RECENT EXPERIMENTS IN HYBRIDISATION. 189 



stated, infertile, the oviducts containing no ripened eggs. 

 Pairing also took place, though with much less readiness 

 than in either of the preceding cases, between the hybrid 

 males and some females of J?, pyri. The number of fertile 

 eggs produced in the latter case was far smaller than in the 

 cross with .S. pavonia. 



4. 6". bornemanni S and S. pavonia ? {S.bornemanni is the 

 cross-product of S. pavonia S and ^. spini $ ). The larvae 

 at first closely resembled those of S. pavonia, but in subse- 

 quent stages the influence of S. spini began to assert itself. 

 They presented a very variable appearance on reaching the 

 fourth stage, which period unfortunately they did not sur- 

 vive. Fresh batches, however, have since been raised to 

 maturity, though no record of their history has yet been 

 published. 1 



5. S. cmilicp $ and S. pavonia ? ( S. entities is a cross- 

 product of S. pavonia $ and S. pyri ? ). The larvae of this 

 hybrid (named .S. standfussi by Wiskott) are again very 

 variable. Their general appearance is that of a large S. 

 pavonia. The cocoon and pupa are also near the same 

 parent species. The perfect insect, like the larva, is vari- 

 able ; it always, however, shows much resemblance to S. 

 pavonia, and the sexes are dissimilar as in that species. 

 The margins of the wings are apt to be scalloped. The 

 oviducts of the only female that emerged contained mature 

 eggs, but only about twenty, or one-tenth of the normal 

 number in S. pavonia or 6*. pyri. It is possible that these 

 hybrids may be fertile inter sc. 



6. S. cmilice S and S. pyri ? (S. risii Stdfs.). This 

 pairing was only obtained with great difficulty, and in four 

 cases out of nine the eggs, though laid in normal numbers, 

 did not hatch. In the remaining five broods only one per 

 cent, produced caterpillars. These at first closely resembled 

 S. pyri, and in the second stage still showed more likeness 

 to S. pyri than to the male parent form. In the third stage 

 the 6*. pyri characters began to be lost, and in the fourth 



1 Specimens of this hybrid have been reared by the present writer from 

 eggs kindly sent him by Dr. Standfuss in 1895. Other individuals raised 

 from the same batch of eggs are in the Hope Collection at Oxford. 



