64 ZOOLOGY, ' 



form). Some insects have a threefold metamorphosis; 

 in others, the transformation is incomplete, and a few 

 appear to remain unchanged. They 

 have, accordingly, been divided into 

 three sections, corresponding with the 

 degree of transformation which they 

 pass through : 



1. Holometabolic (Gr. holos, whole; 

 metabole, change) insects. These pass 

 through three stages in progressing 

 from the egg to the perfect insect. 

 The first stage is termed the larva or 

 caterpillar. In this state, the insect 

 resembles a worm, and generally has 

 numerous legs. It eats voraciously; 

 and, as it increases in size, often changes 

 its skin, acquiring a new covering of 

 FIG. 26. NERVOUS SYSTEM larger size as often as it does so. It 

 OF THE BEE. then passes into a quiescent state in 



which it is termed a pupa (Lat. pupa, a doll) or chrysalis. 

 Sometimes the pupa is covered with a " cocoon," spun by 

 the larva; in other cases it is enclosed in a chitinous 

 skin. While in this state, the legs, wings, and other 

 organs are developed ; and at length, the perfect insect, or 

 imago, emerges from its prison. Beetles, butterflies, 

 moths, &c., belong to this group. 



2. Hemimetabolic (Gr. hemi, half; metabole, change) 

 insects also undergo three stages of transformation. The 

 larva, however, differs little from the imago, except in its 

 being wingless, and of smaller size. The pupa is some- 

 what larger than the larva, and possesses rudimentary 

 wings in the form of thick lobes, enclosed in cases. The 

 pupa is active, instead of being quiescent, as in the 

 holometabolic insects. Ultimately the wings are de- 

 veloped, and it then becomes the imago or perfect insect. 

 This kind of metamorphosis is termed incomplete. 



Grasshoppers, crickets, dragon-flies, &c., belong to this 

 group. The larva and pupa of the dragon-fly live in water. 



