14 
BULLETIN 1428, U. S. DEPAKTMENT OF AGRICULTURE 
THE ADULT 
A few days before the pupa transforms to the adult (fig. 10), the 
eyes become dark and the mouth parts an,d tips of the tarsi begin to 
color. When first emerged from the pupal skin, the adult is light 
in\color, soft in texture, and very feeble. If exposed it would be un- 
able to protect itself from other carnivorous insects, and therefore it 
remains within the shelter of its pupal chamber for a week or longer 
while its tissues are hardening and its color changing to dark red- 
dish brown or black. It then emerges from its cell by eating a 
characteristically shaped hole (fig. 8, B) through the pupal cell 
and takes up the struggle for existence. 
The beetles prefer darkness to light and usually may be found 
in dark corners of mills and granaries, between sacks that are 
stacked close together or in other similar situations. 
The food habits of the beetles are very similar to those of the 
larvae; but, in addition to eating everything that the larvae feed on, 
they will attack and devour the larvae of almost any insect that they 
encounter. Beetles were fed in the laboratory with the larvae of the 
cheese skipper (Piophila casei L.) 
and larvae of various flour beetles 
(Tribolium, etc.). Observations 
seem to indicate that oviposition is 
stimulated by the addition of fresh 
meat to the diet. Beetles do not 
hesitate to devour larvae of their own 
species, or even a newly emerged 
adult that is prematurely exposed. 
The beetles are rather pugnacious, 
and if confined in restricted quar- 
ters they will fight until most of 
them have lost their legs. 
ADULT LONGEVITY 
The cadelle adult is usually 
long-lived. Kirkup (17) records a 
single specimen that lived for one 
year and nine months. Slingerland 
in Herrick (12) observed two adults 
that lived for about one year. As 
the data of Table 1 indicate, female beetles reared in the laboratory 
and given food were all very long-lived and many survived for con- 
siderably more than a year, the longest record being 668 days. 
AGE AT WHICH MATING AND OVIPOSITION BEGIN 
During the week or more that the adult cadelle remains sealed 
within its pupal chamber, there is of course no opportunity for 
mating. Mating occurs, however, soon after emergence from the 
pupal chamber and is repeated at irregular intervals throughout life. 
In summer egg laying begins about two weeks after transforma- 
tion to the adult, but in the spring months the preoviposition period 
appears to be considerably longer. In the case of adults emerging 
in late summer or early fall, no oviposition takes place until the 
following spring. Data indicating a preoviposition period of from 
15 to 210 days are given in Table 1. 
Fig. 10. — The cadelle : Adult beetle. 
Tlie cadelle is a flattened, black beetle 
about one-third of an inch long 
