HYMENOPTEROUS PARASITES. 265 



wood." That the insect occurs generally about Ithaca is evident as 

 it was again taken by Prof. C. R. Crosby in 1910. My own first 

 acquaintance with Dolichotrypes was during the summer of 1911 

 when Mr. W. F. Fiske, then director of the Gipsy-moth Laboratory at 

 Melrose, Mass., gave me several vials containing numerous specimens 

 of minute Platygastridse that he had collected upon freshly cut stumps 

 not far from his laboratory. He was quite certain that the females 

 were ovipositing in objects concealed within the wood, and from the 

 known habits of numerous related genera, surmised that Dolichotrypes 

 attacks the larvae of some Itonidid midge. ^ 



At the time I noticed that there was a great variation in the size and 

 appearance of jMr. Fiske's specimens and on having them mounted, 

 found that more than one species was represented. This material 

 received no further study, however, till Professor ^Yheeler showed me 

 the series of similar insects obtained at Kartabo. A re-examination of 

 my New England material then showed the presence of not only 

 Dolichotrypes, but also of two of the other genera found at Kartabo. 

 Mr. Fiske's material then, includes the following: 



Polymecus (Dolichotrypes) hopkinsi Bradley & Crawford. 

 Synopeas sp. (perhaps S. cornicola Ashm.). . 

 Gastrotrypes caudatus sp. nov. 



I found no males, and there appears to be considerable doubt also, 

 whether the males of Dolichotrypes described and figured by Bradley 

 and Crawford ('11) are really such. Thiols a minor matter, however, 

 in the present connection, as the interesting points here dealt with 

 relate to the females. 



If one examines a large series of Dolichotrypes minor under the micro- 

 scope it is at once evident that the individuals vaiy greatly in length, 

 and that this variation is confined almost entirely to the apical seg- 

 ments of the abdomen. The head, thorax and the first three abdominal 

 segments which form the gaster are uniform in conformation and equal 

 in size, apart from the small differences which are always exhibited 

 even by the least variable insects. Among the Platygastridse in 

 particular, variations in body size are usually well marked as the spe- 

 cies are parasites of the larvae of Diptera, and they reflect not only the 

 intraspecific variability of the host, but also to some extent, its change 



1 Since then the genus Dohchotrypes has been found in AustraUa by Dodd 

 who described ('16) a species from Queensland. The single female known was 

 taken on foUage of sugar-cane. 



