USEFUL INSECTS EATEN BY THE ROSEBREAST. 43 



As just noted, almost 6.5 percent of the total food is Hymenoptera, 

 and as this group contains some of the most useful of all insects, it 

 must be ascertained how many, if any, of these forms fall a prey to 

 the bird. The beneficial Hymenoptera are the small parasitic species, 

 the eggs of which are deposited in the bodies of caterpillars and in 

 the eggs of many insects, to develop there and later destroy their 

 hosts, and the larger wasps, which store up caterpillars and other 

 creatures as food for their }^oung. Very few parasitic species were 

 found in the stomachs, the larger Hymenoptera apparently being 

 preferred. In many cases a single wasp composed from 40 to 90 

 percent of the stomach contents of individual grosbeaks. It is pos- 

 sible that among these are some of the highly beneficial solitary 

 wasps, but the probabilities are that most of them belong to the more 

 abundant, gregarious species, which although often beneficial would 

 lose little by the destruction of few of their number. 



Fifty-four of the 176 grosbeaks examined were found to have 

 eaten Hymenoptera of some sort, which shows that the bird has a 

 decided liking for these insects; but, as just mentioned, few bene- 

 ficial species are eaten, while a number of injurious ones are devoured. 

 One grosbeak secured a cuckoo fly (Chrysis sp.), which is a parasite 

 of the useful solitary wasps. Three fed upon sawfly larvae, which 

 have habits like caterpillars, and are injurious to roses, currants, 

 pear, Avillow, and other plants. One bird when collected had 10 

 sawfly larvae in its beak, which it was probably gathering for its 

 young; while in the stomach of another grosbeak were 24 of these 

 larvae, which constituted 60 percent of the contents. The few ants 

 taken are injurious, especially those of the genus Camponotus, which 

 sometimes devour the wood of living trees, hollowing them out to 

 mere shells. Two rosebreasts ate little mining bees (Andrena) , one 

 consuming 26 of these and nothing else. They have no special 

 economic significance except as carriers of pollen. 



Passing now to beetles, this gTosbeak was found to prey upon 

 members of three useful families, the ground-beetles (Carabidae), 

 ladybirds (Coccinellida?), and fireflies (Lampyridae). Seven birds 

 ate predaceous ground-beetles, but since they compose only a little 

 more than 0.5 percent of the food from May to September, little 

 harm is done. One of the 7 grosbeaks captured a large shining black 

 ground-beetle (Pasimachus depressns) , which is about an inch in 

 length and is one of the most powerful insects of the family. 



Three birds ate coccinellid beetles, one securing a twice-stabbed 

 ladybird (Chilocorus bivulnerus), a noted enemy of scale insects. 

 If many such beetles were eaten, damage would be done, but as they 

 compose less than 0.2 percent of the total food, it is evident that only 

 occasionally one is snapped up. Moreover, the grosbeak compensates 



