290 THE entomologist's RECOftU. 



In tlie lowest Invertebrates, as is well-known, reproduction takes 

 })lace either by cleavage or by gemmation. In the latter case, little cells 

 grow out of the parent cell, which finally become detached, and mature 

 into pei-fect cells ; in the former, the parent cell itself sub-divides by fis- 

 sion, each part becoming an indei^endent organism. There is yet a third 

 method in which the whole cell becomes covered with a gelatinous cyst, 

 within which the protoplasmic body is broken up into a number of 

 cells ; these after a time break open the cyst, and leave it as separate 

 individuals, the process being termed encystation. In the Hydrozoa, 

 reproduction is carried on all the summer by gemmation, but in the 

 autumn, sperm cells and germ cells are produced in the same individual, 

 the former fertilizing the latter and producing ova, in which stage these 

 creatures pass the winter. This method of sexual reproduction (minus 

 the summer gemmation) is very common as we ascend in the animal 

 scale, but when we come to insects we find that the sexes are differ- 

 entiated in separate individuals, and, as a rule, that coition is necessary 

 for reproduction. 



Among the Crustaceans, to which insects are closely allied, we find 

 such species as Poli/phemus ooiJus, Apus cancrlformis and Li'mnadia (jlijaa, 

 which, according to Newman, " contain only female individuals, the 

 presence of a male being the exception." Dajthnia has males as well 

 as females, but the females, according to Lubbock, appear equally 

 prolific in the absence of the males. 



Newman also states (Essay on the employment of physlolotikal 

 characters in classification, etc., 1856), that " in Arachnida, males and 

 females are familiarl}^ known ; but the fertility of the female is not de- 

 })endent on coition with the male. I have found the isolated female of 

 Epeira diadenia, invariabl}^ produce her circular mass of eggs, and have 

 as invariably found these to be fertile. If coition had taken place at 

 all, it would have been while the females on which I experimented 

 were in the infant or larval state, and prior to the first ecdysis ; afford- 

 ing, if this be made out, an instance of a phenomenon altogether 

 abnormal." 



Most of the records of the occurrence of parthenogenesis in Lej^i- 

 doptera are, from a scientific point of view, of the most unsatisfactory 

 nature, being based rather on chance observations than on any specially 

 devised experiments. This, however, need not be wondered at, for 

 those entomologists wlio breed insects in the largest numbers, usually 

 do so in order to ol)tain fine imagines for their collections, and if they 

 wish to inbreed any species, they, as a matter of course, pair their females 

 with males, to ensure the fertilization of the eggs. For even when a 

 species has a parthenogenetic tendency, only a very foAv of the eggs 

 that are laid by an imimpregnated female are found to be fertile, and a 

 very large number of female moths have to l)e sacrificed in order to 

 obtain a very small su})ply of parthenogenetically fertile eggs. 



This has been well illustrated by Mons. Jourdan in his article dealing 

 with this subject as exemplified in Botnhyx mori {Comptes Ttendus Hehdo- 

 madaires des Seances de F Acadcmie des Sciences, Paris, vol. liii., 1861, 

 pp. 1093-1096), where he remarks that the reproduction of " papillons " 

 by virgin females has often been noticed by scientific observers, and 

 that it has long been customary in the silk-producing countries of 

 France, "to regenerate a worn-out race by using 'la graine viei'ge,' " 

 that is to say, eggs produced from females without contact with the 



