IV. INSECTA: HEXAPODA. 



465 



which bears the unpaired tongue or glossa (gl), which corresponds 

 to the fused glossae (or to the hypopharynx?) of the first type and 

 which is used for sucking honey and hence has the form of a 

 nearly closed tube. Beside it lie the rudimentary paraglossse (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 

 (Ehynchota) can be compared with those of the bees in so far as 

 the labium forms the groundwork of the whole (fig. 488). The 



FIG. 488. FIG. 489. 



PIG. 488. Sucking mouth parts of mosquito, Culex pipiens. (After Muhr.) The 



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

 FIG. 489. Sucking mouth parts of a butterfly. (After Savigny.) ma:', ma;", shows how 



right and left maxillae unite into a tube; right labial palpus (pi) with hairs 



removed. 



beak (rostrum, haustellum) of these animals corresponds to the 

 labium; it is a grooved structure, either fleshy and flexible, or 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 retrorse hooks at the tip. These are the 



