ANNULOSA: INSECTA. 337 



The lower or basal portion of the labium is called the " men- 

 turn," or chin, whilst the upper portion is more flexible, and is 

 termed the " ligula." The central portion of the ligula is often 

 developed into a kind of tongue, which is very distinct in some 

 Insects (as in Bees), and is termed the " lingua." 



In the typical suctorial mouth, as seen in the Butterflies 

 (fig. 176, B) the following is the arrangement of parts: The 

 labrum and the mandibles are now quite rudimentary ; the 

 first pair of maxillae is greatly elongated, each maxilla forming 

 a half-tube. These maxillae adhere together by their inner 

 surfaces, and thus form a spiral " trunk," or " antlia " (inap- 

 propriately called the "proboscis"), by which the juices of 

 flowers are sucked up. Each maxilla, besides the half- tube 

 on one side, contains also a tube in its interior ; consequently 

 on a transverse section the trunk is found really to consist of 

 three canals, one in the interior of each maxilla, and the 

 third formed between them by their apposition. To the base 

 of the trunk are attached the maxillary palpi, which are ex- 

 tremely small. Behind the trunk is a small labium, composed 

 of the united second pair of maxillae. The " labial palpi " are 

 greatly developed, and form two hairy cushions, between 

 which the trunk is coiled up when not in use. 



In the Bee there exists an intermediate condition of parts, 

 the mouth being fitted partly for biting, and partly for suction. 

 The labrum and mandibles are well developed, and retain 

 their usual form. The maxillae and tire labium are greatly 

 elongated ; the former being apposed to the lengthened tongue 

 in such a manner as to form a tubular trunk, which cannot be 

 rolled up, as in the Butterflies, but is capable of efficient suc- 

 tion. The labial palpi are also greatly elongated. 



In the Hemiptera, the "trophi" consist of four lancet-shaped 

 needles, which are the modified mandibles and maxillae, en- 

 closed in a tubular sheath formed by the elongated labium 

 (fig. 176, C). Lastly, in the Diptera as in the common 

 House-fly there is an elongated labium, which is channelled 

 on its upper surface for the reception of the mandibles and 

 maxillae, these being modified into bristles or lancets. 



The mouth in the Masticating Insects leads by a pharynx 

 and oesophagus into a membranous, usually folded, stomach 

 the "crop," or "ingluvies" from which the food is trans- 

 mitted to a second muscular stomach, called the "gizzard" 

 (fig. 177). The gizzard, or proventriculus, is adapted for 

 crushing the food, often having plates or teeth of chitine de- 

 veloped in its walls, and is succeeded by the true digestive 

 cavity, called the " chylific stomach" (ventriculus chylopoieticus). 



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