Typua Insects: THEIR EcoLocicaAL RELATIONSHIPS 481 
behind the sheath of the outer leaf, where they feed for a time before they 
enter the stem and become true stem borers. If the larvae emerge from 
the leaf soon after the first molt, they usually go down to the sheath of 
one of the first-formed leaves and there mine in the sheath for some time 
before entering the stem. Occasionally they feed for a while between 
two contiguous leaves. The effect of Nonagria oblonga Grote is easily 
recognized on the plant, since the work of the first-instar larva always 
causes the leaf at first to bend over and wither, and later, after the severed 
portion has become dry, to break off and fall to the ground. The leaf 
thus broken at the end, and the presence of the mine, are indicative of the 
work of these larvae. The writer once found a plant in which five leaves 
had been cut off by these larvae (Plate XLII, 36). 
On entering the stem, the larvae work toward the center, where their 
borings materially hinder the further growth and development of the 
plant (Plate XLVII, 70). The presence of the larvae in the stems is in- 
dicated by the dried and withered central leaves of the leaf bundle. A 
plant so affected never heads, because the larva keeps the center tunneled 
out. The habits of the later larval stages of N. oblonga and Arzama 
obliqua, and their effect on the plant, are very similar. 
Walton (1908) says of the habits of the larvae: ‘‘ From all appearances 
the larva feeds for a time on the sheath of the stem, . . . As it increases 
in size it bores directly into the succulent central shoot, where it 
afterward remains until emerging as a mature insect.” 
When the larvae become full-grown, they transform to the pupal stage 
in the burrow of the plant. The larva lies with its head upward in the 
burrow. The exit hole is from two to four inches above the pupa and 
is carefully plugged up with a combination of frass and plant fibers. 
Bird (1902) states that Nonagria has an extremely short pupal stage, 
from seven to nine days being the record of one brood. 
At Ithaca, New York, the writer first found pupae on August 2, 1916. 
In Kansas the insects mature much earlier. There one larva pupated 
on June 24, 1917, and emerged on July 5, 1917, the pupal stage covering 
only eleven days. 
The adult—— Around Ithaca the first adults were noticed on August 8, 
1916, while in Kansas they were beginning to emerge by the 30th of June. 
Whether there is a second generation, especially in Kansas where the 
adults emerge so early, the writer has not been able to ascertain. The 
