LARVA OF PRIVET HAWK MOTH. 149 



scale. The mandibles of Sphinx are only slightly toothed. In the embryo the 

 maxillae and labial limbs are separate as in other Insecta. A few Lepidopterous 

 larvae are apodal, e. g. Micropteryx among Tineinae. The coxa and trochanter of 

 the thoracic limbs are but slightly indicated. The tarsus is neither jointed nor 

 clawed. In these points the limb contrasts strongly with the limb of an insect 

 with an active pupa stage, e.g. Cockroach, which closely resembles that of the 

 imago. In a few instances, e. g. in Stauropus Fagi, the second and third pairs of 

 limbs are large with conspicuous joints. The prolegs vary much in number and 

 character. In the embryo Sphinx Populi^ as figured by Kowalewsky (Me'm. de 1'Acad. 

 Imp. St. Petersburg (7), xvi. 1871, PI. xii. fig. 10), there is a pair to each of the ten 

 abdominal somites. In the Caterpillar they may be reduced to the last and the 

 anal pairs (Geometridae), or to the anal pair alone (some Tineinae). They are as a 

 rule armed with hooks, alternately long and short, arranged either in a complete 

 circle round the terminal disc or only on its inner side. The anal pair is produced 

 in the Puss Moth (Cerura vinula) into a pair of long whip-like processes, each con- 

 taining a protrusible filament, used to drive away Ichneumons. Abdominal limbs 

 are also found in the Thysanura, in the larvae of Panorpatae, of Tenthredinidae 

 among Hymenoptera, and of some Coleoptera (?). 



Many larval Tenthredinidae closely resemble caterpillars. They differ from 

 them in the following points : the ocellus is single ; the antennae are 3-jointed and 

 conical, but 7-jointed in the genus Lyda ; the maxillae are membranous, bilobed 

 and furnished with 3-5-jointed palpi ; the labium is small, fleshy, and provided with 

 3-jointed palpi and a spinneret. The majority have prolegs which vary from 6-8 

 pairs in number. These legs have no hooks, and there is a pair on the second ab- 

 dominal somite, which never bears one in the Lepidoptera. The larvae of the 

 autumnal brood rest in the cocoon without pupating through the winter. Such a 

 phenomenon is rare among Lepidoptera. 



The duration of a caterpillar's life varies. It may extend only to a fort- 

 night, or to three years in Cossus. The number of moults is generally three or four. 

 In this process the old cuticle as a rule splits on the back of the thoracic somites, 

 and the split extends to a variable degree both forwards and backwards. The 

 three scales of the head may separate also. The cuticle of the oesophagus and in- 

 testine appears to be cast at least in the final moult. Previous to pupation the 

 caterpillar may suspend itself either by the anal prolegs, e.g. Vanessa, or secure 

 itself by the anal prolegs and a band of silk round the thorax, e. g. Pieris or may 

 fashion a silken cocoon with or without an admixture of foreign bodies ; or else it 

 buries itself as do the majority of Sphingidae. A few members of this family, 

 however, e.g. Chaerocampa Nerii, form a cocoon on or near the surface of the ground. 



Note the following points of internal anatomy. The nervous system comprises 

 a supra- and an infra-oesophageal ganglion and a series of ten ventral ganglia, of 

 which three are thoracic and seven abdominal. The tenth is often double, e. g. in 

 Acherontia. The commissures between the three thoracic ganglia are generally 

 divaricated. The respiratory sympathetic system consists of a nerve running on the 

 dorsal aspect of the nerve-chain from one ganglion to the ganglion next following. 

 In the abdominal region this nerve branches to right and left just in front of the 

 ganglion, with which two short filaments connect the branches at their origin. 

 The branches are the nervi transversi or respiratorii, and supply the tracheae and 



