A NEW HYMENOPTEROUS PARASITE UPON ADULT 



BEETLES. 



A. B. GAHAN 



Branch of Cereal, and Forage Crop Insects, Bureau of Entomology, 

 U. S. Department of Agriculture 



The writer has recently received from Mr. W. V. Balduf, 

 Assistant Entomologist of the Ohio Agricultural Experiment 

 Station and graduate student at Ohio State University, speci- 

 mens of an interesting parasite, which appears to be new to 

 science. This parasite is interesting not only because it attacks 

 a well known garden pest, the cucumber beetle {Diabrotica 

 vittata), but it is interesting also structurally and biologically. 



The writer is indebted to Mr. Balduf for the following 

 facts regarding its life history : The parasite attacks the adult 

 beetle by mounting on the back of its host and thrusting its 

 ovipositor into the thorax, apparently through one of the 

 sutures near the base of the elytra, and depositing its egg 

 within. The parasite larva feeds internally. In its earlier 

 stages it has a sort of tail like terminal appendage which is lost 

 before maturity. The mature larva escapes from the body of 

 its host either at the junction of head and thorax or of the 

 thorax and abdomen, and although the host is not outwardly 

 defaced, it is killed. The parasite larva undergoes its trans- 

 formation just below the surface of the soil in a closely woven 

 silken cocoon. Pupation lasts approximately ten days. The 

 parasite is not plentiful, having been found in an average of 

 about one or two beetles per hundred late in the summer and 

 somewhat more commonly in May and June. 



In its mode of development the parasite reminds one of the 

 common parasite of lady-bird beetles [Dmocampus terminalis 

 Nees], but differs in many important details. It is perhaps 

 more nearly like Perilitus eleodis Viereck, but here again there 

 are marked differences in details, such as the manner and place 

 of oviposition, the place of emergence from the host, and the 

 method of pupation. 



Following is a description of the adult female parasite: 



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