12 BRITISH LEPIDOPTERA. 



and short, the former running from the base to the summit, the latter 

 stopping short at about one-fourth the distance from the top. Eeally 

 the arrangement is rather irregular ; in one egg examined there were 

 two short ribs between two successive long ones, whilst in another case 

 the short one was missing. In the egg of Tiliacea (Xanthia) aurago 

 there are 15 ribs running from base to apex, each alternate one failing 

 before reaching the summit ; but there is considerable variation in 

 their arrangement,. one, two, and even three of the shorter ones being 

 sometimes obsolete in one egg. Theoretically, the 27 longitudinal ribs 

 of Dasycampa rubiginea should be alternately long and short, but 

 frequently two short ones are adjacent, more rarely two long ones. 

 The manner in which the longitudinal ribs unite just before reaching 

 the micropylar area is also very variable.- 



The number of eggs laid by various species differs greatly, and, 

 among different individuals of the same species, there is considerable 

 variation. Hellins records 1,200 as the number laid by a female Tri- 

 phaena fimbria ; Eiding gives 700-800 as the number laid by T. pronuba ; 

 Hollis says that Spilosoma lubricipeda lays from 400 to 500 ; Nicholson 

 gives above a thousand as the number laid by three Peridroma saucia; 

 Zeuzera pijrlna is reported to lay between 1,000 and 1,100 ; a female 

 Dasychira pudibunda laid 274 eggs ; whilst Epwula lichenea is accredited 

 with laying above 200. There is no doubt that the average number 

 laid by many species is a very high one. 



The eggs are laid in a variety of ways and positions. The 

 Hepialids drop their ova among the herbage loosely, the tiny eggs 

 quickly finding their way to the roots of the plants on which the 

 larvae feed. Lasiocampa quercus does the same, and so does one of the 

 most highly specialised of our British butterflies, Melanargia galatea. 

 A large number of moths lay their eggs solitarily on, or near, the 

 food-plant of the larvae, whilst others lay them side by side in clusters. 

 The Zygamids often heap their eggs in two or three layers. Clisio- 

 campa (Malacosoma) neustria, C. castrensis, Eriogaster lanestris, and 

 Anisopteryx aescularia lay their eggs in rings around the twigs 

 of their respective food-plants, forming a kind of necklace around 

 the stem. The Amphidasyds (A. beUdaria and A. strataria), and 

 the Tephrosiids (T. . bistortata and T. crepuscular ia), like Zeuzera 

 pyrina, are provided with long ovipositors, to enable them to 

 lay their eggs deep in the crevices of the bark of the trees on 

 which their larvae feed. The egg of Trochilmm bembeciforme is laid on 

 the underside of the leaf of an osier, although the larva is a borer, and 

 feeds on the solid wood. The female Leucania littoralis folds over the 

 edge of a grass leaf, and lays her eggs in a string within the fold. The 

 Geometrid moth, Iodis vernaria, lays its eggs one upon the other in 

 rouleaux, seven or eight in each row, and resembling a slender twig or 

 tendril of Clematis, on which plant the eggs are laid. Polyyonia 

 c-album and P. interrogationis have a precisely similar habit. The 

 eggs of the Pyralids usually partially overlap, and the same imbricate 

 arrangement is found in certain Geometrids, e.g., Ennomos quercinaria, 

 and certain Noctuids, e.g., Mellinia circellaris (ferruginea), the 

 Acronyctid tribe, Viminidi, etc. This method, of course, depends 

 largely upon the flatness of the egg. The Micropterygids and Adelids 

 are provided with a most complex cutting apparatus, with which they 

 cut out pockets in a leaf, and then insert an egg (or eggs) within the 



