1924 ENTOMOLOGICAL SOCIETY 17 



1923 that Ainslie, of the U. S. Bureau of Entomology, and I found a fifty per cent, 

 parasitism in certain fields near Bottineau, North Dakota. In Canada, K. M. 

 King, of the Dominion Entomological Branch, discovered a ten per cent, infes- 

 tation in plots near Saskatoon, Sask., and we in Manitoba found the parasite to 

 be quite widely prevalent in grain fields, though still mostly on the edges of the 

 crop. Hence a beginning has been made, but the parasite will have to make far 

 greater progress before we can expect to reap much benefit from its activities. 

 Once a start has been made, however, and a foothold obtained, we can hope for 

 further gains. There is this consolation, too, that the Cephus damage in North 

 Dakota during 1923 was less than half what it was some years ago. 



There are other parasites of the Wheat-stem Sawfly which, as yet, have been 

 very rarely recovered from grain stems. There are also, I regret to say, some 

 secondary parasites, one of which, Eupalmus alyni, we have reared from Micro- 

 bracon cephi. There is also a much smaller Hymenopteron, probably a parasite 

 on Eupalmus. Thus the wheels within wheels complicate our problem of natural 

 control, though they obviously add to its interest. 



I have some hesitation in appearing as a student of forest insects, but we 

 have been so long without adequate investigators of shade-tree and forest insects 

 on the prairies that it has seemed absolutely necessary to study some of the more 

 important forms with which our people have had to contend. 



Two of these insects have been forced upon me with particular emphasis 

 during the last two years, namely, the Forest Tent Caterpillar, which has 

 defoliated more than a hundred square miles of trees in Saskatchewan, and the Fall 

 Webworm, which has cleaned up local areas of trees with equal thoroughness. 

 I am not going into details of these outbreaks other than to state that the 

 insects involved have certain parasites in common. One in particular has 

 turned up quite frequently, namely, Itoplectis conquisitor Say. We reared it 

 last year from the Fall Webworm in small numbers. This year it parasitized 

 tent caterpillars to the extent of about twenty per cent., and it occurred in great 

 numbers among the Hyphantria this fall. Another species, Ephialtis pedalis 

 Cress., has been reared from the Malacosoma larvae and has been seen amid the 

 fall webworms, so we may suspect that there is a linkage between the two hosts 

 and the two parasites. Other Hymenopterous parasites as well as certain 

 Tachinidae have been reared or collected from, or near, one host or the other, but 

 I am emphasizing Itoplectis because of its commonness and because of its 

 dependence upon at least two hosts for its perpetuation. In the shrubby or semi- 

 wooded country its usual hosts appear to be Malacosoma fragilis and certain 

 Tortricidce, all tent-building species. In the more wooded country it may attack 

 the insects already mentioned but readily infests as alternatives both Malacosoma 

 disstria and Hyphantria textor. 



Judging from the number of Itoplectis present it would seem as if this and 

 other parasites will practically eliminate the webworm outbreak next year, but 

 we cannot predict as much for the tent caterpillar, because the two pests have 

 occurred at widely separated places and we do not know what intermediate hosts 

 are present in the tent caterpillar region, or whether Itoplectis is a strong enough 

 flier to migrate long distances in search of hosts. 



If we could only transport the heavily parasitized Hyphantria pupae to the 

 Malacosoma-iniested area much good might result. Perhaps, however, it would 

 be better still to have actually shipped the healthy webworm pupae to the tent 

 caterpillar district in order to insure a supply of alternate hosts for the parasite. 

 The shipping of a healthy pest to a comparatively free region may seem a 

 rather risky recommendation, and doubtless it would be were we to transport 



