258 MEANS OF DEFENCE OF INSECTS. 



ment 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 a . The larvae 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 be- 

 sides 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 b . 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. ma- 

 culata, L. c . In the cognate genus Imatidium, the larva? 

 also are merdigerous ; and that of /. 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 Tinea, clothes-moths and others, and also 



a Reaum. iii. 220 Compare Vallisnieri Esperienz. ed Osservaz, 

 195. Ed. 1726. " Reaum. 233 



c Kirby in Linn. Trans, iii. 10. 



