USEFUL INSECTS EATEN BY THE BLACKHEAD. 69 
‘ 
members of this order are the parasitic Hymenoptera, which lay 
their eggs in the eggs or young of other insects. Remains of insects 
of this class from the stomach of one grosbeak were identified and 
they amounted to 22 percent of its contents. Two bees were found 
in another stomach, one of which was a worker honeybee. These 
are the only beneficial species of Hymenoptera from stomachs of 
this grosbeak positively identified, but it is probable that many of 
the unidentified forms belong in the same category. In all, 58 gros- 
beaks fed upon wasps, bees, and ants, very many of which selected 
large wasps, which were most probably workers of some social 
species the loss of which would not 
be noticed. Eleven blackheads ate 
ants, including both pupe and 
adults, for which the birds are to 
be commended, as many ants are 
prejudicial to the interests of man. 
Summing up the relations of the 
black-headed grosbeak to beneficial 
insects, Hymenoptera constitute 2.56 
percent of the food, not all of 
which, as just noted, is to be set 
down against the bird. The wholly 
useful fireflies amount to 2.38 per- 
cent, the mainly beneficial ground 
beetles to about 1 percent, while the 
ladybirds are a mere trace. Thus 
only about 5 percent, or a little 
more, of the bird’s food consists of 
insects the destruction of which is 
prejudicial to the. welfare of man. 
Even were the bird not useful other- 
wise, this showing would hardly jus- Fie. 33.—An Australian ladybird 
= . (Rhizobius ventralis). (From Mar- 
ify q 
t reprisals latt, Bureau of Entomology.) 
As a matter of fact, however, the 
blackhead is far from useless, since the remainder of the animal food, 
which is fully 11 times the bulk of the useful insects, consists of pests 
upon some of which no other bird is known to prey so extensively. 
Beetles of various families constitute about half the bulk of these 
harmful insects, and 28.71 percent of the total food. A much greater 
number of grosbeaks preyed upon leaf beetles (Chrysomelidx) than 
any other family, these composing 17.98 per cent of the diet. One 
hundred and seventy-two blackheads, or almost four-fifths of the 
total number examined, captured leaf beetles, which are said to in- 
clude among their ranks more enemies of crops, shade trees, and 
ornamental plants than any other family of beetles. 
