1968] 
M at thews — Microstig?nus 
39 
collected nests containing one or more adult females. While 
fragmentary, they suggest that, as in other social insects, colony 
reproductivity rises with colony size. However, reproductivity per 
female appears to remain more or less constant regardless of colony 
size, a situation seemingly analagous to that of P ' seudagapostemon 
divaricatus, a communally nesting bee which lacks morphological 
caste determination (Michener, 1964). In contrast, more highly 
evolved hymenopterous societies have a relatively high productivity 
per female when colony size is small, this steadily decreasing as the 
number of nest inhabitants rises. It should be remembered that the 
data reported herein represent a census of nests of various sizes taken 
at a given point in time; no information was obtained for nests 
earlier or later in the season. 
Evidence strongly suggests that cooperative provisioning occurs 
among M. comes females. As previously mentioned, no two cells of 
the same nest were ever found to be at the same stage of development, 
a fact also noted for M. theridii (Myers, 1934). Recalling also 
that the cells are mass-provisioned, it is significant to note that no 
nest, regardless of size or number of females present, was found 
to have more than one incompletely provisioned cell. Observations 
at a nest containing two females and a male showed both females 
carrying prey to the nest ; when the nest was collected later the same 
day, only one cell contained prey. Thus it appears reasonably cer- 
tain that foraging females from a single nest cooperate and provision 
one cell at a time. 
Similarly, the individuals present in multi-adult nests cooperatively 
participate in its defense, responding almost instantaneously to any 
disturbance (as noted above, see Nest Maintenance and Defense). 
Of significance in this regard is the fact that all such nests observed 
in the field had at least one adult present at all times. While the 
sexes of these adults were not confirmed, the indication is that some 
division of labor between foraging and nest maintenance and pro- 
tection may exist. 1 ) 
Evidence for the existence of parental care was discovered rather 
fortuitously. Cells in the nests, at first loosely closed, are apparently 
reopened while the larvae feed. The absence of fecal pellets or 
meconial remains in larval or pupal cells in the night-collected 
J Wasps in the genera Trypargilum and Pison (Trypoxyloninae) are ex- 
ceptional in being the only sphecids in which males are known to actively 
participate in nesting. Nests generally contain a pair of wasps, the male 
guarding the entrance while the female is away. (See Medler, 1967 and 
Masuda, 1939). 
