450 



COMPARATIVE ANATOMY 



CHAP. 



the basal portions are fused, the 2 4 -jointed palps are well retained, the outer 

 masticatory ridges are separate, but the 2 inner ridges fuse to form a tube. In the 

 other Hymenoptera (Fig. 309) the mandibles are always retained in a condition 

 capable of masticating or biting ; both the maxillae go to form sucking or licking 

 mouth parts. The palps on the anterior maxillae become reduced, the basal 

 portions elongate and the masticatory ridges grow together on each side into a 

 long piece (mm). On the under lip also the basal portion elongates, the feeler 

 remains well developed, and slender, 2-4 jointed ; the inner ridges together form the 

 long tongue, and the outer ridges small lateral appendages to it, called the accessory 

 tongues (paraglossa). 



The mouth parts of the Diptera (Fig. 310) are adapted for piercing and sucking, 

 and together form a peculiar proboscis. The bristle-shaped mandibles in the male, 



A 3 



FIG. 310. Mouth parts of the Diptera. A, of Tabanus. B, of Culex. Lettering as before. 

 a, Antenna , an, facet eye ; oc, simple eye (ocellus). 



and occasionally in both sexes, are wanting as separate pieces, and are then no doubt 

 fused with the upper lip. The proboscis is principally formed out of the following 

 parts much elongated : first, the upper lip ; second, the basal portion of the lower lip, 

 2 lips (labella) at the end of this representing the transformed palps ; and third, 

 a prolongation of the lower oesophageal wall (hypopharynx), developed into a pierc- 

 ing setae, at whose point the salivary vessels emerge. The anterior maxillae form 2 

 slender setae, which lie together with the seta-like mandibles in the sucking proboscis. 

 Their 1-5-jointed palps are mostly well developed. 



The mouth parts of the Rhynchota (Fig. 311) together form a proboscis adapted 

 for piercing and sucking. The elongated, generally 4 -jointed lower lip (posterior 

 maxillae) forms a channel in which lie the mandibles and interior maxillae, trans- 

 formed into setae covered at their basal part by the- upper lip (labrum). 



