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vv POSTILLA

UNversig PEABODY MUSEUM
YALE UNIVERSITY

NUMBER 162 30 AUGUST 1973

DESCRIPTION OF IMMATURE STAGES OF
PHILOLITHUS DENSICOLLIS AND STENO-
MORPHA PUNCTICOLLIS WITH NOTES ON
THEIR BIOLOGY (COLEOPTERA, TENEBRI-
ONIDAE, TENTYRIINAE)

KIRBY W. BROWN

POSTILLA

Published by the Peabody Museum of Natural History, Yale University

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DESCRIPTION OF IMMATURE STAGES OF PHILOLITHUS DENSICOL-
LIS AND STENOMORPHA PUNCTICOLLIS WITH NOTES ON THEIR
BIOLOGY (COLEOPTERA, TENEBRIONIDAE, TENTYRIINAE).

KIRBY W. BROWN

Peabody Museum of Natural History
Yale University, New Haven, Connecticut 06520

(Received 2 August 1972)

ABSTRACT

Mature larvae of the tribe Asidini are characterized by an unsclerotized
body, dorsally concave mandibles with preapical gibbosity and submarginal
setose area, granulate cranium, swollen preepipleurum, and huge granulate
forelegs with contiguous coxae surrounded by an enlarged sternellum. The
pygidial terminus is rounded in Philolithus densicollis (Horn) and _ bifur-
cate in Stenomorpha_ puncticollis (eConte). First-instar larvae lack
granules on cranium and forelegs, have 2 setae on the labrum, possess egg
bursters, and are very similar in both species. Eggs are large, averaging 2.5
mm in length in P. densicollis and 3.1 mm in S. puncticollis. Pupae are not
known. The two species are sympatric in eastern Washington state. Adults
occur in autumn, living only one month. A female deposits about | egg
per day. Eggs of P. densicollis hatch quickly and the first winter is passed
in an early larval stage. Eggs of S. puncticollis apparently overwinter and
hatch in early spring. The full life cycle probably takes two years. Cold
temperature of the second winter breaks a developmental diapause and
leads to adult eclosion the following autumn; S. puncticollis emerges some-
what later than P. densicollis. The prolonged immature phase as a sub-
terranean scavenger is seen as a major adaptation to xeric environments.

EOSTILEA 162: 28p. 30 AUGUST 1973

2 POSTILLA 162

INTRODUCTION

Up to the present time there have appeared no descriptions of the imma-
ture stages of any North American species in the tenebrionid tribe Asidini.
The only significant information on the biology of any of these beetles has
come from ecological studies at the Hanford Reservation, Washington
(Rickard and Haverfield, 1965; Rickard, 1970; Hinds and Rickard, 1973),
and at the Nevada Test Site (Tanner and Packham, 1965).

In the process of conducting systematic studies of the tribe Asidini
(Brown, 1971), I have reared immature stages of many species, with the
intention of describing them all together in a single monograph. However,
completion of that project is several years away. As there are active eco-
logical studies being conducted at the Hanford Reservation, it is im-
portant to make available the findings of life history studies pertinent to
that region. Also there is current interest in the higher classification of the
Tenebrionoidea with much attention focused on larvae, lending additional
importance to the prompt dissemination of information on the morphology
of immature Asidini.

Philolithus densicollis (Horn) and Stenomorpha puncticollis (eConte)
are the dominant ground-dwelling beetles found in southeastern Washing-
ton in autumn (Rickard, 1970). Both species were redescribed and _ illus-
trated (adults) by Boddy (1965). Brown (1971) transferred P. densicollis
from Pelecyphorus Solier to Philolithus Lacordaire.

On 11 October 1968 I received living adults of both species from Dr. W.
H. Rickard of the Battelle Pacific Northwest Laboratories, which he had
removed from pit traps at the Hanford Reservation near Richland, Wash-
ington, on 5 October 1968. The following information is based on studies

of those insects, supplemented by observations of other species of
Philolithus and Stenomorpha.

MATERIALS AND METHODS

Upon receipt, the living adults were sexed. The male has the apical seg-
ment of the maxillary palpus larger than that of the female (Brown, 1971),
a feature that is reasonably easy to see in living specimens. Each female
was given a number and placed in a separate container. About half the
females each had a single male; the rest were alone.

The culture containers consisted of standard 16 oz. (.475 1) plastic
‘ood containers with about 20 mm of sand that had been washed and
passed through a U.S. Standard No. 30 sieve (590-micron opening). The
pectles were fed lettuce and ground-up chicken feed. The sand was
‘d periodically to stimulate oviposition.

IMMATURE PHILOLITHUS AND STENOMORPHA 3

On approximately 5-day intervals, the cultures were checked and adult
mortality recorded. When any female died, the culture was checked for
eggs. After the first 10 days all cultures were checked for eggs.

Eggs were recovered by passing the substrate sand successfully through
U.S. Standard No. 20 (841 micron opening) and No. 30 sieves. Virtually
all eggs were caught on the No. 20 sieve. Eggs were picked up singly with
a small, dampened camel-hair brush.

The eggs were incubated in 60 mm by 15 mm covered plastic petri
dishes. These were maintained in a moisture saturated environment by
placing the dishes on a wire rack over water in plastic shoe boxes which
were kept in a controlled temperature room at 70 F (21.1 C). The dishes
were checked at intervals ranging from 4 to 7 days and the following series
of data recorded; number of viable eggs (creamy color), number of dead
eggs (brown color), number of first-instar larvae, and number of second-
instar larvae. The number of larvae removed for preservation or culturing
was also noted.

The larvae are actively cannibalistic, and attempts at mass rearing were
not successful. Two rearing methods were used. The first requires little atten-
tion and is ideal for long-term rearing of asidine larvae when periodic
checks for exuviae are not needed. The container consists of a common
8 oz (.238 1) clear plastic, disposable cold-drink cup. About 15 mm of
plaster of paris containing 10 percent powdered charcoal by volume is
poured in and a section of plastic Tygon tubing, one-half inch (12.7 mm)
inside diameter inserted into the center of the fresh plaster. This serves
as a watering tube. After the plaster hardens, a thin layer of plain sand is
added, the larva placed on the sand, and the cup filled about half way with
a sand-and-food mixture. This arrangement requires watering about once
a week, and changing of food every three to four months. It offers the
larva a moisture gradient similar to its natural habitat.

The second method used in this study was a modification of Wade and
St. George’s (1923) salve boxes as developed by R. E. Somerby (1972). It
consists of a round plastic box 45 mm in diameter and 15 mm deep with
a 5 mm layer of the plaster-of-paris and charcoal mixture. The tight-fitting
lid has a 15 mm round hole covered with fine nylon netting. The plaster-
of-paris is saturated with water, a thin layer of sand added, the larva
placed on the sand, and covered with a sand-and-food mixture. The sand
must be changed about once a week.

For the present study the sand used was river sand that had been washed,
passed through a No. 30 sieve (590-micron opening), and sterilized. The
food was common chicken feed that was ground up, passed through the
No. 30 sieve, and sterilized. No effort was made to define a diet. Larvae
have also been reared on ground-up rabbit pellets, oatmeal, alfalfa, or dry
dog food. The food was mixed homogeneously with sand at a ratio of 10
parts sand to | part food by volume.

The first larvae were cultured on 14 November 1968. Rearing was termi-

4 POSTILLA 162

nated on 25 March 1969 because I was leaving Riverside, California
where the work was being carried out. Larvae were killed and fixed in
van Emden’s solution (Emden, 1942), and later transferred to 80% ethyl
alcohol with 4% glycerine.

Drawings of fresh eggs were made with an AO Spencer stereoscopic
microscope with 2X objectives and a 10 mm grid with | mm squares in the
10X eyepiece. Overall views of larvae were drawn from specimens in
alcohol. The labium, maxillae, and epipharynx were dissected from alcohol
specimens and dry exuviae. A No. 2 insect pin with the point beaten flat
and honed on a whetstone was used as a scalpel. This instrument was found
superior to those commercially available for such minute dissections. Draw-
ings were made by the author using a Wild M-5 stereoscopic microscope
with drawing tube. The scale was drawn from a stage micrometer.

The terminology is based on that of Wade and St. George (1923). The
descriptive sequence follows that of Spilman (1963).

The primary specimens and voucher adults are deposited in the Peabody
Museum of Natural History, Yale University. Additional specimens will
be deposited in the United States National Museum, Battelle Pacific North-
west Laboratories, and in the collection of the author.

DESCRIPTIONS

Tribe Asidini

MATURE LARVA. Body elongate, straight, weakly moniliform and semi-
cylindrical dorsally (Figs. 2A, 5A), relatively flattened ventrally; generally
unsclerotized except for mandibles, claws, and urogomphi; overall color
creamy white to yellowish.

Head prognathus, golden brown in color, covered dorsally with darker,
globular granules, at least on anterior half; setae short and sparse dorsally,
becoming longer and denser laterally and ventrally. Apparently four poorly
defined ocelli present. Clypeus transverse, united with frons, but set off by
a deep sulcus (Fig. 1C, c); density of granules on clypeus equal to or
exceeding density on frons. Labrum (Figs. 3C, 5C) emarginate and densely
setose apically, with a median transverse band of flattened, spinose setae;
sclerotized only on basal third and connected to clypeus by a broad, un-
sclerotized membrane. Epipharynx (Figs. 3D, 6D) with dense midlateral
series of prostrate spinose setae facing medioposteriorly. Antenna (Figs.

\, 6A) glabrous, arising from a fleshy swelling near ventral fossa of

total length about two thirds that of mandible; first and second
ider but each slightly swollen apically, the first longer than
-ement minute, set in center of flattened apex of second

a single terminal seta. Mandible (Figs. 3A, 6A)

IMMATURE PHILOLITHUS AND STENOMORPHA 5

bidentate, strongly developed and darkly sclerotized especially at apex and
mola; distinctly concave dorsally, convex ventrally; lateral margin cari-
nate, broadly expanded, with a preapical gibbosity (Fig. 3A, pg), usually
more prominent on right mandible; dorsal margin between apex and mola
sometimes with a small gibbosity or tooth on right mandible, occasionally
on left (Fig. 6A, t3); submargin of mandible ventrally with an elongate,
membranous area densely packed with long setae; mola relatively flat.
Maxilla (Figs. 3B, 6B) with mala and stipes fused, bearing numerous long
setae; mala reaching to about apex of mandibles, bearing on inner margin
a double row of stout, pointed, recurved spines, becoming longer at apex
of mala; palpus slender, three segmented; cardo flattened, transverse; articu-
lating area swollen and prominent. Submentum and gula appear fused with
cranium, sutures often not visible; setae numerous and long. Labium (Figs.
1C, 3B, 6B) slightly shorter than maxillae, bearing numerous long setae;
mentum barrel shaped, slightly longer than wide; prementum smaller, trape-
zoidal, connected to mentum by a broad, glabrous membrane; ligula a
single median apical projection; palpi two segmented, the second segment
slightly smaller and narrower than the first. Hypopharynx with a large
irregular fleshy lobe (Fig. 1C, h) bearing numerous setae directed toward
pharynx (p); hypopharyngeal sclerome (hs) strongly sclerotized and tooth-
like, partially embedded in fleshy tissue of hypopharynx but remaining
firmly attached to cranium by the hypopharyngeal bracon when maxillae
and labium are removed; hypopharyngeal bracon (Figs. 3A, 6A) in two
parts, the lateral part integrated with cranium in region of ventral mandi-
bular fossa, the median part bearing the sclerome separated from the
lateral part by a distinct membranous area.

Prothorax with sparse, fine setae dorsally; tergum semicylindrical, wider
than long, and longer than meso- or metathorax; usually with a pigmented
anterior border and narrower posterior border; sternum (Fig. 1A) with
eusternum, prehypopleurum and preepipleurum fused into a single collar-
like unit; preepipleurum swollen, visible from above, completely separated
from epipleurum, and set off from prehypopleurum by a deep sulcus;
epipleur'um fused with prothoracic tergum, lacking any visible suture;
sternellum (articulating membrane of Schulze, 1962) greatly developed,
swollen and shaped somewhat as a quarter sphere, almost surrounding
coxae, and bearing scattered short, stiff setae on basal area. Mesothorax
shorter than all other segments, widest in middle, with scattered, fine, short
setae dorsally, and more numerous, long setae ventrally; sternum with
eusternum and sternellum fused into a lumpy swollen central mass, bor-
dered laterally by the folded epipleurum; preepipleurum bearing very large,
elliptical first thoracic spiracle, which is deeply sunken and almost hidden
by protruding sternal tissue. Metathorax similar to mesothorax, but longer,
and from above more nearly resembling abdominal segments. Second
thoracic spiracle much smaller than first spiracle, borne on preepipleurum
and usually hidden.

6 POSTILLA 162

ab

0 Een
OU Fi

FIG. 1. Larval morphology of generalized Asidini: A) sternum of prothorax
and part of mesothorax, legs removed; B) terminal abdominal segments, lateral
view; C) lateral view of head with right mandible, maxilla, and part of
cranium removed (jagged line); D-F) Philolithus densicollis, outline of hypo-
pharyngeal sclerome of 3 specimens to show variation; D) right, lateral view
(orientation of 1C); E) ventral view (aboral side facing viewer, see Fig. 3A);
F) apical view (aboral side at bottom of drawing); G-I) Stenomorpha puncticol-
lis, outline of hypopharyngeal sclerome; G) right, lateral view; H) ventral view

(see Fig. 6A); I) apical view. Terminology: a = anus; am = articulating mem-
brane; c = clypeus; cx = coxa; e] = prothoracic epipleurum; e2 — mesothoracic
epipleurum; ep = epipharynx; ew = eusternum; fh = hypopharynx; hb =
hypopharyngeal bracon; hs = hypopharyngeal sclerome; /i = labium; Ir

labrum; oe = oesophagus; p = pharynx; pe = preepipleurum; peu
— precusternal subdivision of eusternum; ph = prehypopleurum; pfp =
preterminal pseudopod; py = pygopod; sp = Ist thoracic spiracle; st/
— Sternellum; wu = urogomphus; vm = ventral margin of pygidium;
95 2th abdominal sternum; 9T = 9th abdominal tergum (pygidium); /0

10th abdominal segment.

IMMATURE PHILOLITHUS AND STENOMORPHA if

Abdominal segments 1 to 7 very similar in size and shape; each widest
in middle, convex laterally in dorsal view and slightly wider than long
(Figs. 2A, SA); dorsum generally glabrous, but setae present laterally and
ventrally; spiracles elliptical, located laterodorsally, about one-sixth seg-
ment length behind anterior base (Figs. 2B, 5B), with a single nearby
seta dorsad; a small oblique sclerotized stigma located in approximately
the same plane but about one-fifth segment length ahead of posterior base,
with a single seta directly anterior; sternum undifferentiated except for
lateral fold of epipleurum, more flattened than the evenly convex dorsum,
but may be swollen and protruding in turgid specimens. Abdominal seg-
ment 8 similar to preceding but more abruptly widened laterally, and with
dorsal setae more. evident, especially posteriorly. Abdominal segment 9
varying from a rounded (Fig. 2A) to deeply bifurcate terminus (Fig. 5A);
urogomphi weak to well developed; dorsum variously armed with stout
spines and setae; sternum about half the length of tergum and bearing a
ventrolateral swelling (preterminal pseudopod, Fig. 1B, ptp) armed with
several stout spines. Abdominal segment 10 with distinct lobed, but not
elongate pygopodia (py), variously armed with stout spines; anus dorsal
to pygopodia and located between their bases, surrounded by four broadly
joined papillae generally forming a circle. United ninth sternum and tenth
segment retractile into a cavity in ninth tergum (Fig. 2C) and joined to it
by a wide articulating membrane (Fig. 1B, am); tenth segment always
partially exposed and never enclosed by ninth sternum when retracted.

Prothoracic leg (Figs. 3E, 6E) greatly enlarged, almost twice the length,
and two to three times the girth of the other legs; coxa massive, left and
right coxae contiguous along a straight midline, partially to completely
concealed by sternellum (Fig. 1A, stl); trochanter conical, arising from
ventral surface of coxa, but appearing anterior because of normal position
of legs in preserved specimens, bearing numerous globular granules simi-
lar to those on head, becoming especially dense at apex; femur massive,
roughly triangular, arising on dorsoanterior portion of trochanter, with
similar granules, ventrally with a set of comb-like, thick, long setae ar-
ranged in an irregular row, and dorsally with numerous thinner, often
longer setae; tibia and tarsungulus immovably united, but divided into
three segments, the tibia, unsclerotized basal part of tarsungulus, and
strongly sclerotized claw; tibia often with large granules and with a single
ventral row of long thickened setae forming a comb extending onto un-
sclerotized base of claw, dorsally with numerous, irregularly placed, long,
thin setae; claw large, equal in length to trochanter, asymmetrical, curved
and strongly concave ventrally, convex dorsally, and blunt to sharply
pointed apically. Meso- and metathoracic legs much smaller, very similar
to each other; coxae separated by at least half of one coxal diameter, and
not concealed by sternellum, bearing scattered setae but no distinctive
spines; orientation of legs lateral rather than anterior; configuration of
trochanter, femur, tibia and tarsungulus similar to prothoracic legs except

8 POSTILLA 162

for smaller size and relatively more elongate members, the claw especially
thin; granules lacking but two irregular rows of thick spines present, one
posterior and one ventral, running from trochanter to tarsungulus, with
thinner and longer setae on other surfaces.

SECOND-INSTAR LARVA. Closely resembles mature larva in form, but with
fewer granules, setae and spines (Figs. 3F-K, 6F-H), and with antennae
relatively stouter.

FIRST-INSTAR LARVA. Differs from all other instars in the following char-
acters. Body compact, widest in middle (Figs. 4A, 7A), unsclerotized and
pale white in color except for tips of mandibles, claws, egg bursters, and
urogomphi.

Head surface faintly rugulose and lacking any granules (Figs. 4B, 7B).
Ocelli apparently four in number. Labrum bearing only two distinct
conical, spinose setae. Clypeus apparently lacking setae. Antenna relatively
broader than in later instars; second segment swollen, longer and broader
than first. Mandible lacking ventral membranous setose area, and bearing
a distinct conical spine near dorsal base.

Prothorax longer than other segments, lacking any pigmentation or
granulation; may or may not bear spine-like egg bursters. Mesothorax and
metathorax subequal, about two-thirds as long as prothorax; spine-like egg
bursters present dorsolaterally.

Abdominal segments 1 to 8 subequal, similar in length to meso- and
metathorax; body widest at about third or fourth abdominal segments;
spine-like egg bursters present dorsolaterally on all segments. Abdominal
segment 9 with terminus rounded to weakly emarginate; urogomphi small,
usually terminal; dorsal spines lacking; sternum with faint swelling in
position of preterminal pseudopod, spines lacking. Abdominal segment 10
lacking spines on pygopodia.

Prothoracic leg lacking granules, but with one to three distinct pig-
mented spines each on ventroposterior surface of trochanter, femur, and
tibia. Meso- and metathoracic legs with few faint, unpigmented spines.

EGG. Elongate elliptical, slightly narrower at one end than the other (Figs.
4C, 7C); width approximately one-third length, widest point slightly off
center toward blunt end; in cross section, outline forms a circle flattened
at one pole (Fig. 4D). Surface smooth and shiny, with no sculpturing
visible under dissecting microscope. Color creamy white when fresh,
becoming brownish yellow with age. Size relatively large, always greater

than 2 mm in length.

Ss. The above detailed description at the tribal level is testimony
sme uniformity of the larvae of North American Asidini that
n to date. The mature larvae can be briefly characterized by

IMMATURE PHILOLITHUS AND STENOMORPHA 9

the unsclerotized, fleshy appearing body, the dorsally concave mandibles
with preapical gibbosity and submarginal setose area, the pronounced
granulation of the cranium, the collar-like eusternum and swollen pre-
epipleurum, the huge granulate prothoracic legs with contiguous coxae
surrounded by the enlarged sternellum, the distinctly swollen and spinose
preterminal pseudopodia of the ninth abdominal sternum, and the lobed,
but not prolonged spinose pygopodia. This is based on examination of
larvae of the genera Astrotus LeConte, Philolithus Lacordaire, Gonasida
Casey, Glyptasida Casey, Pelecyphorus Solier, Asidina Casey, Trichiasida
Casey, Asidopsis Casey, Stethasida Casey, and Stenomorpha Solier (Brown,
unpublished); a representation sufficiently diverse that the addition of data
from other genera will probably not alter characterization in any sig-
nificant degree. Whether the Palearctic and African Asidini fit this picture
is unknown as yet. However, the illustration of posterior abdominal seg-
ments of Asida lutosa Solier from Russia (Ogloblin and Kolobova, 1927,
fig. 24) is very similar to the North American Asidini.

Descriptions of the other genera must await later monographic treat-
ment, but a brief discussion of the variation at the generic level may be
of value at this time. The first-instar larvae are so uniform that they are
very difficult to separate at the generic level. The only obvious variation
seen in later instars of the genera observed is the shape of the pygidium
and development of the urogomphi. The larvae fall into three main groups;
1) Astrotus, Philolithus, Gonasida, and Glyptasida with the pygidium
rounded posteriorly and the urogomphi very small; 2) Pelecyphorus, Asi-
dina, and Trichiasida with the pygidium emarginate to weakly bifurcate
posteriorly and with moderate-sized urogomphi; and 3) Asidopsis, Stetha-
sida, and Stenomorpha with the pygidium deeply bifurcate and the uro-
gomphi large.

Differentiation of genera and species within these three groups will be
difficult in most cases. Much further study is needed of the specimens on
hand before the problems can be resolved. For the purposes of this paper,
no attempt is made to distinguish generic from specific characters of Philo-
lithus densicollis and Stenomorpha puncticollis. These two species are
largely sympatric; no other species of Asidini occur in their ranges.

Morphological changes during the growth of the larvae add to the diffi-
culties in characterizing genera and species. The second through final
prepupal instars are very similar in general appearance, but differ in
quantitative characters such as number of setae, spines, granules, and of
course in overall size. As the larva grows larger, the surface area in-
creases, allowing an increase in number of spines, granules, etc. Also
there are more subtle changes with age; the bifurcation of the pygidium
becomes deeper, the antennae become thinner, and bald spots (areas de-
void of setae or granules) develop on the cranium and pygidium.

The higher classification of the family Tenebrionidae is in an unsettled
state. However there is a growing body of evidence from both adult and

10 POSTILLA 162

larval morphology that the family has two fundamental divisions, the
“tentyroid” and “tenebrioid” lines (Blaisdell, 1939; Koch, 1955; Kelejni-
kova, 1971; Doyen, 1972). However, there is little agreement as to the
subdivisions or ranks of the two lines. Doyen (1972) considers the two
lines to be of family rank (Tentyriidae and Tenebrionidae) whereas Watt
(1966, 1972) includes both lines within one family (Tenebrionidae). Fur-
ther study is needed, particularly of immature stages, before the con-
troversies can be settled. For the present, I am considering both lines as
belonging in one family, the Tenebrionidae, with the tentyroids constitu-
ting the subfamily Tentyriinae, and the tenebrioids divided into several
subfamilies as listed by Watt (1966) and including Alleculinae, Lagriinae
and Nilioninae as proposed by Doyen (1972) and Watt (1972).

The larvae described here confirm the placement of the Asidini in the
Tentyriinae. They also add significant information regarding characters of
importance in larval classification. Scopin (1964) emphasized the struc-
ture of the pygidium. He stated that urogomphi are always absent in
Tentyriinae (his ‘“Tentyromorpha” and ‘“Asidomorpha”). The larvae of
Stenomorpha have large urogomphi, the first such recorded case in the
Tentyriinae. This case indicates that the pygidium is a relatively poor
indicator of higher phyletic relationships in the Tenebrionidae. It points
out the difficulty of generalized descriptions of higher categories, such as
subfamily, based on few samples from limited parts of the world. However,
a general picture of larvae of Tentyriinae is emerging based on a scatter-
ing of American, European, and African material. The mandibles possess
a lateral strongly setose area that may be ventral, as in the Asidini, or
dorsal in other tribes as pointed out by Doyen (1972). The pygopodia are
armed with distinct spines and the forelegs are greatly enlarged (Skopin,
1964). Another character that has not been stressed before is the enlarged
sternellum partly surrounding the contiguous procoxae. Other characteris-
tics of Tentyriinae are the large eggs (Doyen, 1972) and the presence of
only two spines on the labrum of the first-instar larva (Kelejnikova, 1971).

Based on the larval features discussed above, it is possible to clarify
the status of other tribes. Marcuzzi and Rampazzo (1966) described larvae
of the American genera Coniontis and Coelus (tribe Coniontini). They
concluded that the placement of the Coniontini in the Tenebrioninae after
the Eleodini (Gebien, 1910) was correct, perhaps because the pygidium is
superficially similar to that of the Eleodini. However, a comparison of
larvae of Coniontini with the Asidini shows that the Coniontini clearly
belong in the Tentyriinae. The structure of the mandibles, prothoracic
sternum, pygopodia and preterminal pseudopodia are typically tentyrine.
On the basis of adult characters Casey (1908), and Blaisdell (1939) also
considered the Coniontini to be tentyrine, and Doyen (1972) using adult

larval characters reaffirmed the placement of the Coniontini in
fentyriinae. Why Gebien (1910) placed the Coniontini in the Tene-

IMMATURE PHILOLITHUS AND STENOMORPHA dia

brioninae is unknown, but the error has been transmitted into major works
on North American Coleoptera (Leng, 1920; Arnett, 1960).

No other larvae of American Tentyriinae have been described. Larvae
of two genera of Cryptoglossini, Cryptoglossa Solier and Schizillus Horn,
have been reared (Brown, unpublished) and clearly belong in the Tentyrii-
nae. Probably the most serious gaps in our knowledge of larvae of the
American Tentyriinae are the large tribes Epitragini and Eurymetopini.

KEY TO MATURE LARVAE OF ASIDINI IN EASTERN WASHINGTON.

Terminus of pygidium rounded; urogomphi small and slightly preterminal;
ventral margin of pygidium lacking spines; tibia of prothoracic leg with 6
to many granules posteriorly; prothorax with sparse small granules
dorsally fea eee eee rR ccc te ei Philolithus densicollis

Terminus of pygidium bifurcate; urogomphi large and terminal; ventral
margin of pygidium armed with small spines; tibia of prothoracic leg with
2 to 5 granules posteriorly; prothorax lacking granules .... ara Ae

Stenomorpha puncticollis

Philolithus densicollis (Horn)
Figures 1-4

MATURE LARVA. Length 29 mm; head capsule width 2 mm. About 8th to
9th instar (out of estimated 11 instars), 4 specimens of about equal size.
Cranium densely granulate over most of dorsal surface (Fig. 2A);
granules less numerous posteriorly and suppressed along epicranial suture
and paired median and lateral bald spots; a few short setae present
between granules. Labrum (Fig. 3C) with transverse median row of mod-
erate length, flattened spines. Epipharynx (Fig. 3D) with dense midlateral
series of prostrate spines directed medioposteriorly, some spines present
on basal membrane. Antenna (Fig. 3A) with apex of second segment
symmetrical. Mandible (Fig. 3A) with preapical gibbosity (pg) well de-
veloped, convex, slightly more prominent on right mandible; left mandible
with a small but distinct tooth on inner dorsal margin; no similar tooth on
right mandible. Hypopharyngeal sclerome (Fig. 1D-F) deeply excavate
(Fig. 1E), trapezoidal in cross section (Fig. 1F), bicuspidate; the wider
adoral margin more prolonged apically and bearing cusp at each corner;
the narrower aboral margin excavated, appearing stepped in lateral view

Philolithus densicollis, mature larva: A) overall, dorsal view; B)

terior, lateral

Same, ventral

view.

view; C) posterior, lateral view, ventral segments retracted;

segments extended; E) anterior, ventral view; F) posterior,

IMMATURE PHILOLITHUS AND STENOMORPHA 13

ry ee II 2
as e oP? Seqe'e 0® e@

FIG. 3. Philolithus densicollis: A-E) details of intermediate stage larva: A)
buccal area with maxillae and labium removed, ventral view (pg = preapical
gibbosity of mandible); B) right maxilla and labium, ventral view: C) labrum.
dorsal view; D) epipharynx; E) right prothoracic leg. posterior view: F) 2nd
instar larva, head, dorsal view; G-K) 2nd instar larva. pygidium, dorsal view.
5 specimens showing variation.

14 POSTILLA 162

(Fig. 1D), cusp lacking; inner excavation vaguely keyhole shaped when
viewed from apex (Fig. 1F); margin usually smooth and rounded, but may
be sharp and irregular.

Prothorax (Fig. 3A, B) with a rather broad, golden-brown anterior
border, and a narrower posterior border on the tergum; scattered granules
present over anterior half of tergum; sternellum short, about two thirds
as long as wide. Meso- and metathorax lacking pigmented borders and
granules.

Abdominal segments 1 to 8 (Fig. 2A) glabrous dorsally except for
posterior region of segment 8; but laterally with a cluster of fine setae near
anterior segmental base; sternum (Fig. 2E,F) with a few setae anteriorly
and fewer posteriorly, two being longer than the others. Pygidium of ab-
dominal segment 9 rounded posteriorly; urogomphi (Fig. 2A) very small,
upturned, placed ahead of terminus of pygidium at a distance about equal
to their own length; surface of pygidium covered with sharp, stout, conical
spines, distributed randomly over posterior three quarters of pygidium, a
few posterior to urogomphi, but none in a small, flattened bald area be-
tween and anterior to urogomphi; rounded lateral border of pygidium with
numerous long, fine setae, but ventral margin lacking setae or spines (Fig.
3C); articulating membrane with scattered minute setae; sternum about half
as long as tergum; preterminal pseudopod broadly swollen, with irregularly
distributed conical spines. Abdominal segment 10 with prominent pygo-
podia; spines widely distributed over pygopod surface and tending to be
directed anteriorly.

Prothoracic leg (Fig. 3E) with fine setae present on coxa, but spinose
setae or granules absent; trochanter with granules densely packed apically
forming a callus, spinose setae lacking; femur with a broad posterior
apical callus of densely packed granules, and with a ventral comb of long,
spinose setae; tibia with granules less numerous, but becoming densely
packed posteriorly in mature larva (Fig. 3E is of a mid-instar larva with
weaker development of granules); a regular comb of long spinose setae
running along entire ventral length of tibia and onward with a slight off-
setting onto unsclerotized basal part of tarsungulus, and with a parallel

row of finer setae just anterior; no single erect seta near posterior base
of claw.

SECOND-INSTAR LARVA. Length 4.77-5.68 mm (average of 3 normally ex-
tended specimens = 4.87); head capsule width 0.57-0.60 mm (average of
5 specimens = 0.59). Total specimens = 7.

Generally similar in form to later instars. Cranium with relatively large
granules distributed sparsely over anterior two thirds to three quarters
(Fig. 3F). Labrum usually with 5 flattened spines in transverse band. Sec-
ond antennal segment slightly longer and more swollen than first, sym-
metrical at apex. Mandible with a distinct globular granule at lateral
margin near base. Prothorax lacking granules or pigmented borders. Pygi-

IMMATURE PHILOLITHUS AND STENOMORPHA 15

dium with 24-41 elongate spines (average of 5 specimens = 34) un-
equally distributed on left and right sides (Fig. 3G-K); urogomphi only
slightly larger than spines; preterminal pseudopod usually with 5 spines
in a double row. Pygopod with 14-22 spines (average of 5 specimens = 17)
distributed somewhat irregularly, the posterior 3 or 4 spines more isolated
and tending to be shorter and thicker. Prothoracic leg with spines and
granules as follows; trochanter with 8-10 globular granules (average of
5 specimens = 9) and no spines; femur with 11-26 globular granules
(average of 5 specimens = 15), and 2 ventral small pale colored spines;
tibia with 2 posterioventral globular granules, 2 large anterioventral spines
and | smaller together forming a comb; unsclerotized base of tarsungulus
with 2 long thin spines.

FIRST-INSTAR LARVA. Length 4.08 mm; head capsule width 0.49 mm. Total
specimens = 4, all with similar measurements.

Mandible with a large spindle-shaped spine at lateral margin near base
(Fig. 4B). Prothorax with egg bursters present but extremely weak (Fig.
4A); egg bursters conical, spine-like, well developed on meso- and meta-
thorax, and on abdominal segments 1 to 8; a distinct, long thin seta
visible just behind egg burster on segment 8, and similar but extremely
faint seta visible behind each egg burster on segments 2 to 7, but not
visible on other segments. Pygidium of abdominal segment 9 with a few

1.0 mm.

FIG. 4. Philolithus densicollis: A) first instar larva, overall dorsal view; B)
same, head, dorsal view; C) egg, lateral view; D) egg, cross section.

16 POSTILLA 162

scattered, faint setae; urogomphi slightly preterminal on pygidium, strongly
divergent; terminus of pygidium rounded. Prothoracic leg with following
arrangement of spines; trochanter with 2 short thick spines located ven-
trally near apex; femur with 1 similar spine ventrally and a much smaller
spine posteriorly; tibia with 1 long thin spine midventrally, 1 shorter thin
spine mid-ventro-posteriorly, and 1 thick short spine midposteriorly.

EGG. (Fig. 4C, D). Length 2.42-2.97 mm (average of. 19 eggs = 2.55);
width 0.82-0.95 mm (average of 19 eggs = 0.91); average width/length =
0.360.

REMARKS. Although the specimens upon which the description of the ma-
ture larval stage is based were probably not final instars, they were well
enough advanced to be considered “mature” larvae. Chaetotaxy of the
second instar larvae did not show much promise for constant characters
at species level. For example, the position and number of spines on the
pygidium were different and asymmetrical on each specimen examined
(Fig. 3G-K). Spines and granules on the legs were highly variable. The
hypopharyngeal sclerome (Fig. 1D-F) was more uniform and may prove
to be a useful character.

Stenomorpha puncticollis (LeConte)
Figures 5-7

INTERMEDIATE STAGE LARVA. Length 20 mm; head capsule width 1.6 mm.
About 6th to 7th instar (out of estimated 11 instars), 1 specimen with
above measurements and 1 smaller specimen.

Cranium moderately densely granulate over most of dorsal surface
(Fig. 5A), granules rather sparse posteriorly, and suppressed along epi-
cranial suture and several median and lateral bald spots; only a few short
setae present between granules. Labrum (Fig. 6C) with a transverse median
row of short to moderate length flattened spines. Epipharynx (Fig. 6D)
with moderately dense midlateral series of prostrate spines directed medi-
ally, spines absent on basal membrane. Antenna (Fig. 6A) with apex of
second segment asymmetrical. Mandible with preapical gibbosity well de-
veloped, convex, slightly more prominent on right mandible; both mandibles
with a distinct third tooth on inner dorsal margin (Fig. 6A, ¢3), slightly
more developed and farther from apex on left mandible. Hypopharyngeal
clerome (Fig. 1G-I) vaguely triangular in cross section with adoral margin

(Fig. 11); tricuspidate (Fig. 1H), the cusps subequal, the single
> flatter and broader.
“ig. SA) with anterior border narrow and weakly pigmented;

IMMATURE PHILOLITHUS AND STENOMORPHA ii

posterior border unpigmented (but may be pigmented in more mature
larva); granules absent on tergum; sternellum short, about one-half as long
as wide. Meso- and metathorax lacking pigmented borders and granules.

Abdominal segments | to 8 (Fig. 5A) glabrous dorsally and laterally
except for a few setae near spiracles and stigmas; sternum (Fig. 5D, E) with
few setae. Pygidium bifurcate posteriorly (Fig. SA) and with a broad
median depressed area extending to base of forks; urogomphi large, up-
turned, and terminal (Fig. 5C); surface of pygidium covered with sharp,
stout, conical spines distributed unevenly over posterior 9/10, leaving
numerous bald areas, fine short setae scattered dorsally and laterally; ven-
tral margin of pygidium (Fig. 5C, E) with a band of small but distinct
and numerous spines; articulating membrane glabrous; sternum about
one-half as long as tergum (Fig. 5C); preterminal pseudopod broadly
swollen, with irregularly distributed conical spines. Abdominal segment 10
with prominent pygopodia, spines of varying sizes directed anteriorly, dis-
tributed in a transverse band of about 3-4 irregular rows.

Prothoracic leg (Fig. 6E) with fine setae present on coxa, but spinose
setae or granules absent; trochanter with granules tightly packed apically,
rapidly becoming sparse subapically, a single seta present midposteriorly;
femur with a broad posterior apical callus of densely packed granules, and
with an irregular ventral cluster of short to medium length spinose setae,
a single seta present midposteriorly; tibia with 2 globular posterioventral
granules (up to 5 in larger larvae), with a ventral comb of 2 to many
moderately long spinose setae, and a parallel row of finer and longer setae
just anterior; unsclerotized basal part of tarsungulus with a similar but
slightly offset comb, a single erect seta present near posterior base of claw.

SECOND-INSTAR LARVA. Length 5.23-5.54 mm (average of 3 specimens =
5.38); head capsule width 0.59-0.64 mm (average of 3 specimens = 0.60).
Total specimens = 3.

Generally similar in form to later instars. Cranium with relatively large
granules distributed moderately densely over anterior three-quarters (Fig.
6F). Labrum witn 4-5 flattened spines in transverse row. Second antennal
segment slightly longer and more swollen than first, only slightly asym-
metrical at apex. Mandible with an indistinct globular granule at lateral
margin near base. Prothorax lacking granules or pigmented borders. Pygi-
dium with 12-16 spines (average of 3 specimens = 13) mostly located
laterally (Fig. 6G, H); urogomphi much larger than spines, terminal and
upturned; bifurcation of pygidium less pronounced than in later instars;
preterminal pseudopod with 5-6 spines in an irregular double row. Pygo-
pod with 12-16 subequal spines (average of 3 specimens = 14) in a
double transverse row. Prothoracic leg with spines and granules as follows;
trochanter with 8-9 globular granules and no spines; femur with 16-19
globular granules (average of 3 specimens = 18) and 2 ventral, small,
curved pale spines: tibia with 2 posterioventral globular granules, 2 large

POSTILLA 162

>. Stenomorpha puncticollis, intermediate stage larva: A) overall dorsal

nterior, lateral view; C) posterior, lateral view; D) anterior, ventral
posterior, ventral view.

IMMATURE PHILOLITHUS AND STENOMORPHA 19

FIG. 6. Stenomorpha puncticollis: A-E) details of intermediate stage larva;
A) buccal area with maxillae and labium removed, ventral view (#3 = inner
dorsal tooth of mandible); B) right maxilla and labium, ventral view; C)
labrum, dorsal view; D) epipharynx; E) right prothoracic leg, posterior view;
F) 2nd instar larva, head, dorsal view; G, H) 2nd instar larva, pygidium, dorsal
view, 2 specimens showing variation.

20 POSTILLA 162

anterioventral spines, and 1! much thinner and slightly more ventral;
unsclerotized base of tarsungulus with 1-2 long thin spines.

FIRST-INSTAR LARVA. Length 4.15-4.38 mm; head capsule width 0.55 mm.
Total specimens = 2.

Mandible with a large, spindle-shaped spine at lateral margin near base
(Fig. 7B). Egg bursters not visible on prothorax, but present on all other
thoracic and abdominal segments except pygidium, increasing in size
posteriorly; no setae visible behind egg bursters. Pygidium with a few
scattered faint setae; urogomphi terminal, directed dorsally and only
slightly divergent; terminus of pygidium weakly emarginate. Prothoracic leg
with the following arrangement of spines; trochanter with 2 short thick
spines located ventrally near apex: femur with 1 similar spine located ven-
trally and a much smaller spine posteriorly; tibia with 1 long, moderately
thin spine midventrally, 1 very short spine mid-ventro-posteriorly, and 1
slightly longer and thicker spine midposteriorly.

EGG. (Fig. 7C). Length 2.92-3.41 mm (average of 18 eggs = 3.08); width
1.04-1.21 mm (average of 18 eggs = 1.12); average width/length = 0.364.

REMARKS. After completion of the description and illustrations of the
intermediate stage larva, I obtained from the United States National
Museum a series of larvae from Roosevelt, Washington, collected 7 April
1942 and determined as Euschides puncticollis LeC. by M. C. Lane in
1942. Euschides is a synonym of Stenomorpha. Comparison with the
reared larvae confirms that they are indeed S. puncticollis. There were
4 larvae about the size of the largest described here, and 3 larvae of much
larger size. The large larvae measure about 35-40 mm in length, 3.5 mm
in head capsule width, and fit the description of the intermediate-stage larva
quite well. The only modifications of that description would involve
characters that change with larval growth. The number of granules on the
cranium increases; the comb of setae and spines on the prothoracic leg
becomes denser; and the granules on the trochanter and femur become very
numerous and tightly packed. One large specimen had 5 granules on one
tibia, but all others had 2-4 granules, indicating that 5 is probably the
maximum number for tibial granules. A narrow, faintly pigmented posterior
border is visible on the tergum of the prothorax. The dorsum of the
pygidium is depressed and concave in the posterior two-thirds, a feature not
so strongly developed in younger larvae. This characteristic appears to be
unique among larvae of the genus Stenomorpha and will probably serve to
separate S. puncticollis from other larvae in the genus.

The presence of two distinct sizes of larvae in the USNM series strongly
suggests that two generations were collected at one time. This lends added

weight to the hypothesis of a two-year life cycle that will be discussed in
the next section of this paper.

IMMATURE PHILOLITHUS AND STENOMORPHA 21

FIG. 7. Stenomorpha puncticollis: A) first instar larva, overall dorsal view; B)
same, head, dorsal view; C) egg, lateral view.

BIOLOGICAL NOTES

ADULT LONGEVITY. The beetles were placed on sand substrate on 12
October 1968, one day after receipt. All beetles were alive on arrival, but
parts of the legs of most specimens of S. puncticollis had been chewed off,
while only a few of P. densicollis showed such damage.

Since the beetles could have been in traps several days before being re-
moved on 5 October, it is reasonable to estimate 1 October as the average
date of trapping. The major difficulty in estimating longevity from field-
collected specimens is that the date of eclosion is unknown. In the case
of the species considered here, many years of trapping indicate that the
first adults appear in mid-September (Rickard and Haverfield, 1965:
Rickard, 1970). Therefore it is unlikely that any of the individuals were
more than 15 days old by | October.

Trauma during travel could also influence laboratory—observed longevity.
Compared with other Asidini I have collected, the longevity figures in
Table | appear somewhat low. For example, a series of 69 living specimens
of Philolithus actuosus (Horn) collected at Twentynine Palms, California,

22 POSTILLA 162

TABLE 1. Mortality of P. densicollis and S. puncticollis adults.

Probable
Date Days days
of after after P. densicollis S. puncticollis

death receipt trapping Females Males Total Females Males Total

12-X 1 12 2 5 5 1 2 3
16-X 5 16 2 3 5) 5 6 jist
21-X 10 pa | 17, 5 22 12 10 22
25-X 14 25 2 2
30-X 19 30 1 1 4 1 5
4-X]I 24 35 1 1
8-XI 28 39 1 1 1 1
Totas 23 11 34 26 19 45

Average longevity after

receipt, days 10.0 6.2 8.7 116 7.9 10.1
Average longevity after

trapping, days 210 UFZ Noha 2246 18.9 Dial

on 9 September 1966 showed an average longevity of 24.5 days, with a
maximum of 43 days. These specimens suffered a minimum of travel
trauma as they were collected at dusk and transported by automobile at
night to Riverside in little more than an hour. Other species of Philolithus
and Stenomorpha are similar in longevity (Brown, unpublished).

By assuming that the adults of P. densicollis and S. puncticollis had
eclosed an average of 10 days before trapping, a rough estimate of about
30 days for adult life is derived. It is clear that even after adjusting the
data on mortality by estimating times of trapping and eclosion, both species
are short lived as adults. This is completely consistent with data reported
by Rickard (1970). However death appears to be a genetic factor, rather
than environmental; in other words, the insects do not seem to be killed
by winter cold, but die of old age. A major evolutionary adaptation of
species in the tribe Asidini to xeric environments appears to be a reduction
of the adult phase and a prolongation of the larval phase in the more
hospitable subsoil environment.

Adults will feed readily on food provided them. However, when some
adults of Philolithus actuosus were denied food and moisture, they con-
tinued to live an almost normal period and females laid eggs.

The data in Table 1 seem to indicate that S. puncticollis lived longer
than P. densicollis, and that females of both species lived longer than

IMMATURE PHILOLITHUS AND STENOMORPHA 23

males. Student’s t-test was applied with the following results. The dif-
ference between means of total longevity of P. densicollis and S. puncticollis
was not significant (.2 << p < .3). The difference between means of female
and male longevity in S. puncticollis was significant (.02 < p < .05);
the difference between means of female and male longevity in P.
densicollis was almost, but not quite significant (.0S < p < .1). The
data of Rickard and Haverfield (1965) show that S. puncticollis appears
somewhat later in the season than P. densicollis. Therefore, it is possible
that the specimens of S. puncticollis sent to me were younger, but the
sample was not adequate to show this. The differential longevity of females
and males may be a function of earlier eclosion of males. Attention in
future pit trap surveys to the proportions of females and males recovered
throughout the season may cast further light on this matter.

OVIPOSITION. Females in the tribe Asidini, including P. densicollis and S.
puncticollis, have a well-developed ovipositor that is about half as long
as the entire insect. The apical coxites are strongly sclerotized and function
as drill bits. Eggs are laid to a depth of about 1 cm in the soil. The female
is able to penetrate a very hard soil crust to deposit her eggs. They notably
prefer damp spots in the soil for oviposition, a behavior that aids in re-
ducing the risk of dessication. In contrast, tenebrionids in the genus Eleodes
simply drop their eggs on the surface or partially bury them in loose soil
or litter.

TABLE 2. Oviposition by females of P. densicollis and S. puncticollis.

P. densicollis S. puncticollis
Total females 23 26
Females laying eggs 11 5
Percentage of females laying eggs 47.8 19:2
Total eggs laid 60 29
Average eggs/laying female 525 5.8
Maximum eggs from 1 female 16 1

Even more than with longevity, these data seem depressed when com-
pared with that of other Asidini, due possibly to trauma in shipment. For
example, of the 34 female Philolithus actuosus in the California sample
mentioned before, 22 (64.7%) laid eggs, with an average of 26.1 eggs per
laying female, and a maximum of 60. Compared with figures reported for
Eleodes (an average of 287 eggs per female, Wakeland, 1926; and 300 from
a single female in a 24-hour period, Matteson, 1966), even the figures for
P. actuosus seem low. However, the total biomass of eggs in the two groups
may not be so different. considering that asidine eggs are much larger than
eleodine eggs. Also because of their more careful placement, there is

24 POSTILLA 162

probably higher survival among eggs of the Asidini, than those of Eleodes.

Estimates of the rate of oviposition are difficult to make. The physiolog-
ical strain of egg production on tiny species such as P. densicollis and
S. puncticollis must be great, as the length of an egg is fully 20% of the
length of the beetle. The fact that the eggs of these species are not much
smaller than those of other species of Asidini having adults three times
as large indicates that there must be a strong adaptive advantage for the
production of large eggs by these beetles. Comparing data in Tables | and
2 shows that an average of one egg was laid every other day. Data from
other species of Asidini that suffered less trauma in transport, suggest that
one egg each day is probably a better estimate. For those females of P.
densicollis and S. puncticollis that lived longer, eggs were recovered several
times in numbers that indicated that egg production was fairly regular,
rather than in spurts.

EGG INCUBATION. While P. densicollis and S. puncticollis are similar in

longevity and oviposition, they differ in egg incubation periods. The eggs
of P. densicollis hatched about 2 weeks after oviposition; the eggs of

TABLE 3. P. densicollis and S. puncticollis egg hatch at 70 F (21.1 ©)

Days after S. puncticollis P. densicollis
recovery of Viable Dead New Ist Viable Dead New Ist
eggs eggs eggs instar eggs eggs instar
0 29 55
a 26 3 45 10
14 23 3 19 5 21
18 23 11 8
24 23 0 115
30 23
38 23
43 23
53 20 1 Z
63 11 1 8
7a 9 1 1
81 8 1
93 3 5)
103 2 1
114 2,
122 0 2
Total hatch 12 40
Average days to hatch 62.6 MieS:

Average viability 41.4% TZN Ze,

IMMATURE PHILOLITHUS AND STENOMORPHA 25

S. puncticollis took 2 months. Also the viability of S. puncticollis eggs
appeared lower. (Of the original 60 eggs recovered from P. densicollis,
only 55 are listed in Table 3 as “viable” because 5 were accidentally
destroyed in handling.)

The first eggs of S. puncticollis were observed to have hatched on 23
December 1968. The rest hatched in early January. In southeastern
Washington the near-surface soil temperature at this same time would
have been close to freezing and the eggs probably would not have hatched
until the spring. The evidence indicates therefore that S. puncticollis passes
its first winter in the egg stage, while P. densicollis winters as an early in-
star larva. This could explain the later appearance of S. puncticollis adults.

FIRST LARVAL MOLT. The first-instar larva is inactive and does not feed.
Although individual first instars were not isolated to determine time to
the first molt, virtually all first instars of P. densicollis and S. puncticollis
molted to second instars in less than two weeks. The second instar is active,
burrows into the soil, and feeds. It appears to be much more resistant to
dessication than the first instar.

While it may appear that P. densicollis obtains a strong developmental
head start by its rapid egg hatch, its lead over S. puncticollis is probably
only slight. Controlled temperature experiments with other species of
Philolithus and Stenomorpha (Brown, unpublished) showed that temper-
atures of 40 F (4.4 C) or below completely stopped larval development.
Thus, the majority of overwintering P. densicollis larvae remain in the
second instar. By the time S. puncticollis hatches in the spring and rapidly
molts to second instar, P. densicollis may not have reached any further
than third or fourth instar.

LATER LIFE STAGES. Since study of P. densicollis and S. puncticollis was
terminated before pupation, speculations on their later development
must be extrapolated from studies of other species (Brown, unpublished).

It is clear from all the life history studies that have been conducted
to date, that the larvae of the Asidini are subterranean scavengers of or-
ganic detritus. No living plant material was used in successfully rearing
several species from egg to adult. The larvae are well adapted for their
underground existence, the scooped mandibles and enlarged forelegs
serving as excellent digging tools. Digging is accomplished by downward
thrusts of the forelegs and opposing upward thrusts of the head. Forward
leverage is achieved by expansion of the spinose abdominal terminus.
The larvae easily bore through hardened plaster of paris, but do not
ingest it. They do not appear to feed by passing the soil in which they
burrow through their alimentary tract, but rather by selection of the
edible material encountered in the soil. Larvae in the large cup cultures
almost never came to the surface. Their unsclerotized bodies are poorly
suited for exposure to surface conditions. Eleodes larvae in contrast, often

26 POSTILLA 162

surface and graze on plants and seeds. Therefore, it seems probable that
developing asidine larvae are relatively independent of transient surface
events such as rainfall, plant growth, and fires. Deep-boring larvae would
be adversely affected only by a very prolonged drought. Specimens have
been collected at depths exceeding 1 m. Growth rates would be effected
by soil temperature. Rainfall and temperature probably have a particularly
profound effect on survival of eggs, early instar larvae, and pupae.

Estimation of the total life cycle time from laboratory data is difficult
because of differences in temperature regime and food. Temperatures
used in the laboratory were probably above the average encountered in
the field. While growth of early instar larvae probably almost stops for 3-4
months of winter in the field, the laboratory specimens were kept at
70-80 F. A two-month period of under 50 F (10 C) was needed to break
diapause in late instar larvae before pupation occurred. Only here did the
laboratory regime resemble the field. Overall the warmer lab temperature
probably resulted in faster growth. The food medium used was more
concentrated and probably more nutritious than food encountered in the
field. This also could have accelerated larval growth.

Pupation is probably in cells near the surface or under protective ob-
jects, as the emerged adults are too fragile to dig through much soil.
The majority of pupations in the lab were 1-2 years after oviposition,
with an average of about 1.5 years. Taking into account the accelerated
growth in the lab, it is probable that 2 years is the normal duration of the
life cycle for most Asidini in the field. The role of cold in breaking an
apparent developmental diapause in late instars is critical. From 4-5 months
after restoration of normal temperature the larvae will pupate. Thus there
seems to be a temperature-entrained biological clock that governs pupation
in late summer and early fall. Preliminary experiments with varying photo-
periods indicate that the light-dark cycle has no effect.

Larvae of other species of Philolithus and Stenomorpha had a variable
number of instars before pupation, generally around 11-12. The pupal stage
lasted only about a month. Larvae not subjected to a cold period con-
tinued to add instars and eventually died.

Although P. densicollis and S. puncticollis are smaller than the other
species studied, it is probable that they also have a 2-year life cycle with
about 11 instars. It is assumed that both species require prolonged low
temperature in late instars before pupation occurs. Although future study
may alter details of this hypothesis, it should serve as a useful model in
ecological studies of these insects.

The occurrence of adult Asidini in the field is often characterized by
massive but very local population outbreaks. P. densicollis is particularly
well known for this phenomenon (Boddy, 1965). This may indicate an
evolutionary trend toward periodic population explosions that dampen: the

‘fects of predation by simply swamping predators. As with all Tentyriinae,

IMMATURE PHILOLITHUS AND STENOMORPHA AT

the Asidini lack defensive secretions. Population outbreaks were considered
by Alexander and Moore (1962) to be significant in the evolution of
periodical cicadas.

ACKNOWLEDGMENTS

This paper would not have been possible without the help of Dr. W.
H. Rickard of the Battelle Pacific Northwest Laboratories, Richland, Wash-
ington, who sent the specimens upon which this paper is based. Mr. W. T.
Hinds, of the same institution, encouraged me to write this paper and
offered valuable suggestions. Mr. T. J. Spilman, United States National
Museum, loaned larvae of Tenebrionidae, and reviewed this manuscript.
His helpful comments led to several important improvements. Dr. J. F.
Lawrence, Museum of Comparative Zoology, Harvard University, provided
a translation of Skopin (1964). Part of this work was carried out at the
University of California, Riverside, under a National Defense Education
Act graduate fellowship.

LITERATURE CITED

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17-year and 13-year cicadas, and three new species (Homoptera, Cicadidae,
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Arnett, R. H. 1960. The beetles of the United States. Catholic Univ. Amer.
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Blaisdell, F. E. 1939. Studies in the relationships of the subfamilies and tribes
of the Tenebrionidae based on the primary genital characters, also de-
scriptions of new species (Coleoptera). Trans. Amer. ent. Soc. 65: 43-60, 2 pl.

Boddy, D. W. 1965. Tenebrionidae, p. 170-189. Jn M. H. Hatch [ed.] The
beetles of the Pacific Northwest, part IV. Univ. Wash. Pub. Biol. 16.

Brown, K. W. 1971. Redefinition of the genera Pelecyphorus and Philolithus
with a key to the genera of the tribe Asidini (Coleoptera: Tenebrionidae).
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Casey, T. L. 1908. A revision of the tenebrionid subfamily Coniontinae. Proc.
Wash. Acad. Sci. 10: 51-166.

Doyen, J. T. 1972. Familial and subfamilial classification of the Tenebrionoidea
(Coleoptera) and a revised generic classification of the Coniontini (Tenty-
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Emden, F. I. van. 1942. The collection and study of beetle larvae. Ent. mon.
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Hinds, W. T. and W. H. Rickard. 1973. Correlations between climatological
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Leng, C. W. 1920. Catalogue of the Coleoptera of America, north of Mexico.
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