Title: Comparative ecology of two sibling species of wolf spiders (Araneae, Lycosidae)
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 Material Information
Title: Comparative ecology of two sibling species of wolf spiders (Araneae, Lycosidae)
Physical Description: x, 99 leaves : illus. ; 28 cm.
Language: English
Creator: Harper, Charles Alan, 1942-
Publication Date: 1971
Copyright Date: 1971
 Subjects
Subject: Spiders -- Florida   ( lcsh )
Zoology thesis Ph. D
Dissertations, Academic -- Zoology -- UF
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Thesis: Thesis - University of Florida.
Bibliography: Bibliography: leaves 95-98.
Additional Physical Form: Also available on World Wide Web
General Note: Manuscript copy.
General Note: Vita.
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Bibliographic ID: UF00097672
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: alephbibnum - 000565879
oclc - 13590486
notis - ACZ2302

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Comparative Ecology of Two Sibling Species of
Wolf Spiders (Araneae, Lycosidae)












By

CHARLES ALAN HARPER


A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF
THE UNIVERSITY OF FLORIDA IN PARTIAL
FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY


UNIVERSITY OF FLORIDA
1971

































DEDICATION

To the memory of ry father; he left with me his philosophy of

life:

"Anything worth doing is worth doing right."















ACKNOW'LEDGEMENTS


I wish to thank the n.enbers of my colnrnittee. Dr. F. Clifford

Johnson, Dr. Thomas J. Walker, Dr. Brian K. McYNb, Dr. H. K, :'allace,

and Dr. Jonathan Reiskind, for the advice they provided during this

study. During the preparation of the manuscript, they were very

patient ihen confronted with the "waste" generated by my haste and

gave considerable direction in the shaping and organization of my

ideas.

Dr. John D. YcCrone served as my chairman during the period

when I was first defining my research problem. He gave generously

of his time and ideas and employed me as a research assistant for

several quarters.

I especially wish to acknowledge the contribution Dr. John F.

Anderson made to this project. Hle was my primary "sounding board"

for hypotheses and he provided research space and materials from his

laboratory.

'My wife, Carol, was especially helpful .itlh the grueling jobs

of typing the early drafts of the manuscript and mapping the study

areas D--r support apil ncoiuragenment were always present and

sustin'cd thro')':' so:!e rather depressing times.

I alco it h o thbrk Lhe Ipartlmnsls of Zoology and Couprohinsive

Bioltgic l Scjiace- for financial support during my graduate career.

Finai!y;n 1 tInk Mrs. Donna Gillis, my I.ypist.















TABLE OF CONTENTS

Dedication . . . . . . .. .. . . . . . i

Acknowledgements ....... ........ .... .. .... iii

List of Tables . . . . . . .... .. . . . . vi

List of Figures . . . . . . . . . . . . . vii

Abstract . . . . . . . . .. ...... .. viii

Introduction . . . . . . . ... . . . . I.

Descriptions of'Study Areas . . . . . . . .... ... 4

Station 1 . . . . . . . . ... . . . . 4
Station 2 . . . . . . . . . . . . 4
Station 3 . . . . . . . .. . . . . .. 5
Station 4 . . . . . . . . . . . . . 5
Station 5 . . . . . . . . ... . . . . 8
Station 6 . . . . . . .... .. ....... 8
Station 7 . . . . . . . . ... . . . . 11
Station 8 . . . . . . . . ... . . . . 11

Methods and Materials . . . . . . . . ... . . 12

Field Observations . . . . . . . . ... . . 12
Laboratory Procedures . . . . . . . .. ... 14

Results ........... .. .. ............. 18

Thle Habitats . . . . . . . . ...... 18
Tc:mperature and Rainfall .................. 18
the Fauna ...... ........ . ...... 25
The Species ................ . . .... 29
Comparative Morphology . . . . . . . ... 29
Natural History . . . . . . . . ... .. . 35
Reproductive Biology . . . . . . . . . 42
Field observations . . . . . . . . . 42
Mating experiments . . . . . . . . .. 43
Comparative Physiology . . . ... . . . . 45
Burrow Claracteristics . . . . . . . . . 57
Home Range and Resighting Data ............ 62
Distribuc:ion and Habitet Preferences . . . . . 70








Discussion . . . . . . . . . . . . 79

Evolution of the Species . . . . . . . . ... 79
The Niches of L. armophila and L. Icnta . . . ... . 80

Sun-mary . . . . . . . . . . . . . . . 92

Literature Cited . . . . . . . . .. . . . . 95

Biographical Sketch ......... ............. 99














LIST OF TABLES

1. Mean daily high and low soil temperatures at
Stations 3, 5, and 6 . . . . . . . .... 19

2. Mean daily soil temperature fluctuations at
Stations 3, 5, and 6 . . . . . . . . . . . 21

3. Nean weights of field collected adults . . . . ... 34

4. Field observations of Lycosa ammophila prey . . . . .. 40

5. Field observations of L. lenta prey . . . . . ... 41

6. Estimated survival differences for various weight classes
of L. lenta and L. ammophila ................. 51

7. Mean temperature for responses to heating following
acclimation at 200C and 300C . . . . . . .... 53

S. Burroe characteristics of T_ lenta . . . . . . . 58

9. Bucrow characteristics of L. arnophila .......... . 61

10. Days between resightings for L. lenta females with
home ra .es . . . . . . . . . . . . . 64

11. Days between rosightings for L. anmophila females with
home r esn.3s ........ .......... ....... 65

12. Known movements of mature females from one home range
to another . . . . . . . . ... . . . . 71

13. HabitaE distributions of mature spiders at capture
points in L970 . . . . . . . . . . .. 72

14. Observed density of marked spiders and home ranges
per 1000 'm in 1970 . . . . . . . . . . . 73

15. 1Migration and distribution of marked mature L. lenta and
L. anobilta one month or nmre after release at one of
six habitats within Station 6 . . . . . . . ... 76

16. Water los compcrioon in xpric adapted arachnids with
L. Ir.c and L. -iDhila . . . ................... 85

17. Terperatures of suspected cuticle wax disruption and heat
death fo: some arachnids . . . . . . . . . 87














LIST OF FIGURES

1. a, The study area at Station 3. b, The study area at
Station 5 .. . . . . . . . . . . . 7

2. The study area at Station 6 .. . . . . . . . 10

3. Lean surface temperatures during the afternoon and evening
at localities in Stations 3 and 5 . . . . . . ... .24

4. Sixty-year mean monthly high and low air temperatures and
sixty-year average monthly rainfall for Gainesville,
Florida . . . . . . . . . . . . . 27

5. Mean cephalothorax length and width for samples of
adult females . . . . . . . . ... .... . 31

6. Mean leg lengths of females . . . . . . . ... 33

7. Numbers of unmarked mature spiders observed each month . . 37

8. Relationships between total water loss per hour and
initial body weight at three temperature-humidity
combinations . . . . . . . . . . . ... 47

9. Relationships between percent weight loss per hour and
initial body weight at three temperature-humidity
combinations ..................... ... .. 49

10. Mean percent weight loss per hour at high environmental
temperatures ........... ............ . 56

11. Mean home range sizes .... . . . . . . .. .68

12. Proposed life cycles for Lycosa armobhila and L. lenta in
north-central Florida . . . . . . . .... .... 83














Abstract of Dissertation Presented to the Graduate Council
of the University of Florida in Partial Fulfillnent of
the REquirements for the Degree of Doctor of Philosophy

COiMPARATIVE ECOLOGY OF TWO SIBLING SPECIES OF
WOLF SPIDERS (ARANEAE, LYCOSIDAE)

By

Charles Alan Harper

August, 1971

Chairman: v. C. Johnson
Major Department: Zoology

A previous investigator found that several sibling (cryptic)

species of lycosid spiders occurred in mutually exclusive local

habitats in northern Florida. The objective of my study was to

identify the factors responsible for the local allopatry of two

of the species. The first, Lycosa ammophila is restricted to the

sandhill (]oingleaf pine-turkey oak) community, while the second,

L. lentai occurs in more mesic communities. L. amm2pEhila may have

originated from L. lenta or some common ancestor on Pliocene islands

hav5.ng sandhill comliunities.

yom'ca ar.'ophila shows an array of adaptations to living in the

,:sijhill cc'r.nity whichh JL. lenta lacks. It compensates for extreme

dbily tempcracture fluctuation in the sandhill community by breeding

o.-iiy Juing the t? s:munr months and by being seni-active during the

Jrd.er portions of the ye-ir. Tie evolution of this limited activity

pattern has occurred in the absence of a marked increase in Lhe

ability to r;egulate sacer ios, physiologically, and has resulted in

.a two-year life cycle for the species. LVyco.a lenta breeds from

Di:c.:.be through A.:;,'.t and t-yicelly has a cone-y'ar life cycle.







Adaptations of the species to high temperatures are similar.

Both show similar behavioral responses whie heated, have critical

thermal maxima of ca. 480C and show marked increases in the rate

of water loss at ca. 380C. The latter change is irreversible and

suggests a cuticular wax disruption described for many either

arthropods.

The larger average size of mature L. anmophila results in a

slightly lower percent weight loss per hour during periods of

desiccation than experienced by L. lenta. The larger L. annophila

can utilize larger prey, including L. lenta, and better escape

predators; however, its greatest hunting efficiency probably occurs

in unvegetated areas where it need not climb to forage. This latter

requirement correlates with the observed preference of larger instars

for open sandy areas both in the sandhill community and in masic

areas -.iCw relocated. Lyrcsa l'nta, however, avoids open sendy arcas

and areas with dense vegetation and prefers regions with well-shaded

l.%.f 1iLcer. In these regions, the microclimate is moderate and

la~;e aT- oohila are not encountered.

t.oh species dig burrows, provide them with silken lids, and

occupy I-he:. during the day. Nature females enlarge a portion of the

burr o: i;ro a chi.-lber 5 to 6 cm in die trer and i to 5 cn deep. lhe

char-er prcb'bhly functions as a space tor construction and holding

o0 in'e W,. s.J ani for hatching of the young.

o:'e raet 'es for tmatiure if' es ,f both seccies averaged about

2.5 i c as hila fn.-alc ha'd laIrgc hoin cnasges than L.

lr- nj Co .ls in lhe same habitat.

i- :l:cti. e isolafioi :l..iul'ts not only fr-'s different habitat

Ip L:ercs co bic from cues, perhaps dOchical in nauiae, associated







with the dragline silk of females and perhaps the females them-

selves,which males use in avoiding females of the other species.

The courtship behavior of the two species appears to be identical.














INTRODUCTION


Past studies of spider ecology related plant associations and

mic:rohabitats with the species of spiders inhabiting them. Elliot

(1930) was one of the first to quantitatively show spatial and temporal

orderliness of certain species in the beech-maple forest community.

Since that time, numero-s reports of specific spider-plant associ-

ations appeared. Such studies included the following habitat types;

shores, dunes and piedmonts (Barnes, 1953; Barnes and Barnes, 1954;

Berry, 1968; Duffey, 1968; Lowrie, 1942; Lowrie, 1948), forest areas

(Branson and Batch, 1968; Gibson, 1947; Kuhta, 1965; Lowrie, 1968;

Luczak, 1959; Luczak, 1966; Peck, 1966), prairies, meadows and fields

(Bailey and Chada, 1968; Barnes and Barnes, 1955; Brepineyer, 1969;

DoniIle et al.: 1970; Duffey, 1962; Kajak, 1963; Muma and Muna, 1949),

deserts (7ixler, 1970; Chew, 1961) and studies of islands (Dr-iw.

1967; Tr1'-an, 1942). ihary authors suggested that specific niche

reqli remcncs of each species (Lir:porature, humidity, specific food

typ, s i lilaticn Crom predators and cc!ipeLitors, ot uctcra) W'are moet

a,'- lr ii tIe habiLat uioherc it was normally found, but fow

p:,ad 'O L I.ir hypoLh UseI.

S-, 1 i:.vst.i.dgai'ors ,':asalehrd hI:Ih microclimnates and phy:;;.ological

:qic." is ad 'to! lc-.Cs of .'diV iidu' 1 .-pcj'ci mcre closely

(tli. an0, [9:'7; -r -p-'z and JI yas, 1959; :A,, gard, 1956). Others

ar.:..yzed eo ''lol cal i;cs :d rclatior hipi s oi t',o or ii.ore species

(C.dsy-T;rsci, ; u .195; a 98; ra,'i;Ua 1951). Van Fook








(1971) analyzed the energetic of a grassland community in which

lycosids were the major consumers. These studies provided some of

the information necessary to explain the microhabitat preferences

and discribation of synpatric, and even congeneric, species.

In cne study, Wallace (1938) found that wolf spiders (Lycosidae)

in the Ciinesville, Florida region were distributed in specific

habitats. These data correlated with the discovery that Lycosa

"lenta" was a complex of at least eight South-eastern United States

species, each having a more-or-less typical local habitat preference

(Wallace, 1942). He toted, for example, L. lenta (sensu strict)

occurred in mesic habitats ranging from swamps and low harmocks

through the nesic hanmcock (the local climax conununity) and palmetto-

pine flItwoods. It ranged frosn central-Florida north to the

Appalachian Mountains and west into Texas. The species appeared

also in drier plant association, the xeric hammock and old field

cocimunities. It rarely existed in the long]eaf pine-turkey oak

"PI Plau tris-Oercus laevis) cornunity. Instead, one of the

siblinfj species, L. arr.ophila, found exclusively in north Florida,

occurred in this community. L. ar-ophila also inhabited old field

cma.ril.uiti'ts and was normally iore abundant than L. lenta. On the

basis of this allopatric distribution in local habitats and marked

differe'c s ii nmale and female genitalia, WUllace described L.

" m?:hila,a new species related to L. lenta.

Wallace er-,bLpastied ihe sharp segregaiion of the two species at

the ecotone betI.een the longleaf pine-turkey oak and neighboring

cc-.nuinicies, often the xecic hammock ccrz:-. iity. lie noted the corre-

latioiu 'Dortwieen the presence of leaf mold and shade and the presence








of L. lenta and the absence of L. amrnophila and suggested that these

factors iere the inajor niche parameters not shared by the species.

In the current study, T sought to identify the factors responsible

for the allopatric distribution of L. lenta and L. a sliophila. I

exanincd the physical characteristics of the ncsic habitat and the

loa gleaf pine-turkey oak habitat, the life history of the species,

their reproductive biology, their physiological adaptations to

xeric conditions, characteristics of the burrow, the home range,

and their habitat preferences.














DESCRIPTIONS OF STUDY AREAS

During the two-year study, I used eight field stations, three

iutenrsively. Four stations have longleaf pine-turkey oak (sandhill)

ccnunitiLs i. while three have mesic communities. The eighth is a

segment of road with turkey oak on one side and pine flatwoods on

the other.

Station 1 (290 29' 9" N, 820 15' 38" E)

This station, 5.3 km due east of the Alachua County Court House,

is the type locality for L. amocphila. Wallace (1938) described it

as "an almost pure stand of turkey oak, with practically no under-

gro'th of any kind." This area now has many young live oaks (uercus

virt-niaia) and less open sand is present. Annual weeds are en-

croaching from adjacent areas. A non-wooded area in the center of

tie station supports an "old field" community of grasses and weeds

irj.:e borh L. tenta and L. aemophila occur. Only L. lenta inhabited

iighbori'g xeric hammocks, judging from extensive field work.

Station 2 (290 42' 50" N, 820 27' 29" E)

This si:af-ion, located 9.8 km north of the intersecLion of

!li;fhway 26 a'.d S-329 on S-232, is a typical turkey oak community.

Lef drifts baoe developed against wire grass clumps (Aristida

si.rLcta and S. 'ohbolus grcilis), resulting in numerous open patches

cf spottily shaded sand. The turkey oak contnunity grades into a

slash pine flatwouds (Pin's australis) and then into an extensive

nesic I'a.o ock known locally as San Felasco Hanimock.








S cionn 3 (290 38' 14" N, 820 23' 32" E)

!'is statioCn, located 2.1 km. west of S. 1. 34th Street on

S, i. 20th Avenue, in Gainesville, was the L. amophila habitat

studied mros' intensively. It is primarily a turkey oak-wire grass

co-runity. The southern boundary is S. W. 20th Avenue; xeric hamnock,

co -posed almost entirely of live oak and laurel oak (Quercus l2irifolia),

borders on the remaining three sides. The primary portion of the area

used for study (Figure la) was a rectangle 7,700 m2 and included

five distinct habitats. There was a xeric hanmnock (c) on one border,

an old field community (b) on another, and turkey oak and wire grass

(a) on the remaining two. Dense grass (Panicum spp.), 30 to 60 cm in

height (d) dominates approx-iiately one fifth of the area. ihe re-

mainder of the area, with the exception of sone sandy roads (e), is

turkey oak and an unusually dense growth of wire grass. Few open

sar.d areas like those in Station 2 were present. Typical herbacouss

plants of the cor-nunity also occurred (Iaessle, 1968).

.crth of the study area ca. 100 m, a power line right-of-way

'.is beeln cuit itroupjh the xeric ha ock and portions of turkey y oak

r-c."a. IL i ca. 20 m w.ic, oriented east and west, and supports

n atLv-ical old field flora. Prominent ccr'ponents of the right-of-

-,:y co .:rit1y .-r s.1l sadllings oe live and laurae oaik annually

cut : 31- i1 1 )hen spring by n ri.ntepince crlis.

S O io 19 (290 1' 5/" -., 320 15' 43" E)

!;i :ry "ty~iical L;;uhy ok c,: nity lioes 2.3 km cast of

Sti e 'jl h. :ay '- on t'e !'i! vi1:l I "icipal Aiipoct Road. It

ecCiri..Lc of a ci' re' .ii of la-'d t the end of a run-way ca. 0.3

. 1 S;c'i-es c'<' a ,:t' : : of I't lo'!:'] af ino-tu:key oak




























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co':;-runity had invaded it. Adjacent areas are of planted pine

s.gsLiig thai the entire region may have supported the sandhill

cr~n.unity before =nan's influence. Few trees were over 4 m in height

and herbaceous plants were abundant.

Station 5 (29 38' 35" N, 82 20' 39" E)

This T. lenta. habitat, intensively studied during the summer of

1?70 and early spring of 1971, lies on a hillside immediately to the

south-east of Bartram Hall on the University of Florida campus.

Vegetation of the 5,400 m2 area varies, in part, with soil type

(Figure Ib). Very large loblolly pines (Pinus taeda) grow in the

pebbly-clay of the top portion of the hillside (habitat a) while

lve o-sks dominate the more sandy lower habitat (b). An understory

is absent throughout, but grasses and annual weeds cover most of

habitat "a" and reach heights of several meters by late summer. A

more undisturbed woods with dense understory and extensive leaf

litter occurs farther down the hill to the south-east. The nearest

sandhill community is Station 3, about 6 km west.

Station 6 (290 33' 42" N, 820 21' 29" E)

The second intensively studied L. lenta habitat was the M'diciral

Carden, 0.3 km west of Partrram Tall (Figure 2). It became necessary

to ,ove to rhis area in 1971 as a result of construction near

Station 5. The area is generally more mesic in nature than any of
2
the other stations. Tha 14,600 m area studied included a small

strean ald six rather distinct habitats. 1'abitat "a" has ample

shade and dense annual weeds; "b" has similar shade with an extensive

pie needle litter; "c" has der.se, unsishade, lawn grass; "d" has

lightly ,h':ded, lawn grass internnixed with patches of b-re sand;



























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"c" has tall, well-shaded, grasses with little leaf litter; and "f"

has s-arse, tall, wcll-shaded, grasses and appreciable leaf litter

and mulch. Thae presence of Lake Alice 120 in south and 1 to 1.3 m

lower in elevation than the study area contributes to its mosic

nature,

Station 7 (290 25' 8" N, 820 42' 37" E)

The most typical mesic harmiock examined during the study exists

8.0 km north of the intersection of State Highway 26 and S-329 on

S-232. IT has all of the plant species characteristic of the nesic

hhaminmck (Laessle, 1942) and a heavy leaf litter. Limited access to

this property restricted its use.

Station 8 (290 23' 46" N, 820 42' 12" E)

This very artificial habitat is the roadside grass on the road

east of the "Devil's Millhopper." It lies 5.3 km from the inter-

s,'ction of State Highway 26 and S-329 on S-232. The woods on the -west

side of the road are primarily xeric haii.ock species ilile the east

side consists of a mixed oli fiild-turkey oak corimunity. T:co 'a l enta

icc:i'r on the grass bank of the road's west side while L. ''i'i:)ila

prcdc.-inated in the road's cast bank.














NETn}ODS AND MATERIALS

Field Observations

I collected most of the field data for this study between

June, 1970, and June, 1971. During this year, visits to Stations

3, 5 and/or 6 were at two-to three-day intervals or less during

the spring and summer and at one-to two-week intervals during the

fall and winter. Visits to other stations at irregular intervals

were for comparing population activities with the primary three

under observation. I recorded date, time, air temperature, humidity,

day of last rain, and condition of the sky on each collecting trip.

0-her observations included predators, prey, descriptions of burrows,

and other species encountered. Numbers, instar, and sex of spiders

seen or collected and notes on their condition and place of capture

were made.

I used several methods to characterize the physical envirormoents

in the various communities. From September, 1970, through June,

1971, two model 1000 recording thermometers made by Marshalltown

Mfg. Inc., Marshalltown, Iowa, recorded weekly temperature fluctu-

ations from sensors placed at various locations and depths ifi the

soil at the three primary study areas. The seven-day paper di'c

charts, calibrated Lli OC, provided a permanent record for laboratory

analysis. Station 3 data are from September, 1970, to April, 1971;

Station 5 data are for April, 1971; end Stations 3 and 6 were

measured in i'ay and June, 1971.








In addition to the rainfall-hl rtidity dasa taken on each

collecting trip, similar data wore available from the University

of Florida Agrcn-oy Department in conjunction with E. S. S. A.

Identification of individual spiders in the field involved a

marking technique. Ten-dcam plastic snap-top vials held recently

collected, nature spiders iwile they were carried to the laboratory.

CO2 from a fire extinguisher anesthetized the spiders and each such

spider received a painted number on its cephalothorax before it

revived. Marks painted on the cephalothorax could not be scraped

or grooerd off by the spider, and,at the same time, did not disturb

any of the numerous sensory organs on their legs. The paint was

Testors Butyrate Dope. Release of marked spiders to the field

occurred the following evening or as soon as possible.

During the suamer of 1970, I tried to return marked spiders to

the exact point of collection. Wood dowling stakes, 10 to 20 toj

hi:h and 2 to 3 =n in diameter, and having a strip of Scotchli.te

-relEctcr ta.p around Lthe top 2 cm, marked the capture location and

ach s'ubseiuent r sighting point. A piece of Timle laboratory lcel

LTape aLbot 8 cm 1ic, .:-s pressed around tihe dowel below tlia rellector

tape a-nd ress.d roi-thcer to fonn a "flag" for the recording of data.

I tmierd ScL.tirns 3 and 5 at the end of l~h sui:.rer- aall dctcnl'iicd the

.a tiu js o l'I audist'ur'ed iiirker stakes.

Di,,li :he int cr and spring of 1971, I shifted to a dr.tenination

oc t'e Fsu;iv ] id novenients o)f ,eni- rs alitn displaced to diilerent

areis in hePir co -unity or to iff re nt coaY-:ul.nties. C'om Deccimber,

1970, ti; ^:l :' i r 19/1, I rclw sca )t Station 3 58 marked L. lcnta

ctllecr-i I ;.c ':i.ion 5. 1 p!a. ....rk;ng ..t ake at the location of








each resighting. Five open cages made of 0.4 m by 3 m strips of

heavy acetate plastic glued into rings were set into the ground at

various places; each held a specimen. Unfortunately, vandals destroyed

four of these cages.

From December, 1970, through June, 1971, marked L. ar~ophila

froCn Scations 1, 2, 3, and 8 were released in various habitats in

Station 6. At the same time, marked L. lenta collected at Station 6

ware released along with L. armopohila. At each resighting I used

marking stakes with the date, number, and species of the spider

inscribed on the tape flag.

Laboratory Procedures

The maps of each station with the locations of release and re-

sighting points were used to calculate home range areas. Only data

fr~rm individuals resighted four more times were used; the outermost

resighting points of these spiders defined the sides of a polygon.

I used a Keuffei and Esser Planimeter to measure chle area bounded by

the pol ygon.

Morphological comparison of the two species involved leg length

i:les-.urinecnts, cephalothorax measu;-rents and weights. I used twenty-

-3vcn I. a wnphila and 24 L. lenta females in the first two deter-

mitnations. These samples represet collecting and preserving from

all stations. Ihe four legs from .he richt side of each specimen

ware rc:lmovd and inounted, using Duce' ce.enll, to a glass microscope

slide, fully extended and in a row. A imr.saring microscope provided

the longest length of each segment of each leg to the nearest nm.

The cepholothorax lengths (the distance between the notch over the

pedicel and thp furrow between -he anterior median eyes) were

dcLennined using the same instrument.








Adult spiders were weighed during physiological studies in

1(69, and 1970. I deterinined weights, co the nearest tenth of a

reilligram, of every mature spider prior to marking from January through

Yay, 1971. An estimation of nutritional and reproductive state also

was pade. Gravid and well-fed females i ere often indescinguishaLle.

I assu.ed that well-fed, mature females partition most energy into

reproduction and soon become gravid. I therefore classified all

females having a greatly distended abdomen as gravid.

At the outset of the study, a check on the validity of the

species seemed in order. The possibility that there was a behavioral

and genetic compatibility between them or that they were merely

variant populations of a single polymorphic species had not been

examined. Two types of breading tests were perfonicd. The first

test used mature males and non-gravid females of each species collected

from various habitats and at various seasons. Finger bowls, 20 cm

wide, each containing ca. 2 cm of moist sand, held the isolated

indiviluals. Sone groups were fed during acclination; others re-

L-ived no fEcod. After 6 ro 15 days, each male was placed inio a

,:l 't.i.h a fcale. Each of the four possible pairings was made.

I tested for the presence or absence of spccies-rspecific

::: ores using the t cblniiqucs of licldekar aand Doniale (1969).

; i A.r pir ']i.c3 'n:e cut to fit Lthe t:::t'i of 8 n-aide jars.

I soLa i O of Iinaure C[-ales of .:ch species in :,uch jars varied for

p'ice's Ce one o rsvr-n days. T,.icdiatly aftLer eiroval of the

Siles, obi-vAL4 ii f l 1i''d _he behavior of '-igle males.

f'etc nr Ltlionls w, re 'iade for ibesec five primacy physiolieAical

', crrisi s, of ti L ,p,ciis: (1) tatc: loss cn.*acritristics

at various t'e -rt-rcs anid hulniditicS, (2) t- r:prature of cutirular







wax breakdown, (3) critical thermal maxima (and behavioral responses

as the temperature was increased to that point), (4) resting metabolic

rate and (5) ability to survive in a saturated atmosphere.

The water loss studies began following an acclimation period

of at least seven days with water continuously available. Follow-

ing an initial weighing, individuals of each species were confined in

glass cylinders 5 cm long and 2.2 cm wide with each end covered by

a nylon mesh having holes 0.4 cm in width. For spiders small

enough to escape through this mesh size, I substituted pieces of

ladies' nylon hosiery. The squares of screening material were held

in place by rubber bands. The acclimation chamber used in the study

is an Environette by Lab-Line Instruments, Inc., adjusted to maintain

the desired temperature and relative humidity. The photoperiod was

a 12-hour light 12-hour dark cycle. Air circulated at an average

velocity of 3.8 cm/second. Specimens were weighed at 12-hour intervals

until consistent weight changes were observed.

I used the same materials and methods to test for a cuticular

wax breakdown point and used only penultimates or adults. In

addition, I made weighing and temperature changes at two-hour

intervals. The experiment began at 350C with a saturation deficit

of ca. 26 mm Hg. I increased the temperature 2C and adjusted the

humidity to the original saturation deficit at the end of each two-

hour interval. I terminated the study at 430C.

For the determination of the critical thermal maximum for each

species, I used an apparatus modified from Norgaard (1951). A

7 cm wide, 20 cm long glass cylinder with a fine mesh copper screen

on the bottom held each individual. A thermistor probe extended

close to the bottom of the cylinder through a large rubber stopper








sealing he top. A i-liter jar wi th a relative humidity of 50%

:Aittaiind by a saturated ::g0O3 solution served as a chamber for

the cylinder. I then submerged the entire apparatus in a 550C

circulating water bath. This outside temperature produced a

heating rate of frcn 3.0 to 0.50C per minute in the environment

of the spider. I recorded data on behavioral changes and associated

temperatures. Temperatures producing irreversible paralysis in the

spiders are the critical thermal maxima of this study.

J. F. Anderson made the metabolic rate studies. Mature females

of each species, acclimated for ca. 14 days in sealed jars with

free water and a meal of one adult field cricket per week, were

used for determining metabolic rate, to be expressed as pl 02

consurred/g hr. The last feeding occurred at least two days before

the determination. Spiders were weighed the day before and con-

ftned in a glass vial, 9.5 cm by 2.2 cm, taped to the opening of

the respironetcr flasks. This technique allowed the spiders a

brief period to adapt to the flasks. A Gilson Differential Res-

* irc-.i tc r-casured respiration rates the next morning. Consistent

vIlu-s frr..i at least four tcn-minute experimental periods were uscd

to detenLinae an oxygen consumption value for ecch specimen. These

gross *,. lies w rec nverted to ;l 02 consc.tod per gram' hour.

I ,ividl ls were placed i: scaled jars witLh 'cl't s;.nd to

dot iL iin wh;:ei -r a differi-itial sp:,cjes inortali.y occurs i:i very

r.:oi L envir. cnlts. l ; id a were accl iiated at 25C and cld one

adul l ficld :ciclet ech wuk. I ?i";hed each one to two days

folt'b. ir, fh ,dtil I Liot,: i eJ iatues of death ond final ,cighta when

o; ib le.














RESULTS

The Habitats

Tr7-nerature and Rainfall

Soil temperature data for various habitats, microhabitars and

depths appear in Tables 1 and 2. The average daily high and low

temperatures for the various locations are in Table 1, and the

average temperature fluctuation for each locale during the given

time interval is in Table 2. Several facts are evident from

these data. First, maximum surface temperatures differ from 200

to 350C, depending on the season, between the open sand surface

in the sandhill corununity and the shaded leaf litter of mesic

ha:mock. This is especially clear in Figure 3. However, by about

19:00, it is cooler on the open sand in Station 3 than on the leaf

litter of Stations 5 or 6. Second, the surface under heads of

wire grass and, less often, turkey oak leaf little is no more than

a Cfw degrees warmer than the surface in a shaded mesic area. A

similar observation is true for the shaded xeric habitat. Third,

temperatures are nearly constant at a depth of one to two inches

bclo:~ the surface (just underneath the leaf litter) in the shaded

niuic hanm1ock. However, under open sand in the turkey oak cc-r.iunity,

terT.petaturLa fluctuate t..,o to five degrees, depending on the season,

at a depth of seven inches. Fourth, at the depths here temper-atures

are nearly consL-.rt in ithe two communities, the meic hanmmock is

3 to '-C ia ner.





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T0e .:eaan monthly high aid low air temperatures and the mean

raiinfal Cor C-incsvillc, Florida, appear in Figure 4. These

regional dta have limited predictive value due to the effect of

plant c--.munities on the local conditions, the uneven distribution

of summer thunderstorms a.d the annual variability of taie weather.

'ie correlation between macrocliaate and activity of spiders follows

in a later section.

Based on Tower's (1932) study of the evaporation rates in

plant associations of north-central Florida, a prediction of moisture

as a limiting factor especially in the sandhill con unity, is logical.

Tower's study, conducted during winter and spring, revealed evaporation

rates (determined with dark and light bulb atmometers) were twice

as high in the turkey oak cornnunity as in the mesic or xcric hammock.

During this study, I found, however, the relative humidity at the

soil surface in turkey oak almost always over 807, by an hour after

sunset Aich the deCwpoint reached nost nights, especially during che

sarir. 'ihe r-visture evaporating during the day beccnes available,

O,'crfo.re, to s!Pll "t'imadLs at night. During periods of extended

drou'nht (tIiree to four taeeks), free water was less available and

'SpiOrs became Less active.

The 3oil is always saturated within -he first inch below the

r. ace it rite r.esic hai:ilock. 'lie .; co-itiicn was true of lhe

t r'kcy ok co.a 'iity except dirian- periods of dro.:ugt iwen thei first

few inchab of si8 i 'lo conliplctely d>r. moisture (;.iincd inch

lontr ".ouund :, root of wire-grass cl.mps.



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striking differences became apparent during the study. First, segre-

gation of I.. Icnta and L. arz-cihila into their respective habitats

was essentially as Wallace (1938) noted. Lycosa amrophila remains

absent from mesic community collections and infrequently occurred more

than 10 m within a xeric hannmock; however. L. lenta males and females

appeared rarely in turkey oak and wire-grass collections.

In the power line right-of-way north of Station 3, L. lenta was

comnnon at the south shaded borders adjacent to the xeric hammock.

Lycosa am-ophila was most common in areas bordered by turkey oak. There

was a sizeable area, however, where the two species coexisted. Co-

existence was also quice evident at Station 8, the roadside bordered

by mesic and xeric habitats. Several times, each of the species

existed within a meter of each other. Coexistence occurred likewise

ra the roadside bordering Station 2.

Other wolf spider species characteristically inhabited each

habitat. In the mesic areas examined, L. riparia occasionally

occuirrod. Thie nature females of this species are the same size as

L. len!a females and constitute the largest lycosid competitor.

Other smaller species present include L. helluo (restricted to settcr

arcas), L. hentzi (irnfrequeit), L. pulchra (infrequent and reproductive

only in winter), and Schizocosa crassipes and S. ocrcata (very small

and restricted to leaf litter).

[a the :u.-kay oak cr:muniity, L. carolinensis is fairly comn:on.

Ihis very lrge spider can kill both L. lenta and I. ammophila.

yv cos a, ibit is abundant but hunts off the ground in wire grass or

wvrdF. Lbrcosa pgrthjonu. is a small species restricted to the leaf

litter. Oheir species prose-t nre 1, pulchra, L. rabida and L.

puncl.nlata which hunt while climbing.








ec:e-biate p)d-cdators include 'ufo terrcstris and Scaphiopus

holbr'oo
but ;.ere in much greater abundance in the turkey oak con'n-'nity,

especially following spring rains.

The Species

Cc ndra tive o phology

A cop'rison of the cephi' othlerx length and width for adult

females of the two species appears in I'igure 5. Although the ranges

are not exclusive, the means are significantly different (95% con-

fidence intervals shown). The average cephalothorax length of L.

apprhila is 12'i larger than L. lenta while the average width is

10.5% larger.

A comparison of leg lenc- hs in adult females appears in Figure

6. In all ca3es, the range of the lengths do not overlap the 95%

co.: idene interval for the means. Average lengths of legs 1, 2,

3, .rd of L. i._-ophila are 227, 18.5', 18.3% and 16.5% longer than

similar e- s of L. lenta.

The' av o:a.4. we-ights of r!-tu; fuemalcst tak(ln from the field are

i!-t :ign;iic.nly d'ffCrent du-ring winter and spring (Table 3). In

Ap~'l, r significant dif'erenca in rran weights of non-gravid frinales

occarrcd, while in '.ay, all three categories of mean frc iale weights

d, f.-id si 'iicantily (. 0.057). 11is diff, rence rc'aited in the

l r,? tory s co., .berc ~,ider; ':,d ar'ple food and during g the s' eor

f> ) lclt',ocized fild i' 'Iple. Out: Lhe:' iat sprLng r ind sI-tsner,

. a .e-rge .ciht of L.- i':_I '-i a ii t'le field is ca. 0.3 to 0.5 g

L t,,e r latn L. git 'a. ':' 1 c .r :vr 'te ;hL for L. n bophila

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individuals. Ternty to 40 irrcent of the female L. nn-ohila

collected durian these raon.ths ld collapsed .d dons while only

five percent of the L. lenct nere in this condition.

Lvcosa ar.ophila males are significantly heavier than L. lenta

males. With the exception of three specimens from the cumulativee sample

size of 147, the weight ranges were exclusive with all L. amrophila

weighing 0.6 g or more.

A sample of 15 penultimate L. anmouphila taken in January and

February, 1971, had a mean weight of 0.8993 g 0.0785 (P = 0.05).

This average weight is significantly larger than non-gravid L.

lenta for all months tested except during January, 1971, but is

not significantly different from mature L. nirophila for winter

and spring months until May, 1971. This evidence suggests that

the noult to maturity ray occur during a period of fasting in L.

'noplhi] a.

Iaturil History

'Numbers of mature spiders by sex for each species, recorded

Sithly I'r, 'pril, 1970, thruugh May, 1971, appear in Figure 7.

ilhe rclativiy a'Ldciinal size served to classify females as gravid or

no' i- xvid during 1971. The .ijor differences between the two species

arc: (1) the reproductir v peak for L. flophila is one to two -.onths

Oi'iJ: I. 1, *'nt; (2) T,. 1 Snj crP ?nd does reprod-ce during tihe late

winter -c in the spring; and (3) bchi sp eci sho',: a var.keO reduction

of ,-..-'-t 'ult polacti, ic in Aigust. 'lho breeding p.aks of

-:. 1i-1 i S!'.-,ins 5 d 6 nllo. exactly the -. 1, inti population

at Station 3.

Si c ,hi:erce of ivid i[. 2philU S triine' winter a.nd spring and

the un-u to two- ,ith lhg beli:nd ltmi icl bedi ng peaks accomplishes






























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a similar lag in appearance of females carrying egg sees in the

field, females with second instar young on their abdomens, and the

development of imnatures through the winter. By January, third

and fourth instar L. lenta were absent in the field in contrast

to similar instars found for L. aranophila.

Lycosa a-.ophila was most active in the winter and early spring

on all warm nights (200C). Penultimate L. ammophila were common on

such evenings while adults were infrequent. During the same time

period, L. lenta was most active on warm humid nights. Adults of

L. lents were generally more abundant than penultimates. On evenings

when the temperature was 100C at sunset, none of the larger instars

of either species were active. At temperatures of 80C or below, all

sizes were inactive and remained in their burrows.

In late spring and summer, L. armophila were most active on

evenings when the ground was damp following late afternoon rain

storms. Lvycesa lenta were most active one to three evenings after

the r hin shower.

The average liFe span and time required to reach maturity are

not n-ailnble for either species. One L. arnnophila female marked

on July 14, 1970, appeared approximately seven months later on

February 28, 1971. It had overwintered as an adult and lived at least

200 days; no L. lenta ove rintered. 'The longest field existence of

any L. .j.ip-hila male is 27 days while a L. lenta male lived 23 days

aCter b eng marked and released. These valuies are not maximum

pussaile age lim its as the spiders might have -nigrated out of the

study area or simply escaped resighting.








The marked inactivity of L. ir-i, ahili during nuch of the winter

.id the two ionitr lag in development (coipcur d to L. l-tae) are in-

direct evidence for a two-year nininiuin life cycle. Lycosa lenta

seems to have a one-year life cycle, but overlapping generations of

each instar make analysis confusing.

The influence of predation on population size of the species is

unknown. Following marking and release, 50% of the spiders never

reappeared and their fate was unknown. Approximately 10% of mature

spiders observed at Station 3 had one or more legs missing. This

value is higher than exists for Station 5, suggesting heavier pre-

dation in Station 3. This leg damage occurred for only 2 to 3% of

the L. lenta, and equally amwig the sexes for both species. This

difference in leg loss may result from larger populations of vertebrate

predators in turkey oak than in mesic areas. Parasitism by hynenopterans

:as approximately equal in both species at 1 to 2%.

Pc.cords of prey being eal-en in the field appear in Tables 4,

f'r L. 'lojiili, and 5, for I. lent. Observations apply to spiders

1-1/2 en 1- i or greater. Bo'th species appear to be opportunistic

fe'i--rs, Liki prey species in relation to their availability.

[1 isa tor il fed r'ost frequently on large Carpt:nter ants (Canotiu'as

;?.) c-anon i1 the turkey oak co.,-'unity. -_ycosa lenta caught inore

1crls lh an a other type of priy; locally cocion Pill Millipcdes

(ri Ly _i'?i pp.) cert tie -cco::di mIos frequent pcey. Five mature L.

?1 ?!t :d L"o I. -' ;jiiil7 1'-:':s weie found il-ain' in the field.

i 1 Jc ';c i'f c.i ibwl t1, ics .all, especially considering the

hii F lt'cni d it .n o0' s'iallhr instals. It is probable chat

i: tc li has : :, i pLvidin d :00t of exclusive use.

lhis Hlibut- i.-y (Ouce encountors beLween iiilvimuals.








Two cases of interspecific predation between the two species

exist from Station 6 where release of marked individuals of both

species occurred. In both cases, mature female L. ammophila killed

mature female I. lenta, one of which was carrying young. One of the

L. amino2'ila observed weighed 0.1 g less than the L. leata; the other

weighed 0.6 g more.

Re roduc tive Bioogy

Field observations

Mature members of each species exist nearly every month of the

year (Figure 7). Copulation by L. lenta in the field was observed

January 25, 1971 (J. F. Anderson; personal communication) and June 16,

1971. Wallace (1938) observed copulation in September. Pairs will

copulate in the laboratory (250C) every month. I did not observe

copulation by L. anophila in the field; however, copulation occurred

in the laboratory ,hen matings were attempted in February and the

teulrmr months.

Fc.ales with egg sacs were rarely seen in the field. ilTree L.

lunT-a records .ar June 1, 1970, June 16, 1970, and June 26, 1970;

however, no L. i.j.ojhila sightings were made. In the laboratory,

L. lentas i'inals trade egg s ics in late February and early March.

Lyvoqa ':.l mi jJ first made them in late larch and early April. The

feiicales ate ,nearly all t;-cse rg sacs one Ln t three weeks after con-

struction. PerhTaps fertiliLaticn niuver occurred.

Observaticns of iTc a:: s in the L[eld carrying young were more

frequent. Se-'en I. IeutL cords exist, the earliest on May 10, 1971,

and the laitcs on Jula 3, /170. 1T.e earliLst of six L. amnophila

observed was aoy 27, 1971, while the latest was July 3, 1970. These








spiders carried no marks and had not been previously observed. In

addition these females were usually moving when sighted and were

not resighted on subsequent nights. I also noted that first instars

frequently were distributed linearly about 1/2 m on the ground

suggesting that they had left their mother as she was moving.

.a tin ex erinen ts

The courtship sequences of the species as observed in the

laboratory riere indistinguishable. A mature male placed into a

large dish holding a female began, riwile walking about, exploratory

reaching with his forelimbs. As he approached (and occasionally

touched) the fellale, she raised her forelimbs and rushed toward him.

Following contact, this brief attack terminated with the spiders

facing each other and standing quietly with forelegs raised and

touching. Following a period of one to five seconds, their fore-

legs moving against each other, the female lowered her legs and

c'phalothorax. The male responded by climbing over her cephalothorax,

turning her rbdo nen wviLh his forelimb and beginning copulation.

%l er:'ate palps insert into alternate sides of the epygin'um, gollow-

:.i .',dur-inal rotation, at six to eight second intervals; copulation

wrs 30 secondds to 8 minutes il duration.

r,,l thI rcr fr-,l ws were fascai for one. and one bhaf wceks or more,

holie pat;ri rould br .q -cnn-ially molified .n three ways. Fivst, the

i-iity of the initial att ack inc asedd and lasted several seconds

btre be C C.:le bcc.e quiet. Ii some cas ,s, t.he biale dic:-gaged

ad [ t.r the C '.le: in cltrcr- cases she bit ard killed the rale

' in Lhi i'.iiail at :rac' r ,pursuci a:d ;! Lacked b. again follow-

i isp:s "; ,-T. hise ir.,ies wpre rcccptive to other males a

fe. nI,'ghs a-tr r feeding,. nn, once quiet, the tc-'ile refused to







lower her legs and appeared to rear back, spreading her fangs. After

a few seconds of leg touching, the male reached between her forelimbs

with his front legs simultaneously pushing outward. Third, the male

reached hack to the posterior lateral edges of the cephalothorax and

front of the abdomen, stroking these areas with the ends of his fore-

limbs. If the female did not lower her forelimbs, the male either

withdrew his legs and walked away or was attacked.

The response of gravid females to approaching males was similar

to that of fasted females; copulation never occurred. Fasted, gravid

females responded to males as potential food.

Attempts at mating L. lenta with L. ammophila were unsuccessful.

A male of one species placed into a dish with a female of the other,

would remain motionless for periods of 20 minutes or more even without

first contacting the female. When the male finally did move, the

raised foreiisib search pattern described above was lacking. He

claimed the side of the jar, as if to escape. Females in these

att--.ptcd crosses either ignored the males, fled front them or pursued

and attacked tncm. The response seemed to be influenced by the size

of the uale in relation to the fclale and the length of time since

the f,-.a]e had fed. Microscopic examination of the sand in the bottom

of the containers revealed an abundance of dragline silk 25 to 50 p

in dir'aet'er in several of them.

iales placed on filter paper previously exposed to females, re-

spioded as hougah females were present. Wh,:, placed in containers

where females of their species had resided, males either groomed or

tmmediately began the ra sed forelimb search behavior. ,hen placed

wi ere a fe(-iale of the other species had lived, the males stood for








3 to 15 ..inutcs without moving before exhibiting escape behavior.

clithor the response was elicited by an airborne chr-ical or by

contact with the dragline silk was not determined.

CorTaraivc Physiolcgy

Ihe relationship between the log of body weight and the log of

i-ater loss/hour at three different temperature and humidity combinations

for various sized spiders of each species is shown in Figure 8. Rates

of water loss differ for both species at the low temperature, low

humidity and high teL.perature, high humidity combinations; the

elevations of the regression lines are significantly different with

individuals of i. armophila having a lower water loss/hour than an

equivalent 3sizd L. lenta. At the low temperature, high humidity

coCnbination, th:ti more typical for spiders active at night, the slopes

of the regression lines are significantly different with L. amrophila

appearing to have an advantage when large and L. lenta when small

(below 0.1 g).

Ir order to ce'ipare the species in teams of actual survival time

Lide Iu ie c-viuniotecntal conditions described, it was first necessary

to detr iine the relationscli.p bcLwaen percent weighri loss/hour and

initial ,dy l cciht (Figure 9). Sialler spiders lost a higher

pc rentage oif eoly weight/hoLnt th0i larger ones under the low

temperature, low hu:!'dity Ir', LI'h i;a[:u':t're, ]1i:h liu:i.dity

conU tiien-'. In the latter environ'unt, indi.viduals of 1. I n- i.las

lost si,'ifric-ntly c"r erccntao Llhaii 1. lita. At low

tI' GraLuitt, hni h'eidiLy ciditions, no si;nific:int difrere.ice

in pec r :: ril I i;3 .J d lo uicetir 'spcies or any wig;ht

i.iv; Ti. pcr,.ac l : 't loss!/I'.uL- o0.t a 1.0 g L. .I.aia and






























Figure 8. Relationships between total water loss
per hour and initial body weight at
three temperature-humidity combinations.






























Figure 9. Relationships between percent weight loss
per hour and initial body weight at three
temperature-humidity combinations.













---- L. l1nta
-- L. aniiomphl!3
i --s-,-,-.-r----~--~-,-r----p-.----

.0 250C, 55 + 5% R.H.

Sat. Def. = 11.3

-05


Y1 = 0.04 0.29X; r = 0.92*

Ya = 0.01 0.23X; r = 0.93*
1.5 b
e = ea


> 250C, 90 + 5% R.H.
0.0
SSat. Def. = 3.4



_2)
-0.5-



S Yi = -0.86 0.05X; r = 0.11

-!. Y = -0.70 0.02X; r = 0.05

bl = ba; el = ea

r I
-C 35C, 90 + 5% R.11.
0.0.
Sat. Def. = 4.2




-1.*
YI -0.07 '."5X; r = 0.92"
Y -0.13 0.3; r 0.93*
SI = ba


1 2 3 4

Log Initial Gody \h. (graX i0 )

SI.,'.;. lA"! T AT 0.)1 I.EVEL








a 1.0 g L. ajmnophila at 250C, 55% R.H. was 0.144 and 0.120 re-

spectively. At 350C, 90% R.H., a 1.0 g L. lenta lost 0.138? body

weigh't/hour while a 1.0 g i. ammophila lost only 0.114% per hour.

The mean percent weight loss/hour for individuals of 1.0, 0.1

and 0.01 g of each specie? multiplied by 24 gives the percent weight

loss/day. These values divided into 24, the approximate mean lethal

weight loss determined for the species (L. lenta = 24.69% + 1.65;

L. armophila = 23.11% + 1.22; P= 0.05) giwe estimates of the number

of days spiders of each weight could survive at each saturation

deficit. These estimations appear in Table 6. In view of the facts

that: (1) differences are insignificant between the species percent

weight loss at 250C, 55% R.H., the highest saturation deficit used,

(2) no significant difference in % weight loss occurs between any-

sized individual of either species at 250C, 90% R.H., and (3) that the

drying effect of the circulating air in the experimental chamber for

all saturation deficits is not a factor of the spiders microhabitat,

I assume these humidity and temperature combinations do not function

to seg;>-gte the species. However, at 350C, 90" R.H., a situation

possibly encountered by spiders in deep burrows in unshaded open

ssnd in ':,e afternoon, L. ainop~ ila would be able to live longer than

L. le!-L3 if both species had no access to water.

A n,,bt:r of distinct behavior patterns were noted as the critical

hicr-nal maximum approached for bocih species. Spiders were normally

inactive wien placed into :he cool (200 to 250C) test apparatus. As

the tc per;at-ure increased they begi:n to move. The first movement

_::hibit d by the spiders was either slow Walking, reaching through

the bLotoir' scre'a wi;h the forelegs or attempted climbing. The















TABLE 6

Estimated survival differences for various
Lrcosa lenta and L. arvophila*.


weight class-s of


Weight
(g)
Species
1,0 lenta

anrmophila

0.1 lenta

ar xophfila

0.01 lenta

..rophila

1.0 lenta

a, ophi la

0.1 lenta



0.01 !~Ilta


Estirsated
mean
survival
in days

7.00

8.30

4.20

5.00

2.50

2.80

7.16

9.00

4.65

5.60

3.00


a. ophila 3.45


*based on olbscrved mean a
v'lSht loss per hour under
-i'-ororary conditions described
in tx-c. Lothal ',I iQight lors
idle to d:sji c-it onL asspuiited to
be 247.
i*osti atse for ?iOC, 55 : 5%
R. H. 'cr calculateci fro:n
i':i niific'atly dirf-rent
<:eijht loss daita.


-Tperature
and
Relative
IHumidity

250C

55 + 5%

sat. def.
cE 11.26
ig l!g






350C

90 + 5%

sat. def.
ol 4.18
i,; Hg


Advantage 'C
in days


0.45


~








behavior, "forelegs extended through screen," suggests spiders were

either searching for a burrow entrance or were attempting to go

deeper in the tube. Not all spiders exhibited this behavior; some

immediately began trying to climb out of the tube. This "first

climbing," a type of escape behavior, occurred in all spiders.

Climbing spiders were very active and often mixed this behavior with

"forelegs extended through screen" in rapid sequence. These three

behavior patterns would result in thermoregulation if the spiders

could escape to a cooler locale.

As the temperature increased further, spiders showed evidence of

neurophysiological disturbances. First, they showed a loss of equilib-

rium. They fell over on their backs while attempting to climb and

appeared to have difficulty righting themselves. Those acclimated at

300C tended to begin walking in a jerky, uncoordinated manner rather

than falling over. At temperatures nearing the critical thermal

maximuer, spiders became inactive for lengthening periods of time.

Spiders cooled following this "heat torpor" (Heath et al., 1971)

shoed no evidence of neurophysiological damage the next day.

At Lhe critical thlmnal maximum, ca. 8074 of the spiders showed

an irr, -vrsible paralysis. It followed a period of convulsion last-

ing 4 to 8 seconds. 'he remaining spiders observed died quietly

without convnLsions or paralysis.

A sturmary of the temperatures first producing these behavior

patterns appears in Table 7. hlle temperatures of onset for Lher.co-

regulatory responses ecre quite variable except for 200C acclimated

L. lea-a and the differences observed were probably not biologically

significant for any-sized spider of either species at either acclimation





53







0n 4-0 0O3s3

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o l +1 +1 +1 +1 42















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bi 1-3O % O. ,. [ /, o | ^ o 1- -i ,'








tcraperatire. There is a trend for L. lenta to begin each behavioral

pa-ttei-n at a louer temperature when acclimated at 300C than at 200C,

while L. angophila does not change.

The onset of neurophysiological disturbance and final collapse

occurred with much less variability than the behavioral responses at

lower temperatures. Acclimation to 300C elevated the initial tempera-

tire for "loss of equilibrium" and "lack of movement" 0.5 to 1.50C

for both species but did not result in a significant difference be-

tween the species. Acclimation did not change the critical thermal

m-xima fur either species.

The investigation of water loss rates at high temperatures

(Figure 10) failed to reveal any difference between the species.

However, an increasing rate of increase in water loss occurred as

the spiders lost the ability to regulate, suggesting cuticular wax

disruption (Beonent, 1961). Regression lines calculated for the

points at 390, 410 and 430C both intersect the species lines for

Lwcr temperatures at ca. 380 to 38.50C. After being heated to 430C,

well above the suspected wax transition temperature, these spiders

wre-.e returned to the 250C, 55 + 5% R.H. acclimation condition.; and

jiloed to dessicate for 24 hours. Water loss rates were determined

,ver a 12 hour period. Both species had a percent weight loss/hour

apprcxi-ately twice that of spiders not heated to 430C (Control =

0.14%/hr; Ex:pecimental = 0.267/hr).

The resting metabolic rates of mature females of both species

w:are essentially identical. Anderson (1970) reports a mean value for

80 L. lenta of 94 4 10 yl 02/g hr. LTe mean value for 12 1. iE.riophila

exa-li.el in this study was 96.6 + 12 )1/02/g hr.
































Figure 10. 11ean percent weight loss per hour at
high environmental temperatures with
95% confidence intervals. Saturation
deficit was held constant at about 26 mm
11g. The sharp increase in water loss at
about 380C is suggestive of cuticular
wax disruption des-ribed for numerous
insects.







The study of mortality rates of mature females held in jars with

wet sand revealed no differences between the species. During the 38-

day study, two of nine L. lenta and two of nine L. ammo1hila died.

There was no apparent cause of death in any case; one of the L.

ammnophila had a light infestation of probably harmelss mites (genus

unknown) about the mouth parts.

Burrow Characteristics

I found a total of 32 L. lenta and 9 L. ammophila burrows.

Descriptions appear in Tables 8 and 9. Both species typically build

a trapdoor at the mouth of their burrow. These trapdoors probably

contribute significantly to the retention of water vapor within the

burrow. The silk doors and lining of the wall around the mouth of the

L. ammophila burrows were thicker than for L. lenta. The former were

typically spongy and ca. 1.5 imn thick while the latter were compact

and only ca. 0.5 mm thick or less. Often, burrows of L. lenta lacked

any noticeable silk reinforcements around the mouth. The trapdoors

also served to camouflage the burrow. Sand grains, bits of leaves

and other litter in the vicinity were always woven into the top of

the doors of both species. Those burrows lacking trapdoors were

under dense pine needle or leaf litter or among dense shoots of a

clump of grass.

The nature of the burrows varied with the size of spiders, their

reproductive state and, perhaps, with the species. In neither species

was the burrow silk-lined beyond the mouth to any extent. The burrows

of L. lenta can be characterized as follows: (1) the presence of an

enlarged chamber at or near the mouth of the burrow is typical only

of nature fP ales during the reproductive period.. The appearance of















































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the chamber corresponds to the production of egg sacs and females may

use the area for making the egg sac, remaiining with the egg sac and

young after hatching; (2) the frequent occurrence of branching away

from the chambers may allow spiders access to areas with different

saturation deficits. Branches off of nou-chambercd burrows may have

a similar function; (3) immature and non-reproductive mature spiders

noir'ally build non-chambered burrows of highly variable length. Side

branches, more typical of penultimate females, are also variable in

length.

The general nature of burrows was similar in both species; how-

ever, mature females of L, ammophila often had lengthier side branches

off the chamber. These were usually horizontal and about 0.75 cm

beneath the surface. The side branch of one spider ended under a

clump of wire grass, a cool moist microhabitat.

One female, shown in Table 9 by the symbol ***, had a side

branch from the bottom of its chamber ending 25 cm below the surface.

The opening of this branch was sealed off with fresh dirt from the

wtall or botLaC of the chamber. Tha function of this deep burrow

in the winter in a moderately chady area is unknown.

The ol'y ;uspected L. Ienta burrow at Station 3 was near a marked

fiezale. As shjwn in Table 8 (***), the burrow had a chamber and side

b'ancihes tpicIal of n.ma're fc'fiale L.. 'a:crb but the roof of the

burrow -ystcim showcd ri'ms of an extensive cave-in. All L. anmophila

burrows ihad solid roofus ad lacked noticeable structural dam.nge.

Ioy'e Clanme ad Pesieh-l.tg Data

of the 57 rdult L. le'ta females marked and released at Station 5

ii 171. r, nly 37 (21) reappeared two or more times and 16% (9) four








or i cre tires. Resighting values of females at Station 3 in 1970

are. 35 (26) of the 75 L. ar'oprhila and 29% (5) of the 17 L. lenta

appearing two or more times. Twenty-four percent (18) of the L.

a:'aophila reappeared four or nore times. The frequency of multiple

resightings of females is shown in Table 10 for L. lenta and in

Table 11 for L. canr.ophila. Te sudden disappearance of spiders with

home ranges or the lack of any resightings could be the result of

death, extended inactivity within the burrow or migration from the

study area. The frequency of each of these events is not predictable

from the data. One L. amophila, first sighted on 14 July 1970, was

not resighted until Febraary 26, 1971; it presumably overwintered

in ins burrow. One L. lenta marked 26 May 1970, and resighted once

near the release point appeared again 60 days later 40 n away.

Active females reappeared nearly every evening. Gaps of two

or three days between resightinss reflect infrequent observation as

Ix.,ch as spiler inactivity. Caps of seven or more days are not, however,

d'e to lck of ,bservations. 'lie reason or reasons for these periods

O i .a. 'iry i'e nkao1.nv .

i"e c; i ci ~ range sizeos \itth 95% confidence intervals based

o. I :- s >h':ed fontr or ;oie Li.s are shown ii Figure 11.

-tiU c/i' i .';c: hC ine ranze in Lbo field, I feel that Lbe high

.leL, o*f i ;bi iity in area ireflc.e. an adaptation of .ach spider

to 1. ch- ctr of the "'e around the borrow rath-r than to the

Genpr-l "nLu-c of the co..rt:'ity ,,, irt it is found. V1o siuiEj.icant

corrct!m. i,:as roted t e:-..n Lh1 ;.i-ight of individuals a:rl borne

rs': a si i .o.' '' 'id tend '-o have larger horic: Ira:gs than

L. Ir-ta Co, t 'e ; ii: c Cion, an obs rvacin corrclatin, wtthl Ote

i.ar,. c .v :rnc a iz. ,d i,'h: of thle ,peciLs.










TABLE 10

Days between resightings for L. le4ta females with home ranges*
Initial Days between subsequent resightings
Sighting 1st 2nd 3rd 4th 5th 6th 7th 8th 9th 10th 11th 12th
STATION 5
21/V 6 3
21/V 10 6 1 1

26/V 4 15 1
1/VI 7 1 3
4/VI 3** 1 1
7/VI 2 1 2 1 1 1 7 7
9/VI 3 1 1 1 1 2 1 1 2 1 1 2

13/VI 1 1 1 3 4 1
13/VI 3 4 3

16/VI 2 1 1 3

16/VI 2 2 3 7 15

17/VI 6 2

19/VI 4 2

22/VI 21 1

25/VI 4 1 14
24j/[ 19 1
24/V[ 5 1

.20/1 5 2
30/VI 5 1 1
3/VIl 4 6 1 1 1 4

6/,I.I 2 6

IAlY I 3
/1 10 3 6 7

4/Vi 1 9 3 3

7/VI 1 4 4 2 1 1 1 1 3 7

/VI 3 6 1 1 i 5 2 4

17/VT 1 8 1

bhascd on two or more resightings
**Touvsd from previous home range


















0-










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in












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01i 4-4 01 0-43 03 -40 01 01 01~



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140

4)4


0w









314.







0- 'A~
r00





3-34
.- 3 0








Mature males of both species wander and do not, therefore, have

a lih- range as characterized above. Of 69 male L. lenta marked at

Station 5, 31% (21) were resighted once, 17% (12) twice, 4% (3) three

times .nd only 1.5' (1) were resighted a fourth time. At Station 3,

only 24% (13) of 53 L. a -ophila miles marked reappeared once, 7.5%

(4) twice, and 2% (1) a third time. Of the 21 L. lenta males marked

at Station 3, resighting consisted of 19% (4) orce and only 5% (1)

twice. The lower resighting frequency of both species at Station 3

may result from a lack of barriers such as the stream present in

Station 5, and the large areas adjacent to the study area suitable

for invasion.

No burrows harbored adult males and no males built burrows in the

laboratory. It is unknown, therefore, whether males build or occupy

burrows.

The infrequent resighting of males and the variable distances

between rcsightings makes it impossible to calculate a meaningful

average daily movement rate. Two noteworthy resightings include:

1' an r. Lca- male roved from one side of Stalion 5 in two days to

tlhe ot' L sile (23.75 m), :as seen in copulation, end returned at

Ie;st [-'o dys later to the first side (22 m). These were the third

;;d fourth -i -sihtiigs for t is ncale within 12 days of release. He

w.-s lot siJt'd *:;?i; (2) an T1. a scl'i. ale relc'ased in d-nse

wi5 e rass reappeared 12 .i ,iway one half hour later. If the spider

had contiUued at this ppce fore hours, ic Iould h.ive oved nearly

'00 n. '!os : sais o,-' -v.'d ccre noic ,c>k iit, however, but were stand-

Si, quietly; therefore, 7,e ;aver:ie Cnihtly nig;ration di;Ltance is

Prob^bLly lc;s than 2CO m.








Females occasionally move from their burrows and establish new

ones; the pertineht field observations are in Table 12. The reason

for the moves is unknown; however, in the few cases observed, spiders

remained in the same habitat.

Since all females wich young had no marks, they had presumably

migrated into the study areas. Perhaps abandonment of the home range

normallyy follows the emergence of the young from egg sac.

Distribution and Habitat Preferences

The capture localities of mature spiders and the number of home

ranges in the various habitats of Stations 3 and 5 appear in Table 13.

The observed densities of females and home ranges given per 1000 m2

appear in Table 14. A chi-square analysis of the null hypothesis that

the distribution of L. amrophila females was random using an expected

density of 12.7 females/1000 m2 in all habitats of Station 3 resulted

in rejection at the 0.5% significance level. Similar tests for L.

lenta females at Stations 3 and 5 showed that the species had a non-

random distribution (P = 0.05).

At Station 3, densities of aImnophila females were not highest

icn te tuthey oak-wire grass area as might have been expected, but

raiihr in the sandy old field area and, secondly, in the ecotone be-

tws-en turk-y o'k-wire grass and live oak havnsock. This distribution

holsJ as well for hoi. range densities, being higher in the old

field region. TIea disparity in density of females and hore ranges

between the tut!eJy oak-wire grass and live oak habitats suggests that

matuce frial s e:iiuigrated ora.n the former habitat soon after they

entered or, in -he case of residents, soon after emerging from the

pecultimate ii:oult (discussion of inmiatures follows). This idea is
















TABLE 12

Kno:nr novereonts of mature fmcalas from one home range* to another

Time between sightings Distance
Species Station (days) moved (m)**

a2iphila 3 56 20

_anoohila 3 10 3.5

ainophila 3 20 20

anoph ila 3 180 14

an-ophila 3 1 10

leata 3 1 2.6

*based on two or rore resightings
**from last resiShting in first home-
range to first rcsighting in second.
IThe second and sixth spiders were re-
sighted over four times in both
horerangcs.




















44 0 04 0 0









-0 0 40 .4


Ci


400~





0.






g





0~










01
0

.00















0.0



t!


-t 04


.4- 0 4




0. 040
4- 0 .
.4 0 10 t


v 0

b.0 .0
'-4 0 0


o
N^


.0
40





















-4 .
0 0

-..0 40-..-
0. .004-i


I 40


m7 r-i si


I 0


n r-
C" ^1 .


i- C


I












TABLE 14

Observed density of marked spiders and home ranges per 1000 m2 in 1970
Lycosa ag hila Lycosa lenta
Station Habitat Home Ranges* Females Home Ranges* Females

3 turkey cak-
wire 4.2 10.8 0.9 1.3
grass (a)

old
field (b) 26.6 50.0 0.0 0.0

live
oak (c) 11.4 28.6 8.5 22.9

grass (d) 0.8 3.3 0.0 0.8

road (e) 6.0 12.0 0.0 0.0

5 annual
weed (a) 2.1 6.3

grass and
leaf 12.5 26.9
litter (b)

*based on spiders with two or
more resightings








supported by the observations that high densities occurred at the

borders of this habitat and that unmarked fe ales in wire grass

were almost always moving when sighted. Females moving into the edge

of the live oak harmock occasionally established home ranges; those

moving into the old field region did so more frequently. The extreme

density of the wire grass and the relative paucity of open sandy

spaces in habitat "a" (Figure la) is probably a major factor influencing

this distribution. In other regions adjacent to Station 3 and in

Stations 1 and 2, where wire grass was sparse and open sandy spaces

common, mature L. ammophila females were more abundant; they were

found most frequently on the open sandy patches between leaf drifts.

The higher density of females and home ranges in the hazardous "road

habitat" again reflects the species' preference for open sandy areas.

L. leuta females at Station 3 were almost exclusively in the

1 iv oak ecotone. hosee with home ranges in the turkey oak-wire

grass habitat were under fairly dense stands of 3 to 4 m tall turkey

o ..s here leaf litter had begun to accumulate in and between mats

or w-ire grass. Females of the species were not in unshaded or open

s3;dy arc s and rarely occurred in tall garss.

ThIe imale of the two specie>' moved through all habitats at

StLtion 3. 3 -jcsa anoeghila males were abundant in the ecutone with

thre I ive c-k but rarely entered the live oak habitat. The high

frcq:iCecy of nonresidents at this site suggests an ecological barrier

effect where individuals accumulate before returning to the turkey oak-

wire gross or old fLeld habitats. I observed L. lenta males outside

the live oak ha l.i.ock infrequently; the frequency of their occurrence

in the :.ore xeric harbitats corc',lated roughly with the area of the

habitats.








'he distribution of L. lenta males and females at Station 5

co0rcla-~ es v-e-y :ell with the presence of scattered low grasses

and well-nulched leaf litter and the absence of tall dense weeds.

The difference in nnuibers was four to one, and in home range densities,

six to one.

Irmatures of L. a-nohila in all stations where the species

occurred were found in association with leaf litter and wire grass and

were uncon imon on open sand. All of the borrows of irnature spiders

were irt or very near leaf litter or wire grass. These nicrohabitats,

besides being rore moderate in temperature and moisture fluctuations,

afford a degree of isolation and protection from larger predaceous

spiders.

The results of the 1971 study at Station 6 (Table 15) again

domnons rated L. aTophila's preference for open lightly shaded sandy

arcas l'-iile 1. lenta prefers shaded areas with leaf litter or :ulch

and fer' dense grasses or weeds. When given the choice of six fairly

distinct habitats, both species avoided habitat "a" (Figure 2) with

s lo, dcrse ,eds. In habitat "b", however, differing from "a" by

its %ac o d,. -se weeds and the presence of extensive broadleaf and

pine ,rcedle I'.cr, i. .1oe: frequently became. established following

r.- I.ae, iirty-f., percent (7) of choe ,acked fetiales reappIjared

Shi. \ r-i-i -7, l.1 wi'iit -. 5 -,1 Ladi's of Lbh release points.

Only 7 (') of 'tb. 7, hi.j!.2 fe,,al^ decvcl5pl d a ho e range.

This inJivisJ i was ca 40 -:n fIcm its release point. he other L.

T:i7oiil ~!i ;i"s ,'trc V,- -Eghti 'e ro 50 nm rcm ;hi release point.

Two i. c-iol i ri ics :d one i .lc were s,'sibhtcd in bhibitat "c"

S , fr thc reicis poinl i.L "b". No .*irkd L. l]onlt

we re Ln ti r;s oi hab( "c".

















o 02 1















> .b 0- '0 >
jJ CC i 44-l CI .2 CO C




S 20o d



14 40 41 -v 4 3

c.










j$4 01 CC 0- (.- 4- Eu
S C I-r CI
o i'-J C
- 0 *-ll -a


0 ii ,-0 u 1i -21 41 i 41 4-0









44 [3 4 .- 14 44





a 4, C C D


O E -5 .-21
0 0J -i












r-'1 -^ nn








On the other side of Ihe stream, L. lenta showed a small tendency

to rn'ain in habitat "d" following release. Only 65 (4) were in home

ranges and all of these were in microhabitats with well-shaded leaf

litter. 1. arnoLphila, however, established in this habitat most

frequently. Of six hone ranges, 4 were in nicrohabitais with scattered

patches of sand in light to moderately shaded areas. Two of the six

ho.7e ranges represented females having emigrated from habitats "e"

and "f". It is important to note that six unmarked mature females

of L e-.ophila appeared during the late spring and early sunmner near

the release point in habitat "c". Penulcimate females were released

earlier in the year and were frequently resighted, indicating L. an'opil

can undcergo the final moult to maturity in a "mesic" habitat.

ieiLhcr species became established in habitat "e" with its tall

grasses and few uprarked L. lenta were ever seen there. Habitatt "f"

was apparently quite suitable for L. lenta, since three of eight

fenales there established home ranges. This habitat had moderate

to heavy 'shade and extensive regions of leaf litter similar to

'h-',itat "3", th_ pine woods.

Of the 58 L. lenta femalcs marked and released in an open-sand

turi'ey oak-I'ire grass habitat near Station 3 in 1971, eleven re-

appc-' I:. at least once, Lhreei t;ica. a;d only one three times. Seven

r~a tiegs were within 3 1, of the a'tl"e po '.at and the spiders

survLve d frr 1 30 t d0 ays. 'tre c'-e'.inin four wcre seen from 8

to 20 a ,icurs aw-,y; one- !h;id livid 20 iays, the oth-.ers 105, 10/ and

108 iJy' s. AIL;Ih.ji 1' 54 I.iir'd ii al:iLres ure ilrIcased, no nrt~arked

-dailtc a',,:' coll ct'd iin ihc 'rea and very few i;n:af L-res were scen

-io_-; i.-n a f& :; .rc'!s foTlcow a' release.





78


The L. Icnta female placed in the cage on unshaded open sand

lived 63 days, from February to April. It was resighted regularly

before being destroyed during construction activities in the area.

This observation and the data for unconfined marked females in the

same habitat support the conclusion that mature L. lenta can survive

in the harshest areas where L. ammophila normally occur but typically

avoid these areas. Any L. lenta burrowing in such areas would

experience increasing thermal stress as summer arrived, a situation

absent in their more normal shaded mesic habitat.















DISCUSSION

Evolution of the Species

review of the current theories of geological events in the

S-uth-eastern United States during the Quaternary reveals L. aramoohila

had ample time and the necessary isolation to adapt to the sandhill

ccnaunity. A submersion of Florida existed during the Oligocene

idlen spiders w ere undergoing adaptive radiation and the first lycosids

appear in the fossil record. Perhaps as early as the Late Miocene

the sea level dropped exposing the peninsula to invasion from the

mainland (Alt and Brooks, 1964; S. D. Webb, personal communication).

Laessle (1968) reports evidence that sone modern sandhill cor-munities

(lo,1gle-af pine-turkey oak) have existed essentially unchanged since

Pliocene or Late lioccene; consequently, the presence of stocks of

the L. ps shila precursor was possible. The precursor was likely

T. lenta or ,o'e corar.on aricestor since the two species are so similar

ii-. o:p'!oloy .~ind reprotuctivo behavior.

,:lging ihe first clearly recogni:ed interglacial period, sea

lev.! iose, '5 : to -h.c Okcfrlkre shoreline, isolatilsg bveral isl-ands

S1 l:;,'d ';roua (Lac.el1, 1950; -icCrone, 1963). Only the highest

~, 1 ass u- :c cl',st rac's of nodera; Florida oere exposed. 'iese

i pr rily s: t.[ ill ssociatoi. due to their eroded,

* ll-dr i, 1 l andy ri- aur. '"e .s ll nlmbcr of ,lant species typical

of 'hc ,';: i' i au is;'L tci )L oAly Cro poor ioi stac r-hi' ltding

ah:c; l-s L .1 i ,] tiicy of a s ot aua' to I 'cliag h1t also








from fires which prevented the cor.mnunity from undergoing succession

through xeric hannock to mesic hananock (Laessle, ].958, 1968; A. Carr,

personal communication). The present distribution of the species

suggests that L. ainnophila evolved on one or more of the northern-most

islands.

Thr-ee other known glacial periods occurred during the Pliocene

and Pleistocene. During each interglacial, sea level rose to a lower

level than in the one previous. During the first, it rose to the

30 m level, again isolating numerous islands. Nearly all the current

sandhill communities were established on the lower wave-eroded hill-

tops exposed during this interglacial. If speciation of L. anmophila

did not occur during the previous interglacial, a second chance

occurred.

During the final two interglacials, northern and central Florida

rere not inundated and extensive mesic areas surrounded the sandhill

cc iunities. Presumably, L. lpnta occupied many of these mesic areas

end has maintained fhis distribution pattern without successfully

.oloni"ing the sandhill communities. The change in pheromones may

hav occurred during isolation or when the species came into contact.

u',.crous other examples of speciation during the Late Quaternary

in r'c.ri_: have been documeentcd. They include studies of the wolf

spi'.dcs of lhe GCoysacosa pi'i nlmplex (McCro..e, 1963), beetles of

genus yIcotruaesL ((Hubbell. 1954), grasshoppers of the Ielac- nopus

2uetr coinplex (iubbell, 1932, 3956) and snakes of the genus Stilosoma

(lighton, 1956).

'he niches of J. alnophila and L. lenta

One of the major adi-apt-r ions of L. airgnhila to the sandhill

c aunity is th- 'limitatcin of productionn and geonral -ctivity to








the wet sunrer months (Figures 4 and 7). During this period, the

clii tc is most moderate and survival of the young is apparently

maxi iized. Mature spiders are uncommon during other seasons ilen

rainfall is infrequent and inconsistent, daily temperature fluctuations

are large, evening temperatures cool and the habitat less inesic

(Figure 12); younger instars are infrequently active, remaining in

their burro-s many evenings. In contrast, L. lenta breeds from

late winter to early autumn and the younger instars are active on any

warm, hunid evening. The difference is correlated with the presence

of a daily and seasonally moderated microclina te in the shaded mesic

habitat.

A further adaptation of L. acmmophila to seasonal quiescence is

an increase in life span to two years (Figure 12). Recognition of

specific life stages in the field is much easier for L. ar-nophila

any given ncnth than for L. lenta populations; the overlap of life

stages of L. lenta results front the prolonged breeding period. !'_osqa

1nia. poplclations may be resolved into spring and summer generations

up:n f tcLhr study; it appears, however, that most spiders reach

Tznaturicy in onr year. T'he life cycle of the L. loenta population at

St-tion 3 w.is in phasee with ciOse rt LSations 5 and 6, suggesting

e;;o 'inlus control. Similar disa for I'. ; a'PhillJ populations are

lacking .

-.,r- sa aC..pli.a hiis sev':.i characteristics ibettui adapting it

to ::eric c:vi-',e;rsitts than L. ?pl-ti. first in odueictoly dry test

ei,-io",, ;r ihe p:-cect weight loss p'r hour of L. C' iopila is

-,;: tI..n thlti of 1. len-ta of equil weight (Fiigre 9, Table 6).

t d. m: of cater rcte Ction 'ains Lo be idniLified. 'lhe



























'j

4 0
H *H .3




?m13 (U 0
0J> 0H COH


-4- 0 .0 0 j-J r-.
H) 4 (44- 0 0H


0 000.0 t
(0 -4 0.0 0Q

0! 144 0 4l4 4 04

^ r : 0 ; H I-'





o -3 1' 0
440.00
ni E -ij






4 4o 4 0
,-|[ ^ J*,



'0 4- (0

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0 40. 0.0*- <
3 0 -01. 0'>
o .0. 0 44 -


rjY-I: "3 ^
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0 0r -4; 0 CJrS

0 44- 444 .44 04 0
44 44 0-


(TI > 4^ .0* >0 H
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i 3 a a i- a>p-0
; u oc ^ia n
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ii" K

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advantage in survival time is small but is correlated with the in-

activity pattern of L. a!'omhila during dry seasons. Second, the

average weight of mature L. anmophila is larger than that of mature

L. lenta (Table 3), allowing them to tolerate dessication longer

before drinking.

Although the resting metabolic rates of well-fed spiders are

identical, incomplete preliminary studies of fasting spiders suggest

that L. a nophila may undergo a greater reduction of resting metabolic

rate than L. lenta. This increased energy conservation would allow

L. arinophila to feed less frequently, e.g., when inactive within the

burrow. This would be a third adaptation of L. aneophila to the

sandhill community.

Other physiological characteristics determined for the species,

critical therral maxima (Table 7) and the temperature of suspected

cuticJlar wax disruption (Figure 10), were essentially identical.

Lvcocta acohila shows no differential adaptation with respect to

t fas.' factors to a xeric environment. In addition, neither species

shot 1 any significantly different behavioral responses when heated

(Gable 7).

lhe water loss rates of L. ammogphila and L_. lenta, compared

with z-tes for other arachnids (Table 16), are higher than most

"eric-Adcptcd species which have been studied. Reasonably accurate

czOparisons are possible if the data are adjusted ro constant

saturation deficits (e.g., 3.3X for the desert scorpion Hadrurus

a -izcea. sis) a d the rate of water loss for L. lenta and L. a:r-nlhila

increased accordingly (e.g., 3 X 0.144 = 0.428 percent weight loss per

hour for L. lenta at 300C, 0% R.H.). A 1.0 g H. arizononsis would

















C



C)


"a i N
C C) C

Ci C ) C








'-4 -i I v '.


0


A 0 N C '




Cl Ao Ni 03 A A



44 A A A


00
'C
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2E
&-i
20











03
.v











Q -








r3 -




















t-Q

*)-


o w
Cl








S r4- r--



' rC rC
V


A 0 A A- -t3 AN
01 "1 el 'd- CMr-

0 0 0 0 00




N 0 0 00 0 0 0



Or c c cO O O O








0 0 0 0 -O 00





A 0 0 0 0 00
A A A A o oA


0


ui

U Uv


i i o
3 0


I 2 C






4
V 4 I.; ? ri I a
^ ~ ~ ~ ~ ~ 1 i1 1' 0 3 r

m ~ ~ ~ ~ 0 (* "a^ ^ t
_:. -i u ** ^ 1 .' ? '


Ca j A3 .-* CC.1 V O '; ^


In

N
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:3 O-t
13
ri
C
I ~


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en o








lose about one-fifth and one-sixth as much body water per hour as

1.0 _. arno2hila and I. lenta, respectively, at 300C, 0% R.H.

A 1.0 g whipscorpion, ajstigop roctus, would lose 1.75 and 2.0 times

as nuch body water as 1.0 g L. anmophila and L. lenta, respectively.

Nastigo~ roctus, studied in Arizona, is less efficient at physiological

water conservation than either of the lycosids. It avoids rapid

dessication by burrowing beneath rocks and logs, and is even found

in semi-nesic areas of Florida. Unfortunately, data for 1.0 g hunting

spiders is not available and comparisons with 12.0 g spiders may be

invalid.

The sparse data available for critical thermal maxima and temper-

atures of suspected cuticular wax disruption of other arachnids

(Table 17) show that L. ammophila and L. lenta have higher tolerances

than any Scandinavian lycosids studied. Tolerances are lower than that

of thu desert scorpion. These comparisons support the conclusion that

L. a'm sila is nearly as mesically adapted as L. lenta. Lycosa

a i 'ohlia does not possess physiological adaptations sufficient for

w'at'r conservation in a continuously xeric mi croclimate.

DuI:rtws provide concealment from predators and help in the main-

tenance of an optimal nicrclimate when conditions on the surface

restrict activity. The latter factor is more important for L.

aLpphil- in the f.andhill co-m.unity thea for L. leata in more mesic

areas. W hicn suirer surface te-iperatures reach over 60C, L. Pno-ophila

must bulrrow at lgast 3 em deep to avoid heating above the critical

thermal iaxi-.urhs at least 5.5 cm. to avoid the suspected cuticular

wax disruption, and at least 6 to 6.5 cm to reach a maximinm daily

temerature which is behaviorally acceptable (Tables 1 and 7).









C (
141
-4 1 0 0 1 1
-1 4- 1' l 1


'14 '14 1 -- 41 1
C~ ~ ~ 14-4 1 4 -
-1 4 14 14 14 1 4


Cll 14 -1 114 -'4C

0 14~ r
4.4
14CC 01 0c .41




o 11
al ? 9 ~ c~
'4 14 44n o
14 44 14m




.44 -4 I I 41


*, *o 1 C'~1


.14 .14
'14 0141 C C
14 -44 1411 14 14 14
'.4 '4'1 F. '1 142 C'
.-; .14O 414,41 .1 *1 14 141 4--




I

j 14





A:' 2 '








Temperature regulation may be possible for mature spiders by moving

along the side branches typical of the borrows located. Small in-

stars of L. am-mohila burrow in areas of wire grass and leaf litter

and need not dig as deep to avoid high temperatures (Table 1). During

winter and spring when I1. arnophila is least active, energy and water

conservation could be maximized if the burrow were about 17.5 cm deep,

the depth where the lowest constant temperature occurs (Table 2).

One burrow found was nearly 50 cm deep; it is not possible to say

whether or not deep winter burrows are characteristic of the species.

The major similarity between summer burrows of mature L. lenta

and L. ernmophila females is the shallow chamber, presumably serving

as an area for the production and carrying of the egg sac and newly

emerged young. In the sandhill community, the shallow climbers

probably heat to 30 to 400C or more in the afternoon (Table 2),

hypothetically requiring the females to move the egg sacs to cooler

areas of the burrow system. Behavioral thermoregulation of the egg

sac has been demonstrated for an orb weaver, Theridion saxatile

(;.rgaard, 19561 and a wolf spider, irata piraticus (Ndrgaard, 1951).

TL is conceivable that the optif'-un temperature for development of the

eggs of I. sisnhl- i Ij may be higher than thl.t for L, le_.nta eggs, and

tiliat T. '-nrqhila fe-.aales can reduce tleir resting metabolism even

lo'-er chan the 20% compensation by I. lenta when changed from 200C

cclimaeticn to 300C demonstrated by Anderson (1970). This would

allow mother and egg sac to survive in or near the heated chamber

without increasing energy requirements unduly. These speculations

sugg,=st further lines of investigation.

Several factors in addition to reduced tater loss relate '-o the

larger size of L. armmopila. The primary selective force for increased








leg and cephalothorax dimensions may have been the need to support a

large abdoern, the region of water and energy storage. The increase

of size hypothetically places mature L. aranophila in a different

feeding niche than L. lenta, although data front this study do not

show any significant difference (Tables 4 and 5). It is apparent,

however, that in encounters between mature spiders, L. ar-mophila

would eventually eliminate L. lenta. This effect was demonstrated

at Station 6 when L. airophila was released into the habitat of L.

lenta (Table 4).

Another factor involved with increase in body size of L.

ammonhila is the requirement for more food. The larger average home

range size of rhe species as compared to that of L. lenta studied in

the sane habitats supports this speculation (Figure 11). Adaptations

in energy conservation nay have reduced the need for even larger home

ranges for L. anmophila. In the only study of home ranges in south-

castein United States lycosids, Kuenzler (1958) studied L. tiru-ua,

thie ;I rbcr of the lenta complex replacing .L ar7nohila in the Florida

scrib co-,runity and in the longleaf pine-turkey oak cort:unizy from

ori nor-Lh to Virsinia. lie reported a mean home range size of 9.2

rM2 (103 fL2) for a population in South Carolina, value considerably

-'rr th-n thit of either species ex.-in-ed ino his study. The

diiie'rcrnce m.y be a respon.e t. :he local cli::ate; a fiorida popula-

ti-n shituld be stu.ii d b fecne Lt.-. iipting further : c-r.:paisons.

Tic larger average size of rlatir, spiders in cthe lenta group

S.:,- IC to a-llrr lycosids tiains the spildes of lhri lnta group

i!-;"i pted 'o a cli biag i.ode of fora,-ing. This restriction affects

S, -r'* il.i tore t an: L,. ianl ini in part e:plains their hitiat

distributions and profrecnces. liallandcr (1967) used this same




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