42 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 121 



Biology. — Larvae of this species have been collected from under 

 cow mannre and rotting vegetation at the edge of highly alkaline 

 lakes (pH 8.6). 



Material examined. — Alberta: Chappice Lake, 18 miles north of 

 Medicine Hat, June 7, 1960, Ball, Madge and McFadden, 3 puparia, 

 MWM; Gooseberry Lake Provincial Park, 9 miles north of Consort, 

 June 5, 1960, Ball, Madge and McFadden, 8 puparia, MWM. 



Subfamily Pachygastrinae 



In their recent revision of this subfamily, Kraft and Cook (1961) 

 have presented an up-to-date resume of the biology and taxonomy 

 of both adults and larvae. Keys were presented for distinguishing be- 

 tween larvae in each of the 5 genera and within the 2 genera Zabrachia 

 and Eupachygaster. 



I have found variation in the measurements given by Ki-aft and 

 Cook as compared with those taken by myself. In one species, 

 Eupachygaster henshawi MaUoch, this variation is one millimeter and 

 represents an error of 25 percent. In spite of this, I do not believe 

 that these mensural variations represent specific differences but, 

 rather, indicate a small sample that may have been taken from a | 

 limited geographic area. I have placed the measurements given by 

 Kraft and Cook in brackets and have presented my own measure- 

 ments including range and mean. 



SuBFAMiLTAL CHARACTERS. — As given in key to subfamilies. 



Habitat of larvae. — Pachygastrine larvae have been found under 

 the bark of both deciduous and coniferous trees. Oviposition usually 

 occm's on wounded or dead trees but in either case there must be 

 enough moisture present in the host for the larvae to be able to obtain 

 nourishment. Host trees mentioned by Ki'aft and Cook are: apple, 

 quaking aspen, dwarf elm, American elm, cottonwood, hickory, white 

 pine, Douglas fir, Engelmann spruce, and shore pine. 



The larvae are gregarious (I have collected approximately 100 

 larvae beneath the bark of a single log), extremely slow moving, and 

 feed on the sap or microorganisms that occur in the moist areas i 

 beneath the bark. MaUoch (1917) has suggested that pachygastrine 

 larvae are predatory on other insect larvae but this has not been 

 observed. 



Key to Genera of Subfamily Pachygastrinae 



(modified after Kraft and Cook, 1961) 



1. Teeth along anal opening prominent; setae on margin of last segment short, 



no longer than one-fourth width of last segment (fig. 141) 2 



No prominent teeth along anal opening; setae on margin of last segment long, 

 at least one-third as long as width of last segment (fig. 140) 3 



