THE CANADIAN ENTOMOLOGIST. 117 



To the student of animal instinct it is no doubt far more wonderful 

 that an insect in its comparatively short life should at different stages 

 respond to two quite distinct food-stimuli. The syrphus fly, Eristalis 

 tenax, whose larva feeds in liquid manure, is, at maturity, a honey-sucking 

 haunter of blossoms ; in extreme cases, like that of the parasitic oil beetles, 

 as many as three distinct food-stimuli occur in the life of the individual. 



But in my ramble through the realm of Coleoptera, it is the opposite 

 phenomenon which has struck me most. I mean the number of beetles 

 that are attracted to the food of their larva. I have noticed this especially 

 among the Cerambycidae. In many of them the smell of fermenting sap 

 (where a tree is newly felled or has been injured by the lopping of branches 

 or the mutilation of bark) seems to act as a direct and powerful stimulus 

 in liberating the instinct of reproduction. This is specially noticeable in 

 the Monohammi. In others again, where perhaps the smell of sap has 

 first drawn the insects to the tree for breeding purposes, the sight of the 

 foliage seems to impel the beetles to eat the leaves. This is particularly 

 the case in some genera that approach most nearly to the Chrysomelians. 

 We have a familiar illustration of it in Tetraopes, the Milkweed beetle, 

 whose larva feeds in the stem of the plant, while the beetle resorts in large 

 numbers to the leaves, on which it feeds freely as well as breeding. Less 

 conspicuous examples of the same phenomenon are the Oberea, and still 

 more the Saperda. I have several times captured Saperda vestita feeding 

 on the sheaf of leafy twigs surrounding the basswood stumps, under whose 

 bark the eggs are laid. I have found Saperda moesta eating the leaves 

 of the poplar where its larva develops, and on a single willow I once 

 counted over 200 specimens of Saperda concolor breeding on the leaves 

 and eating the foliage with evident relish. 



These last few paragraphs have brought me right into the great group 

 of Phytophagous beetles, properly so called, whose larvae, without excep- 

 tion, find support on living vegetable tissue. They comprise three families, 

 the Bruchids, which devour seeds ; the Cerambycids, which attack the 

 woody tissue of trees and shrubs, and the Chrysomelids, which feed at all 

 stages on foliage and the more succulent parts of vegetation. 



The Bruchids form only a small group, and the genus Brtichus is the 

 only one of much importance ; besides the Pea and Bean Weevils (so 

 called), the only species I have found at all abundant is a minute insect, 

 Bruchiis discoideus, sometimes plentiful in the blossoms of the white 

 Convolvulus or Morning Glory. 



