1964] 
Evans — Nesting behavior 
143 
Ecology. — I first encountered Philanthus lepidus in an area of 
extensive small sand dunes and blow-outs near Granby Center, 
Oswego Co., N. Y., on August 31, i960. Here I found some 
thirty nests, mostly in two well separated aggregations about ten 
meters apart. Within each colony the nest entrances were separated 
at times by no more than 10 cm. Many of the nests were in 
depressions amongst ferns, and the soil was so full of roots as to 
make it very difficult to dig out the nests successfully. I spent only 
a few hours with these nests, as I was gathering data on Bembix 
pruinosa and on a species of Tachytes which nested in more open 
sand in the same locality. I noted no other philanthine wasps in 
the area on that date. 
For the past several summers P. lepidus has nested in considerable 
numbers in a large, eroded sand bank near my home in Lexington, 
Massachusetts. Each year the species appears at the end of August 
and remains active well into September. In 1962, when most of 
my studies were made, I noted much activity on September 7, 
which was a cool day (73°F maximum), and on September 23 a 
few females were noted digging sluggishly at an air temperature of 
6o°F, after several nights of frost. On this date virtually all other 
solitary wasps had disappeared. Even P. solivagus , another species 
characteristic of the late summer, emerges and disappears one to 
two weeks before lepidus. However, the nesting cycle of the two 
species overlaps for two or three weeks at Lexington, and the nests 
of the two species are sometimes intermingled. However, in this 
particular sand bank solivagus occurs mostly near the top, in a 
moderately steep slope, while most nests of lepidus are near the 
bottom, in weakly sloping, firm sand eroded from above. In this 
very same place, P. politus is common in early summer, but I saw 
none nesting after mid-August. P. gibbosus also occurs in this sand 
bank, nesting in small numbers both in the solivagus and lepidus 
areas, but mainly in mid-summer. 
Both males and females of P. lepidus visit the flowers of Solidago 
in considerable numbers. The males are otherwise rarely seen, 
though they do appear from time to time around the nests of the 
females, landing on the sand with their antennae extended rigidly 
and now and then pursuing females. I have taken males as late as 
September 14 at Lexington. 
Nesting behavior. — From three to six hours are required to 
complete the burrow. Then sand is allowed to plug the entrance, 
and from time to time the wasp comes out and clears it away, 
