157 
insects were abundant in the beetle stage, making, indeed, the greater 
part of the insect food of all the crows collected at that time. 
To these well-known facts I have to add two significant items of 
observation reported to me by my field assistants. One of these, 
Mr. E. O. G. Kelly, who was engaged during much of the season 
of 1906 in a field study of injuries by white-grubs, unusually serious 
that year in central Illinois, tells me that he often saw considerable 
numbers of crows following after the plow in fall, evidently picking 
up white-grubs, and that he has also seen flocks of! crows alight in 
a badly infested pasture and tear tlie sod in pieces in search of the 
grubs, fighting with each other for their possession when thus ex- 
posed. Another assistant, Mr. A. O. Gross, employed last fall in 
collecting data for a census of the bird life of Illinois, found, in a 
trip across the state made on foot in September and October, that 
next to the horned lark, crows were the most abundant birds on 
plowed ground, averaging seventy-nine per square mile in all the 
recently plowed fields crossed on that trip. They could have had no 
other object there than the search for insect food.* 
In a study of the food of blackbirds, made by Mr. F. E. L. Beal 
for the U. S. Department of Agriculture in 1894, it was found that 
these birds ate either beetles or grubs in every month from March 
to October inclusive. In May these insects made more than a sixth, 
and in June one ninth, of the entire food. Many stomachs were 
found to be literally crammed with grubs ; and in many more, grubs 
had formed a large part of the previous meal. 
The Common Gnih Wasp (Tiphia). — Much the most important 
insect enemy of the white-grubs is a wasplike insect belonging to the 
hymenopterous genus Tiphia. It is a slender, jet-black species, usu- 
ally about two thirds of an inch long, but sometimes smaller, and 
with wings either clear or more or less deeply tinged with dusky 
yellow. It enters the ground in search of the grubs, follows them 
up in their burrows, and lays on the back of each grub a single egg, 
which hatches in a little over a week into a footless, maggot-like 
larva. This larva adheres to the surface of the insect, punctures its 
skin and sucks its blood for a time, but finally eats it up. The Tiphia 
larva then spins, under ground, an oval brown coccoon within which 
it goes through its transformations, coming out as a winged insect 
the following summer. The rate of multiplication of the species 
is not known, but it is certainly sufficient to enable the Tiphia vir- 
tually to destroy, under favorable circumstances, the entire grub 
population of a badly infested field. 
*"An Ornitholog'ical Cross-section of Illinois in Autumn." By S. A. Forbes. Bull. III. 
State Lab. Nat. Hist., Vol. VII., Art. IX., p. 318. 
