Oct 13,1923 
Biology of Tenebroides mauritanicus 
67 
LENGTH OF LARVAL STAGE 
Under favorable conditions and with the right kind of food the larval 
growth is very rapid. The shortest larval period observed was 39 days, 
from the date of hatching to the formation of the pupal cell. (See Table 
II.) This larva hatched on June 20, 1922, and was fed on corn. This 
case was not unusual, as many more individuals had larval periods of 
about the same length. Larvae that hatch during the late summer or 
early fall do not transform that season but enter into hibernation and 
complete their growth the following spring. 
Unfavorable conditions and improper food will lengthen the larval 
stage almost indefinitely. The larva will feed on an almost endless 
variety of foodstuffs but does not thrive equally well on all of them. 
Several hundred larvae were reared in the laboratory under conditions 
that were identical except in the matter of food. It was found that the 
larvae that were fed upon corn, wheat, and Graham flour grew rapidly, 
and completed their growth in approximately the same length of time, 
about 69 days. Larvae fed upon barley flour did not grow quite so rapidly, 
but a few of them completed their growth about two weeks after the 
com-wheat-Graham flour-fed larvae. Larvae fed upon rough rice grew 
still more slowly, and although apparently full grown at this time, six 
months after birth, none had transformed and it was presumed that they 
would not do so before the spring of 1923. Larvae fed upon refined white 
flour were still quite small after six months of feeding and, judging from 
the present slow rate of growth, would have a very long larval life. 
The foregoing observations may in part explain the phenomenally long 
larval period reported, first by Kirkup 1 in 1812 and recently by Mc- 
Colloch 2 in 1922. The single larva observed by Kirkup lived for more 
than 15 months without transforming, and larvae observed by McColloch 
lived from 628 to 1,248 days before transforming. 
The cadelle larvae are generally believed to be carnivorous. The 
writer has found that they rarely molest any other insect larva and 
apparently never feed on the bodies of dead larvae. 
NUMBER OF LARVAL MOLTS 
The cadelle larva as a rule molts either three or four times, although 
when for some reason or other the larval period is prolonged beyond its 
normal length many more molts may occur. (See Table II.) McColloch 
observed one larva to molt no less than 11 times. 
Observations made show that larvae that hatch in early summer may 
molt four times but usually molt but three times. Those hatching later 
in the season almost invariably molt four times. Data showing the 
number of molts and the length of time between molts are given in 
Table II. 
PUPATION 
After attaining its growth the larva becomes restless and wanders off 
to find a place of safety in which to transform. It prefers to burrow into 
a piece of soft wood, hollow out a small chamber, and close up the open 
end with cement made from the larval borings mixed with a larval 
secretion. The walls and floors of many wooden bins used to hold wheat 
1 Kirkup. Jos. Account of tenebrio mauritanicus. In Trans. Ent. Soc. London. 1812, p. 329- 
33j McCoeloch, J. W. Longevity of the ea r vai. stage of the cadeeee. In Jour. Eo 
p. 242. 1922. 
