ANNULOSA : INSECTA. 



235 



anterior wings, the apices of which remain membranous, and 

 to these the term u hernelytra ; ' is applied. In the Diptera the 

 posterior pair of wings are rudimentary, and are converted 

 into two capitate filaments, called " halteres," or " balancers." 

 In the Strepsiptera the anterior pair of wings are rudimentary, 

 and are converted into twisted filaments. 



The abdomen in Insects is normally composed of nine 

 somites, which are usually more or less freely movable upon 

 one another, and never carry locomotive limbs. The extremity 

 of the abdomen is, however, not infrequently furnished with 

 appendages, which are connected with the generative function, 

 and not infrequently serve as offensive and defensive weapons. 

 Of this nature are the ovipositors of Ichneumons and other 

 Insects, and the sting of Bees and Wasps. In the Earwig 

 (Forficula) these caudal appendages form a' pair of forceps; 

 whilst in many Insects they are in the form of bristles, by 

 which powerful leaps can be effected, as is seen in the Spring- 

 tails (Podura). 



The organs about the mouth in Insects are collectively 

 termed the " trophi," or " instrumenta cibaria." Two principal 

 types require consideration namely, the masticatory and the 

 suctorial both types being sometimes modified, and occasion- 

 ally combined. 



In the Masticatory Insects, such as the Beetles (fig. 81, i), 



Fig. 81. Organs of the mouth in Insects, i. Trophi of a masticating Insect (Beetle): 

 a Labrum or upper lip ; b Mandibles ; c Maxillae with their palpi ; d Labium or 

 lower lip with its palpi. 2. Mouth of a Butterfly: o Eye; ./"Base of antennae; g 

 Labial palp ; h Spiral trunk or "antlia." 3. Mouth of a Hemipterous Insect {Nepa 

 cinerea): I Labium ; m Maxillae ; n Mandibles. 



the trophi consist of the following parts, from before back- 

 wards : (i.) An upper lip, or " labrum," attached below the 

 front of the head. (2.) A pair of biting jaws, or "mandibles." 



