ridges by size and sex in Rhadinaea flavilata.
Specimens plotted above the horizontal lines have anal ridges, those below
lack them.

The degree of development of anal ridges varies considerably in
flavilata, but females tend to have them less strongly developed than
males. The most conspicuous anal ridges are found in the larger
males, but some of the largest specimens have them poorly developed.


1967








BULLETIN FLORIDA STATE MUSEUM


TAIL BREAKAGE. Incomplete tails are present in 27 males and
28 females, or 29.4 per cent of the total sample. There is no sig-
nignificant sexual dimorphism in the place of breakage, although the
break is closer to the anal plate in some females than in males. The
hemipenial muscles normally extend to the 21st subcaudal (to the
24th in an Alabama specimen), and only one male, with 18 pairs of
caudals, has less than this number. Seven females, however, have
20 or fewer pairs of caudals. Females with broken tails have 12-70
pairs of subcaudals remaining, with a mean of 38.75 3.30; males
have 18-69 pairs with a mean of 42.37 2.59.
VENTRALS. The number of ventral plates varies both geographi-
cally and sexually. For the entire sample the number of ventrals in
males ranges from 112 to 134, and for females 118 to 139. For given
populations the overlap is not nearly so great, and the means are
well separated (fig. 11); females usually average four or five more
ventrals than males (table 6). The greater number of ventrals in
females is correlated with larger body size.

TABLE 6. SEXUAL DIMORPHISM OF Rhadinaea flavilata IN
NUMBER OF VENTRAL PLATES.

Males Differences Females
Series N M SE DM CD N M SE

North and
South Carolina 8 119.88 8.40 6.77 7 128.28 -
Alabama, Louisiana,
and Mississippi 37 123.30 .31 4.70 3.74 26 128.00 .58
Alachua and Marion
counties, Florida 25 125.32 .28 4.70 3.68 43 130.02 .37
Entire range 91 124.20 .28 5.50 4.33 93 129.70 .30

N = number; M = mean; SE standard error of mean; DM = difference
between means; CD coefficient of divergence (in per cent).

SUBCAUDALS. Males have longer tails (fig. 8) and hence more
subcaudal plates than females. For the entire sample males have
68-83 pairs of subcaudals, females 59-75 pairs; there is little or no
geographic variation (fig. 12). In given populations males average
five or six more subcaudals than females (table 7). As expressed by
the coefficients of divergence (tables 6, 7), sexual dimorphism is
more marked in subcaudals than in ventrals.


74


Vol. 11








MYERS: THE PINE WOODS SNAKE


TABLE 7. SEXUAL DIMORPHISM OF Rhadinaea flavilata IN
NUMBER OF SUBCAUDAL PLATES.

Males Differences Females
Series N M SE DM CD N M SE

North and
South Carolina 8 71.62 4.62 6.67 4 67.00 -
Alabama, Louisiana,
and Mississippi 22 72.64 .55 5.95 8.54 13 66.69 .99
Alachua and Marion
counties, Florida 18 73.61 .51 5.58 7.88 33 68.03 .51
Entire range 60 72.87 .31 5.24 7.46 60 67.63 .40

N = number; M mean; SE = standard error of mean; DM = difference
between means; CD = coefficient of divergence (in per cent).

UNCORRELATED VARIATION
Several uncorrelated variations of Rhadinaea flavilata seem to
have distributional significance and are discussed under geographic
variation. These are certain aspects of color pattern and of labial,
temporal, and dorsal scale scutellation. It seems likely that addi-
tional data would give geographical significance to many of the re-
maining uncorrelated variations. Only in the case of an aberration
of the last ventral plate are there sufficient data to indicate an un-
correlated variation that may not undergo interpopulational shifts
in frequency.
COLOR AND PATTERN. Color pattern variation is discussed under
geographic variation. Also of possible geographic significance is the
coloration of labials and venter, but too few color descriptions of
living individuals are available to document this. Cope (1871) says
that the labials and venter of the type specimen (North Carolina)
were white; this was in life, for Cope received the type alive (Coues
and Yarrow, 1878), kept it alive for several months (Cope, 1900), and
published his description of the specimen less than two months after
receiving it. Ditmars (1907) states without elaboration that the upper
lip is "bright-yellow." In a combined description of two living speci-
mens from Florida and Mississippi Brown (1901) states that the
ventrals and labials were light yellow. Malnate (1939) gives the fol-
lowing description, probably from South Carolina specimens: "(color
nomenclature from Ridgway) . Ventral surface pale martius or
marguerite yellow, fading to whitish on the chin and throat ....
Labials light maize yellow or sulphur yellow." Ventral coloration


1967


75







BULLETIN FLORIDA STATE MUSEUM


of living specimens from northern Florida ranges from white to
chartreuse (yellow-green), and the labials are white, sometimes with
a trace of the brown head coloring as well as the usual black spot-
ting. A specimen in the Duke University collections has bright
yellow labials-from a slip of yellow paper that faded in the jar
of preservative.
LOREALS. A male from Mississippi lacks a loreal on the left and
has the right one very much reduced.
OCULARS. A female from Hancock County, Mississippi has the
right preocular fused with the supraocular. Netting (1936) notes
that a supposed Texas female has the same condition on the left
side of the head. Pseudo-oculars rarely appear anterior to the lower
edge of the eye, but these arise from labial divisions as discussed
under geographic variation.
LABIALS AND TEMPORALS. All variation in these plates is for con-
venience considered under geographic variation, although it is pos-
sible that a few rare conditions of the supralabials and temporals
might be uninfluenced by geography.
DORSAL SCALES. See under geographic variation.
VENTRALS. The last ventral is abnormal in 11 per cent of all
specimens examined. In most cases (17 of 21) only a half-ventral is
present; in the others two half-ventrals lie side by side, giving the
appearance of a full plate divided sagittally. The percentage of
aberrant specimens is nearly the same in the Florida and western
samples, but higher in a series from the Carolinas (table 8). The
Carolinas sample was tested for statistical difference from the com-
bined Florida and western sample. The results (x2 = 0.509;
P < 0.50> 0.30) suggest that this anomaly is not characteristic of any
one part of the country; also no evidence suggests that local popula-

TABLE 8. ABERRANCY* OF THE LAST VENTRAL PLATE IN Rhadinaea flavilata.

Series No. aberrant Total sample % aberrant
FLORIDA 12 110 10.9
WESTERN 6 64 9.3
(Alabama, Louisiana,
and Mississippi)
NORTHERN 3 15 20.0
(North and South Carolina)

Total 21 189 11.1

*"Divided" or "half-ventral," probably indicative of vertebra duplication.


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MYERS: THE PINE WOODS SNAKE


tions vary significantly from one another in this respect. There is
no sexual dimorphism, as 11 variants are males and 10 females.
Rarely do aberrations occur other than in the last ventral. Half-
ventrals are present on the anterior part of the body in two males
(Mississippi and Florida). A female from Florida has several anterior
ventrals "divided."
King (1959) demonstrated that half-ventrals correspond to verte-
bral duplication (duplicate accessory processes and rib) on one side
of the body. Consequently a ventral scute that seems to be divided
at the midline probably represents two half-ventrals corresponding
to vertebral duplication on both sides. The half-ventral is illustrated
diagrammatically by King (1959, fig. 1-E) and Peters (1956, fig. 3-1;
1960, fig. 2-1); the "divided" type of ventral is illustrated by Peters
(1956, fig. 3-2; 1960, fig. 2-2). The conditions observed in Rhadinaea
flavilata are similar to these illustrations; the other types of anoma-
lous ventrals figured by King and by Peters were not observed.
King (1959) mentions that half-ventrals were found in Rhadinaea;
this statement was based on R. flavilata (King, verbal communica-
tion), although I can state that it also occurs in other members of
the genus.
SUBCAUDALS. Two males and two females have one or more sin-
gle subcaudal plates. A specimen from Okeechobee County, Florida
has the first caudal undivided, and one from Alachua County, Florida
has the last undivided. One of two snakes collected 5 miles west of
Slidell, St. Tammany Parish, Louisiana has the first two plates un-
divided, the other has the second, third, and fourth plates entire.
DENTITION. No attempt was made to ascertain possible geo-
graphic variation in the number of teeth, which does occur in some

TABLE 9. VARIATION IN THE NUMBER OF TEETH IN FLORIDA SPECIMENS
OF Rhadinaea flavilata.

No. Number of teeth
Bone bones 11 12 13 14 15 16 17 18 19 20 21 22 23
MAXILLARY 16 14* 2
(anterior to
diastema)
PALATINE 13 8* 8 2
PTERYGOID 12 1 2 1 5 2
DENTARY 12 5* 6 1

*Location of counts for Polk County specimen (1 maxilla, 1 palatine, and 1
dentary were available). All other specimens from Alachua County.


1967







BULLETIN FLORIDA STATE MUSEUM


snakes (e.g. Coluber constrictor, Auffenberg, 1955). A small series of
skeletons from Alachua County, Florida and one from Polk County,
Florida indicate the extent of variation in one geographic area (ta-
ble 9).
Malnate (1939) apparently attempted to count the teeth of R.
flavilata in situ, and perhaps for this reason obtained lower counts
than given in table 9.

GEOGRAPHIC VARIATION
COLOR PATTERN. The most conspicuous geographic variation in
R. flavilata is the dark pigmentation on the labials (fig. 10), which
increases from south to north. In Florida the labials are usually un-
marked except for a few plates anterior to the eyes, although some
Florida individuals show scattered spots of pigment on all the supra-
labials and most of the infralabials. In specimens from Alabama,
Louisiana, and Mississippi most of the labials are usually spotted
and generally more pigmented than in Florida individuals. Some
South Carolina specimens have still more pigment, and in North
Carolina all the labials and even the genials may be profusely pig-
mented. Some snakes from the Carolinas resemble southern speci-
mens in labial pigmentation, but no southern individual (Florida,
Georgia, Alabama, Mississippi, or Louisiana) remotely approaches
the extreme peppered condition shown in fig. 10.
The dorsal stripe also varies geographically. When present this
stripe consists of a band of diffused pigment on the vertebral scale
row, the pigment normally being restricted to the distal ends of the
vertebral scales. The stripe is absent in about 45 percent of the
Florida sample and usually only faintly indicated in the rest. Only
about 10 percent of the Alabama, Louisiana, and Mississippi speci-
mens lack a middorsal stripe, and it is usually more distinct than
on Florida specimens. One of eight specimens from South Carolina
does not have a vertebral stripe, but on most it is distinct. The stripe
is best developed in the North Carolina sample (seven specimens);
vertebral scale row pigmentation is more or less continuous on four
specimens, a rare condition anywhere else in the range. I fail to
detect geographic variation in the lateral stripe, which is rarely ab-
sent but is often weak. Neill (1963: 205) mistakenly attributes pres-
ence or absence of striping in flavilata to polychromatism, but varia-
tion in this character is continuous.
VENTRALS AND SUBCAUDALS. The number of ventrals decreases
slightly from south to north (fig. 11). Geographic variation in the


Vol. 11







MYERS: THE PINE WOODS SNAKE


number of subcaudal plates is either nonexistent or too slight to
demonstrate in the available sample (fig. 12.)


NORTH

CAROLINA


~pj'd.


SOUTH

CAROLINA


FLORIDA


a7-- -__ -


Figure 10. Geographic trends in labial pigmentation of Rhadinaea flavilata.
Top-DU specimen from 24 miles SW Morehead City, Carteret County, North
Carolina; Center-CM 25190, Berkely County, South Carolina; Bottom-speci-
men from Alachua County, Florida. Robert McFarlane


k










BULLETIN FLORIDA STATE MUSEUM


NORTH CAROLINA -


SOUTH CAROLINA



SOUTH CAROLINA


Icf
I

I


ALABAMA,
MISSISSIPPI, &
LOUISIANA


r


II


'\ I


i1. .II


NORTH FLORIDA


CENTRAL FLORIDA





SOUTH FLORIDA


...


112 114 116 118 120 122 124 126 128 130 132 134 136 138

NUMBER OF VENTRALS

Figure 11. Geographic and sexual variation in the number of ventral plates
in Rhadinaea flavilata. Horizontal lines represent the ranges of variation, and
small triangles the means. A solid rectangle represents two standard errors on
each side of the mean; this plus the open rectangle, one standard deviation on
each side of the mean.
Sample sizes: North Carolina-4 males, 3 females; South Carolina-4 males,
4 females; Alabama, Mississippi, and Louisiana-37 males, 26 females; North
Florida (Alachua and Marion counties)-25 males, 43 females; Central Florida
(Brevard, Orange, Polk, and Seminole counties)-5 males, 5 females; South
Florida (Glades, Okeechobee, and Palm Beach counties)-4 males, 5 females.


_


i q % I


r
r
r
,o
I
I


80


Vol. 11


r
I
r
r


t-_









MYERS: THE PINE WOODS SNAKE


NORTH CAROLINA


'"C'


+


SOUTH CAROLINA


a


I II


NORTH FLORIDA


ALI


SOUTH FLORIDA


60 62 64 66 68 70 72 74 76 78 80 82

NUMBER OF SUBCAUDALS



Figure 12. Geographic and sexual variation in the number of subcaudal
plates in Rhadinaea flavilata. See fig. 11 for interpretation.
Sample sizes: North Carolina-4 males, 1 female; South Carolina-4 males,
3 females; Alabama, Mississippi, and Louisiana, 22 males, 13 females; North
Florida (Alachua and Marion counties)-18 males, 33 females; South Florida
(Glades, Okeechobee, and Palm Beach counties)-4 males, 3 females.


ALABAMA,
MISSISSIPPI,
LOUISIANA


I 1 1 r 1 1 1 .1 P


iii


r


I


1967


81








BULLETIN FLORIDA STATE MUSEUM


INFRALABIALS. The lower labials usually number 9/9, but there
are occasionally 7, 8, or 10. Observed variation is listed in table 10;
several formulae (e. g. 7/7) that may exist in nature were not observed.
Sexual dimorphism appears not to be involved in deviations from the
normal (13 males to 18 females). Deviations in upper and lower
labial counts occur independently more often than not; only four
specimens (from Florida) showed deviations in both the supra- and
infralabial formulae.
Reduction or increment of the infralabials occurs most commonly
in Florida (table 10); elsewhere such cases are known only from
Alabama (1) and Mississippi (2). The Florida sample differs signifi-
cantly even when compared only to the western population (x2
13.396; P<0.001). A greater percentage of variant specimens occurs
in the Alachua-Marion counties sample than all other Florida locali-

TABLE 10. VARIATION IN THE NUMBER OF INFRALABIALS OF Rhadinaea flavilata.*

Number of labials (left/right)
Series 7/8 7/9 8/8 8/9 9/8 9/9 9/10 10/9 8/10 10/10 Total

FLORIDA 1 1 7 5 5 70 4 4 1 1 99
Alachua Co. 3 3 16 1 1 24
Marion Co. 1 3 2 25 2 3 1 1 38
Brevard Co. 2 3 5
Duval Co. 1 1
Okeechobee Co. 1 1 5 7
Orange Co. 1 1
St. Johns Co. 3 1 4
Other counties (8) 14 14
Unknown 1** 4 5
GEORGIA 1 1
WESTERN (Alabama, 1 61 1 1 0 64
Louisiana, and
Mississippi)
NORTHERN (North 15 15
and South Carolina)
UNKNOWN ("Texas") 1 1

Total 1 1 8 5 5 148 4 5 1 2 180

*A mutilated male with the formula 10/? (St. Johns Co., Fla.) was not in-
cluded, nor were a few similar specimens with formulae 9/? or ?/9.
**Specimens mentioned by Malnate (1939, p. 363) that were not available
for the present study.


82


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MYERS: THE PINE WOODS SNAKE


ties combined (table 10), but the difference is not statistically signifi-
cant (x2 = 1.139; P <0.25> 0.20).
Infralabial variation is best explained by assuming the division or
fusion of plates during embryonic development. The reduction to
8 plates involves the fusion of the eighth and ninth or the second and
third plates; a reduction to 7 plates involves both of the above com-
binations. An increase to 10 plates is the result of a division in one
of the first several plates (second to fourth, apparently) or in one
of the last. Fox et al. (1961) report a significant correlation between
low supra- and infralabial counts and low environmental tempera-
tures during embryonic development in the snake Thamnophis ele-
gans.
SUPRALABIALS. The upper labials usually number 7/7, but oc-
casional combinations of 7/8, 8/7, and 8/8 appear with equal fre-
quency to one another. No apparent sexual dimorphism is involved,
as six males and nine females were among the variants studied.
Deviations from the normal count may appear anywhere in the
range, but seem most common in Florida (table 11) where 81 percent
of the observed variation occurred. Statistically the Florida sample
does not differ significantly from the rest of the range (x2 = 3.398;

TABLE 11. VARIATION IN THE NUMBER OF SUPRALABIALS OF
Rhadinaea flavilata.

Number of labials (left/right)
Series 7/7 7/8 8/7 8/8 Total

FLORIDA 91 4 5 4 104
Alachua Co. 19 1 3 2 25
Marion Co. 38 1 1 1 41
Polk Co. 3 1 4
Seminole Co. 1 1
Unknown 3 1 1 5
Other 28 28
GEORGIA 1 1
ALABAMA 7 1* 8
LOUISIANA 13 13
MISSISSIPPI 42 1 43
NORTH CAROLINA 7 7
SOUTH CAROLINA 7 1 8
UNKNOWN ("Texas") 1 1

Total 169 5 6 5 185


*A specimen mentioned by Malnate
during the present study.


(1939, p. 363) that was not available


1967


83







BULLETIN FLORIDA STATE MUSEUM


P < 0.10 > 0.05), although the probability obtained is not much above
the level (0.05) here accorded significance. While the possibility of
chance collecting cannot be ruled out, I suspect that supralabial num-
bers do vary more frequently in Florida. Most supralabial variants
in Florida occurred in the large Alachua-Marion counties sample
(table 11), but no significance can be attached to this in comparison
with the rest of the state (x2 = 0.0237; P < 0.90 > 0.80).
Several anomalous supralabial conditions were observed. A fe-
male from Alachua County, Florida and another from adjoining
Marion County each have a small extra plate (pseudopreocular) added
at the anterodorsal corer of the third labial on the left. In a Geor-
gia female a small plate present above the third labial on both sides
of the head gives an apparent preocular formula of 2/2. A female
from Putnam County, Florida has the first labial on the left excessive-
ly elongated along the horizontal axis.
Some specimens have an extra plate between the fifth labial (sixth
labial in a specimen with 8 supralabials) and the first temporal. In
the sample from Alabama, Louisiana, and Mississippi, 19 have such
a plate on one or both sides of the head and 43 do not. The anomaly
is absent in the small series from Georgia and the Carolinas but
present in four of 104 specimens from Florida. By comparing the
Florida sample with the western one it is seen that geographic dif-
ferences are probably not due to chance alone (x2 = 21.134; P
< 0.001). This is the only head plate anomaly found to be character-
istic of the western population. No sexual dimorphism seems to be
involved, for the ratio of 15 aberrant males to 8 females can be
explained on the basis of an unbalanced sex ratio in the western
sample (table 3).
As with the infralabials, supralabial variation is best explained
by assuming the division or fusion of plates during embryonic de-
velopment. The addition of extra plates at the dorsal borders of the
third and fifth labials is caused by a division of those plates, as is
evident from their reduced area and altered shape. Increase from
a normal number of seven to one of eight seems to be the result of
a vertical split of the second or third labial, most often the latter.
The single instance where the first labial was elongate probably was
caused by a fusion of the first two plates and a division of the third.
TEMPORALS. The normal temporal formula is 1 + 2, but these
plates are frequently altered by division, fusion, enlargement, or
reduction; 33 percent of all specimens examined have one or more
aberrant temporals, but usually on only one side of the head. The
following kinds of variation were observed.


Vol. 11







MYERS: THE PINE WOODS SNAKE


1) Vertical division of one or rarely both plates in row 2. This
1 2 2
gives the formula 1 + -, 1 + -, or rarely 1 + -. (52 specimens:
2 1 2
Florida 36, Louisiana 5, Mississippi 9, North Carolina 1, South
Carolina 1).
2) Reduction in size of one or both plates in row 2, usually
with a noticeable enlargement of an adjoining post-temporal. (7
specimens: Florida 6, Mississippi 1).
3) Fusion of the top plate in row 2 with the adjoining post-
temporal, thereby forming an elongated plate. (7 specimens:
Florida 6, South Carolina 1).
4) Enlargement of the bottom plate in row 2 and a correspond-
ing reduction of the top plate. (2 specimens: Florida 1, Missis-
sippi 1).
5) Fusion of both plates in row 2 on the left side of the head.
(1 specimen: Mississippi).
6) Fusion of the single plate in row 1 with the top plate in
row 2 on the right side of the head. This was the only observed
instance in which the first temporal was affected. (1 specimen:
Mississippi).
The various temporal conditions are so mixed in some samples
that they are best considered all together. Only 11 specimens had
the same temporal aberration on both sides of the head; only four
specimens had more than one kind of temporal defect; aberrations
occurred as frequently on one side of the head as on the other. As
they occurred in 34 males and 28 females, no sexual dimorphism is
evident. Although the observed sex ratio in the Alachua-Marion
counties, Florida population was 37 per cent males to 63 per cent
females, temporal variants occurred in nearly a 1:1 sex ratio (16
males: 17 females); however, no statistical significance can be at-
tached to these differences (x2 = 2.360; P < 0.20 > 0.10).
Temporal plate anomalies may be slightly more common in Flor-
ida than elsewhere (table 12), but differences based on the available
sample are not really significant (x2 3.442; P < 0.10 > 0.05). The
issue is further confused by sample bias: The number of anomalous
specimens in the Alachua-Marion counties series differs significantly
from the rest of the Florida specimens combined (x2 = 7.035;
P < 0.01 > 0.005). Specimens with aberrant temporals are also


1967








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known from Brevard, Duval, and Volusia counties on the east Florida
coast; 6 of 12 individuals from these counties have anomalous tem-
porals compared with 25 normal specimens from 11 other Florida
counties (table 12). This distribution is not random (x2 = 10.444;
P < 0.005 > 0.001), and the amount of temporal plate aberrancy in
Florida differs significantly from one local population to the next.

TABLE 12. GEOGRAPHIC DISTRIBUTION AND FREQUENCY OF SPECIMENS OF
Rhadinaea flavilata HAVING ANOMALOUS TEMPORAL PLATES.

Per cent
Series Anomalous Normal Total anomalous

FLORIDA 42 67 109 38.5
Alachua Co. 12 13 25 48.0
Marion Co. 21 21 42 50.0
Brevard Co. 3 2 5 60.0
Duval Co. 1 3 4 25.0
Volusia Co. 2 1 3 66.7
Counties unknown 3 2 5 60.0
Other counties (11) 0 25 25 0.0

GEORGIA 0 1 1 0.0

WESTERN 17 46 63 27.0
Alabama 0 7 7 0.0
Louisiana 5 8 13 38.5
Mississippi 12 31 43 28.0

NORTHERN 3 12 15 20.0
North Carolina 1 6 7 14.3
South Carolina 2 6 8 25.0

UNKNOWN ("Texas") 0 1 1 0.0

COMBINED 62 127 189 32.8


DORSAL SCALES. The dorsal scale row formula is normally 18 +
17 + 17 + 17, but occasionally the first count (immediately behind
the head) is reduced to 17 or very rarely increased to 19. Deviations
were observed in Florida and Mississippi specimens (table 13). A
significantly higher number of deviations occurred in Florida than
in the western sample (x2 = 5.822; P < 0.02 > 0.01). The Alachua-
Marion series showed no significant difference from other Florida
localities combined (x2 = 0.075; P < 0.80 > 0.75).


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MYERS: THE PINE WOODS SNAKE


TABLE 13. GEOGRAPHIC


VARIATION IN NUMBERS OF DORSAL SCALES ON THE
NECK OF Rhadinaea flavilata.


Per cent
deviation
Number of scales on neckro
from
Series 18 17 19 Total normal (18)

FLORIDA 77 23 100 23.0
Alachua Co. 17 8 25 32.0
Marion Co. 32 8 40 20.0
Brevard Co. 2 2 4
Duval Co. 1 2 3
Glades Co. 1 1
Levy Co. 1 1
Taylor Co. 1 1
Other counties (9) 22 22
Counties unknown 3 3
GEORGIA 1 1 0.0
WESTERN 55 :3 1* 59 6.8
NORTHERN 14 14 0.0
UNKNOWN ("Texas") 1 1 0.0

Total 148 26 1 175 18.2

*From Mississippi.

SUMMARY. Interpopulational variation in Rhadinaea flavilata is
compounded from intrapopulational uncorrelated variation, except for
the geographic changes in numbers of ventral plates, which first vary
according to sex. Clinal variation is seen in features of color pattern
and ventral numbers, pigmentation increasing from south to north
and ventrals decreasing. Other geographically variable characters
vary regionally and/or microgeographically: Variation in labial num-
bers, presence of anomalous supralabials, and deviation from an an-
terior count of 17 dorsal scale rows, all occur in highest frequencies
in Florida. An extra plate between the fifth supralabial and anterior
temporal occurs most frequently in the western portion of the range
in Alabama, Mississippi and Louisiana. Frequency of occurrence
of anomalous temporal plates seems to vary from population to
population on a distinctly microgeographic basis.
Except for clinal changes in color pattern, geographic variation
in the pine woods snake is not striking. The present study confirms
Malnate's (1939) view that no subspecies are recognizable.


87


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AFFINITIES

Rhadinaea flavilata is a relatively generalized member of its genus,
as shown by the following characters: 1) Dorsal body scales in 17
rows and not reduced posteriorly. 2) Two enlarged and ungrooved
rear maxillary teeth, set off by a diastema. 3) Hemipenis clearly
single, capitate, and calyculate. 4) Oculars 1 + 2, temporals 1 + 2.
The species is unusual in normally having only 7 supralabials, and
is unique in its strong tendency toward a uniform golden-brown
dorsal color (most species are conspicuously striped) and in itA north-
ern distribution, widely isolated from other species of the genus.
Concerning a more specific relationship for R. flavilata within the
genus, I concur with an idea advanced independently by Malnate
and by Bailey 27 years ago. Malnate (1939) suspected that the
dorsal striping on some Rhadinaea flavilata indicated relationship
with R. laureate (Giinther) of the highlands of western Mexico.
Bailey (1940, p. 16) expresses the same conclusion as follows (remarks
in brackets mine):
"A third species, laureate, offers a clue to the relationships of the isolated
flavilata of the southeastern United States. In these species the upper labials are
normally 7, a reduction from the usual 8 in other forms. Recent examination of
a living specimen of flavilata revealed further similarities to laureate which were
unsuspected from preserved material. The head is uniform above for 2 or 3
scales on the neck, as in laureate, and a very faint trace of striped body pattern
is present in flavilata for which the same scale-row relationship is found as in
laureate. [In flavilata the middorsal stripe, when present, occupies the vertebral
scale row, whereas in laureate this stripe includes the paravertebral rows. The
weak lateral stripes in flavilata and laureate bear exactly the same scale-row re-
lationship.] The stripes of laureate show unmistakable signs of diffusion (see
P1. I) which is simply further developed in flavilata, resulting in an almost uni-
color pattern [except that body stripes are fairly well developed in North Caro-
lina]. In keeping with this general pattern weakness, the white collar of
laureate is lacking and the light temporal stripes are less distinct in flavilata."
An additional characteristic shared by flavilata and laureate is
the color pattern of the chin and lips. R. laureate throughout its
range has the labials and genials profusely peppered with dark pig-
ment as in some R. flavilata from North Carolina (fig. 10). The fact
that this pattern occasionally occurs in other sections of the genus
(e.g. in R. pachyura fulviceps) does not lessen its significance as
an indicator of relationship between flavilata and laureate.

EVOLUTION

The following hypothesis presumes that Rhadinaea flavilata or
an ancestral predecessor reached the southeastern United States


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MYERS: THE PINE WOODS SNAKE


via a coastal route from the west. This assumption is based on the
present coastal distribution of flavilata and its apparent relationship
to Mexican Rhadinaea (especially laureate). A number of other ani-
mals seem to have had similar origins (Blair, 1958; Coin, 1958).
Fossil vertebrae assigned to R. flavilata are known from Pleisto-
cene localities in Florida as follows: Reddick I B, Marion County
(Auffenberg, 1963); Williston, Levy County (Holman, 1959); and
Saber-tooth Cave, Citrus County (Holman, 1958). The Reddick and
Williston localities seemingly represent the third (Illinoian) glacial
stage (Holman, 1959); the Saber-tooth Cave deposit is assigned to
the last (fourth or Wisconsin) glacial stage (Holman, 1958). The
present-day habitat preferences of R. flavilata may have been devel-
oped early, for Holman (1958, 1959) interprets the Williston and
Saber-tooth Cave faunas as indicative of pine flatwood regions with
associated ponds. Thus flavilata possibly migrated into the south-
eastern states during the second glacial period, when the Gulf Coast
probably afforded a low, damp corridor from the west and south-
west. An earlier entry is possible, even into Florida, where land
may have persisted since Miocene time (Vernon, 1951 and Vernon
in Goin, 1958). Auffenberg (1963) shows Recent Florida snake genera
present in the Pliocene and visualizes little change in distribution of
snake genera since then. He further states that, "On the basis of
data obtained from the amphibians of the Florida Middle Pliocene
. there is every reason to believe that it was between Lower
Miocene and Middle Pliocene that Florida felt the effects of a west-
ern herpetofaunal immigration. This is also suggested by the pres-
ence of certain genera of snakes in the Middle Pliocene which are
thought to have their ancestral home in southwestern North America
(Crotalus, Micrurus, etc.)." He also suggests an eastward coastal
immigration "during the time represented by Stratum 2 at Vero,"
which is subsequent to the entry of Rhadinaea.
Regardless of exact time of arrival, the east-west distribution of
this species was perhaps reduced by climatic changes during glacia-
tion, quite possibly in the third (Illinoian) glacial period. The third
great glacier extended farther south than any of the others, and
climatic changes are thought to have driven many warmth-requiring
animals into separate refuges in Mexico and Florida. At that time
flavilata was presumably isolated in Florida where it has survived
to the present. During the late Pleistocene the Florida land mass
was occupied by such now-extinct animals as lions, saber-tooth
tigers, camels, horses, mammoths, mastodons, ground sloths, giant
armadillos, dire wolves, and peccaries (Simpson, 1929). But where-


1967







BULLETIN FLORIDA STATE MUSEUM


as the mammals (and birds) underwent considerable extinction, the
snake fauna of Florida differs little between late Pleistocene and
modern times (Auffenberg, 1963).
With the retreat of the Pleistocene ice sheets and subsequent
climatic changes, R. flavilata spread out of Florida and followed an
expanding habitat westward and northward. The hypothesis of a
relatively recent dispersal of a homogeneous stock into relatively
uniform habitat (pine flatwoods) explains nicely the absence of any
marked geographic variation in the species. Resemblance in color
pattern of North Carolina flavilata to Mexican laureate suggests
that the pine woods snake retains primitive characteristics at the
northern limits of its range. Because a northward shift in climate
since glaciation is very probable, possibly the tendency toward
loss of color pattern and toward increased variability in scutellation
in the southern populations represent adaptation to a changing en-
vironment. Much variability in scutellation is anomalous, indicating
that southern populations are in some ways less adjusted than north-
thern ones, which exist in a climate closer to that for which flavilata
has been longest adapted.*
Thus it seems that the southern populations of Rhadinaea flavilata
are evolving faster than the northern ones, presumably in response
to a warming postglacial climate. Though laboratory studies have
shown temperature increase to be an effective mutagen in Drosophila,
it is not wise to demand a genetic basis for all cases of intraspecific
variation in snakes. Scutellation variations similar to some in Rhadi-
naea have been induced experimentally in Thamnophis elegans by
lowering environmental temperatures during embryonic growth (Fox
et al., 1961). Possibly R. flavilata is also showing phenotypic suscept-
ibility to environmental change, but the implications of the Thamno-
phis study are not easily applied. The two main reasons for this diffi-
culty are: 1) In the absence of adequate breeding data, nearly im-
possible to obtain for many or most snakes, one can seldom distin-
guish between heritable and non-heritable variation; comparing en-
vironmentally-induced variation in Thamnophis with evolutionary
trends in this and other genera, it seems certain that a single kind

Telford (1966) presents an excellent analysis of variation in southeastern
snakes of the genus Tantilla, in which the peninsular Florida species, T. oolitica
and relicta, "clearly show a trend toward more aberrant individuals than does
T. coronata" which occurs north of the peninsula. The fact that the peninsular
Tantilla are comprised of rather isolated demes does not seem sufficient to ex-
plain this particular case of regional variation; one would expect a low frequency
of aberrations in some demes to balance out a high frequency in others, unless
a nonrandom factor were involved. I suggest that these differences in Tantilla
may be related to the phenomenon discussed here in Rhadinaea flavilata.


90


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MYERS: THE PINE WOODS SNAKE


of variation is sometimes strictly phenotypic and othertimes genetic,
even possibly within single species. 2) We lack comparative data on
the potential effects of temperature on the developing embryo. Can,
for example, the same sort of phenotype be induced by lowered tem-
peratures in some species of snakes and by increased.temperatures in
others, or can temperature shifts to either side of the physiological
optimum induce similar results in the same species? These are a few
questions that come to mind when assuming environmental causes
of variation in the scutellation of R. flavilata. Ventral plate numbers
in the pine woods snake are lower in the north in accordance with the
findings in Thamnophis, but what about scales and plates that are
most variable in the warmer parts of the range? If some of this
variability is indeed nonheritable and if it is induced by temperatures
below physiological optimum (as in Thamnophis), we must assume
that, because of genetic adaptation to overall warming trends, the
southern populations have become more responsive than northern
ones to local periods of cool weather during ontogeny.
Such speculation as above is warranted by the extreme impor-
tance of the work of Fox et al., but should not be extended to over-
shadow suggestive, albeit indirect, evidence that some interpopula-
tional variation in flavilata is attributable to non-selective genetic
mechanisms. Differences between local populations in frequency
of anomalous temporal plates, for example, are easily explained by
genetic drift or the founder principle (see Mayr, 1963 and Ford,
1964, for recent discussions of such mechanisms). Regional differ-
ences may also have arisen by non-selective genetic mechanisms
under certain circumstances; fragmentation of the pine flatwoods, as
in northwestern Florida, provides sufficient isolation to maintain
regional differences developed from pioneer stock. An extra plate
between a supralabial and the first temporal occurs in 30.6 percent
of the western population, but in only 3.8 percent of Florida snakes;
that this is a genetic trait responsive to drift in pioneer populations
is strongly suggested by the fact that of the four (of 104) Florida
individuals having the extra plate, three are from an island popula-
tion (Anastasia Island, St. Johns County) represented by only five
specimens.
In addition to mechanisms discussed above, natural selection
probably accounts for some geographic variation. The basis for
selection may be that R. flavilata has shifted habits in response to
climatic change directly, or to some ecological situation for which
higher temperatures increase the number of favorable mutations.
As inferred from study of variation and relationships, the principle








BULLETIN FLORIDA STATE MUSEUM


evolutionary trend is reduction-in color pattern, in supralabials, and
perhaps in certain other head plates. Such traits are most developed
in truly fossorial snakes and lead me to suggest that flavilata is be-
coming more secretive in habits. Certainly the pine woods snake is
not often found away from cover, in contrast to several species of
tropical Rhadinaea with which I have had field experience.

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1967 MYERS: THE PINE WOODS SNAKE 93

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vol. 20, pp. 229-279.


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Small, John Kunkel
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1967







vF


Contributions to the BULLETIN OF THE FLORIDA STATE MUSEUM may be in any
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