THE ROUGH-HEADED CORN STALK-BEETLE 5 
- September. The new generation of beetles do not appear to be 
very active, remaining usually where they emerge, though they have 
been found soon after emergence feeding upon the culms of Juncus 
effusus and certain grasses of the genus Paspalum. 
EGG 
DESCRIPTION 
The egg when first laid is oblong, pure white, and perfectly smooth 
(Pl. II, B).- Subsequently the egg enlarges until it is nearly double 
its original size and changes its form until almost globular (PI. 
Il, B, C, D, and #). Eggs measured by the senior writer averaged 
about 2 millimeters in length and 1.5 millimeters in diameter. 
These were several days old and approximately full size. No meas- 
urements of freshly deposited eggs were made. 
METHODS OF COLLECTING AND INCUBATING 
A smail number of the eggs used in the investigations were gath- . 
ered in the field, but the greater number were obtained from the 
breeding cages. 
In the field the eggs were found in the ground, where it was usually 
possible to obtain them by digging. 
To obtain eggs which were known with certainty to belong to the 
present species, adult beetles were confined in suitable breeding cages, 
from which the eggs were gathered at regular intervals. Each cage 
consisted of a 12-inch standard-size flowerpot filled with finely-sifted 
soil and covered with a cylindrical wire-screen top; the whole outfit 
had essentially the same form and arrangement as that portrayed 
by Davis (4, pl. 3, fig. 4). The soil in these cages was kept mod- 
erately moist, and at intervals, varying from a few days to a week 
and a half, was passed through a fine-mesh sieve. The meshes in 
this were fine enough to retain the eggs, which were then transferred 
to the incubating boxes. 
In the breeding cages the beetles were first fed by transplanting 
young corn plants to the cages, but as the labor of replacing the 
food plants every few days proved burdensome, a handful or so of 
corn kernels was buried in the soil. These proved to be a highly 
satisfactory substitute, the beetles feeding upon them as readily as 
upon the living pliant. 
The receptacles used in incubating the eggs were rectangular tin 
boxes like those used by Davis for the same purpose (4, pl. 4, fig. 7). 
These boxes were about three-fourths filled with finely-sifted earth, 
which was kept to the right degree of moisture by occasionally add- 
ing a few drops of water with a pipette. As the eggs were trans- 
ferred to a box each was placed in a small pit made with the blunt 
end of a pencil, and as the boxes were filled the hd was replaced 
and they were then kept in the shade. Usually the lid would so 
conserve the moisture originally in the soil that in most instances 
it was unnecessary to add more water during the period of incuba- 
tion. 
: PLACE OF DEPOSITION 
The eggs are deposited in the ground, and apparently the females 
exercise no particular care in the choice of a place in which to 
