428 Trans. Acad. Sci. of St. Louis 
the second week in August and no new nests were started 
after August 15th. 
Tue Pipr-Orcan Wasp, Trypoxylon politum Say." 
This creature is a beautiful, shining black wasp with 
white feet; she is much better known by the illuminating 
name of T. albitarsis. In this species the adults emerge 
usually in late June? after wintering in the larval stage. 
The prey that the mother catches and stores in the cells 
with her eggs is spiders of various species, which are 
usually paralyzed. The nests made by these wasps are 
long, parallel tubes of mud and are commonly called Pipes 
of Pan, or pipe-organ nests. Fig. 57 shows the nest as it 
usually occurs; the short tier is in course of construction. 
This dainty builder does not daub the cell over with mud, 
thereby hiding the pretty rings that tell the progress of 
her work, as does the yellow-legged mud-dauber, Sceli- 
phron caementarium, but it, like the latter, smooths the in- 
terior of each cell carefully. The holes usually apparent 
on the upper surface of old nests are made by the emerg- 
ing adults, and the white spots are the hardened chalky 
substance which the insects emit from their bodies imme- 
diately after they emerge. This white substance is emitted 
by Sceliphron caementarium also, but in the form of 
many minute pellets discharged before emergence. 
The larva of T. politum spins a very light web about 
the walls of its cell (fig. 58X); just inside this it con- 
structs its cocoon, black, very strong and brittle (fig. 58). 
This it makes of the excrement which it clears from its 
alimentary tract after it has finished feeding, and utilizes 
for a cocoon by throwing it all over itself. This is 
oT “Behavior, 6:36 gi from an article by P. and N. Rau in Journ. 
2In 1920 I had one nest from Ag three adults emerged on July 
4 and six more between July 8 and 13. 
