A contribution to our knowledge of the Stylopidae. 261 
larvae these detached cells almost completely fill the alimentary tract, 
which in turn occupies the greater part of the body cavity. The ex- 
tremely irregular character of the ‘intestinal cells and their great 
tenuity at certain places seem to indicate that a considerable part of 
the nourishment of the larva at this stage may be obtained through 
the hypodermis and be taken up by the digestive cells from the body 
cavity. Most of the liquid food must undoubtedly enter through the 
mouth, however. 
The simple eyes of the triungulin have undergone considerable 
degeneration; they no longer retain the structure of ocelli, although 
when viewed externally they may appear like them. In sections the 
only structure that can be seen is an irregular mass of dark colored 
pigment granules, sunk at a considerable distance below the surface 
of the head. Von SIEBOLD (1843) thinks these spots are remnants 
of color spots of the triungulins and not of the eyes. This may pos- 
sibly be the case, although I can recall no such spots upon the heads 
of some triangulins which later escaped. This spot of pigment remains 
unchanged during the first larval instar. Its apparent decrease in 
size is due only to the fact that the larva grows greatly during this 
period and they appear to grow smaller by comparison. 
The first larva has usually been referred to as legless, but has 
in reality well developed ambulatorial protuberances, 12 in number, 
that resemble prolegs in appearance. That they cannot be homologous 
with prolegs iis readily seen, however, since they are unpaired and 
arranged serially along the median ventral line, one to each body 
segment. They are quite retractile and may serve to enable the larva 
to move about among the viscera in the body cavity of the Polistes 
larva. They are simple evaginations of the hypodermis and are re- 
tracted by a very simple muscle consisting of a few strands of un- 
striated cells. In certain of these muscle strands the cells are fusing 
and a faint striation can be seen. 
During this instar considerable growth takes place, the larva in- 
creasing in size from 1.66 mm to 4.5 mm in length and becoming 
comparatively somewhat stouter, but not changing otherwise in external 
form. At the end of this period the sexes can already be easily dis- 
tinguished externally, as the imaginal discs of the male are visible 
through the translucent larval cuticle. In section they are still more 
distinct by the form of the reproductive organs, which undergo a 
precocious enlargement and differentiation in both sexes during early 
larval life. 
