Field Studies of the Non-Social Wasps 437 
last I found on the supporting timbers of a club-house 
built on stilts about twenty of these pipe-organ nests. 
The majority of them were comparatively new, and I 
remembered that only three years before there had been 
in this place only two of these nests. Since no others 
were to be found thereabouts, this is strong evidence that 
wasps of this species do not wander far from their birth- 
place to build. 
The duration of the pupal stage was, in the only speci- 
men accurately observed, 27 days, July 23 to August 
20. A study of the proportion of sexes at the time of 
emergence shows a predominance of males. Nine small 
nests of TJ. politwm in June, 1913, gave forth 65 adult 
wasps, of which 41 were males and 24 were females. 
In some nests the males equaled the females in num- 
ber, but in no case did they exceed, while the males ac- 
tually predominated in the majority of nests in this 
small collection. One wonders if this proportion exists 
at all times later in the season, and also whether the 
males continue to predominate in numbers after they 
are out in the world, or if one sex is eliminated more 
rapidly by enemies or environmental conditions. 
T. politum on the authority of Walsh is cited in Mc- 
Cook’s Nature’s Craftsmen (p. 216) as a guest wasp 
not building a nest for itself, but laying its eggs in cells 
made and provisioned by another species. This politum 
of Walsh should not be confused with the politum of the 
present article, which was formerly T. albitarsis. 
These wasps, of course, suffer from the ravages of 
the parasites. I have bred the hymenopterous parasite 
Melittobia from their larve, and on several occasions 
the Mutillid parasite, Sphaerophthalma scaeva, has been 
bred from the cocoons, but here too, like those of this 
Species bred from Sceliphron nests, all were males. I 
