SILK-PRODUCING LEPIDOPTERA. 209 



ciently developed ; besides, the moths, for the most part, refused 

 to pair in captivity. It would, however, be easy to deal success- 

 fully with these two drawbacks. I have already in former 

 reports recommended the use of small oak trees in pots, to rear 

 the worms till the oak buds are sufficiently developed. On the 

 other hand, premature hatching of the worms may be avoided by 

 placing the eggs, during the winter, in muslin bags suspended in 

 the open air in a northern aspect and protected from the rays of 

 the sun. As soon as the oak buds have burst open, the eggs 

 may be submitted to a gentle and moist temperature, so that 

 they should all hatch as rapidly as possible. With respect to 

 the other difficulty, that of the pairing of the moths, the cages 

 containing the latter should be placed in the open air, and even 

 tied to branches of trees, when this is possible. In rooms the 

 yama-ma'l moths pair with the greatest difficulty, and it is the 

 same with many other species. Of course cages containing 

 moths must be protected from would-be enemies. 



Like the ova of Bomhijx mori, A. yama-mdi ova are naturally 

 preserved all the winter, and hatch in the spring. But in reality 

 there is a notable difference between the two species. The eggs 

 of B. mori only contain a germ during the winter ; they remain 

 liquid. It is only in the spring, after the eggs have been sub- 

 mitted to the heat, that the larva is formed and hatches after it 

 is fully developed. The fertile yama-ma'i ovum, on the contrary, 

 contains a larva which is formed about three weeks after the 

 laying, and this larva, fully developed in the month of August or 

 September, remains in the ovum till March or April, and some- 

 times later, before hatching. Therefore Bomhyx mori hybernates 

 in the ovum state and yama-mdi in the larval state. 



Ova of the other silk-producing Bombyces which I have bred 

 could never hybernate ; they always hatched a few weeks after 

 they were laid or the larvae died in the egg, if the weather was 

 too cold for them to hatch. The eggs of the second brood of 

 AnthercEa pernyi and Attacus cynthia, lor instance, laid in October, 

 were never of any use for the following spring, and it was the same 

 respecting the eggs of Anthercea mylitta, Attacus atlas, and others. 



Ova of the yama-ma'i in the southern parts of Europe may 

 hatch in March ; in central parts they hatch in April, in 

 northern parts in May, and in Scotland in June. All depends 

 on the temperature of the various countries ; besides, the 

 hatching of the eggs, like the emergence of the moths from the 

 pupae, may be retarded or accelerated by the variations of tem- 

 perature, as is the case with our native Lepidoptera. 



It is the same with respect to the duration of the rearing of 

 the various species ; no time can be specified, unless a uniform 

 temperature can be obtained. Once, in London, in the open air, 

 the duration of a rearing of yama-mdi larvae lasted one hundred 

 and ten days ; on the contrary, a rearing made in a conservatory, 



