224 THE entomologist's record. 



respect the series certainly meet if they do not overlap. This 

 frequency of yellow scales in ordinary 0. at rata makes the absolute 

 silence of authors about them somewhat remarkable. It would 

 appear therefore that var. pyrenaica is not in any way a discontinuous 

 form of the species, but merely presents an extreme amount of a 

 coloration that is usual in the ordinary race. It is also the case, if 

 my experience is at all typical, that pyrenaica as a variety, that is as a 

 local race, varies from nearly the normal type to an extreme sprink- 

 ling of yellow, the latter being in fact rather an aberration than a 

 variety, i.e., a race. I have already noted the possibility that my 

 specimens have varied towards the type owing to their changed envi- 

 ronment. This may be so, I do not know of any records of more than 

 a few specimens of either pyrenaica or costai. I find no reference to it 

 in Oberthiir's Etudes. 



The egg is a most specialised structure, and unlike any other egg I 

 happen to know. It is egg-shaped, like most Geometrid eggs, flattened 

 at the micropylar end, 0-7mm. long and 0.46mm. wide. It has, how- 

 ever, two remarkable sulci, one on each side, running not quite from 

 end to end, but some 0-5mm. long. These sulci, though on opposite 

 sides, are not exactly opposite each other, but rather nearer one margin, 

 so that, in cross-section, the outline would be not unlike that of a 

 "cottage loaf," with a larger portion on one side than the other, some- 

 thing like that shown on diagram (2). The same fact may be noticed 



Diagram of egg of Odezia atrata. 



in Mr. Tonge's photograph of the eggs (pi. xix., fig. 1), where one or 

 two eggs at the right hand of the group are seen end on. The sulci are 

 portions of the egg- surface depressed to a lower level, with rather thick 

 edges of darker texture, whose margins are sharp and crenulated. The 

 structure is well shown in the photograph, pi. xix., fig. 2, by Mr. Clark 

 (x 140). The bottom of the sulcus (here flattened out) has much less 

 sculpture than the egg-surface, it is, indeed, difficult to see that it has 

 any. The general surface is covered with fine dots, which are 

 arranged in hexagons. Under a low power the hexagons are more 

 visible than the dots, which are well shown in both Mr. Clark's photo- 

 graphs. The micropyle has a rosette of about twelve cells ; it is well 

 demonstrated in pi. xix., fig. 3 ( x 350). The hexagons seen under a low 

 power are hollows, to which the dots more or less conform, but do not, 

 strictly speaking, outline. 



There can be little doubt that the egg is subject to great variations 

 of moisture during its prolonged and exposed existence. It seemed 

 therefore probable that the furrows enabled the egg to expand and 



