72 THE ENTOMOLOGIST. 



stood, but a small fraction of the whole), and in what follows I 

 shall either completely pass over or merely touch upon the 

 remainder, at the same time warmly commending them to the 

 notice of zoologists, and especially of entomologists, for experi- 

 ment. 



Forms diverging from the normal imaginal aspect may be 

 occasioned by the influence of external conditions on the stage 

 of egg, larva, pupa, or imago ; that is to say, on the perfect 

 insect itself, or any one or more of the preliminary stages. Of 

 the cases falling under these difl'erent categories we shall naturally 

 discuss only those that have been actually examined. 



I. The Egg. 



The only experiments I have made on the egg-stage of Lepi- 

 doptera — and these are only partial — have been in reference to 

 the effect upon them of a raised temperature. Eggs of Arctia 

 fasciata, Esp., Dasychira ahietis, Schiff., Lasiocamim prtmi, L., 

 and L. pi?ii, L., which were exposed to a temperature of 34° C. 

 (93° F.) during the process of laying by the female and up to the 

 time of hatching, produced the larvae in two-thirds or less of the 

 normal time, and there emerged as perfect insects in the same 

 year, i. e., without hybernation of the larva, in the case of 

 fasciata, 71 per cent. ; of ahietis, 90 per cent. ; of pruni, 100 per 

 cent. ; and of pini, 81 per cent. The larvae and pupae of the 

 above broods were kept as far as possible at a mean temperature 

 of 25° C. (77° F.). 



The eggs of the same females as those used in the above 

 experiment, which had already been laid at a normal temperature 

 (about 22° C., 72° F.), and were left in this until hatched, after- 

 wards remaining as larvae and pupae in the same mean tempera- 

 ture of 25° C. (77° F.), produced a considerably smaller number of 

 perfect insects without hybernation of the larvae, viz., A. fasciata, 

 23 per cent. ; D. ahietis, 12 per cent. ; L. pruni, 64 per cent. ; 

 L, inni, 28 per cent. 



The prematurely developed moths of both series showed on 

 comparison with each other no differences of importance, with 

 the exception of three females of A. fasciata, whose larvae and 

 pupae had, however, been subjected to different biological con- 

 ditions from the rest of the early-developed specimens. The 

 different percentage in the two cases, of individuals showing 

 divergence in biological peculiarities from the rest of the brood 

 of the same parent-moth, must therefore be undoubtedly con- 

 sidered as dependent on the difference of temperature to which 

 the two series used in the experiment were exposed in the egg- 

 stage. The acceleration of development, that is to say, which 

 the larva had already undergone in the egg, seems in these cases 

 to have transferred its energy to the later stages of growth. 

 It is well known (see * Insekten-Borse,' Leipzig, April 15th, 1894, 



