10 BULLETIN 1016, U. S. DEPARTMENT OE AGRICULTURE. 



had only five stages instead of six. The specimens used for the 

 figures in this paper all had fed for some time after casting their 

 last molt. In most cases the specimens were preserved for three, 

 but in some cases for only two days after molting and during this 

 period the individual was permitted to feed. Illustrations of speci- 

 mens which have just molted and have not fed, or specimens about 

 to molt, are likely to be misleading, as they are not normal repre- 

 sentatives of the stage desired. Very often the color pattern of a 

 specimen fades considerably just before molting, and if drawings 

 are made at that time the color pattern for that instar will be 

 wrongly recorded. 



The nymphs of the chinch bug during the molting period feed 

 very little, and their color pattern fades toward the close of the 



period. This fading is due to the 

 loosening of the transparent cuticular 

 layer, which is about to be cast. The 

 darker color pattern of the succeeding* 

 instar can often be seen through the 

 "N thin layer. 



One nymph was caught in the act of 



C^-^ casting its skin. When first observed 



\jp it had already freed part of the ab- 



fig. i.— The chinch hug (bussus domen and thorax. It then drew its 



leucopterus) : Cluster of eggs, -■ . . 



showing tubercles at the trun- legs out one at a time and by a ]erky 

 eated or blunt ends. Greatly motion of the abdomen freed itself 



entirely from the old skin. The 



nymph utilized its last pair of legs to push off the skin from the tip 



of the abdomen. 



DESCRIPTION OF THE EGG AND NYMPHAL STAGES. 



A description of the egg (fig. 1) and nymphal stages is given be- 

 low. It does not seem necessary to describe the adult or the sixth 

 instar (fig. 2, /), but a brief discussion of the sexual differences 

 in the adult stage is included. It seems important that the sexual 

 differences be known in order to facilitate biological work on this 

 insect. 



EGG. 



The egg is elongate ovate, slightly reniform in shape, rounded at one end 

 and truncate at the other. The truncate end is supplied with from three to 

 five, usually four, tubercles 0.1 millimeter in length; opaque white in color 

 when just deposited, turning amber in a few clays and deep red several days 

 before hatching. Just prior to hatching the embryo shows through the chorion 

 which is smooth, shiny, and somewhat iridescent. 



Length, 0.858 mm.; width, 0.308 mm. 



