54 
Psyche 
[September 
their activities for the day. On the third day we noted a few females 
provisioning their nests about 1600, and remained in the area until 
1 9 1 5 • We discovered that there was a great emergence of females 
from their nests just before sunset. During the two-day period of 
observation, the first female carrying prey was seen at 1520, the last 
at 1905, with the great bulk of the provisioning occurring between 
1700 and 1900. Sunset was at about 1830. Some females and males 
were still active at 1 9 1 5 > when it was too dark for us to see them well, 
but apparently these individuals were merely digging in for the night. 
In order to determine what types of dies the wasps were taking at 
this unusual hour, we took 97 dies from females or from the nests. 
These dies represented 33 species of nine families; that is, there was 
an average of only three dies of any one kind. The most numerous 
dies were those of the genus Acrosticta (Otitidae) (26 examples). 
Bombyliidae, Asilidae, and Tachinidae were represented in roughly 
equal numbers, each family by several species. A complete list is pre- 
sented in Table III. Although many species of Berubix are relatively 
unselective of their dies, I have never encountered a more remarkable 
diversity of prey in any one locality. Most of the dies used were rel- 
atively small, and a great many of them were used per cell ( about 40) . 
However, some relatively large dies were found in some nests. 
It required very little study to determine that virtually all Diptera 
had ceased activity by the time the Bembix began to provision in num- 
bers. Some of the dies (e.g., the otitids, and some of the bombyliids 
and sarcophagids) were seen commonly on the beach during the middle 
of the day, but in the evening they had disappeared. 1 he Bembix ap- 
parently hunt widely in the vegetation and take virtually any “sleep- 
ing” dies within a certain size range which they encounter there. 
Females carrying dies enter the nesting area with a rather loud buz- 
zing only 10-20 centimeters high. They plunge quickly into the nest 
entrance which, as noted above, is never closed during provisioning. 
In less than a minute, they re-emerge from the burrow and quickly 
take wing. Several instances were observed of females attempting 
to steal dies from one another. 
Oviposition and development. — The first dy is placed deep in the 
cell on its back, head-in, with one wing somewhat extended. The egg 
is laid erect, glued to the side of the dy near the base of the extended 
wing, or actually glued to the wing-base. One instance of abnormal 
oviposition was observed. In this case the dy (Acrosticta sp.) was 
actually smaller than the egg and was dorsum-up, with the egg of the 
wasp glued to the base of the abdomen and extending obliquely for- 
