70 INJURIOUS AND USEFUL INSECTS 



and hygrometers. Separate rooms are provided for hatching 

 the eggs, rearing the larvae, and storing the mulberry-leaves, 

 which are carefully stripped from the trees, and half-dried. A 

 single annual brood is considered to answer best. It is pos- 

 sible to raise more than one, and there are races of silkworms 

 which regularly produce two or three generations in the year, 

 but the difficulty of procuring a sufficient supply of food late in 

 the summer is an effective check to the multiphcation of annual 

 broods. The eggs are laid upon pieces of cloth or stout paper, 

 to which they adhere. A gramme of graine (eggs) contains 

 1500-1600 eggs, of which one moth will lay from 400 to 550. 

 The eggs are kept from hatching prematurely by storing in ice- 

 houses or other cool places, and are hatched out by artificial 

 heat when the mulberry-leaves are ready to be gathered. The 

 grub forms in the egg not long after laying( in summer), and 

 can be artificially hatched at any later time if required. It 

 bites its way through the firm egg-shell, but sometimes finds 

 a difficulty in freeing its body from the fragments. Pieces of 

 paper with small holes pierced in them are put over the 

 hatching-trays, the larvae creep through the holes to the light, 

 and in doing so, scrape off any bits of the envelope that still 

 adhere. As a rule, the larval period is interrupted by four 

 moults (there may be only three), and is therefore naturally 

 divisible into five stages. Great pains are taken to cause all 

 the larvae of one magnanerie to go through these stages 

 simultaneously. A batch of larvae which lag behind the rest 

 may give much trouble in such matters as food-supply, or the 

 regulation of the temperature of the rearing-chamber. At 

 times of moult the larva becomes motionless, and ceases to 

 feed for a day or more. The old skin becomes loose and 

 wrinkled, and is fixed to the support by a few silken threads 

 paid out from the mouth. At length it splits along the fore 

 part of the back, and the larva disengages itself. The follow- 

 ing points characterise the various stages : — 



Stage 1. (From hatching to the ist moult, 5 days.) The fresh- 

 hatched larva is only i mm. long, but immediately lengthens to 

 2 mm. It is dark, almost black, and covered with hair. The 

 head is relatively larger than in succeeding stages. 



Stage 2. (Between ist and 2nd moults, 4 days.) The 

 larva is 9 mm. long at the beginning of this stage. The hair 

 is scanty, and the colour grey. 



