18 PRINCIPAL CACTUS INSECTS OF UNITED STATES. 



LIFE HISTORY, ANE) DESCRIPTION OF STAGES. 



The oreeding of this insect in the cactus area begins early in the 

 season. At San Diego, Tex., in March, Mr. J. D. Mitchell observed 

 that the first brood had appeared. In April the first young were 

 noticed in Victoria County. The bugs breed continuously throughout 

 the summer and fall. Owing to the fact that certain individuals are 

 retarded in their development no definite number of broods is deter- 

 minable. It has frequently been observed that some specimens reach 

 the adult stage before others from the same mass of eggs have passed 

 the third nymphal stage. This explains the observation of many per- 

 sons that the bugs can be found in all stages on the plants at all times 

 except during cold weather. 



The eggs are deposited generally on the spines, although in confine- 

 ment the females deposit on the sides of rearing cages and in some 

 instances eggs have been observed on the sides of dead as well as of 

 living joints. The spines, however, are undoubtedly the normal place 

 for deposition of the eggs. (See PI. VII, fig. 2.) During the summer 

 season 5 adults produced 198 eggs in 15 days, averaging practically 

 40 to the individual. These females were not reared, so that it is more 

 than likely that the capacity for egg laying is much larger than the 

 figures would indicate. The method of oviposition was observed by 

 Mr. C. E. Hood. He noted that the female begins by rubbing the 

 spines or surface on which the eggs are to be laid with the tip of the 

 abdomen, probably discharging a sticky substance. After the egg is 

 about halfway protruded a circular motion of the abdomen is ob- 

 served. The female then appears to rub the egg over the spine before 

 finally discharging it. In this manner 4 eggs were deposited in 6 

 minutes. It was observed in the breeding cages, and frequently in 

 the field, that the eggs are not securely fastened to the spines. The 

 attachment is so weak that they fall as the result of even a slight 



disturbance. 



The Egg. 



Length, 1.25 nun. ; width, 0.75 mm. Dark brown, opaque, very finely and 

 uniformly punctured, mottled with a whitish exudation. Elliptical; lid sub- 

 dorsal, large elliptical. Placed with great regularity about 0.5 mm. apart on 

 spines, with longitudinal axis parallel to spine, each string of eggs from 6 to 25 

 mm. in length. Duration of egg period, from 12 to 20 days. 



The Nymphal Stages. 



First instar. — Length, 2 mm. Brownish black, except abdomen, which is pea- 

 green in some individuals and a dark crimson in others. The former variety 

 shows a slightly red callosity and margins. Antenna? 4-jointed ; club short ; 

 first joint slightly flabellate; second joint scarcely one-third longer than the 

 third ; first and second joints with apical tips terminating in short spine. Head 

 produced, bifurcate. Length of stage, 7 days. 



