BIONOMICS OF THE CHINCH BUG. 13 
small area of tliis segment visible on the meson and appearing whitish. Wing 
pads now conspicuous and extending about half way across the first abdominal 
segment. 
Abdomen, 0.696 mm. in width. Segments 1 and 2 pale whitish as before, re- 
maining segments 'dark red with streaks of black, giving it a blackish appear- 
ance. The black spot on the meson of the fourth abdominal segment very con- 
spicuous. The other spot has moved farther caudad and is now found just 
below the suture separating the fifth from the sixth abdominal segment, or on 
the meson of the cephalic border of the sixth segment. Tip of abdomen black, 
including a small area around the anal opening. 
Length, 2.114 mm. 
FIFTH INSTAR. 
Fig. 2, e. 
Head black ; width, 0.591 mm. ; polished ; eyes very dark red ; proboscis 
amber, except tip which is black ; antennal segment 1 amber, 0.157 mm. long, 
segment 2 amber, 0.314 mm. long, segment 3 black, 0.282 mm. long, segment 4 
black, 0.518 mm. long ; points of articulation pale. 
Thorax, 0.937 mm. in width ; legs dark ; femora almost black ; tibiae light 
amber except tibia of third pair of legs, which is darker; tarsi dark amber; 
joints lighter. Pronotum, mesonotum, and metanotum black, polished. Wing 
pads now extending to the caudal margin of the third abdominal segment. 
Abdomen, 0.957 mm. in width ; widest in region of fourth segment as before. 
First and second segments not visible except for a small portion on the meson, 
remainder of these segments covered by the wing pads, whitish. Remaining 
segments very dark red, almost black, with a number of dark areas and 
blotches almost black in color, tinged with blue, iridescent. Under the un- ' 
aided eye the abdomen appears black. There is a velvety area on the meson 
of the third segment, sometimes extending partly over the fourth segment as 
well. The black patch which was on meson of abdominal segment 4 in preced- 
ing stages is now on the suture separating segments 4 and 5. The other, which 
was on the meson of the fifth segment in the first, second, and third instars, 
and on the sixth abdominal in the fourth, is now on the suture separating 
the fifth and sixth segments. These patches are very conspicuous. The tip 
of the abdomen is black as well as a considerable area surrounding it ; in fact, 
most of the abdomen caudad of the seventh segment is black. 
Length, 2.967 mm. 
SEXUAL DIFFERENCES AMONG ADULTS. 
The male chinch bug generally is not so large and robust as the 
female. There are other more conspicuous characters, however, that 
distinguish the sexes. If the lower, ventral part of the abdomen 
of either sex is closely examined, it will be noted that the abdomen 
of the male is rounded (fig. 2, A) , while that of the female has a dis- 
tinct ridge on the ventro-meson, giving the abdomen an outline in 
the form of an inverted V (fig. 2, g). Furthermore, the tip of the 
abdomen in the male is rounded, and surrounding the genital open- 
ing, especially along the upper border and the sides, the area is well 
supplied with moderately long hairs. In the female the last segment 
on the ventro-meson is adjusted to shield the ovipositor and its mecha- 
nism. 
