184 INSTRUCTIONS FOR COLLECTING INSECTS. 



not to include the epidermis of the larva. He must learn early to 

 distinguish the larvae of saio-jiies from the true caterpiUar. These 

 false caterpillars have globular heads and cylindrical, naked bodies, 

 sometimes covered with a white flaky substance that easily rubs off, 

 or have a dark-colored, slimy skin, and are either entirely deprived of 

 abdominal legs, or have from eighteen to tiventy-tivo, and are unarmed 

 with hooks. The true caterpillar never has more than ten ahdominal 

 legs, which are always armed with minute hooks. 



Every caterpillar undergoes periodical moultings, and they must on 

 no account be disturbed whilst undergoing this change. When one 

 of these periods arrive they cease to eat, and appear to be sick and 

 languishing, remaining steadfastly fixed on some portion of their 

 food plant, with the hooks of their false legs fastened in a little web 

 of silk, and, even though irritated, are unwilling to change their po- 

 sition. It is always a critical time in the life of the larva, during 

 which it not only changes its skin, but appears in one or two new 

 dresses before reaching that characteristic of its maturity. The stu- 

 dent should, therefore, learn early to recognize it, and to respect the 

 necessities of the little creature of which he has made a captive. When 

 larvae are dissatisfied with their food plant or about to change to pupae, 

 they never indicate it in this manner, but traverse their place of con- 

 finement incessantly and restlessly, travelling over the same track 

 until they wear it into a pathway. 



The chief indications to be observed in rearing larvae is to place 

 them in as nearly a natural condition as possible, and to keep their 

 food plant fresh for the longest practicable period. In order to fulfil 

 these conditions in all cases, something must be left to individual in- 

 genuity and intelligence, but for the great majority of larvae I would 

 heartily recommend the following elegant and easily constructed 

 vivarium : 



It consists of a circular wooden box, from six to twelve inches in 

 diameter or more, at the option of the observer, and from four to six 

 inches deep, lined with sheet zinc or lead, so as to be water-tight. A 

 stratum about an inch or two inches thick of washed, fine gravel- 

 stones is placed on the bottom, and the remaining space is filled with 

 moisiened but not wet loam, and the surface covered with moss. Into 

 this various small, humble plants may be set for the purpose of gen- 

 erating oxygen, and consuming the carbonic acid gas exhaled by the 

 larvae, and the whole is covered with a bell glass, that rests upon the 

 rim, proportioned in height to the diameter of the box. When it is 

 to be used, a portion of the food plant of the larva should be stuck 

 into the moistened loam, where it will remain fresh quite a long 

 time, in consequence of the atmosphere within the bell glass being 

 saturated with watery vapor, which condenses on the sides, and 

 trickles down to the soil again. 



The arrangement of the earthy materials closely resembles that of 

 natural soil, and if the transformation of the larva is subterranean, 

 there is no necessity to remove it in order that it may undergo the 

 change to a jjupa. If the larva is a large one, or if it contains more 

 than one, the bell glass should be elevated every few days, and their 

 ejcctamenta removed from the surface. 



