NOTES ON THE NESTING BEHAVIOR OF 
PHIL A N THUS LEPIDUS CRESSON 
(HYMENOPTERA, SPHECIDAE)* 
By Howard E. Evans 
Museum of Comparative Zoology 
Several years ago Evans and Lin (1959) discussed the nesting 
behavior of four species of Philanthus which occur commonly in 
the northeastern United States. The four species were found to 
have many ethological similarities as well as several interesting 
differences. The larger species tend to take larger bees as prey, and 
certain of the species nest earlier in the season than others or seem 
to prefer more sloping earth in which to nest. The fact that there 
is much overlapping with respect to these slight ecological differences 
suggests that competition for prey and nesting sites has been of 
minor importance in the evolution of these species; this may in part 
be a consequence of the fact that populations of all four species 
appear to be kept well below their maxima by parasites. In point 
of fact, all of the major behavior differences between these four 
species appear “to represent mechanisms which have evolved as a 
response to parasite pressure” : for example, differences in closure, 
in mound-leveling, and in burrow profile. 
I am now able to add a fifth species to this picture without 
necessitating any change in these conclusions. Philanthus lepidus is 
a locally common species which occurs in much the same situations 
as the four studied earlier and preys upon much the same kinds of 
bees: in fact one common green “sweat bee”, Augochlorella striata , 
has been found in the nests of all five species, and several others 
have been found to be used by three or four of them. The distinc- 
tive features of P. lepiduSj as in the case of the other four species, 
appear to be associated with parasitism. In particular, this species 
prepares one or more “false burrows”, which remain open at all 
times, although the true burrow is closed. False burrows have to 
my knowledge not been reported for other philanthine wasps, but 
they occur in certain species of at least two other subfamilies, as 
discussed further in the final section of this paper. It cannot be 
proved that these false burrows do, in fact, divert parasites in any 
important way, but there is now considerable circumstantial evidence 
that this is their function. 
^Manuscript received by the editor October 29, 1964. 
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