2 
and feet yellow. The young or grub is whitish, with brown Jaws, the 
length being about the same as that of the adult, and the form much 
like that shown in figure 2, which represents the larva of a nearly 
related species. 
LIFE HISTORY. 
The insect may be found throughout the year in its various stages of 
development in wheat stems. It lives over winter as a larva or grub in 
cells formed in the stems prior 
to the ripening of the grain, 
the adult emerging therefrom 
in April or May, according to 
latitude, 
or some 
time after 
the young 
grain has 
thrown up 
stems and 
several 
joints have 
become ex- 
posed. The 
female, 
using her 
slender, 
pointed 
ovipositor, 
places her 
eggs in the Fig. 2,—Isosoma grande 
straws. The Riley: Larva of the 
wheat-straw worm—e, 
exact POSI- antenna: f, jaw; lineat 
t TOMMNANCE right indicates natural 
length (after Riley). 
sumed is 
shown in figure3, photographed 
| from life by Mr. G. I. Reeves. 
FiG. 3.—Female Isosoma in act of depositing egg in The eggs hatch and the young 
stem—about life size (original). grubs, forming cells, feed in 
the walls of the stem, reaching their maximum growth by the time the 
straw becomes fully hardened and ripe. Wintering in the larval state, 
they pass a short pupal stage and emerge as adults in the spring. 
EFFECT ON THE STRAW. 
This is exceedingly variable. Sometimes a distortion of the straw 
occurs like that illustrated in figure 4; at other times the straw is bent 
or twisted in almost every conceivable shape; again there will be no 
