140 Mr. J. O. Westwood’s Memoirs 
or elongated nodules. The substance of which they are composed 
is evidently earthy, as it will not burn, but retains its form when 
thrown into the fire. 
On opening these cells I found in each a delicate white slender 
membraneous sac, affixed by its base to the bottom of each cell, 
the upper end being free, and generally open, the insect having 
made its escape ; on the outside of this membraneous bag I found 
in several of the cells portions of the chelicerze of a large species 
of spider, which had evidently been devoured by the inhabitant of 
the cell whilst in the larva state, and previous to the formation of 
the membraneous sac. Within one of these sacs I found a dead larva, 
represented in PI. X. fig. 18, not differing in its structure from the 
larva of other fossorial species ; whilst in each of two other of the 
sacs I found the dead pupa of the insect, which I at first mistook 
for an Ichneumon, from the great length of the antenne, and the 
slenderness of the body. These pupz were almost arrived at the 
perfect state, so that, with the exception of the wings, all the parts 
could be distinctly traced, as well as the colours of the future 
imago. The antenne are laid along the sides of the breast, and 
are long and slender, extending rather beyond the posterior cox, 
and consist of thirteen joints, thus indicating the specimens to be 
males. The basal joint is robust, the second very short, and the 
remainder slender, and rather elongated. The fore wing, when 
moistened with water, and placed under the microscope, was seen 
to have two deep folds on the costa, whereby its length was re- 
duced nearly one-half. The most peculiar feature was the large 
square prothorax, resembling that of the genus dporus, and of 
various exotic Pompili ; it is, in fact, by the structure of this part 
of the thorax, which is employed amongst the fossorial Hymenop- 
tera as a primary distinctive character of the several families, that 
we are enabled to determine the natural relations of this insect. 
The entire body is black, and clothed with a very slight griseous 
pubescence. The antenne are white, and the tibiz and tarsi 
brownish white. ‘The abdomen is slender, and composed of seven 
segments; at first the dorsal portion of the abdomen appeared to 
have the segments posteriorly margined with grey bands, but I 
found this to result entirely from the pellicle of the pupa having 
been scaled off from the base of each segment. 
The strength of the founder of these nests may be imagined from 
the fact, that the single jaw of the spider found in one of the cells 
was as large as the entire head and prothorax of the perfect insect. 
The combat between the parent fossor and its prey must therefore 
