THE FLY. 31 



maturity. Of this group, which is hut limited, the 

 Louse {Pediculm) is a well-known, hut not very 

 agreeable example, and, in common with the other 

 genera that constitute this suhclass, the Louse is 

 apterous, or wingless. 



The second group {Hemi-metabola) undergoes one 

 metamorphosis, namely from the larval to the imago, 

 or perfect form; their appearance, however, in the 

 first of these stages varies but little from that of the 

 fall-grown insect, the principal distinction being, that 

 the wings are wanting in the larva, and only make 

 their appearance at a later period of the insect's ex- 

 istence. This group is far more numerous than the 

 last ; and as familiar examples, we may quote the 

 Earwig {Forficula),ihie. Locust [Acridium), the Dragon- 

 fly [Libellula), and that terror of all good housewives, 

 the Bug [Cimex) . 



Lastly, we have an extensive race of insects that 

 undergo a complete transformation {Holometabola) , or, 

 more correctly speaking, two changes ; the first from 

 larva to pupa, the second irovapupa to imago. These 

 three stages of growth are so familiar to all who have 

 any knowledge of natural history, that we need but 

 allude to the metamorphosis of the Butterfly, first from 

 the caterpillar to the chrysalis, and from the latter to 

 the winged insect, by way of passing illustration. The 

 Bee {Apis), the Wasp ( Vespa), the Butterfly {Papilio), 

 the Beetle tribes (Coleoptera), and, amongst many 

 other similar forms, the common House-fly {Musca do- 

 mestica), are all members of this extensive group. 



