Transactions Texas Academy oe Science. 23 
Then she crawled up and with her head stuffed all the caterpillars 
as far back into the chamber as possible' This done, she cleaned 
her antennge and flew away without seeming to take her bearings. 
She had evidently made so many trips to the spot that a study of 
the locality had become unnecessary. 
By 7 p. m. the cell had been closed and another built, which 
the wasp was occupying for the night. A day’s work with dorsalis 
evidently consisted of storing a cell, closing it, and building another 
to be used in the first instance as a lodging place for the night. 
Thus I found her still at home at 7 :45 the next morning ( Sep- 
tember 4th), as shown in Fig. 4. She was lying in the cell, which 
her body comfortably filled, and was amusing herself with picking 
up unwary ants that chanced to pass too close to her threshold 
and, like the Harpies of old, grinding them in her jaws. I allowed 
her to store this cell, as well as build another; then I caught her 
and carried the cells home. 
0. dorsalis, builds pretty mud-cells on the ground, choosing a 
place hidden from view by a clump of grass. The cells are broadly 
spindle-shaped, pointed at one end, which is left open until the 
cell is stored. The chambers do not touch each other for more 
of their length than is necessary for their mutual agglutination. 
This almost entire independence of the cells entails a considerable 
waste of building material as compared with the habit of Pelopaeus 
cemeniarius, which builds her cells side by side in rows 
and tiers of rows. It seems probable that the former method is 
the more primitive one, and that the latter has been superinduced 
by the mud-dauber’s habit of building on flat surfaces. It is to 
be noticed that the lumen of a mud-dauber’s cell still remains, in 
spite of the irregularity of the outer surface, cylindrical. The 
entire structure made by dorsalis is not only held together by the 
slight adhesion of the more or less fragile cells which compose it, 
but is also partially suspended by grass-roots imbedded in the 
plastered walls. The shape of this nest with the grass-roots at- 
tached can best be seen in the figures which are photographs taken 
at different stages in the construction. (Figs. 3, 4, 10, 11.) 
The first wasplet emerged on October 7th, the others on October 
8th, 9th, and 11th, respectively. One wasp failed to emerge and 
was probably from the fourth egg laid, and would normally have 
emerged on October 10th. If one cell was stored each day, the 
first egg laid was on August 30, and the total period of develop- 
ment would be thirty-nine days. The wasps emerged (Fig. 11) by 
a small round opening gnawed'* in the cell wall. This hole was 
