THREE HYBRID SILK-MOTHS, 175 



proves that the fertile liybrid is a cross between a species and its 

 variety. 



That the Saturniidee offers, on account of the sembling habit 

 of their males, unusual facilities for hybridisation, there is, I 

 think, no doubt; and this, I suppose, is the reason there are 

 more cases of hybridisation in this group. Miss Morton having 

 produced no less than four, and three of these four are 

 accountable for my writing on the subject. Miss Morton's 

 method is as natural as it is ingenious and simple, and briefly 

 speaking is as follows : — A fresh female of the rarer species is 

 tied on the outside of a muslin cage, and inside the cage are one 

 or two fresh females of the commoner species. This cage is taken 

 to the spot where the common species occurs and hung upon a 

 tree. The males are attracted by those of their species in the 

 cage, and being unable to pair with them, pair with the tied 

 female of the other species. This seems to me to be a very 

 simple method, and far more natural than the forcible pairing of 

 two insects by apposition, which I know is done, especially to 

 produce ova from rare insects. 



Two remarkable points I wish here to mention : Miss Morton 

 wrote to me in April or May last, " Is it not strange I have just 

 had imagos " of hybrids "out of 22-months-old cocoons." I 

 had a few of these cocoons sent to me last March, along with 

 some other cocoons, but, owing to that pernicious Washington 

 post office, these did not arrive till May, when all the pupse had 

 emerged except one hybrid and one P. ceanothi ; these I have 

 now living and apparently healthy, their lives having been saved 

 to me by their laying over for another year. The hybrid has 

 thus been in pupa 33 months, surely a long time without 

 nourishment. 



Another remarkable result of hybridisation in the Platy- 

 samias is the excessive amount of silk spun by the hybrid larvae ; 

 cocoons in my collection and from which the moths have 

 emerged, average as follows : — 



Platysamia-cecropia . . . 12'5 grains. 



,, gloveri . . . 8 „ 



„ ceanothi . . . 6*5 ,, 



Ceanothi-cecropia, hybrid . . 19 '5 ,, 



Qloveri-cecro'pia ,, . . 19 „ 



Whether this great increase of silk production is common to 

 all hybrid Saturniidge I do not know, and it would be interesting 

 if others who have series of cocoons of hybrids and their 

 parents, would weigh them and record their weights. The 

 three hybrids I have on exhibition now are — 



A. The result of Actias selene (female), India, paired with 

 Actias luna (male), N. America. 



B. Platysamia gloveri female, paired P. cecropia male. 



R 2 



