J. W. H. Harrison 269 



noted in minor characters by Denso^ and myself^ in larvae of Sphingid 

 and Bistonine hybrids. In my opinion the latter, from the evidence 

 presented, is the correct view, i.e. that we have a precocious develop- 

 ment of imaginal organs induced by the disturbing influence of hybridity. 



Rare as this occurrence is, it is not unknown even in pure species, 

 although as far as the Lepidoptera are concerned only one previous case 

 is on record^ that of larvae of Bomhyx mori reared by Cesare Majoli in 

 1 813 ; these were in every way similar to my Oporabia. In the Coleoptera 

 — still holometabolous but not so complex in the mode of origin of its 

 wings — other cases are known ; in this group it is not so wonderful, for 

 the invagination of the hypodermal cells destined to give rise to the 

 wing buds is of a much simpler type, and very little displacement would 

 cause their appearance externally. To the best of my knowledge the 

 recorded instances in the beetles relate to the common Tenehrio molitor, 

 and to Anthrenus varius and Dendroides canadensis. Our knowledge of 

 the first case is the most extensive, for Prof Heymons^, after his discovery 

 of the first larva, was able to find others and give them detailed study. 

 Busck* added Anthrenus varius and Riley ■* Dendroides canadensis to the 

 meagre list of species displaying this abnormality. Making due allowance 

 for the difference in order, these coleopterous freaks do not difffer widely 

 either from the conditions of Majoli's silkworms or of my Oporabia and 

 are therefore directly comparable with them. 



We shall now return to the fate of the larvae pupating normally. 

 Anticipating as usual an aestivation of some four months I allowed the 

 pupae to harden for a fortnight or so and then proceeded to dig them 

 up in order to store them under natural conditions. When I examined 

 the cage for this purpose sixteen days after pupation, I was greatly 

 astonished to find that a female had already emerged, and this observa- 

 tion caused me to scrutinise the pupae daily. And this proved a very 

 fortunate thing, for during the next few days approximately one half of 

 my stock emerged and every individual doing so proved to be a female. 



^ Denso, "Die Erscheinung der Anticipation in der ontogenetischen Entwicklung 

 hybrider Schmetterlingsraupen," Zeit. filr Insektenbiol. iv. (xiii.) pp. 128 — 135, 170 — 176, 

 201—208 (1908). 



2 Harrison, " Studies in the Hybrid Bistoninae," Journal of Genetics, Vol. vi. No. 2, 

 p. 102 (1916). 



8 Heymons, " Fliigelbildung bei der Larva von Tenebrio molitor," Sitz. Ber. Ges. Nat. 

 Freunde, pp. 142—144 (1896). 



* Busck, "Larvae of Anthrenus varius showing wing pads," Proc. Ent. Soc. Wash. 

 Vol. IV. p. 123 (1897). 



^ Riley, " The abnormal appearance of external wingbuds in larvae of holometaboloas 

 insects," Ent. News, Vol. xix. No. 9, pp. 136—137 (1908). 



