8 BEITISH LEPIDOPTEKA. 



on the edge or rim of the micropylar depression. In the Noctuids 

 this hexagonal cell structure, which is separated by the longitudinal 

 ribs, is entirely lost, and there is a series of transverse ribs running 

 parallel to the base, dividing the depressions between the longitudinal 

 ribs into a series of ladder-like spaces. This is also a common form of 

 sculpture in the Pierid and Nymphalid eggs. 



The micropyle is usually placed at the base of a slight depression situ- 

 ated at the summit of an upright egg {i.e., at the extremity of its vertical 

 axis), and at one of the ends of the long (horizontal) axis of a flat egg. 

 It consists of a number of delicate microscopic canals, which vary in 

 number, but there are rarely less than four or more than six. They 

 radiate from a minute depression, surrounded by a rosette or circle of 

 cells of the greatest delicacy. In some eggs, even when viewed under 

 a powerful lens, no alteration in the ordinary outline of the egg is 

 caused by the micropylar depression ; in others, however, where it is 

 more depressed it is readily distinguished. In some eggs, again, there 

 is a considerable micropylar basin, the micropyle proper being situated 

 at the base of this. 



The upright egg, as we have seen, exhibits what is probably the 

 most specialised type, and we find the eggs of some Noctuids and 

 Papilionids very highly specialised. The Noctuid egg is usually of a 

 hemispherical shape, somewhat flattened at the base, but those of the 

 Xanthids have raised ribs rising above the central point, or apex, 

 and curving down thereto; they are, therefore/not unlike, in a general 

 way, the egg of a Vanessid. The egg of Phytometra viridaria (aenea) 

 is cut up by two sets of oblique lines into diamond shaped spaces, at 

 each point of which there is a large red-brown spine, standing perpen- 

 dicularly to the surface of the egg. But the eggs of certain Papilionids 

 are, probably, the most specialised. Among these, the Vanessid egg- 

 is of a barrel-shape, with eight or ten highly developed longitudinal 

 ribs. The nine-pin shaped eggs of the Pierids may have as many as 

 thirty or forty longitudinal ribs, whilst the tiarate eggs of the 

 Lyca3nids have a most complicated ornamentation, owing to the 

 prominence of the longitudinal ribs, and the depth of the transverse 

 pitting. The egg of Polyommatus corydon, with its dahlia-like appear- 

 ance, must be seen under a microscope to be appreciated, whilst those 

 of P. icarns and Plebeius aegon are equally complicated and beautiful. 

 The egg of Thecla w-album has a series of layers of prominent white 

 pointed cells forming a saucer-like base, which holds a flat, truncated 

 cone of a dark reddish colour, with a conspicuous, circular, micropylar 

 basin at the summit. The egg of Limenitis sibylla is covered with 

 fine transparent hairs, resembling spun glass. In cross-section, too, 

 the Lycanid egg gives a polyhedral or hexahedral appearance, and 

 not the more or less circular one common to butterflies. 



There are other peculiarities that may now be briefly noticed. The 

 typical Geometrid egg is usually oval or ovoid in form, with a de- 

 pression on the upper face, but in Ennomos, it assumes the appearance 

 of a rather square-based parallelopiped, and a somewhat similar shape 

 is seen in the egg of Crocallis elinyuaria. Brephos and Thyatira, which 

 have been placed by various systematists among the Noctuids, have 

 eggs of Geometrid appearance. The eggs of Tortricids and Cochlio- 

 podids have the appearance of flat scales, and so have those of many 

 Pyralids. 



