170 SEVENTEENTH Report STATE ENTOMOLOGIST OF MINNESOTA—1918 
A striking peculiarity of the family is noted in the fact that the 
abdomen is attached to the top of the metathorax, not to the posterior 
end. The abdomen is compressed and has a very slender base. 
Certain species in this group deposit their eggs in egg capsules of 
cockroaches, and have been reared from them. They are met with 
where cockroaches are abundant, and are reported to have been ob- 
served on board ships, where, quite commonly, roaches are a pest. 
Gasteruption incertum Cress., Odontaulocus abdominalis Cress., Hyp- 
tia harpyoides Bradley, and the genus Aulacus occur in Minnesota. 
TRIGONALIDAE 
First abdominal segment broadened or bulbous at apex, not cylindrical. Costal 
cell distinct. 
A family of parasites living in nests of Polistes and Vespa and 
preying upon the occupants. 
Geo. W. Taylor reports (Can. Ent. XXX p. 14, 1898) taking nine 
male Trigonalids in the vicinity of a large nest of Vespa occidentalis 
in October. He says “The day was dull and the wasps sluggish, but 
quite a number of males and perfect females were crawling about 
around the entrance to the nest. Among the wasps were some speci- 
mens of a conspicuous yellow and black Hymenopteron.” 
These were identified as Trigonalys canadensis Hargm. 
ICHNEUMONIDAE 
As in Trigonalidae, but costal 
cell obliterated by approximation 
of costal and sub-costal veins. 
Typical -parasites’ ‘of 
many forms of insect life, 
such as army worms, cut- 
worms, and other injuri- 
ous Lepadoptera. “As 
parasites, however, their 
attacks are by no means 
limited to the butterflies 
and moths, for they also 
prey upon certain Coleop- 
tera and Hymenoptera, as 
well as on plant lice. The 
larvae of Phryganids, al- 
Fig. 49. Thyreodon brullei Vier. 
