LIFE-HISTORY STUDIES OF THREE JOINTWORM 
PARASITES 
By W. J. Phillips and F. W. Poos, Entomological Assistants, Cereal and Forage Insect 
Investigations, Bureau of Entomology, United States Department of Agriculture 
INTRODUCTION 1 
The importance of the control of the jointworm ( Harmolila tritici Fitch) 
by its parasites can not easily be overestimated. Up to the present time 
parasites have been the only means of control, and when these natural 
agencies fail whole fields of wheat often are destroyed. It is the opinion 
of the writers that effective control measures would have been put into 
practice or wheat growing in the Eastern States abandoned years ago 
had not the parasites of the jointworm in a large measure taken care of 
the situation. ' 
The present system of crop rotation in the wheat-growing districts of 
the Eastern States furnishes ideal breeding grounds for the jointworm. 
This, however, is also true for the parasites; but we have learned by 
experience that we can not rely entirely upon the parasitic enemies of 
the jointworm to effect its control. It has been the common belief among 
scientists that the parasites check severe outbreaks of this pest within 
a few years, but the writers after studying closely a severe outbreak of 
the jointworm in Fauquier County, Va., have come to the conclusion that 
this is not always true. In that locality infestation by the jointworm has 
been very intense for several years, and according to observations of 
the past few seasons the numerical ratio of parasites to the jointworm has 
increased very slowly, until at the close of the year 1919 the jointworm 
is 92.6 per cent parasitized. 
This paper treats of the life histories of three of the more important 
parasites of the jointworm. They are all hymenopterous parasites of the 
superfamily Chalcidoidea and have been mentioned frequently in litera¬ 
ture, though no detailed accounts of their life histories as parasites of the 
jointworm have ever been recorded. 
DISTRIBUTION 
Ditropinotus aureoviridis Crawford and Homoporus chalcidiphagus 
Walsh and Riley are primary parasites, while Eupelmus allynii French 
was found to be both primary and secondary. The distribution of 
D . aureoviridis and H. chalcidiphagus is similar to that of the jointworm 
(fig. 1). E. allynii is commonly found wherever the Hessian fly 
1 The observations on which this paper is based were made at the United States Entomological Laboratory 
at Charlottesville, Va., during 1917, 1918, and 1919. 
Vol. XXI, No. 6 
June 15, 1921 
Key No. K-96 
Journal of Agricultural Research, 
Washington, D. C. 
yd 
(405) 
