142 MISC. PUBLICATION" 17 4, U.S. DEPT. OF AGBICULTURE 



The American material studied includes one female sent to Eiley 

 by Forbes and believed to be a paratype, another specimen which 

 was compared with the actual type by both J. C. Crawford and the 

 writer and pronounced a homotype, and many additional specimens 

 reared from the hessian fly by "Webster, McConnell, Myers, Larrimer, 

 Keener, and others. 



HOSTS AND LIFE HISTORY 



Hosts thus far recorded for T. carinatus are Phytophaga destruc- 

 tor (Say), Dasyneura legum'micola (Lintner), Mayetiola phalaris 

 Barnes, and Platygaster sp. Myers states in his unpublished manu- 

 script that at least 9 instances have been observed in which minute 

 female specimens of T . carinatus emerged from hessian-fly puparia 

 containing Platygaster cocoons and in 5 of these instances the Platy- 

 gaster has been identified as P. vernalis ~Myevs = zosine Walker. 



Early authors, such as Riley, Lindeman, and Osborn, regarded 

 this species as a true secondary parasite, but more recent investiga- 

 tions by McConnell, Myers, Hill, and others have shown it to be 

 normally a primary, internal, solitary parasite of hessian-fly larvae 

 of the spring generation, becoming secondary only occasionally when 

 by accident the female oviposits in a larva that is already occupied 

 by Platygaster, 



Details of its life history are unknown to the writer. Emergence 

 takes place from the fly puparium. 



DISTRIBUTION 



European literature, so far as known, records the species from 

 England, Germany, and Russia. European material seen by the 

 writer is limited to England and Russia. It is highly improbable, 

 however, that its distribution in Europe is so limited as the few 

 available records indicate. 



In North America T. carinatus appears to be distributed through- 

 out the wheat-growing area east of the Mississippi River, but it has 

 not, to the writer's knowledge, been taken west of that river except 

 in the far Northwestern State of Washington. Definite records of 

 its occurrence have been obtained from New York, New Jersey. 

 Pennsylvania, Maryland, Delaware, Virginia, North Carolina, West 

 Virginia, Kentucky. Ohio, Michigan, Indiana, Illinois, Washington, 

 and the Province of Ontario, Canada. It seems highly improbable 

 that the species, which was first found in Illinois nearly 50 years 

 ago, does not occur in the neighboring States of Iowa, Missouri, and 

 Minnesota. Future investigations will very likely disclose its pres- 

 ence in all three of these States and possibly farther west, although 

 the dry climate and higher temperatures of Kansas and Nebraska 

 may account for its absence there. 



IMPORTANCE 



According to Hill and Smith, T. carinatus ranks seventh in im- 

 portance among parasites of the fly in the Eastern States. Myers' 

 manuscript states that the maximum percentage of parasitization 

 by this species obtained in a single collection of puparia was 12 per- 

 cent, Avhile Smith and Hill found an average parasitization by it over 

 a 10-year period of only 0.57 percent, with a maximum for any one 

 season of 2.07 percent. 



