LEPIDOPTERA. 581 



optic lobes, and special swellings for the origin of the antennal 

 nerves. The ventral ganglionic chain is reduced, leaving the subceso- 

 phageal ganglion out of consideration, to two thoracic ganglia (of which 

 the larger second ganglion shows traces of constrictions and arises 

 from the fusion of four ganglia) and four or five ganglia in the 

 abdomen. In the larval condition, on the other hand, there are 

 eleven pairs of ventral ganglia. 



The alimentary canal possesses a long oesophagus, which is 

 connected with a stalked suctorial stomach, and usually six much 

 coiled Malpighian tubes, of which the three on either side open by a 

 common duct (figs. 47 and 48). 



Generative organs. The ovaries consist on either side of four 

 very long many-chambered egg-tubes, which contain a great quantity 

 of eggs, and have, in consequence, a moniliform appearance. The 

 duct apparatus always possesses a long-stalked receptaculum seminis 

 with glandular appendages, and a large 

 bursa copulatrix which opens indepen- 

 dently beneath the genital opening. The 

 two long testicular canals are packed to- 

 gether so as to form an unpaired, usually 

 brightly coloured body, from which pass 

 off the two vasa deferentia, which are 

 much convoluted and receive the con- 

 tents of two accessory glandular tubes 

 before uniting to form a ductus ejacu- Fm.482. a, Female of Psyche helix. 

 latorius. The two sexes are often so 6 - Male - ', Case of the male ; d, 



of the ferhale caterpillar. 



different in size, colour, and the struc- 

 ture of the wings, that there is a sexual dimorphism. The 

 males are often more brightly and beautifully coloured (a means 

 of exciting the females). The dimorphism, or even polymorphism 

 (seasonal dimorphism), found in the female sex of many butterflies, 

 is worthy of remark. Parthenogenesis occurs exceptionally in silk- 

 worms (Eomljyx mori), in many Psychidce, and some moths (Soleno- 

 bia), the larva-like females of which have no wings (fig. 482). 



Development. The larvae when hatched (caterpillars) possess 

 masticating mouth parts and feed principally on plants, leaves and 

 wood. On the head, which is large and covered with hard skin, 

 there are a pair of three- jointed antennae and six ocelli, each of 

 which is divided into three parts. In all cases there are abdominal 

 feet behind the three pairs of conical five- jointed thoracic legs. 

 There may be only two pairs of such legs, as in the caterpillars of the 



