BIONOMICS OF THE CHINCH BUG. 13 



small area of this 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, h), 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. 



