584 SIDNEY I. KORNHAUSER 
these cells within the pockets produce the appendages of the 
next stage. In molting the newly formed appendages are with- 
drawn from these pockets cephalad, and the soft, wrinkled in- 
tegument unfolds to produce the larger gonapophyses. Thus 
there is a gradual growth of the external genitalia. In the male 
third instar there are two pairs of pockets, one placed dorsally to 
the other on the ninth segment. Each pair is separated into its 
right and left components by a median chitinous partition extend- 
ing cephalad from the apex of the triangular genital area. The 
inner pair of pockets is smaller than the pair more ventrally 
placed. There is no evidence for any appendage arising from 
the eighth somite in the male. The ninth segment has a band 
of melanie pigment about its anterior portion and this pigmented 
band is slightly more intense where it crosses the genital area. 
The sternum of the eighth segment bears a pigmentation char- 
acteristic of this stage and of the male sex. There is a lght 
medium stripe and a light patch extending from each side toward 
the median plane, and this is quite different from the pattern 
on the eighth sternum of the female third instar. In the fourth 
instar (fig. 41), the triangular genital area increases considerably 
in size and the two pairs of chitinous pockets are more easily 
seen at its apex. The pair more dorsally placed does not extend 
quite so far caudad as the larger ventral pockets. The pig- 
mented ring of the ninth segment remains and broadens out 
on the genital area, while the melanin on the eighth sternum 
retains its former pattern, but is less intense. In the fifth instar 
(fig. 42), the ventral pockets which produce the ventral valves 
of the adult retain the form seen in the previous stage, a median 
partition separating the right from the left, but the dorsal pair 
change greatly. Instead of a median chitinous partition, there 
are two lamellae, which divide the pocket into there subdivi- 
sions: a larger median compartment and two smaller lateral 
compartments. In the median pocket the oedagus develops, 
and in the lateral pockets, the claspers. The melanie pigment is 
restricted to the caudal end of the genital area. 
Turning now to the development of the ovipositing apparatus, 
we find in the third instar (fig. 44) a pair of darkly pigmented, 
