PERIODS OF HATCHING. 127 



remark, however, that the periods of hatching corre- 

 spond in a striking manner with the leafing of trees, 

 and the appearance of other materials fitted for the 

 food of the young. We observed a good example of 

 this in the spring of 18*29. A lackey moth had de- 

 posited during autumn a spiral ring of her eggs on the 

 branch of a sweet-briar planted in a garden-pot out 

 of doors. We removed this into our stwdy during the 

 winter. Here the warmth caused the tree to bud, 

 and at the same time hatched the lackeys about a 

 month sooner than those out of doors. Owing to the 

 same cause, several colonies of the caterpillars of the 

 brown-tail moth revived from their torpidity, and came 

 forth from their winter nests before the hawthorns 

 were in leaf, a circumstance which would not have 

 happened to them out of doors.* Kirby and Spence 

 give an instance precisely similar, of the eggs of an 

 aphis found on the birch, and hatched in-doors a full 

 month before those in the open air."]* 



It is a remarkable circumstance, long observed by 

 collectovs, that the male broods of insects appear 

 earlier than the female broods; and it would appear 

 from the following fact, that there is a similar retarda- 

 tion in the hatching of female eggs. ' Upon the leaf 

 of a poplar tree were found three eggs of the puss 

 moth {Cerura vinula),t\vo of which were hatched 

 about two weeks before the other. The first were 

 males, the last a female. As they were on the same 

 leaf, and presumed, therefore, to have been laid by 

 the same parent, at the same time, the difierence of 

 hatching could not have arisen from difference of wea- 

 ther, exposure, Stc.'J In the case of the lackeys on 

 the sweet-briar above-mentioned, some were hatch- 

 ed several days before others, but whether these were 

 of different sexes we did not ascertain, 



* J. R. t Kirby and Spence, Intr. ii, 434. 



t J. Rennie, in Mag. of JNat. hist., vol. i, p. 373. 



