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1924 ] The Biology of Trichopoda pennipes Fah. 
THE BIOLOGY OF TRICHOPODA PENNIPES FAB. 
(DIPTERA, TACHINIDiE), 
A PARASITE OF THE COMMON SQUASH BUG.* 
By Harlan N. Worthley. 
Massachusetts Agricultural Experiment Station, Amherst, Mass. 
PART I. 
INTRODUCTION. 
The common squash bug, Anasa tristis de Geer, is an ever- 
present and often troublesome pest in Massachusetts, and has 
been a subject for investigation at the Massachusetts Agri- 
cultural Experiment Station for the past three years. While 
studying the life history and habits of this pest, the writer dis- 
covered abundant evidence of the presence and activity of the 
parasite Trichopoda pennipes. A review of the literature showed 
that comparatively little is known of the life history and habits 
of this beneficial fly. Much to the surprise of the writer, in 
view of his own observations, it was found that some authors 
have even intimated that little good is derived by mankind 
from the work of this supposedly beneficial species. 
Failure of the written records to substantiate observations 
of the writer furnished the initial stimulus to a study of the 
habits of the fly, the object of this study being to discover the 
exact relationship existing between parasite and host. A portion 
of the following account is the result of these studies. 
During the course of the work it was found necessary to 
confine adults of both sexes in the same cage to induce mating. 
Some difficulty was experienced at first in determining the sex 
*Thesis submitted for the degree of Master of Science at the Massachu- 
setts Agricultural College, and published with the consent of the Director 
of the Graduate School. The writer takes this opportunity to express his 
thanks to Dr. H. T. Fernald, whose kindly interest has made the present 
study possible, and who has criticized, to their benefit, the drawings accom- 
panying the paper; to Dr. G. C. Crampton, under whose supervision the 
morphological study has been carried on, for aid in matters of technic and 
the interpretation of parts; and to Dr. C. P. Alexander for assistance with 
the literature of dipterology. 
