1901.] 269 



that of an oixMnary quercus in the South of England, it will be seen how considera- 

 bly their lives have been shortened. 



The first larva of the winter brood hatched on August 17th, and the first 

 cocoon was formed on December 15th, showing a larval period of 116 days. The 

 first larva of the summer brood hatched on April 29th, and the first cocoon was 

 formed about July 15th, allowing a larval period of 77 days. The average life of a 

 \ai'va o? quercus in the south of England is, roughly, about 290 days. It may 

 therefore be owing to this rapid growth that a large number of the summer brood 

 have failed. 



As far as I am aware no signs of sickness manifested themselves until my larvae 

 were full fed; then more than a dozen and a half died. After devouring with the 

 usual voracity the fresh willow with which I kept them constantly supplied, they 

 became limp, fell to the bottom of their cage, and rapidly decomposed into a pulpy 

 mass as black and dense as pitch. A certain weakness appears to have spread 

 throughout the entire brood, for many of the cocoons are so frail and brittle that 

 they may be smashed with the greatest ease between the fingers ; and some of the 

 pupae are so soft that they have become partly flattened merely by the pressure 

 resulting from their own weight against the sides of their cocoons. The earlier 

 cocoons were the strongest, and the later ones were the weakest. 



The larvse appeared to suffer from a too loose or watery condition of the body ; 

 it is thus possible to lay the blame on the young willow with which I chiefly fur- 

 nished them, for willow is certainly a soft and juicy foliage compared with what 

 they devour in the natural state. But Mr. Barrett has suggested that some inherent 

 weakness may have existed in the original female which I took in the New Forest 

 early in August, 1900. There is evidently a constitutional peculiarity to account 

 for somewhere, setting apart warm conditions and clean fresh food. I will cite one 

 curious instance. The first imago of the winter brood emerged about February 23rd, 

 showing a pupal existence of 70 days ; yet I have still in my possession one pupa of 

 this winter brood, which, in spite of being kept in exactly the same temperature 

 and place as all the others, still evinces no sign of emerging; it is alive, and in all 

 probability will pass through the winter. Here we seem to have an example of 

 constitutional peculiarity as marked as can be desii'ed. 



All the imagos which have at present resulted from the summer brood are 

 lax'ge, and only slightly variable in tint. I have paired a couple, and now am 

 awaiting the arrival of another generation of larvse, which will be forced to face 

 the winter. With regard to the winter brood it may be of interest to state, that 

 the imagos bore the characteristics of the variety calluna, which appears to be 

 taking the place of quercus in the southern parts of England. On exhibiting a spe- 

 cimen of the summer brood to an authority upon this point, however, I was told 

 that it was a true quercus. The fact therefore stands, that I have reared both 

 quercus and callunce from one female imago — calluna resulting from the slow and 

 cold period of winter, and quercus resulting from the swift and warm period of 

 summer. 



192, Devonshire Eoad, Forest Hill, S.E. : 

 October \st, 1901. 



