Microscopical Essays. 325 



We (hall firft give a general defcription of the animal itfelf, and 

 then proceed to explain thofe anatomical parts of it which are 

 Eeprefented at Fig. i, 2, 3, 4, 5, 6, 7, of Plate XII. This 

 infect., like every other caterpillar, proceeds from an egg, which 

 the parent moth takes care to depofit in general againft the trunk 

 of the willow ; to- this it is attached by a vifcous humor, which 

 foon becomes fo hard that the rain cannot diffolve it. 



The egg is very fmall, of an oblong fpheroidal fhape ; when 

 examined by the microfeope, we find broad waving furrows run- 

 ning through the whole length of it, which are again croffed by 

 clofe {breaks, giving it the appearance of a wicker balket. It is 

 probable that they are hatched fome time in, Auguft, becaufe the 

 fmall caterpillars are often to be found in September. When 

 fmall, they are generally to be met with under the bark of the 

 tree to which the eggs were fixed ; a humid oozing from the hole 

 they have made to get under the hark, is often a direction where 

 to fearch for them ; though it is not always a certain fign, becaufe 

 the fame effect is often occafioned by other infeels. 



Thefe caterpillars change- very little in their colour, be^ng 

 nearly the fame when they are full grown as when they are very 

 young. Like many others they are capable of fpinning as foon 

 as they are born. They change alfo feveral times- their fkin^. 

 but as it is almofl impoffible to raife them under a glafs, it is 

 not eafy to determine how many times, they moult or put off 

 their fkin ; if we are to judge of the number of times by the dif- 

 ference in fize between the new born and full grown caterpillar ; 

 and if we cornpare thefe with the increafe of the head, every 

 time it moults; we may reafonably conclude, that it changes. 



oftener 



