THORAX. 



525 



totally aborted, or, at any rate, become functionless, it is obvious 



Lr 



a 



FIG. 432. Oral apparatus of Butterflies (after Savigny). a, 

 Of Zygaena; b, of Noctua. A, Antennae; Oc, eyes; Lr, 

 upper lip ; Md, mandible ; Mxt, maxillary palp ; MX, 

 maxilla (first) ; Lt, labial palp, cut away. 



that no sharp line can be drawn between 

 the piercing and sucking forms of oral 

 apparatus (fig. 434). 



The next principal region of the body 

 in Insects is the thorax, which is con- 

 nected with the head by a slender neck. 

 It consists of three segments, and bears 

 three pairs of legs and usually two pairs 

 of wings on the dorsal surface. These 

 three segments, the prothorax, the meso- 

 t/wrax and the metathorax are rarely 

 simple horny rings, but are usually com- 

 posed of several parts united by sutures. 

 In each segment a dorsal plate, lateral 

 regions and a ventral plate can be dis- 

 tinguished. These may be termed notum, 

 pleura and sternum respectively, and 

 they may further be described, according 

 to the segments in which they occur, as 

 pro-, meso- and meta-notum, and pro-, 

 meso-, and meta- sternum. The lateral 

 regions are divided into an anterior piece 

 (episternum) and a posterior (epimerum), 



FIG. 433. Mcuth parts o< 

 Nepa cinerea (after Sa-, 

 vigny). Z77, Lower lip 

 ( abium) or rostrum ; Lr 

 upper lip ; M.I, mandible ; 

 MX, maxilla (first). 



FIG. 434. Houth parts of Culex 

 memoroxus ^ (after Becher). 

 Lbr, Upper lip ; Lb, lower lip 

 (proboscis) ; Lt, labial palp ; 

 Md, mandibles; MX, maxilla; 

 (first) ; H. hypopharynx (pierc- 

 ing weapon). 



