374 Trans. Acad. Sci. of St. Louis 
was a neat heap of sawdust. A little black wasp was 
seen to leave the hole and return at ten-minute intervals. 
The prey which she carried could not be recognized, but 
when later the burrow was opened, aphids of the species 
Macrosiphum sp. [J. J. Davis] were found. One cell 
contained 32 aphids, another 25, and a third one 11 
aphids and a half-grown larva. The burrows in the 
wood were a little over 4% inch long and 1% inch wide, 
and they were plugged with finely-chewed wood. Whether 
this wasp had the power to do her own tunneling in the 
hard wood, or whether some beetle or other insect had 
done the excavating and she had merely scraped the 
shavings for plugs, I do not know, but from the unique 
type and condition of the burrow I can only surmise 
that the work had been done by this little aphid-hunter. 
A second wasp of the same species was seen nearby, 
which indicates that this must have been a good place, 
although the unique character of this nesting site throws 
little light upon the nature of the usual place of nidifi- 
cation. 
Another was subsequently discovered in February, in 
a cut catalpa twig in a St. Louis park, and in May one 
was found in the dead twig of a rose-bush in the door- 
yard. The mother was in the vestibule of this one, and 
remained in it while the twig lay on my table for twenty- 
four hours; although the twig was opened, the faithful 
mother was loath to leave. The channel was about 1/16 
inch wide, 4 inches deep; each of the five chambers was 
% inch in length, and the partitions were of pith. The 
two uppermost cells contained immature aphids, Macro- 
siphum sp. [J. J. Davis], and the lower cells brown ones 
of the same species. There were approximately thirty- 
five or forty in each cell. The cells were situated one 
