HISTORY OF INSECTS. 9 



hatching to first change, seven days ; changing, 

 two days ; before the second change, seven days ; 

 changing, two days ; before the third change, 

 seven days ; changing, three days ; before the 

 fourth change, seven days ; changing, four days ; 

 before beginning to spin, eight days ; spinning, 

 five days. 



22. When the caterpillar is about to change 

 its skin, it ceases to eat, holds its head up stiff, 

 and appears ill and sulky ; the new head is plainly 

 to be discovered through the transparent skin, 

 behind the old one, and rather of a triangular 

 shape the apex of the triangle being uppermost ; 

 after remaining in this state two or three days, as 

 above stated, the skin opens behind the head, 

 which cracks longitudinally, and is cast with the 

 skin ; the caterpillar then twists itself from side 

 to side, and writhes about, while the skin gra- 

 dually slips from its body, and comes off at the 

 tail. 



23. Whilst the silk- worms are feeding, they 

 should be kept very clean, and abundantly sup- 

 plied with fresh leaves ; open trays, made of 

 pasteboard, are very convenient for holding them ; 

 and from these, if supplied with food, they never 

 wander. 



24. Care should be taken to preserve silk- 

 worms from birds and mice, both of which are 

 excessively fond of them ; the influence of the 

 sun is highly injurious to them, as are also cold 



