1903.] E. P. Stebbing — Life-History of Chermes abietis-picees Steb. 235 



various forms of the Chermes upon the silver fir, and the following 

 summary of conclusions arrived at is given here : — 



As already seen, eggs placed in branches at the base of the leaf 

 buds hatch out in May, as the young needles unfold, and the minute 

 larvae crawl up on to the leaves. After a time these young larvaa 

 apparently develop the white cottony substance and then die and lay 

 fresh eggs on the needles. Later on a generation from these eggs (or a 

 portion of the first generation) collect down towards the base of the 

 needles, and feeding here set up an irritation which results in an exuda- 

 tion of turpentine, and also causes the needles to curl up in a corkscrew 

 manner, the stickey excretions binding them together into a large twisted 

 bud. Within or near the corkscrew bud the following are to be found : — 

 (a) Ordinary crimson-coloured larval form. 

 (6) Yellow apterous form. 



(c) The yellow-green, silvery winged forms. 



(d) A few dark orange -coloured black-winged forms. 



By the end of the first week in July the twisted-up leaves are found 

 to contain numerous eggs covered by the usual dead mother skin and 

 white cottony substance. These are also to be found on the twig and 

 stem of the tree and are very visible. The apterous yellow larvas will now 

 have mostly left the corkscrew buds, and the numerous white papery 

 skins on the twigs and the untwisted needles in the neighbourhood 

 showed that they moulted after quitting the deformed shoots. This 

 moult, I am of opinion, is the last one gone through, the Chermes after 

 shedding this last skin appearing as the light green and yellow silvery- 

 winged insect described above. Although the writer has not absolute- 

 ly watched the change in colour, he is of opinion that the orange-yellow 

 dark-winged forms are but a later stage of the bright coloured 

 silvery forms, the bright tints assumed after the last change of 

 skin darkening in a similar manner to that of the SprUce gall 

 form described in the previous paper read before this Society. 

 This winged form will probably fly off to the Spruce and lay eggs on it 

 in a similar manner to that of the Spruce gall form which flies to the 

 silver fir on leaving the pseudo-cone and acquiring its wings. I am not 

 prepared as yet, however, to say exactly what happens to these winged 

 forms. I found many dead upon the trees, and this would point to their 

 lives being short in this stage. It is probable that during the heaviest 

 of the monsoon rains the Chermes would not be active, and it is possible 

 that this season is passed in the egg stage. I have not yet had an 

 opportunity of observing whether the aphid resumes its activity during 

 the brilliant warm autumn months which succeed the monsoon season 

 in the Himalayan Region. 



