236 MANUAL OF ZOOLOGY. 



(3.) A pair of chewing jaws, or " maxillae," provided with one 

 or more pairs of "maxillary palps," or sensory and tactile 

 filaments. (4.) A lower lip, or " labium," composed of a 

 second coalescent pair of maxillae, and also bearing a pair 

 of palpi, the " labial palps." The lower or basal portion of 

 the labium is called the " mentum " or chin, whilst the upper 

 portion is more flexible, and is termed the "ligula." The 

 upper portion of the ligula is often developed into a kind of 

 tongue, which is very distinct in some Insects, and is termed 

 the " lingua." 



In the typical suctorial mouth, as seen in the Butterflies 

 (fig. 8 1, 2), 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 " (inappro- 

 priately called the " proboscis ") f 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 extremely small. 

 Behind the trunk is a small labium, composed of the united 

 second pair of maxillae. The " labial palpi " are greatly devel- 

 oped, 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 the labium are greatly elon- 

 gated ; 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 ffemiptera, the " trophi " consist of four lancet-shaped 

 needles, which are the modified mandibles and maxillae, enclosed 

 in a tubular sheath formed by the elongated labium (fig. 81, 3). 

 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- 



