148 



INVERTEBKATE ANIMALS. 



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

 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- 

 d M^\- tained the maxUlse and mandi- 



'^^:J bles, which are modified so as 



sI'-W iF?\^ *° form piercing organs or lan- 



^^ cets. In the common bee, the 



e-f II %x /^s=* masticatory and suctorial types 



"^ ^'^ of mouth are combined. The 



mandibles or biting-jaws are re- 

 tained, to enable the honeycomb 

 ■f -... ^<P\ ^ 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- 

 h\ rt=:^r%^ ^ y 1^^%^ ly adapted for suction, the cater- 



pillar is furnished with a mas- 

 ticating mouth, so that it can 

 feed upon leaves or other solid 



Fig. 63. — ^Digestive apparatus of a Beetle gubstancCS. 

 (Cardbm auraius). aG-uUet; &Crop; _„ ' ,i . ,i ,• 



e Gizzard; d Chylifio stomach; « Mai- The mOuth m the mastica- 



iS^esseb''-^^*""""""^""^''^ ting Insects (Fig. 63, a) leads 



into a membranous and often 

 folded cavity, termed the "crop" (5), 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- 



