4 BULLETIN 808, U. S. DEPARTMENT OF AGRICULTURE. 
festation, as the plants are thus made much more top-heavy. As the 
growing larvae consume proportionately large amounts of sap, the 
developing wheat kernels are constantly robbed of their nourish- 
ment and suffer accordingly. 
A field of wheat badly straw-fallen usually is attributed to the 
depredations of the Hessian fly by the average farmer, and very 
often the fly is wrongly credited year after year, in the States east 
of the Mississippi River, with serious and widespread injury that is 
chargeable to the jointworm. 
HOST PLANTS. 
During repeated trials covering a number of years this species was 
never induced to breed in any plant but wheat. It never has even 
Fig. 1. — The wheat jointworm (Harmolita tritici) : Adult female. 
Greatly enlarged. (The head is tilted back somewhat so as to 
show the groove in front.) (Author's illustration.) 
been observed to attempt oviposition in any other plant. The stems 
of barley and rye particularly do not differ greatly from wheat, but 
they seem to be distasteful to tritici. 
LIFE HISTORY. 
There is only one generation a year. The adults (fig. 1) emerge 
in May and deposit their eggs in the stems of growing wheat just 
about the time the heads begin to appear. The life of adults lasts 
from a few days to a week or more, depending upon the temperature. 
The eggs (fig. 2, a, b) hatch in about 10 days. The larvae mature in 
