212 MEANS OF DEFENCE OF INSECTS. 



from the body, instead of being pushed away and falling, is 

 lifted up above the back in the direction of the head. When 

 entirely clear of the passage, it falls, and is retained, though 

 slightly, by its viscosity. The grub next, by a movement of 

 its segments, conducts it from the place where it fell to the 

 vicinity of the head. It effects this by swelling the segment 

 on which the excrement is deposited, and contracting the 

 following one, so that it necessarily moves that way. 

 Although, when discharged, it has a longitudinal direction, by 

 the same action of the segments the animal contrives to place 

 every grain transversely. Thus, when laid quite bare, it will 

 cover itself in about two hours. There are often many layers 

 of these grains upon the back of the insect, so as to form a coat 

 of greater diameter than its body. When it becomes too heavy 

 and stiff, it is thrown off, and a new one begun. 1 — Thelarvae 

 of the various species of the tortoise-beetles (Cassida L.) 

 have all of them, as far as they are known, similar habits, 

 and are furnished besides with a singular apparatus, by 

 means of which they can elevate or drop their stercorarious 

 parasol so as most effectually to shelter or shade them. The 

 instrument by which they effect this is an anal fork, upon 

 which they deposit their excrement, and which in some is turned 

 up and lies flat upon their backs ; and in others forms different 

 angles, from very acute to very obtuse, with their body ; and 

 occasionally is unbent and in the same direction with it. 2 

 In some species the excrement is not so disgusting as you 

 may suppose, being formed into fine branching filaments. 

 This is the case with C. maculata L. 3 — In the cognate 

 genus Imatidium, the larvae also are merdigerous ; and that 

 of L Leayanum Latr., taken by Major-General Hardwicke in 

 the East Indies, also produces an assemblage of very long 

 filaments, that resemble a dried fucus or a filamentous lichen. 

 The clothing of the Tinece, clothes-moths, and others, and 

 also of the case-worms, having enlarged upon in a former 

 letter, I need not describe here. 



Some insects, that they may not be discovered and become 



1 Reaum. iii. 220. Compare Vallisnieri, Esperienz. ed Osservaz. 195. Ed. 

 1726. 



2 Reaum. 233. 3 Kirby in Linn. Trans, iii. 10. 



