THE SILKWORM 



71 



Stage 3. (6 days.) The larva is 14 mm. long at the 

 beginning of this stage, smooth, and of yellowish-white colour, 

 showing crescentic markings on the 2nd and 5th abdominal 

 segments, as was the case also in the latter part of stage 2. 

 The head is red, sometimes black. 



Stage 4. (7 days.) The larva is 27 mm. long at the 

 beginning of this stage. The space allowed to the larvae has 

 now to be increased, and a number of them are removed to 

 fresh trays. 



Stage 5. (10 days.) The larva is 40 mm. long at the 

 beginning of this stage. Its voracity is now marvellous. 

 Where many are kept in one room, the sound of their jaws 

 resembles the patter of heavy rain. At length, when they 

 have attained a length of about 90 mm., they pause, and 

 show an inclination to leave their food. During this sth 

 and last stage diseases, sometimes contracted long before, it 

 may be before 

 the larva was 

 hatched, often 

 show themselves 

 for the first time, 

 and the larvae 

 are watched with 

 much anxiety. 

 They require a somewhat higher temperature than before, 

 and the air of the room is kept at 23°-25° C. (73°-77° F.). 

 Sudden changes of weather, foul air, or vitiated food produce 

 heavy mortality at this time in ill-kept establishments. 



We will interrupt the life-history in order to describe the 

 larva at the time of its maturity. When full-fed and of large 

 size, it may attain a length of 90 mm. (upwards of 3J inches), 

 but the different breeds vary a good deal in this respect, and 

 75 mm. (3 in.) is a maximum with some of them. The body 

 is slender in comparison with most Bombycidse. The colour, 

 which was dark, approaching to black, in the fresh-hatched 

 larva, grows paler at each moult, and at last becomes a trans- 

 lucent greenish or yellowish white, like that of a muscatel 

 grape. The head is small, hard, and red or blackish. Behind 

 it come twelve segments to outward appearance, but really 

 thirteen, of which the last but one is only obscurely indicated ; 

 its distinctness is established by comparison with the imago, 



Fig. 51. — Silkworm. After Westwood. 



