THE LARGER GRAIN-BORER. 
51 
insect might have an opportunity to escape from confinement, A 
number of adults, 14 in all, were placed, on June 21, in a rearing jar 
containing an ear of corn. At the end of two months the ear, includ- 
ing the cob, was fully half destroyed, and later the bored ear was 
converted into dust and other debris. 
A similar number of beetles was confined in a rearing jar with 
shelled corn, June 25. Late in the afternoon and the following 
morning three kernels of corn were found to have been entered, two 
having been bored entirely through. Figure 10 shows the work of 
the beetle in a kernel of corn. 
These experiments show the rapidity with which the adults work, 
as also partiality for corn in the ear, the insect scarcely being at home 
in shelled corn, while in other material with which it was fed in other 
experiments the insect did not breed at all. 
There seems little doubt that the grain-feeding habit of this species 
is an acquired one of comparatively recent times, and that it normally, 
or under natural conditions, breeds in roots and 
tubers. 
During the course of these experiments it was 
ascertained that the pupal stage varied from about 
four and one-half days in the very hottest weather 
to six days in a little cooler weather during June and 
July, while in October the pupal period lasted twelve 
days, from October 17 to 29. The egg was not ob- 
served, but the egg period is with little doubt about 
the same as for the pupa under the same atmospheric 
conditions. By experiment it was learned that the 
entire life cycle from the placing of beetles in corn 
until the issuance of the new generation, i. e., from 
August 25 to October 9, was forty-five days, or 
about six and one-half weeks. The temperature was moderately 
warm during this period. 
Still another experiment was made with this species by confining 
it with some others in a superheated atmosphere, which was also very 
dry. As evidence of its tropical nature this species thrived better 
than any of the other insects exposed to the same conditions. Indeed, 
it appears to be the only insect that did not suffer from the extreme 
dryness to which it was subjected. The temperature in this case was 
upward of 100° F. and ran as high as 115° F. 
The limited supply of this species did not permit of any experi- 
ments with remedies. As has already been briefly pointed out in the 
introduction, it is an insect which should be carefully watched if it 
once gains access to a granary or other storehouse, as it is apt to do 
considerable injury to the woodwork, perforating it with holes even 
when grain is available for food. Undoubtedly bisulphid of carbon, 
Fig. 10. — Kernel 
of corn showing 
work of beetle 
of larger grain- 
borer (Dinode- 
rus truncatus). 
Enlarged. 
(Original.) 
