THE INTERNAL STRUCTURE OP THE LEPIDOPTEROUS LARVA. 59 



dominal segment, in which there is a pair of ganglia, and here the 

 nervous cord terminates. The nerve ganglia of Tischeria are placed 

 very nearly to the front of each segment. [In the lepidopterous imago 

 the union of the ganglia in adjacent segments is sometimes very com- 

 plete. In different families there appear to be sometimes two, at 

 other times three, thoracic ganglia, but always four abdominal ganglia, 

 with the exception of the Hepialids, which appear only to have three.] 



The sympathetic system consists of a median nerve cord, dilating 

 at intervals into ganglia, and placed above the ventral system, with 

 the commissures of which it is connected by nerve fibres. The 

 nerves from this system are distributed to the various organs of the 

 body connected with alimentation, circulation and respiration. 



It must be remembered that, although apparently so different, the 

 development of the nervous system in the embryo is analogous with 

 that in vertebrates, and that, although the nervous system of insects 

 is apparently ventral, whilst that of vertebrates is dorsal, the ventral 

 part of an insect corresponds with the dorsal part of a vertebrate, i.e., 

 in reality, opposite parts of the body are placed ventrally in insects and 

 vertebrates respectively, owing to the limbs being turned in opposite 

 directions in the two cases. 



It used to be a generally accepted belief that the lepidopterous 

 larva had no sexual organs, and this, in spite of the fact that Keaumur, 

 a century and a half ago, stated that he had discovered eggs in the 

 larva of Porthetria dispar, and that Malpighius found them in the larva 

 of Bombyx mori. The reproductive organs, however, are not difficult 

 to observe in some larvae, and can usually be obtained by a little 

 careful dissection. The testes and ovaries are placed just beneath the 

 skin of the 5th abdominal segment. They exist in pairs, one on either 

 side of the dorsal vessel, just above the position of the alimentary 

 canal. The testes form two lobes of a not very distinctly reniform 

 shape, whilst the ovaries, which are only to be seen with a lens, and 

 then in comparatively few species, are much smaller, and consist of 

 tubes. The testes are generally much more readily observed than the 

 ovaries, being, usually, yellow or brown, and may be seen distinctly 

 in the larvse of those species which feed internally, or which have fairly 

 transparent skins. Weniger detected the blind terminations of the 

 ducts from the sexual organs in the larvse of Anther aea yama-mai, A. 

 pernyi, Actias selene and Samia cecropia, " on the underside of the last 

 segment that bears a spiracle " (8th abdominal). In the female of the 

 first of these species is a black blotch, with a yellow central spot, whilst 

 in the male is a similar black blotch, with a dark green central spot. 



Herold represented, as long ago as 1815, the changes which the 

 essential reproductive glands undergo in the larva and succeeding 

 stages of Pieris brassicae, but up to the present time there appears to 

 have been no external openings, in connection with the sexual organs, 

 discovered in any lepidopterous larva. Certain statements which have 

 been made on this subject are mentioned here only in order to draw 

 attention to them, in the hope that they will be disproved or confirmed. 

 De Geer states that the brown larvae of Triphaena pronuba produce 

 males, and the green larvae, females. Doncaster says that the same 

 larval colour distinction, as to sex, holds good in the Satyrid butterflies. 

 He also states that the male larvae of Orgyia antiqaa and 0. gonostigma 

 have yellow dorsal brushes, the female larvae, brown. Suckow distin- 



