BULLETIN OF THE ALLYN MUSEUM
THE ALLYN MUSEUM OF ENTOMOLOGY
Number 9 11 December 1972
A NEW SUBSPECIES OF MEGATHYMUS URSUS
POLING (MEGATHYMIDAE) FROM ARIZONA
WITH OBSERVATIONS AND NOTES ON ITS
DISTRIBUTION AND LIFE HISTORY
Ronald S., Joseph R.* and Dale Wielgus
3434 West Augusta Avenue, Phoenix, Arizona, 85021
The typical subspecies, Megathymus ursus ursus Poling has not been recorded
north of the Santa Catalina Mountains of southern Arizona. It is known to
occur in steep-sided, mountain canyons above 5000 feet elevation where its
larval foodplant, Yucca schottii Engelmann grows (Stallings and Turner, 1956,
and personal observation). The new subspecies was discovered in a lower, desert
situation approximately 120 airline miles northwest of the northernmost known
ursus locality, utilizing another species of Yucca as a foodplant (Wielgus, et al.,
1971). The first specimens were obtained in 1970 and sent to Mr. Don B. Stallings
of Caldwell, Kansas, for examination. It was he who called the attention of the senior
author to certain distinguishing characteristics, and felt that these specimens
may represent a new subspecies (personal communication). Mr. Lloyd M. Martin
of Prescott, Arizona, who also examined these specimens, shared this feeling.
We have subsequently secured additional specimens and believe that the
naming of this subspecies now will afford a necessary reference for those workers
interested in establishing a more thorough knowledge of its distribution and life
Megathymus ursus desert Ronald S., Joseph R. and Dale Wielgus,
Female: Head: front and paraocular area black; vertex gray. Antenna: shaft
white; base black dorsally; tip black. Palpus: very light gray. Thorax: gray above;
blackish below. Abdomen: black dorsally and ventrally; gray latero-ventrally.
Upper surface of primaries: dark, shiny black, with small amount of white hairs
at base of wing creating gray appearance in this area; apex very lightly overscaled
with white just inside fringe. Spot 1 (cell spot) dark yellow. Spots 2,3 and 4 (subapical
spots) elongated, bottom two light yellow in color and top one white. Spots 5
and 6 (submarginal spots) dark yellow, rectangular, with spot 6 approximately
twice as long as spot 5 and connecting with spot 1 by thin, dark yellow line
*Present address: 4315 West Las Palmaritas, Glendale, Arizona
Figs. 1-6, adults of Megathymus ursus desert, new subspecies. 1,
Holotype 9, upper surface; ARIZONA: Maricopa Co.: 1/2 1 1/2 mi. N. Camp
Creek on road to Seven Springs, 3500-3680 ft., 4 June 1971. 2, same specimen,
under surface. 3, Allotype 6, upper surface; same locality, 5 June 1971. 4,
same specimen, under surface. 5, dwarf Paratype S, upper surface; same
locality, 12 May 1971. 6, same specimen, under surface.
along vein M3. Discal band composed of spots 7, 8 and 9 dark yellow. Spots
7 and 8 of approximately equal width and wider than 9. Spots 5, 6, 7, 8 and 9 toothed
very slightly along outer edge. Fringe smoky, checkered at apex.
Upper surface of secondaries: dark, shiny black with small amount of white
hairs at base creating gray appearance in this area. Two narrow yellow spots,
at spots 11 and 12, with spot 11 more prominent than 12. Fringe smoky from anal
angle to outer margin, becoming white with vein tips black at outer margin.
Under surface of primaries: black with tip and outer margin overscaled with
white to vein Cul giving that area gray appearance. All dorsal spots reappearing.
Spots 1, 7, 8 and 9 dark yellow. Spots 2, 3 and 4 white. Spots 5 and 6 light yellow.
Spot 9 (bottom spot) extending inwardly to barely beyond inner edge of spot 7.
Spots gray-centered, ringed with black in cells M2 through Cu2, white-centered
in cell 1A. Costal area heavily overscaled with white and containing two white spots.
Under surface of secondaries: black overscaled with white; white
overscaling confined to limbal area, not invading cell, creating distinct, wide, gray
postmedian-submarginal band following curve of outer margin from anal
margin to vein Rs; outer edge of band curving to meet fringe at vein M3. Veins not
overscaled with white, contrasting with band. Faint postmedian spot band
following curve of outer margin;
Length of forewing 37 mm to 41 mm, average 38.2 mm; measurements of
Holotype: forewing, apex to base 38 mm, apex to outer angle 26mm, outer
angle to base 27 mm; hindwing, base to end of vein Cul 24 mm.
Male: Head: front and paraocular area black; vertex gray. Antenna:
shaft white; base black dorsally; tip black. Palpus: very light gray. Thorax: gray
above; blackish below. Abdomen: Black dorsally and ventrally; light gray latero-
Upper surface of primaries: dark black, with small amount of white
hairs at base of wing creating gray appearance in this area; apex very lightly
overscaled with white just inside fringe. Spot 1 (cell spot) usually twinned, light
yellow. Spots 2, 3 and 4 (subapical spots) elongated, top two white in color
and bottom one light yellow. Spots 5 and 6 (submarginal spots) dark yellow, spot 5
one-half or less width of spot 6 and deeply concave outwardly; spot 6
extending inwardly along vein M3 to inner edge of spot 7. Discal band dark yellow,
composed of spots 7, 8 and 9. Spot 7 slightly wider than spot 8, both spots
rectangular. Spot 9 extending inwardly of spots 7 and 8 sharply pointed basally,
concave distally. Spots 5, 6, 7, 8 and 9 toothed slightly along outer edge. Fringe
at apex checkered smoky black and white, checkering usually not extending
caudad of vein Cul; remainder of fringe smoky black to inner angle with thin line
of gray at bases of fringe scales.
Upper surface of secondaries: dark black with small amount of white
hairs at base creating gray appearance in this area; discal area with small
amount of yellow-gray scaling intermixed distally, outer angle lighter due to
presence of heavier yellow-gray overscaling. Fringe smoky at anal angle, light gray
at outer margin, becoming whiter at outer angle; vein tips black at outer margin.
Under surface of primaries: black with tip and outer margin overscaled with
white to vein Ms giving that area gray appearance. Discal area with yellow
scaling intermixed with black giving that area brownish color. All dorsal spots
reappearing. Spot 1 white, cephalad; yellow, caudad. Spot 5 one-third width of
spot 6, deeply concave outwardly, white. Spot 6 light yellow. Spots 7, 8 and 9
dark yellow; spot 9 extending inwardly of spots 7 and 8.
Under surface of secondaries: black, heavily overscaled with white in
limbal area, white overscaling not invading cell, creating distinct, wide, light
gray postmedian-submarginal band following curve of outer margin from anal angle
to vein MI; outer edge of band curving to meet fringe at vein M3; veins not
overscaled with white, contrasting with band. Heavy overscaling of white in
anal angle and in cell M2 producing distinct quadrate submarginal spot con-
tasting with band and distinct white discal spot in cell 1A. Costal area heavily
overscaled with white and containing two white spots.
Length of forewing 30 mm to 33 mm, average 31.5 mm; measurements of
Allotype: forewing, apex to base 32 mm, apex to outer angle 20 mm, outer
angle to base 23 mm; hindwing, base to end of vein Cu, 19 mm. Preceding 6
forewing lengths based on ten normal-sized individuals. The following wing
measurements are those of one dwarf 8 included in the type series: forewing,
apex to base 24 mm, apex to outer angle 15 mm, outer angle to base 16 mm;
hindwing, base to end of vein Cu1 13 mm.
Holotype 9, and Allotype 6: Arizona, Maricopa County, 1/2 1-1/2 miles
north of Camp Creek on road to Seven Springs, 3500-3680 feet elevation
(Figs. 1 4). Described from 18 specimens (11 males and seven females) collected in
the larval stage by Ronald S., Joseph R. and Dale Wielgus from November 23
to January 30, 1969, 1970 and 1972, from the following localities: 9 a and 7 9,
same locality as Holotype and Allotype; two 8, 11.5 road miles southeast of the
Camp Verde Ranger Station, along Fossil Creek Road (FH9), T13N, R6E,
Yavapai County, Coconino National Forest, Arizona, at an elevation of 4000
feet. Specimens emerged in confinement from 12 May to 20 July, 1970, 1971
and 1972. Holotype 9, 4 June 1971, and Allotype 6, 5 June 1971, will be deposited
in the Los Angeles County Museum of Natural History. Paratypes will be
distributed as follows: one a to the Los Angeles County Museum of Natural
History; one a and one 9 to Mr. Don B. Stallings, Caldwell, Kansas; two a and
two 9 to the American Museum of Natural History; two S and two 9 to the
Allyn Museum of Entomology, Sarasota, Florida; one a and one 9 to the United
States National Museum; the remainder, three a and one 9, will remain in the collec-
tion of the senior author. The larval skins, pupal cases and larval tents are
hereby made a part of the type series.
Foodplant: Yucca baccata Torrey.
The characteristics which distinguish desert from typical ursus are
most evident in desert females. Principally, these are the narrow yellow spots at
spots 11 and 12 on the upper surface of the secondaries and the distinct, wide,
gray postmedian-submarginal band on the under surface of the secondaries. In typical
ursus females, the upper surface of the secondaries is immaculate, rarely marked, and
the white overscaling on the under surface is lightly and evenly distributed
and does not present the appearance of a band. Male specimens of desert are
distinct from typical ursus in having spots 7, 8 and 9 slightly lighter on the
upper surface of the primaries, and in the heavier white overscaling and the
contrasting white, quadrate submarginal spot in cell M2 on the under surface of the
This subspecies was first encountered in December 1969 during the course
of collecting larvae of Megathymus coloradensis navajo Skinner (Wielgus,
op. cit.), which also utilizes Y. baccata as a larval foodplant in this location.
Initially, we were unable to distinguish the first two collected desert larvae from
those of navajo and were not aware of their existence until after the navajo
adults had emerged in February and March of 1970. The two desert larvae continued
to feed beyond the time expected for navajo larval maturation and, still not aware
that these were not navajo, we were at a loss to explain such seemingly unortho-
dox behavior. One of the desert larvae, moulting to final instar on 14 May 1970, fed
until June 1970, whereupon it constructed a loose, silken closure over the tent open-
ing and very heavily powdered its burrow. Pupation followed on 13 June 1970,
and eclosion of an adult female occurred on 5 July 1970. The other pupa closed a
female on 20 July 1970.
Additional field collecting at the type locality in November and December
of 1970, and January 1972, has revealed that desert larvae generally occur in
small to medium-sized baccata plants growing in deep shade under juniper
trees (Juniperus monosperma [Engelmann] Sargent). In contrast, navajo here
prefers open, sunny situations with a tendency to slopes with a southern
exposure, but is also found in similar-sized baccata plants. The area is one of
relatively steep, dry hills in the Upper Sonoran Zone (Merriam, 1898), 3400
- 4000 feet elevation, with dry washes estending west to east (Fig. 7). In this area,
Y. baccata grows abundantly in a strip approximately 1/2 mile wide and is roughly
bisected by the north-south road (Fig. 12). Daily summer temperatures exceeding
1000 F. are common here throughout the months of June, July and August.
At the time of year that we collected larvae, desert larval tents appeared
similar to those of navajo but their burrows were unpowdered. Larval frass
was generally smaller than that of navajo and was frequently incorporated in
of type-locality. 8, third instar larva. 9, dwarf pupa. 10, normal-sized pupa
.i .'-. .. .. ..
Figs. 7-11, Megathymus ursus desert, new subspecies. 7, habitat photo
of type-locality. 8, third instar larva. 9, dwarf a pupa. 10, normal-sized 3 pupa
of M. u. ursus Poling. 1, normal-sized pupae of M. u. desert, scale graduation
the tent along with a resinous-appearing substance. In some cases, a leaf
showed evidence of earlier larval feeding; excavation in the upper leaf surface
and along the margin could be traced downward to the tent. This seems to lend support
to our belief that the first instar larva feeds first upon the leaf prior to entering
the caudex. In contrast, we have found many Y. schottii plants containing typical
ursus larvae with the eggshell still attached to a leaf, and we have never seen
any evidence to indicate earlier feeding on the leaf. First instar larvae of
typical ursus apparently bore directly into the caudex shortly after hatching.
We inspected several desert larvae in the field by pulling off the tents and
vigorously shaking them out. Those inspected appeared to be third instar and had
piceous black head capsules, cervical shields and anal plates. These larvae were
of a creamy, yellowish-white color, lightly clothed with fine black setae and were
unpowdered (Fig. 8), in contrast to the well-powdered navajo larvae. It was
by these larval characteristics that we were able to distinguish desert larvae from
those of navajo.
In the middle of January of 1971 the desert larvae were brought indoors,
along with the navajo larvae, and kept at room temperature. All Yucca plants con-
taining desert larvae had been previously bagged in polyethylene plastic
bags in December of 1970 in order to conserve plant moisture. In the case of small
plants the caudices were, in addition to bagging, wrapped first with aluminum
foil. All plants were subsequently rebagged but were first encased in damp pine
sawdust, the foil having been removed before encasement. The plastic bag was tied
tightly to the neck of the plant leaving the larval tent exposed. At the time of
rebagging a few plants were deemed to be too small to provide sustenance and retain
sufficient moisture, even with a damp sawdust encasement, throughout larvae
development. In these cases, we transferred the desert larvae to larger baccata
caudices from which we had recently removed navajo pupae. Care was taken to insure
the removal of exuviae, powder and other debris from the vacated burrows
prior to the transfer. Each transferred larva accepted its new quarters and
fashioned a new silken closure over the opening. Within 48 hours each
transferred larva had commenced feeding. During the entire remaining larval
period of approximately four months the plants containing the larvae were
maintained at room temperature and no additional water was added to the
still sufficiently damp sawdust. This rearing technique was also used with
typical ursus larvae, omitting only the transfer method, and was sufficient
for the additional month required for larval development.
On 24 January 1971, a comparison was made between desert larvae and
fifteen typical ursus larvae which had been collected in Y. schottii on 23
January 1971 from Peppersauce Canyon, 5600-6000 feet elevation, Santa
Catalina Mountains, Pinal County, Arizona. Except for the fact that the desert
larvae were almost a full instar ahead of the typical ursus, all were similar
From 31 January to 8 February 1971, one desert larva was observed in the
process of moulting. It did not feed during this period. We were acutely apprehensive
at first, upon noticing this cessation of feeding for such an extended period of
time, until we became aware of its significance. This larva remained relatively
quiescent for five days, in a head-downward position, with only occasional movements
up and down its burrow. At the commencement of moulting, the larva backed
up to the burrow entrance, anchored its caudal prolegs in the silken lining,
and began to contract rhythmically. Each contraction began at the first
thoracic segment and proceeded wavelike to the anal segment. This process
continued for several hours until the old larval skin parted at the cervical shield
and midcranial suture. The larva then proceeded literally to walk out of its skin which
remained anchored to the burrow wall. The entire larval color immediately after
moulting is a creamy white, the areas destined to be black being only slightly
darker. It took another three days before full larval coloration was assumed
and feeding commenced. This larva appeared to have entered the fourth instar
and, though now larger, was colored and marked virtually the same as the others.
Later observations of the other desert and typical ursus larvae have confirmed that
there is a span of at least eight days during the moulting period in which the larva
does not feed.
Fig. 12, topographic plan of type-locality of Megathymus ursus desert,
new subspecies (adapted from U. S. G. S. Humboldt Mtn., Ariz. quadrangle, 1: 24000)
Sites yielding desert in 1970 are indicated by arrows. Numerals in circles
indicate number of larvae collected at each site.
Our limited'observations of the habits of desert larvae did not suggest
an explanation for the prolonged larval development characteristic of members
of this genus. We did note the rather casual manner of the larvae throughout
their remaining larval period. In general, they appeared to spend approximately
one-third of the time simply resting with very little moving about, one-third enlarging
or rebuilding their tents and only the remaining one-third of the time in actual
feeding (as evidenced by the expelling of frass). It must be borne in mind,
however, that these observations were made on larvae maintained at room
temperature indoors and thus do not necessarily apply to larvae under field
conditions. We do believe, however, that rearing the larvae indoors at room
temperature had the effect of accelerating larval development in spite of their
apparently limited feeding habits. Emergences of one typical male ursus on 10 May
1971 and one male desert on 12 May 1971 lend support to this belief. With only
two exceptions, the desert larvae were also observed to initiate powdering of
their burrows well in advance of pupation; secretion of the powdery substance
from the abdominal glands was noted to begin discretely three to five weeks
prior to transformation of the larvae. This is in marked contrast to previously
recorded observations on typical ursus larvae by other (Stallings and Turner, op.
cit.). The two larvae noted as the exceptions pupated without ever having powdered
up and one produced a dwarf male on 12 May 1971. The other pupa, also a dwarf,
died prior to eclosion.
We noted that after larval feeding terminates a period of quiescence initiates,
with larval activity virtually ceasing approximately ten days prior to pupation.
In the advanced quiescent stage, the larva continues to secrete the white
powdery substance. Its appearance one day prior to transformation is that of having
been heavily coated with powdered sugar. In most instances the larva will, at this time,
remain with its head at the tent closure. At the initiation of transformation,
the larva generally drops to the bottom of its burrow. The newly formed pupa
remains there until its integument hardens and darkens. The color of the pupa is a
light amber immediately following the casting off of the larval skin. During the
pupal period, the pupa usually moves up and down the burrow, propelling
itself by rotating the end of its abdomen in a circle. Pupal duration at constant 80
degrees Fahrenheit was 22 26 days.
Measurements were taken of four desert pupae, all males, two of
which produced normal-sized individuals, the others being dwarfs. One of
the dwarfs, as noted earlier, died prior to eclosion. The noraml-sized pupae
measured 46 mm and 48 mm in length and 10 mm and 10.5 mm in width,
respectively. The dwarf pupae measured 35 mm and 30 mm in length and 8mm
and 7.5 mm in width, respectively. The figures illustrate a dwarf desert
pupa and three normal-sized desert pupae. For comparison, a normal-sized male
pupa of typical ursus is figured at the same relative scale (Figs. 9 11).
We have not bee able to ascertain the limits of distribution of desert.
On 30 January 1972 the authors discovered two desert larvae feeding on
Y. baccata plants which were in a colony growing on a steep slope approximately
40 airline miles north and slightly east of the type locality. This is the Fossil
Creek Road locality cited earlier. In the locality, both desert and navajo utilize
baccata as the larval foodplant. However, as they also occur at the type
locality, the desert larvae were found in baccata plants growing under the
junipers. On this date, the desert larvae appeared to be late third or early
fourth instar, unpowdered, whereas all the navajo collected concurrently were
pupae. Earlier, on 9 January 1972, the senior author collected three desert larvae in
baccata plants growing under junipers at the type locality. We believe that
these findings afford significant clues to the distribution and habits of desert,
and appear to support our belief that desert will be found in association with
navajo in favorable juniper woodland situations throughout central Arizona.
Such appears to be the case for, on 5 February 1972, the authors found year-old
larval tents and pupal cases in baccata plants growing under junipers on the
steep slopes of Thirteen Mile Rock, 13 miles southeast of Camp Verde, Yavapai
County, Arizona. This locality is slightly north and east of the Fossil Creek Road
one but the habitat is similar.
We also strongly suspect that desert occurs on the lower slopes of
Pinal Peak, Gila County, at about 4000-5000 feet elevation where baccata
grows in the pine forest (Pinus ponderosa Laws.). Support for this suspicion
is based on the finding in 1970 of a year-old larval tent in a baccata plant
growing in this locality; the diameter of the burrow was equivalent to those
made by desert larvae and allowed the senior author to insert his right index
finger into the opening comfortably. He has not been able to do this with the
burrow openings of navajo as they are considerably smaller in diameter. There is a
remarkable similarity between this locality and the one in Peppersauce Canyon
and we feel that concentrated field efforts here may yet turn up desert
though probably not typical ursus, this conclusion being based on our previous
experience with the distribution of navajo. It is our belief that a distinct break
between the northern and southern faunal and floral elements of Arizona
takes place just to the south of Pinal Peak, probably at the natural division
established by the Gila River drainage. This belief is supported in part by
Kearney and Peebles (1960). The estimated range of desert, and other ursus
subspecies, is indicated on Figure 13.
The adult flight period in the field has not been determined. However,
in allowing for a certain amount of larval advancementin the laboratory, we suppose
A I Z O N A N EW M I CO
Srange? V i oI'ae-
PROVINCE T 1 Legend:
recor-B PM.u .ursus
range? ---0 vioae
NA desert i
Fig. 13, distribution of the known subspecies of Megathymus ursus.
Shading indicates estimated ranges; solid figures denote known collection records.
that the normal time for desert adults in the field is from the middle of June
through the end of July.
Several intensive collecting efforts at the type locality in late 1970,
totalling approximately 126 man-hours, yielded only 14 desert larvae (one died of
parasitism in February 1971) in comparison to 80 navajo larvae collected
concurrently. In view of this, and because of its competition with navajo for the
same foodplant in highly localized situations, we believe the desert will remain ex-
tremely rare in collections.
The authors especially wish to thank Mr. Don B. Stallings for generously
devoting time and effort to examine desert specimens and offer valuable
comments and encouragement.
Thanks are also due to Mr. Lloyd M. Martin, Prescott, Arizona, for
examining specimens and giving helpful information. To Dr. Frank F. Hasbrouck,
Associate Professor of Zoology and Curator of Insects, Artizona State
University, Tempe, Arizona, our warmest appreciation for critically reviewing
We also wish to thank the following persons for their helpful cooperation
in granting collecting permits to remove ursus-infested Yucca for comparative
studies: Mr. David G. Stimson, Superintendent, Chiricahua National Monument,
Arizona; Mr. S. R. Albert, District Ranger, Douglas Ranger District, Coronado
National Forest, Arizona; and Mr. R. A. Countryman, Chief, Division of Compliance,
Arizona Commission of Agriculture and Horticulture. Mr. Michael Banville of
Phoenix, Arizona, photographed the desert larva; all other photographs by the
senior author. Foodplant determinations were made by Mr. John Weber,
Horticulturist, Desert Botanical Garden, Papago Park, Phoenix, Arizona.
We sincerely appreciate the generosity of Dr. Lee D. Miller and Mr.
A. C. Allyn for making this publication possible and to them we extend
our heartfelt thanks.
dos Passos, C. F., 1964. A synonymic list of the Nearctic Rhopalocera. Lepid.
Soc. Mem., No. 1, New Haven, Conn. v + 145 pp.
Freeman, H. A., 1969. Systematic review of the Megathymidae. J. Lep. Soc.,
23, Supplement 1, 58 pp., 1 pl.
Kearney, T. H., and R. H. Peebles, 1960. Arizona Flora. University of California
Press, Berkeley. 1085 pp.
Merriam, C. Hart, 1898. Life zones and crop zones of the United States. U. S.
Dept. Agric., Div. Biol. Surv. Bull. No. 10, 79 pp.
Stallings, Don B., and J. R. Turner, 1956. Notes on Megathymus ursus, with
description of a related new species. Lepid. News, 10: 1-8.
Wielgus, Ronald S., Joseph R. and Dale, 1970 (1971). Additional notes on the
distribution and foodplant preferences of Megathymus coloradensis
navajo Skinner. J. Res. Lepid. 9(3):169-174.
The following information was received after the paper was in press: quoting
Ronald Wielgus, "On this day, the 21st of November, we confirmed the existence of
ursus desert at the Thirteen Mile Rock locality cited in our paper by collecting four
viable fourth-instar larvae feeding in Yucca baccata on the steep slopes. We also took
out eight well-powdered navajo larvae concurrently. Three of the desert larvae were
in very small caudices and will ultimately have to be transferred to larger ones. Field
recognition of desert [larvae] is easier now inasmuch as their burrows are unpowder-
ed, tents are smaller and the larvae distinct from navajo. We inspect all larvae by
pulling off the tents and peering into the burrows, using sunlight to illuminate the
larvae at the bottom." Ed.