94 OUR HOUSEHOLD INSECTS 



method of their construction it is manifest that their 

 colour will depend upon that of the material upon which 

 the insect has been feeding, and by judicious variations 

 of its dietary the little tailor can be induced to form 

 cases of all conceivable tints, or mixtures of such. The 

 method employed for adapting the case to the needs of 

 the growing caterpillar is truly marvellous. It is obvious 

 that two kinds of enlargement will be necessary : with 

 the growing stature of the larva the case will need 

 elongation, but it will require an increase of circumfer- 

 ence as well; and though the meeting of the former 

 demand presents no difficulty nor necessitates the exercise 

 of much sagacity in the device of a method, the latter 

 might well be the subject of considerable perplexity, and 

 one is scarcely prepared for the extreme ingenuity mani- 

 fested by the little creature in meeting the difficulty. 

 When it finds its quarters becoming too strait it slits up 

 the case on one side for half its length by means of its 

 scissor-like jaws, and fills up a certain space between the 

 severed edges with the same materials as compose the 

 rest of the case. This done, a similar slit is made, say, 

 at the other end, and the like process gone through 

 again. Though the circumference is now increased 

 throughout, this is not the end of the operation, for the 

 new pieces having been let in only on one side, the case 

 thereby becomes a little un symmetrical ; therefore, to 

 restore the symmetry of its form, two precisely similar 

 operations are carried out on the other side, so that to 

 complete the process no less than four slits have to be 

 made two at each end and to be successively filled up 

 with the usual materials. It would appear, however, 

 from- the observations of Reaumur, that the insect does 

 not always observe the same order in making these slits, 

 but may vary the order indefinitely. 



