324 



LEPIDOPTERA 



CHAP. 



salivary glands proper, which open into the cavity of the mouth, 

 one close to the base of each mandible ; the silk-glands, which 

 terminate by a common canal, continued externally as the spin- 

 neret ; and the glands of Filippi situate in the head itself, and 

 opening into the ducts of the silk-glands, near their union 

 into a common duct. It should be recollected that Fig. 165 

 does not indicate all the details of the anatomy ; the muscular 

 system, for instance, being entirely omitted, though there are 

 an enormous number of muscles ; these however are not very 

 complex, they being mostly repetitions in the successive seg- 

 ments. 1 The mouth -parts are very different from those of the 



4 d.U: 



FIG. 165. A, Section of male caterpillar of Anosia plexippits muscular and tracheal 

 systems and fat-body not shown : I, pro-, II, meso-, III, meta- thorax ; 1-10, 

 abdominal segments ; b, supra-oesophageal ganglion ; c, rectum ; d.v, dorsal vessel ; 

 :f-g 9 , g an glia of ventral chain ; h, head ; i, intestine ; m.v, Malpighian tube ; .c, 

 nerve-cord of ventral chain ; oe, oesophagus ; s, spinneret ; s.o.g, infra-oesophageal 

 ganglion ; st, stomach ; s.i\ silk-vessel ; t, testis. B, One of the jointed prothoracic 

 legs. C, An abdominal foot with its hooks. (After Scudder and Burgess, mag- 

 nification about -j.) 



perfect Insect, inasmuch as the maxillae and labial palpi, which 

 are the most remarkable structures of the imago, are small, and 

 are differently constructed in the caterpillar, while the mandibles, 

 which are the largest organs of the caterpillar, disappear in the 

 adult. The little organ by which the caterpillar exudes its silk 

 is called a spinneret ; according to Packard it is a " homologue 

 of the hypopharynx." It is a more or less prominent point on 

 the middle of the labium (Fig. 166, #) and sometimes forms a 

 conspicuous spine projecting downwards. The eyes are ex- 

 tremely imperfect organs, consisting merely of six, in some cases 



1 For anatomy of caterpillars refer to Lyonnet's famous work, Traite anatomique 

 de la chenille qui range le bois de saule, La Haye, 1762. 



