ODEZIA ATRATA AND ITS VARIATION. 



225 



contract according to the absorption of water, or loss by evaporation. 

 I still think this may be so, but I found that some eggs left for some 

 days in water, compared with others kept very dry, showed no appreci- 

 able difference either in the size or the width of the sulcus. A 

 question as to freezing and consequent expansion may also be an 

 explanation. My observations did not clearly demonstrate, but they 

 suggested that the sulci did afford the means of expansion and con- 

 traction, but not by widening or closing, but simply by acting as 

 hinges, enabling the shell on either side of them to curl or uncurl as 

 greater or less space in the egg was required. The eggs are laid quite 

 loosely, and must naturally fall to, and lie on, the ground, and there 

 they must rest (in England) from June till the end of March, and on 

 the higher slopes of the Pyrenees, where I met with var. pyrenaica, 

 from August till May. I believe there is no evidence of a second- 

 brood, certainly no egg hatched, either of my Pyrenean eggs or of 

 English eggs laid in June. The larva does not develop within the egg 

 till the spring. My eggs hatched just as leaves of Buniiim flexuosum 

 could be found appearing, and my moths emerged before the plant 

 was well in flower, they were therefore rather earlier than they probably 

 are naturally, as the full-fed larvre are reputed to live in the flowers 

 (Buckler). 



I entertain no doubt that the peculiar structure of the egg has 

 some relation to the long period, some eight or nine months, during 

 which the Qgg has to take its chance lying on the ground, but what 

 that may be I cannot say beyond what I have already noted. The 

 egg-shell is very thick and hard for so small an egg, as I had reason 

 to discover when cutting it up to place portions on slides for examina- 

 tion. This is, of course, useful against mechanical and meteorological 

 vicissitudes, and may explain why my experiment of soaking and dry- 

 ing them for a week produced so little result. This very hardness 

 and density would, however, make it all the more necessary for some 

 special provision, such as the sulci appear to be, to exist to meet 

 variations in bulk of a hygrometric character. 



The eggs are greenish when first laid, and after a time become 

 pale ochreous. I brought my eggs from their winter-quarters on 

 March 15th, 1908; most were nearly of the pale luteous tint they were 

 in autumn, but a few were quite dark, these were those in which the 

 larvae were ready for hatching, and as they matured the other eggs 

 assumed in turn the same dark colour, the change occupying some- 

 thing like a week to take place ; none were hatched when 1 brought 

 them in on the 15th, but on the 16th several hatched ; whether these 

 would have hatched earlier had I brought them into the warmer 

 room a day or two earlier, or could have remained unhatched a day or 

 two longer in the cool, I do not know, but do not think after once the 

 larva is developed that they have more than a day or two's discretion. A 

 few hatched daily, then I note on March 23rd eight hatched, and the 

 remaining eggs are some dark and some unchanged in colour. The 

 further hatchings were— 24th, 7 ; 25th, 5 ; 26th, 8 ; 27th, 5 ; 28th, 

 7 ; 29th, 4. 



{To he concluded.) 



