IV. INSECTA: HEXAPODA 



407 



honey and hence has the form of a nearly closed tube. Beside it lie the rudi- 

 mentary paraglossae (pg) and the well-developed palpi. Similarly the maxillae 

 have small cardines and palpi, while the stipites and the undivided lobe (/) are 

 long and well developed. 



The piercing mouth parts of the flies (Diptera) and bugs (Rhynchota) can 

 be compared with those of the bees in so far as the labium forms the groundwork 

 of the whole (fig. 446). The beak (rostrum, haustellum) of these animals cor- 

 responds to the labium; it is a grooved structure, either fleshy and flexible, or 



FIG. 446. FIG. 447. 



FIG. 446. Sucking mouth parts of mosquito, Culex pipiens (after Muhr). The 

 groove of labium opened by removing labrum; the stylets separated. 



FIG. 447. Sucking mouth parts of a butterfly (after Savigny). nix', nix", shows 

 how right and left maxilke unite into a tube; right labial palpus \J)D with hairs 

 removed. 



stiff and jointed. The edges of the groove are inrolled so that there remains a 

 narrow dorsal slit, which can be closed by the slender upper lip (Ir). The 

 tube formed of these parts contains four stylets, toothed or with rctrorse hooks 

 at the tip. These are the mandibles and maxilke, and a fifth stylet, the hypo- 

 pharynx (hy) can be present. The palpi, which only occur in the Diptera, belong 

 to the maxillae (/>). Reduction in number of stylets to four or three, or their 

 complete absence (some flies), is brought about by fusion or by degeneration. 

 The haustellum serves as a case for the sucking tube, which in the Rhynchota is 

 formed by the united maxillae, in the Diptera by labrum and h\popharynx. 



The proboscis, or haustellum (the so-called tongue), of the Lepidoptera 



