350 MISSES K. FOOT AND E. C. STEOBELL : KESULTS OF 



during the height of the breeding season, and it is interesting to note that in 

 this fertility they resemble the Fj generation of servus, but not of vario- 

 larius, for in our experience we have only one case on record in which the 

 Fj generation of pure variolarius mated and deposited fertile eggs the same 

 season. If these records (TV. to X.) are compared with Records I. and II. 

 of pure variolarius, it will be seen that, although the F^ hybrids are not 

 quite normal as to the percentage of eggs that develop, they are entirely 

 normal as to the relation between mating and deposition of eggs, for eggs are 

 deposited only once or twice between two matings, and the matings far exceed 

 in number the deposition of eggs. 



The records show that towards the end of the breeding season matins' 

 became more frequent, in some cases the breeding season being closed by a 

 series of matings of short duration, which continued several days after the 

 last deposition of eggs. This we believe is characteristic of servus, and was 

 typical also of the F^ generation of two other species we received from the 

 South — E. ictericus and E. crassus. 



We realize our experiments have not been sufficiently numerous to warrant 

 definite conclusions as to the breeding habits of the species we have studied, 

 but they furnish reliable data as far as the limited number of experiments 

 admit. The higher death-rate of the F2 generation, both as to the eggs and 

 nymphs, we believe was due in part to the fact that the weather was unseason- 

 ably cold, and a proper degree of temperature and moisture could not always 

 be satisfactorily maintained for all the cages. 



In order to repeat these experiments on a larger scalo^ a much more 

 elaborate equipment should be available. The bugs should be kept in a hot- 

 house where temperature and moisture can be properly regulated, and the 

 lettuce used for food should be cultivated under supervision, to be sure that 

 no insecticides are used in its cultivation. Further, a number of trained 

 assistants is absolutely necessary. The material furnished by a single cross 

 is at some period of the experiments more than two workers can properly 

 care for. We were forced to cut short several important experiments on 

 account of the impossibility of continuing satisfactorily the extra work they 

 involved. 



We believe that our success in being able to cross even one pair of 

 variolarius and servus is due to the fact that the two females used for the 

 experiments, hatched after the close of the breeding season, and were kept 

 through the following winter. This belief is supported by the fact that we 

 did not succeed in repeating the cross-breeding experiments during the 

 summer with bugs of the first generation of that season, though we tried this 

 with 16 female variolarius and 14 male servus. These experiments were 

 carried on in three cages, the first started June 22nd, the second June 28th, 

 and the third July 2nd. All the female vaiiolarius had been raised in our 

 laboratory during the early summer, and were transferred to these cages 



