280 NATURAL HISTORY. [CH. xvi. 



examined, whitish spots or streaks may be observed 

 on their green surface : these mark the paths and 

 progress of the insects which mine them. Some 

 caterpillars form galleries only, some only areas ; 

 while a third tribe, after having made a gallery, mine 

 an area at the end of it. 



Each of these galleries or areas is generally oc- 

 cupied by a single insect ; and when there happens 

 to be more than one tenant, no inconvenience arises 

 from the circumstance ; for the comparative size of 

 the leaf is so great as to furnish an ample territory 

 for the accommodation of a number of these diminu- 

 tive inhabitants. In some cases, many of these in- 

 sects, having arrived at a certain size, may be seen 

 under the same tent, and associating together in the 

 most peaceable and harmonious manner; while 

 others, to the number of twenty or thirty, herd to- 

 gether from the moment in which they are first 

 evolved from the egg, and unite their efforts in ex- 

 cavating a common covering for the whole commu- 

 nity. That beneficent Power which has given ex- 

 istence and life to this minute atom, has at the same 

 time made an ample provision for all its wants by 

 conferring upon it an instinct which operates as 

 surely and as unerringly as the most obvious of 

 nature's laws. This instinct teaches the perfect 

 insect that one leaf is incapable of furnishing nou- 

 rishment to all her young: hence the provident 

 mother never deposites upon the same leaf a greater 

 number of eggs than the number of caterpillars 

 which its pulpy substance will be found capable of 

 sustaining. Having thus placed an adequate number 

 of eggs on one leaf, the insect proceeds to 'another, 

 and then to a third, until her whole stock has been 

 laid. 



The larva, having been evolved from the egg, im- 

 mediately begins to mine ; and the spot at which it 

 commenced its operations may readily be known ; 

 and by holding up the leaf between the eye and the 



