Transactions Texas Academy oe Science. 
25 
only give the total length of development as thirty-nine days and 
that of the egg and larva together twenty days. 
(b) Odynerus . Arvensis, Sauss. 
This species of Odynerus does not posssess the architect aral skill 
of its cousin just described. Its home is not such an elaborate 
domicile, built, as it were, for show as well as for use, but consists 
of any convenient crevice in a wall or fence-post. The nest is 
completed by closing the opening of the crevice with mud, much 
after the fashion of Trypoxylon, I have made a few observations 
on two nests of this Odynerus ; those on the conditions of the cater- 
pillars found in the nests are of particular interest. In general, 
the following facts do not justify Fabre’s conclusions which he 
based on the habits of 0. reniformis. 
At noon, August 4th, a female arvensis was closing her nest 
in the niche of a brick wall. A few days before a Trypoxylon 
had emerged from the very niche now intended to be the cradle 
of another wasplet. I immediately opened the nest and drew out 
eight caterpillars, all of which were alive, six of them, in fact, so 
lively that they wriggled around in the small vial to which I had 
transferred them. I found no egg at first, but, looking carefully 
into the dark recess, I discovered the egg suspended from the 
ceiling of the little room. After breaking the suspensory thread 
with a knife and brushing the egg out, I placed it among the 
caterpillars in the bottom of the vial. Very few wasps’ eggs could 
stand the rough handling which this egg received. The explanation 
of its endurance lies in the toughness of its shell. The larva 
hatched in two and one-half days, having shed a tough, translucent 
shell which could safely be handled with a pair of forceps. After 
fifteen hours the larva had attached itself to a writhing caterpillar 
and had grown perceptibly. The remaining data are as follows : 
August 9. Five days after the nest was closed, two caterpillars 
have been devoured and the remaining six are still alive, of which 
four move spontaneously. The wasp larva is as large as one of 
the caterpillars. The larva takes a long rest this morning. 
August 10, 6 p. m. All parts of all the caterpillars have been 
devoured. 
August 11, 6 p. m. Larva nearly finished spinning cocoon. 
August 29. Adult emerges. 
Thus the length of the egg stage of 0. arvensis is about two and 
a half days of the larval stage, four gnd a half days ; of the pupal 
stage, eighteen days. 
