2 BULLETIN 808, U. S. DEPARTMENT OF AGRICULTURE. 
running into the millions of dollars every year. Despite this fact 
very little has been known concerning the identity and habits of the 
species which cause these losses. For example, it was not known 
definitely whether Harmolita tritici Fitch, the most important mem- 
ber of the genus, had a dozen host plants or whether it was confined 
to wheat alone. The object of this paper, therefore, is to place on 
record in as brief a manner as possible the main facts, in so far as 
they have been developed, in the life histories of the species that 
have been studied thus far, and to propose a basis for control. 
The species infesting the grain crops will be considered first, then 
those affecting the cultivated grasses, and lastly the species living in 
wild grasses. Nearly every species is of either direct or indirect 
economic importance. Those affecting the grain crops and the culti- 
vated grasses are obviously of direct economic importance because 
of the very considerable losses entailed by their depredations or their 
potential capacity for injury. The importance of the different 
species varies greatly since the damage inflicted by some is far 
greater than that caused by others. The economic aspect of those 
species affecting wild grasses is less obvious. They do not cause a 
loss to the farmer, but on the contrary probably are an advantage to 
him, since they serve as intermediate hosts for the many parasitic in- 
sects which play such an important role in the natural control of the 
species infesting cultivated crops. "Without these intermediate hosts 
it is doubtful whether some of the parasites would be able to main- 
tain themselves under the abnormal conditions created by cultiva- 
tion. The more important species of parasites are common to the 
majority of species of Harmolita, however, and consequently are able 
to survive those periods during which there is a lack of hosts breed- 
ing in cultivated crops, by turning their attention to related species 
breeding in wild grasses. 
It is difficult to estimate the value of jointworm parasites in terms 
of dollars and cents to the wheat-growing regions east of the Mis- 
sissippi River. The writer is convinced, however, that farmers would 
have been obliged to resort to artificial measures of control for the 
wheat jointworm years ago had it not been for the efficiency of these 
parasites. The parasites of the jointworms will be treated in a paper 
to be published subsequently. 
SPECIES INFESTING THE GRAIN CROPS. 
THE WHEAT JOINTWORM. 1 
Harmolita tritici probably is the most important species in the 
whole genus, since it causes very serious losses in nearly all the wheat- 
producing States east of the Mississippi River and in a large part of 
1 Harmolita tritici Fitch. 
