lG(j ttiE entomologist's REdOUD. 



of neutrality as regards sex in the newly-laid egg, but I do not know 

 that this has ever been proved, even in the slightest degree. The idea 

 of this sex-determining influence of nutrition has probably arisen from 

 the well-known fact that bees and ants govern the sex of their offspring 

 within certain limits, by special feeding ; i.e. that larvte, which would 

 under ordinary circumstance produce neuters, can be made to produce 

 queens if a special course of ntitritious diet be commenced in the flrst two 

 or three days of larval life. But so-called neuters are essentially females, 

 not fully developed it is true, but of whose sex there can be no doubt, 

 and I would suggest that what hap})ens in these cases is, that the sexual 

 neutrality of the ovum ceases on fertilisation, and that the special feed- 

 ing only causes the production of a well-developed instead of an 

 ill-developed female. 



That neutrality of the ovum ever exists in insects after the egg has 

 been laid is not pi-obable, for in comparatively early stages of some 

 lepidopterous larvae, the sexual organs are clearly distinguishalde. To 

 supjiose, therefore, that any course of feeding of the larva will alter 

 the sex of the resulting imago, is to assume more than scientific ento- 

 mologists are able to grant. Probabl}^ there is a point in its development 

 at which the oval cell is sexually neutral, but this point may be a long 

 way back in its history, possibly as far back as the embryonic stages of 

 the parent. If a process of experimental feeding could be carried 

 out through several successive generations, probably some influence 

 might he exerted ; but that any influence upon the sex of the resulting 

 imagines can be exerted by such a process in a single generation, is in 

 the highest degree doubtful. If it should happen that an experiment 

 seems to yield an affirmative result, it is probably only a fortuitous 

 coincidence. Experiments, to be worth anything, must be begun at a 

 time when the ovum is certainly neutral, and then perhaps some 

 definite impression might be made on the progeny. 



It is of course quite possible, that the sexual neutrality of the ovum 

 may be continued to a much later jDeriod of development in some species of 

 the same class than in others, and in some classes of animals than in 

 others. Further experiments as to the effect of food on sex arc needed, 

 but all Avho have bred large numbers of moths from eggs, know that 

 no amount of nutritious food will ensure a preponderance of females, nor 

 will a strictly starvation diet ensure a preponderance of males, from eggs 

 laid in the ordinary course. 



9. — On the sex of imagines bred fkom successively-laid eggs. — 

 It has often been suggested that there was some general law connecting 

 the succession of the eggs laid by the same moth with the sex of the 

 imagines resulting therefrom, and that this took the form of a regular 

 alternation of sex in successive eggs. It has more than once been 

 asserted that, of two isolated larvae found on the same bush, one would 

 produce a male, the other a female, the assumption being that the two 

 isolated larvae were the progeny of successively-laid eggs, and that their 

 contiguity was due to an attempt to facilitate the operation of pairing. 

 This would, of course, lead to the most complete in-breeding, a result 

 which nature usually abhors, and, as was to be expected, experiment 

 does not bear out the assumption. To test the assumption, however. 

 Professor Poulton undertook some experiments, to dctermiue the sex 

 of the larvrB resultiug from successivelj^-laid eggs of Smerinthm j'Opnh'. 

 The experiment is detailed at length in the Trans. Ent. Sue. London, 



