144 MISC. PUBLICATION" 174, U.S. DEPT. OF AGRICULTURE 



parasites of the fly, but in every instance these references appear to 

 be merely citations to, or repetitions of, the original record. In none 

 of them is it stated that the species has been again reared or 

 collected. 



Furthermore, despite the fact that the fly has been under almost 

 continuous observation and study for many years, during which time 

 numerous investigators of the Bureau of Entomology, as well as 

 other individuals, have carried on extensive and intensive studies of 

 the parasites, literally thousands of all stages of the fly having been 

 collected and many thousands of parasites reared, apparently no one 

 has ever again reared or collected Tetrastichus productus. If the 

 species was actually reared from the fly originally, it is hard to ac- 

 count for its failure to reappear upon that host over a period of 

 nearly 50 years. Although Riley definitely asserts that the type 

 material was reared from coarctate larvae of the hessian fly, state- 

 ments elsewhere in the same paper indicate that infested straws may 

 have been placed in cages for emergence of the parasites, in which 

 case there is a distinct chance that some insect or insects other than 

 the hessian fly may have been introduced and may have served as host 

 to this Tetrastichus. Color is lent to this assumption by the further 

 statement of Riley that a Microgaster was also reared from wheat 

 straw infested with the fly. In this case it is certain that the host 

 was not the hessian fly but some accidentally introduced species, and 

 there is at least a possibility that the same may be true of the host 

 of the Tetrastichus. 



Nothing is known of the real hosts or of the life history of T. 

 productus. Riley believed it to be a secondary parasite, basing this 

 belief on the assumption that, since some species of the genus were 

 secondary, all others must be likewise, a theory now thoroughly 

 exploded insofar as the Chalcidoidea are concerned. 



TETRASTICHUS AINSLIEI Gahan 



Tetrastichus ainsliei Gillian, U.S.Natl. Mus. Proc. 53: 214, 1917. 



DESCRIPTION 



Tetrastichus ainsliei is similar in most structural characters to T. 

 carinatus and T. productus, but distinguishable at once by the broad 

 whitish band at the base of the abdomen in both sexes. It further 

 differs from carinatus by being more slender, by lacking metallic 

 coloration on the head and thorax, by'being less distinctly sculptured, 

 and by having the first and second funicle joints subequal. It dif- 

 fers from productus principally by having the abdomen of the female 

 short ovate, about as long as the thorax, and the femora and tibiae 

 all pale. 



Both sexes are deep shining black ; the flagellum brownish black ; scape, basal 

 third of abdomen, and all legs pale yellow, the front coxae mostly and the 

 median and hind coxae basally black ; mandibles reddish ; wings hyaline, vena- 

 tion pale. The propodeum is distinctly very finely punctate and has a weak 

 median carina. The submarginal vein has only one erect bristle. 



Redescribed from the types and 11 additional specimens in the 

 United States National Museum. 



