INSECTA. 



147 



FIG. 62. Diagram of the external anatomy of an insect: a Head, carrying tho eyes and 

 antennae ; b First segment of the thorax, with the first pair of legs ; c Second segment 

 of the thorax, with the second pair of legs and the first pair of wings ; d Third seg- 

 ment of the thorax, with the third pair of legs and the second pair of wings ; e Abdo- 

 men, without limbs, but carrying terminal appendages concerned in reproduction. 



which are usually more or less freely movable upon one an- 

 other, and which never carry locomotive limbs, as is so com- 

 monly the case in the Crustacea. The extremity of the abdo- 

 men is, however, often furnished with appendages which are 

 primarily connected with reproduction, but which are often 

 converted into weapons of offence and defence. Of this 

 nature are the " ovipositors " of ichneumons, the stings of 

 bees and wasps, and the forceps of the common earwig. 



The organs of the mouth in insects require a brief consid- 

 eration, as being in the closest possible relation with their 

 habits and mode of life. Two chief types of mouth are recog- 

 nizable in insects, termed respectively the " masticatory " and 

 " suctorial," according as the mouth is fitted for biting and 

 chewing, or simply for imbibing fluids. The masticatory 

 mouth is seen in perfection in the beetles, in which the follow- 

 ing organs are present : 1. An upper lip or " labrum " at- 

 tached below the front of the lead. 2. A pair of biting-jaws 



