INSECTA. 161 



primarily connected witli reproduction, but which are often con- 

 verted 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 consideration, 

 as being in the closest possible relation with their habits and mode 



Vig. 108. — Diagram of the external anatomy of an Insect : a Head cariying the eyes 

 (o) and antennaE: (an) ; 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 segment of the thorax, with the third pair of legs and the second 

 pair of wings ; e Abdomen, without limbs, but carrying terminal appendages con- 

 cerned in reproduction ; / Femur ; ( Tibia ; ta Tarsus. 



of life. Two chief types of mouth are recognisable in insects, termed 

 respectively the " masticatory " and the " 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 following organs are present (fig. 109, A) : 1. An upper 

 lip or " labrum " (l), attached below the front of the head. 2. A 

 pair of biting-jaws (m) or " mandibles." 3. A pair of chewing-jaws 

 or " maxillae " (mx) provided with jointed filaments, called the 



