288 BRITISH LEPIDOPTERA. 



genus occurring in Europe, while in North America, north of 

 Mexico, there are six. In tropical America, Africa, and south- 

 eastern Asia, including China, the species and genera are far more 

 numerous, and form a characteristic feature of the fauna. Upon the 

 whole the allied Ceratocampidae ( Citheroniidae ) are also tropical, many 

 more species occurring in Brazil and Central America than in North 

 America, and this may be said of the family Hemileucidae. Mey- 

 rick also notes (Handbook, p. 313) that the Satumiidae (Attacidae) 

 is a small family, occurring mainly within the tropics, but with a 

 few stragglers in temperate climates. The species are all large, and 

 sometimes gigantic, the Indian Attacus atlas measuring ten inches 

 in expanse of wing, and their decoration is often correspondingly 

 magnificent. The single British species is one of the smallest. 



Weniger, writing of the larvse of the Attacinae, states (Ent., xx., 

 pp. 87-89) that after the second or third moult of the larva of Attacus 

 yama-mai, A. vernyi, A. selene and A. cecropia, a coloured mark on the 

 sternal region of the 8th abdominal somite affords a certain test of 

 sex. The mark in the $ is a " black blotch " in the middle, of a 

 yellowish tint, which, in natural size, is not larger than a large pin's 

 head. The male differs from the female in the fact that the black 

 blotch has in its centre a dark green spot. In both sexes the mark 

 disappears when they are killed and the skin emptied."' Jackson 

 thinks (Studies Morph. Lepidoptej'a, p. 147) it may be due to a peculi- 

 arity of the larval cuticle, but emptying does not alter the cuticle, 

 and the mark disappears when the skin is emptied. At any rate he 

 points out that there is no structure belonging to the reproductive 

 organs in both sexes alike which has the position assigned by Weniger. 



Semper observes that, in the development of the antennal hairs 

 of a male Saturnia pavonia, the hairs arise just as do the scales, from 

 a layer of cylindrical cells. The hairs push out between the cells of 

 the epidermis as do the scales, and the only difference, in fact, 

 between the scales and these hairs is merely in the outer form, and 

 this is no real difference, for there may be found between both forms 

 numerous gradatory ones. So long as no cuticle is developed by the 

 epidermis the forming scale consists of a fine membrane which is a 

 direct continuation of the parent cell, and which contains a trans- 

 parent finely-granular content, which is darkened and contracted by 

 acetic acid. But as soon as the cuticle appears, one sees also 

 developed on the scales and hairs — it was especially apparent on the 

 antennal hairs of Saturnia pavonia (caipini) — a thickened layer which, 

 where the hair or scale meets the cuticle of the epidermis of the 

 antenna or wing, fuses with it ; the thin stalk of the scale which unites 

 the scale with its parent cell secretes for a short distance between the 

 cells of the epidermis such a thickened layer as renders the joining of 

 the scale with its supporting membrane much more secure. At first 

 one sees on the scales only a simple membrane, but soon longitudinal 

 striae develop ; these arise at certain places where a further 

 thickening takes place on the secreting membrane, and proceeds till, 

 finally, further depositing is limited to cross-striae which develop 

 between the separate longitudinal stria?. The scale is now complete 

 except for the pigment, which, in many species, is deposited in the 

 scale before its extrusion. After the scale is fully developed, the 

 parent-cell disappears, the granular content of the scale becomes 



