148 



INVERTEBRATE ANIMALS. 



or " mandibles." 3. A pair of chewing-jaws or " maxillae " 

 provided with jointed filaments, called the " maxillary palpi." 

 4. A lower lip or "labium" which also carries a pair of 

 jointed filaments, known as the " labial palpi." In the typical 

 suctorial mouth, as seen in the butterflies and moths, the fol- 

 lowing is the arrangement of parts : The upper lip and man- 

 dibles are quite rudimentary ; the maxillae are greatly length- 

 ened, and form a spiral tube fitted for sucking up the juices of 

 flowers ; and the labial palpi are much developed, and form 

 two hairy cushions between which the trunk can be coiled up 

 when not in use. In many insects, the organs of the mouth 



are essentially adapted for suc- 

 tion, but are also fitted for pierc- 

 ing solid substances, such as the 

 skin of animals or the stems of 

 plants. In these the lower lip 

 forms a kind of sucking-tube or 

 sheath, within which are con- 

 tained the maxillae and mandi- 

 bles, which are modified so as 

 to form piercing organs or lan- 

 cets. In the common bee, the 

 masticatory and suctorial types 

 of mouth are combined. The 

 mandibles or biting-jaws are re- 

 tained, to enable the honeycomb 

 to be manufactured, and there 

 is also a tubular trunk fitted for 

 sucking up the juices of flowers. 

 In the butterflies, too, in which 

 the mouth of the adult is strict- 

 ly adapted for suction, the cater- 

 pillar is furnished with a mas- 

 ticating mouth, so that it can 

 feed upon leaves or other solid 

 substances. 



The mouth in the mastica- 



SUseS'' 7 ' 111 ^ 116 ^ 010 ^^ ting Insects (Fig. 63, a) leads 



into a membranous and often 



folded cavity, termed the "crop" (#), from which the food 

 passes to a second muscular cavity or "gizzard" (c). The 

 gizzard is adapted for crushing the food, and often has plates 

 or teeth of chitine developed in its walls. It is succeeded 

 by the true digestive cavity (d), which is termed the " chy- 



FIG. 63. Digestive apparatus of a Beetle 

 (Carabm auratus). a Gullet; b Crop; 

 c Gizzard; d Chylific stomach; e Mal- 



