78 THE ENTOMOLOGIST. 



Moreover, forms bad to be selected whicb, altbough nearly 

 related, were, bowever, undoubtedly specifically distinct, but 

 with common babitat. 



The Drepana species, falcataria, L., and curvatula, Bkb., and 

 the various species of the genus Pygcera — pigra, Hfn., curtida, 

 L., and anachoreta, F. — fulfilled these conditions. 



Fertile crosses between Drepana curvatula 3" and falcataria ? , 

 and between Pygcera curtida <? and pigra ? , and curtula $ and 

 anachoreta ? , were obtained. All these crossings were success- 

 fully reared to the imago. 



The hybrid of the two hook tips (PL IV. figs. 5 and 6), which, 

 in honour of my colleague. Dr. H. Eebel, of the Vienna Natural 

 History Museum, I have named Drep. iiyhr. rebeli, mihi, paired 

 very easily, and the females laid a varying number of eggs, 

 which, to outward appearance, were normal. 



As a matter of fact, embryos developed in a number of these 

 eggs, but finally none of the larvae escaped from the shells ; they 

 all died in the egg. Three eggs which were opened contained 

 normally developed, though dead, caterpillars.^^ 



The hybrid iDrood of Pygcera curtula <? and pigra ? produced 

 normal male and female (PI. IV. figs. 11 and 12). A pairing of 

 this form, owing to the short life of the imago, would hardly 

 have been possible, as, curiously enough, the male imagines 

 developed much faster than the female, which is not the case to 

 such a degree in pure species of this genus. Therefore a number 

 of large, apparently strong males were placed in the cellar, and 

 again brought into ordinary temperature, when the females 

 belonging to this form commenced to emerge. In this manner 

 five pairings of this hybrid were obtained, and the five females 

 laid eggs in the following numbers : 85, 103, 112, 121, 154. In 

 a fair number of these eggs larvae developed, but the majority 

 of these did not emerge. As a matter of fact, from the 103 

 developed 5; the 121, 12; and the 154, 17 larvae.^ ^ All these 

 took readily to their food, and seemed to promise a successful 

 development. This could, however, only be followed for a short 

 time, as on August 22nd, 1897, I was suddenly called to North 

 Germany on pressing duties. The larvae had to be sleeved out 

 on a willow tree, and there all died. 



The rearing of the last hybrid to be mentioned — P. curtula ^ 

 and P. anachoreta 2 — produced a curious result. The greater 

 number of the larvffi rapidly obtained their growth, and about 



12 In 1898 a small number of these caterpillars emerged from the egg, 

 but breeding them was not successful, although the little larvae were full of 

 life. They took very little or no food, and all died within forty-eight hours 

 after leaving the egg. 



13 In 1898 I also obtained offspring from this hybrid, and again from 

 numerous pairs, but the larvae soon died, in spite of good weather and food ; 

 they apparently were wanting in energy, 



