INSECTS IN GENERAL. 83 



body required, they pass into that state termed by Fabricius 

 incomplete nymph. This is when the larva at its last moult- 

 ing changes form suddenly, and allows the perfect insect to 

 appear, but at first in a state of extreme softness. It gra- 

 dually assumes greater solidity, and the animal appears with 

 all its members, with its six feet, with its wings, but bent, 

 folded back upon themselves, and in a state of almost abso- 

 lute paralysis. From this sort of nymph state the insect does 

 not issue, but by losing the external coating of skin which 

 retained all its parts in a state of forced immobility. With 

 some slight modifications this is the predicament of the flea 

 among the aptera, and many larvae of the tipulse among the 

 diptera, as well as certain neuroptera, such as the antlions, 

 hemerobiae, &c. 



The fourth principal mode of transformation is exhibited 

 by the butterflies and other lepidoptera whose caterpillars are 

 changed into chrysalids. This is the sort of nymph which 

 Fabricius names ohtected, and which is also iermedipupa and 

 aurelia. At the moment in which the insect quits for the 

 last time the skin of the caterpillar, it appears under quite 

 another form than that which it is to assume in the sequel. It 

 is an undivided body, variable in form, most usually conical 

 towards one of its extremities, and presenting on one of the 

 faces of the opposite extremity some prominent traits which 

 mark some parts of the perfect insect, particularly the an- 

 tennae, the feet, and wings, but very closely contracted 

 together. Some of these nymphs or chrysalids, which are 

 almost always condemned to an immoveable state, undergo 

 this change in the open air and naked. Such are the chrysa- 

 lids of the diurnal butterflies. Others come from caterpillars 

 which are sheltered in a cocoon of silk, which they spin 

 around their body, or like the tineae, or some pyrales, they 

 undergo transformation in the case itself which they inhabited. 

 In fine, some chrysalids when about to assume their last 



G 2 



