THE VIXE SAW-FLY. 
523 
dark brown veins. The body of the female (Fig. 244) 
measures one quarter of an inch in length, that 
of the male is somewhat _ shorter. These flies 
rise from the ground in the spring, not all at 
one time, hut at irregular intervals, and lay 
their eggs on the lower side of the terminal leaves of the 
vine. 
In the month of July the false caterpillars, hatched 
from these eggs, may be seen on the leaves, in little 
swarms, of various ages, some very small, and others fully 
grown. They feed in company, side by side, beneath the 
leaves, each swarm or fraternity consisting of a dozen or 
more individuals, and they preserve their ranks with a 
surprising degree of regularity. Beginning at the edge 
they eat the whole of the leaf to the stalk, and then go to 
another, which in like manner they devour, and thus pro- 
ceed, from leaf to leaf, down the branch, till they have 
grown to their full size. They then average five eighths 
of an inch in length, are somewhat slender and tapering 
behind, and thickest before the middle. They have twenty- 
two legs. The head and the tip of the tail are black ; the 
body, above, is light green, paler before and behind, with 
two transverse rows of minute black points across each 
ring; and the lower side of the body is yellowish. After 
their last moulting they become almost entirely yellow, and 
then leave the vine, burrow in the ground, and form for 
themselves small oval cells of earth, which they line with 
a slight silken film. In about a fortnight after going into 
the ground, having in the mean time passed through the 
chrysalis state, they come out of their earthen cells, take 
wing, pair, and lay their eggs for a second brood. The 
young of the second brood arc not transformed to flies until 
the following spring, but remain at rest in their cocoons in 
the ground through the winter. 
For some years previous to the publication of my Dis- 
course, I observed that these insects annually increased 
Fig. 244. 
