THE CANADIAN ENTOMOLOGIST. 63 



when plugged up with clay, assumes the appearance of a button, is pro- 

 bably to prevent the caterpillars first enclosed in the nest from escaping 

 before the full complement of food is made up." 



"No. 2 (Can. Nat, Dec 1865, p. 461) is the nest of a wasp belong- 

 ing to Pompilida\ and differing from true Pompilus in having the front 

 legs of the female nearly smooth. I have bred four or five different species 

 from nests of similar structure, most of them found under dry bark, but 

 one species occurring always under logs where the ground is moist. One 

 of the former species is largely infested by an undescribed ichneumon fly 

 belonging to the genus Mesosienus. The kind you figure is the smallest 

 kind that I have bred from, some kinds being twice as long." In a sub- 

 sequent communication, Mr. Walsh states that " the insect that forms the 

 cell No. 2 belongs, I believe, to St. Fargeau's genus Anoplius : and on 

 account of the legs being unarmed in the female he concludes it to be 

 'parasitic' in his sense of the term, or what Hartig calls an ' Inquiline," 

 and I have called in English a ' Guest-fly.' It is plain, however, that the 

 reason whv the legs of the female are unarmed is because it builds a clay 

 nest and does not dig one out either in wood or in the ground. For the 

 same reason, our common mud-wasp (Pelopceus lunatus Fabr.) has the legs 

 of the female but very slightly armed with spines." 



It will be seen from the above, that Mr. Walsh has bred four or five 

 species belonging to the genus that produced my nest No. 2, and that the 

 nests were all of similar structure. — but these species, he adds, differ from 

 the true Pompilus, by having the front legs of the females devoid of spines. 

 I am sorry that it is not in my power at present to obtain additional infor- 

 mation regarding the species occurring in Canada ; but it may be safely 

 inferred that they do not belong to Pompilus proper. The habits of these 

 insects differ, as he states, in that the majority of the species build under 

 dry bark of trees, while one species constructs cells under logs, &c, in 

 damp places. It may be found that this difference is a selection to suit 

 the larva-food which may be of another kind from that found in the cells 

 made under bark. Many of the mud-building wasps that construct dry 

 cells provide their larvae with caterpillars and spiders, which the parent 

 insect stupefies with a kind of aculeate poison that keeps them fresh for 

 many days. It is, therefore, probable that the similarly-formed cells found 

 under logs in damp, muddy places, may be supplied with a larva-food 

 requiring moisture to keep it fresh while the larvae are feeding.* It 

 would please me greatly, if some young Entomological student of Ontario 



* ] hiring the progress of these articles, it is my intention to make occasional remarks 

 on the similarity of nests f<rmt<l by Canadian Insects, embracing distinct genera in the 



