296 



INSECTA. 



utterly useless to the imago, and consequently are more or less 

 completely wanting in the mature state. 



The whole body of the larva is filled with a peculiar fatty 

 tissue (Jig. 134,/,/,/) called by entomologists the rete, epiploon, 

 or fat-mass. This material, found in great abundance in mature 

 and well-fed larvse, consists of an oily or greasy substance enveloped 

 in a most delicate cellulosity, and seems to correspond to the fat of 

 higher animals, like which it is indubitably a product of digestion, 

 and a repository of superabundant nourishment, stored up, no 

 doubt, for the sustenance of the animal during its helpless con- 

 dition in the dormant or pupa state serving like the fat of hiber- 

 nating quadrupeds, for food during the confinement of the imago. 



(341 .) But the most re- Fig. 135. 



markable peculiarity of the 

 larvse under consideration, 

 is the presence of an appa- 

 ratus employed for produc- 

 ing a tenacious thread of 

 extreme delicacy, appro- 

 priated by different species 

 to various purposes. In 

 many cases (fig. 105), it 

 is made subservient to lo- 

 comotion ; and by its assist- 

 ance, as by a rope, the 

 larva can suspend itself 

 from any object, or let it- 

 self down from one branch 

 to another in search of 

 food. The most import- 

 ant uses however to which 

 this thread is applied are connected with the concealment and pro- 

 tection of the quiescent and defenceless pupa ; either furnishing the 

 means of suspending the chrysalis in a place of safety* (fig. 135), 

 or, as is the case with the silk-worm (fig. 131), supplying the 

 material with which the caterpillar encases itself preparatory to 



* For a most amusing account of the manner in which some chrysalides manage with- 

 out any external limbs to suspend themselves by the tail in a position of security, the rea- 

 der is referred to Kirby and Spence, vol. iii. page 207. The figure above given illustrates 

 the different steps attending the process. The larva, A, having spun some loose silk, and 

 fixed it upon the under side of a leaf or other suitable object, suspends itself therefrom 



C 



