594 HEMIPTERA-HOMOPTERA CHAP. 



distinctions. Though the viviparous method of reproduction 

 and parthenogenesis occur in Coccidae, yet they are only ex- 

 ceptional, and they are not put to the same uses by the species 

 that exhibit the phenomena. Thus we have seen that in Aphidae 

 generations of imperfect individuals are produced with rapidity, 

 while the individual is not directly very prolific. In Coccidae 

 the reverse is the case the generations are usually similar to 

 one another ; they do not, as a rule, follow with rapidity, and the 

 female is usually very prolific, thousands of young being some- 

 times produced by a single individual. The extraordinary poly- 

 morphism of the species of Aphidae is not exhibited by Coccidae, 

 though, contrary to what we find in Aphidae, the males and 

 females are usually excessively different. The two families ap- 

 parently also differ in that Coccidae are specially characteristic 

 of warm climates, Aphidae of the temperate regions. 



Parthenogenesis. Owing to the fact that the males are very 

 minute creatures, totally different from the females, and living 

 but a very short time, they were but little known to the earlier 

 observers. It was therefore only natural to suppose that par- 

 thenogenesis was very common. Of late years the males of a great 

 many species have become known, so that ordinary sexual repro- 

 duction must be considered as the normal method in Coccidae, 

 although, in the great majority of cases, the male is still unknown. 

 It has, however, been shown in numerous cases that parthenogenesis 

 may occur even when males exist ; and there are some abundant 

 species of which it has not been possible to find a male. In 

 1887 Moniez l announced that he had discovered the male of 

 Lecanium hesperidum (one of the notoriously partheiiogenetic 

 species) in an ovarian cul-de-sac in the body of the female, and 

 he therefore considers that sexual reproduction occurs. He does 

 not say how pairing takes place, and we are not aware that his 

 observation has been confirmed. If correct it will be necessary 

 to reconsider the whole question as to parthenogenesis in 

 Coccidae. Apterous males are known in two or three species. 



The post-embryonic development of Coccidae is of the most 

 unusual character. It is quite different in the two sexes, and in 

 each of them it presents features not found elsewhere. It has, 

 however, as yet been studied in only a few forms, and even in 

 them is incompletely known. When hatched from the egg 



1 C. R. Ac. Sci. Paris, civ. 1887, p. 449. 



