4-36 INSECTA. 



bacon, wax, and lard, are not spared by them. Several confine themselves 

 exclusively to a single article of diet ; others are less delicate, and devour all 

 sorts of matters *. 



Some of them form societies, and frequently live under a silken tent, spun 

 by them in common, which even shelters them during the winter. Several 

 construct sheaths for themselves, either fixed or portable. Others make their 

 abode in the parenchyma of leaves, where they form galleries. The greater 

 number are diurnal. The others never issue forth but at night. The severity 

 of winter, so fatal to almost all insects, does not affect certain Phala^nie, which 

 only appear in that season. 



Caterpillars usually change their skin four times, previously to passing into 

 the state of a nymph or chrysalis. Most of them spin a cocoon in which they 

 enclose themselves. A frequently reddish liquor, which lepidopterous insects 

 eject at the moment of their metamorphosis, softens or weakens the extremity 

 of the cocoon, and facilitates their exit ; one of these extremities also is gene- 

 rally thinner than the other, or presents a favourable issue by the peculiar 

 disposition of the fibres. Other caterpillars are contented with connecting 

 leaves, particles of earth, or of the substances on which they have lived, and 

 thus forming a rude cocoon. The chrysalides of the diurnal Lepidoptera, 

 ornamented with golden spots, whence the term chrysalis, are naked and fixed 

 by the posterior extremity of the body. The nymphs of the Lepidoptera 

 present a special character, of which we have spoken in our general observa- 

 tions on the class of insects. They are swathed or resemble mummies. Those 

 of several insects of this order, particularly of the Diurnae, undergo their 

 metamorphosis in a few days ; they even frequently produce two generations 

 in the course of the year. The caterpillars or chrysalides of others, however, 

 remain during the winter in one of these states, and only appear as perfect 

 insects in the spring or summer of the following year. Generally speaking, 

 the eggs laid in the fall are not hatched till the ensuing spring. The Lepi- 

 doptera issue from their envelope in the usual manner, or through a slit, 

 which is effected on the back of the thorax. 



The larvae of the Ichneumonides and Chalcidites deliver us from a great 

 portion of these destructive animals. 



We will divide this order into three families, which correspond to the three 

 genera of which it is composed in the system of Linnseus. 



FAMILY I. 



DIURNA. 



THIS family is the only one in which the exterior margin of the inferior 

 wings does not present a rigid, squamous seta, or kind of bridle, for retaining 



* One of the most evident proofs of the divine providence is the perfect coincidence 

 of the appearance of the caterpillar with that of the plant on which it is to feed. 



