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white and fairly polished. It is very little curved, the rounded 
ends are practically similar, and it measures about 4.70 mm. in 
length by 1.20 mm. in thickness. The incubation period was not 
determined beyond the fact that, for a wasp, it was not rapid, 
From oviposition up to the time when the larva is full-grown, the 
mother exercises great care in protecting her young. During the 
day, if the weather be promising, she occupies herself in part 
with improving the nest, strengthening the cell, extending its 
mouth, forming the protective roof, or putting on an extra layer 
or two of leaf-bits, and in part with keeping guard within the 
ample cell, her stout head blocking the entrance, her antennae 
coming to attention at your movement, and, if hard pressed, 
retreating well within the cell and biting any offending object. 
She is, however, a really timid insect and when frightened away 
keeps at a distance until the danger seems past. She always 
stays in the cell at night and never appears to be asleep, as I have 
found her ever awake and watchful far into the night. 
The egg-shell is quite tough, as is usual with the Eumeninae, 
so that it retains much the same shape as the egg. The young 
larva is more or less curved into an arc, whitish, cylindrical, and 
has a large head. It sheds its skin very shortly after hatching, 
and is active and tough from the first, wriggling its body and 
working its needle-like mandibles hungrily. The mother feeds it 
from time to time with freshly-killed moth caterpillars, appar- 
ently Pyralidina. One such caterpillar I saw captured. The 
wasp flew about the crown of a small tree ( Litsea sp.) and exam- 
ined the leaves for her prey. Finally she found a leaf rolled up 
lengthwise, perched herself upon its distal end and, cutting 
through it with her stout jaws, inserted her head into the open- 
ing thus enlarged and hauled out a small caterpillar. This she 
did not appear to sting, but chewed off the head and most if not 
all of the thorax of the unfortunate captive. It is this remnant 
of caterpillar—all good and tender meat—that Zethus carries 
away beneath her and delivers to her offspring. 
At the close of the day the wasp enters the cell occupied by 
her young and stands watch. This she does also quite frequently 
during the day, especially in dull weather. She goes into the 
cell headfirst and, turning about in the enlarged bottom, advances 
to guard the entrance. But soon the growing larva attains such 
proportions that it occupies most of the enlarged portion of the 
cell, and assuming a curled position, refuses to be dumped out 
