848 
Journal o f Agricultural Research 
Vol. XXX, No. 9 
THE EGG 
The egg of Necrobia rufipes is about 
1 mm. in length and 0.25 mm. wide, 
tapered, and roundly pointed at both 
ends and slightly curved in outline. It 
is smooth, shining, translucent, and is 
glued in place. As shown in Plate 1, 
B, the eggs are usually deposited in 
clusters. Those laid by old females 
often partially collapse laterally within 
a few hours after being deposited, and 
such shrunken eggs do not hatch. 
Toward the end of the incubation 
period (four or five days in length 
during warm weather) the four eye- 
spots of the embryo become visible, 
followed by pigmentation of the tips 
of the mandibles. Shortly after hatch- 
ing, and in some cases before the escape 
of the larva, the caudal plate, head 
capsule, and prothoracic shield assume 
their final color. 
HATCHING 
The struggles of the hatching larva 
cause the posterior extremity to move 
about, with the result that the tubercles 
on the caudal plate tear the eggshell 
open at one end, the mandibles accom¬ 
plishing the same at the anterior end. 
Thus the eggshell is usually torn open 
at both ends before the larva leaves it, 
and the larva often remains in the shell 
as in a short tunnel for several hours, 
feeding on the shell. 
THE LARVA 
TECHNICAL DESCRIPTION {4, J). 597-599) 
Total length of body, about 10 mm. ; extreme 
width, about 2 mm.; fifth to seventh abdominal 
segments widest; anterior width of prothorax 
one-half the width of the seventh abdominal seg¬ 
ment; extreme thickness, 1 l A mm.; seventh ab¬ 
dominal segment thickest. Corneous parts shiny, 
brown ocher; delicately chitinized parts shiny, 
pale clay yellow; membranous parts of thorax and 
abdomen dorsally mauve or lilac with white muscle 
attachments, ventrally whitish with bluish pattern. 
Frons rugose, anteriorly on each side of middle line 
with a shallow deepening. Labrum three times as 
wide as long; width about one-third the length of 
frons. Mandibles half as long as frons; length to 
width as 4 : 2; retinaculum and tooth same size, 
well developed, and rather obtuse. Two short 
mandibular setae. Prothoracic shield two-thirds 
as long as wide, with parallel sides. Both meso- 
thorax and metathorax are about as long as pro¬ 
thorax, surpassing it one-third or more in width; 
metathorax a trifle wider than mesothorax; meso- 
thoracic and metathoracic dorsal plates present, 
small, and about the same size. Basal plate of 
cerci a trifle wider than the prothoracic shield, 
length to width as 2 : 3. Cerci one-third the length 
of basal plate, upward curved, diverging about 60°. 
LARVAL BEHAVIOR 
The delicate, wrinkled, hairy larva 
after leaving the shell moves" about 
but little for awhile, confining its ac¬ 
tivities as it gains strength to feeding 
on the unhatched eggs in the near 
vicinity and eating the shells of empty 
eggs. The shells are usually almost 
wholly consumed. New-laid eggs of 
the ham beetle, exposed to very young 
larvae which were also provided with 
dead skipper maggots, were all eaten. 
Eggs of Dermestes vulpinus Fab. were 
also eaten. 
The postembryonic larvae are re¬ 
pelled by light, and, for the first day or 
so, prefer to spend most of their time 
hidden beneath some object, even when 
food is provided and light excluded. 
The rearing of individual larvae 
(Table VII) was found to be practically 
impossible when fat bacon or skipper 
larvae were used as the only food. By 
feeding the postembryonic "larvae with 
eggs of the ham beetle for 8 or 10 days 
after hatching, then giving both eggs 
and crushed skippers for 4 days and 
crushed skippers thereafter, single 
larvae were easily reared. To prevent 
the very small larvae from escaping or 
becoming entangled in cotton, the 
best container was found to be No. 11 
veterinary capsules, the food being 
placed between two pieces of cardboard. 
The larvae thus reared reached a good 
size and molted two or three times be¬ 
fore pupating. First skins measured 
0.08 mm. between the tips of the caudal 
tubercles, second skins 0.25 mm., and 
third skins 0.5 mm. The molting skin 
splits over the thorax, the head is with¬ 
drawn from the head capsule and ex¬ 
truded through this opening, and the 
insect crawls out of the skin. There is 
much variation between the dimensions 
of the smallest and largest full-grown 
larvae, the latter being 100 per cent 
larger than the former. 
Larvae of all instars are repelled by 
light. Well-grown larvae are able to 
crawl rapidly and to kill migrant skip¬ 
per larvae. In their efforts to escape 
the maggots throw their attackers 
about with considerable force, but the 
latter seldom release their jaws until 
the maggots have become helpless. 
When touched, ham-beetle larvae pro¬ 
tect themselves by thrashing about, 
bending their extremities together first 
on one side and then on the other. 
The full-grown larva is shown in 
Plate 1, C. 
PUPAL CELL OR COCOON 
Following the completion of feeding, 
full-grown larvae infesting smoked 
meat migrate from the greasy material 
in which they develop and seek a dark, 
dry spot in which to build the cocoon. 
At this time the larvae will not usually 
eat if skippers are offered to them. 
