312 Insects and their Surroundings 



legs are developed whereof those on the fifth and 

 sixth abdominal segments are used for walking, while 

 the hindmost are fixed to the case to keep it in 

 position. When fully grown the caterpillar chooses 

 a crack in the bark or a fork between two branches, 

 where it fixes its case, spins a cocoon and pupates, 

 having first taken the precaution to gnaw an opening 

 through which the moth can get out. This habit of 

 gaining protection by making a case or shield of 



—f. Moth {Erastria scitula, Ramb.), S. France, a. larva, under 

 surface ; b. upper view ; c. case in section ; (/. case, outer view ; c. pupa. 

 Twice natural size. From Riley (after Rouzaud), Insect Life, vol. 6 (U.S. 

 Dept. Agr.). 



foreign objects is practised by many insects of 

 different orders. The caterpillars of some clothes- 

 moths (fig. 169) build up cylindrical cases out of frag- 

 ments of the cloth on which they feed. The grubs of 

 the peculiar flattened Leaf-beetles known as " tortoise- 

 beetles " (Cassida) shelter themselves under their own 

 excrement, which is discharged through the long anal 

 tube standing vertically up from the hind-body, and 

 collects to form a kind of flattened umbrella over the 



