264 C. T. BRUES, 
wasp to another and consequently to other nests. Large numbers of 
larvae are often found in one Polistes larva, but their presence does 
not seem to disturb the health of the wasps to any great extent. The 
wasps die soon after the emergence of the male Xenos, seeming to 
become dried up. Infected wasps are usually of a lighter color than 
normal individuals and more feeble of flight. 
Oogenesis is peculiar and does not resemble that of other insects. 
Very small larvae show strings of spherical primitive eggs on each 
side of the gut. These grow and later break up, giving rise to eggs, 
each of which consists of a mass of nurse cells bearing a polar cap 
of cells derived from a primitive egg attached to it. Yolk is formed 
from the contents of each egg and when ripe the eggs are scattered 
about all through the body cavity and lie embedded in the fat body. 
Maturation seems to occur through the fusion of the second polar body 
with the pronucleus of the egg. All of the cleavage cells when formed 
go to make up the blastoderm which does not cover the whole egg 
at first and later draws up to one pole to give rise to the rudiment 
of the germ-band by a rearrangement and multiplication of its cells. 
Older embryos are of the usual generalized type, although on account 
of their length they are curled up in the egg in a peculiar manner. 
The first larval stage, or triungulin, gives rise through the loss 
of its legs and further degeneration of its internal organs, to the 
second, or legless larva, which is provided with median metameric 
protuberances in the place of legs. The sexes begin to differ in ex- 
ternal form after another moult when peculiar asymmetrical muscles 
develop in the thoracic segments, and finally, after another ecdysis, 
the adult form appears. It is perfectly evident from the anatomy of 
the adult female that she protrudes the anterior extremity of her body 
and lies with her ventral side turned towards the dorsal surface of 
the wasp’s body. 
From embryological data we cannot point out any affinities be- 
tween the Stylopidae and the Coleoptera, so they may best be con- 
sidered, at least for the present, as the types of another order, the 
Strepsiptera. 
Zoological Laboratory, University of Texas, 
June Ist, 1902. 
