76 INJURIOUS AND USEFUL INSECTS 



begins, a process which we shall not describe here. The 

 cocoons selected for breeding are divided into males and 

 females. The male cocoons are lighter, less regularly rounded 

 at the ends, and narrowed in the middle. The sexes are kept 

 apart, so that the males may not be excited by the odour 

 of the female, which sets up violent struggles for liberty. A 

 yellow fluid is discharged from the intestine before the moths 

 are considered ripe. Then mating is permitted, and shortly 

 afterwards the female begins to lay. The male moths perish 

 early, but the females live several days, longer in cool weather 

 than in hot. For at least three centuries it has been known 

 that unfertilised females, occasionally though rarely, lay eggs, 

 from which normal larvae proceed. 



The body of the moth is thick (especially in the female) and 



Fig. 52. — Male silkworm moth. After Westwood. 



hairy. The feelers are pectinate (with comb-like projections), 

 especially in the male. The fore wings are falcate (with a 

 concave incision behind the tip). Both wings are cream- 

 coloured, with faint transverse streaks of darker colour, and 

 are extended when at rest ; the legs are densely clothed with 

 hair. The length of the female is about 21 mm., and the 

 expanse of wings 43 mm. The moths occasionally utter a 

 faint sound. 



Silkworms are subject to several infectious diseases, which 

 have caused ruinous losses in the crowded rearing-houses. 

 The story has often been told how, when the prosperity of 

 large districts in the south of France was destroyed by pdbrine 

 and flacherie, Pasteur, who had never treated any animal for 

 any disease, was called in as adviser, how he learned the 



