11G ME. E. P. STEBBING ON THE LIFE-HISTOET OE 



June will show numbers of the ordinary madder-brown larvae feeding at the bases of the 

 needles and ou the stem, and also, in addition, some larger yellowish grubs which now 

 begin to make their appearance for the first time. These yellow larvae are usually found 

 in the axils of the leaves, each having its proboscis firmly fixed, in the tissue of the stem 

 or base of the leaf. 



We have here the distinct separation of the last generation of the insect passed during 

 the year on the needles of the tree into two distinct forms of larvae. The yellow larvae 

 give rise to a generation of winged insects which form either the latest portion of, or the 

 true, fourth (Sextjpak^:) generation. The larvae remain feeding in this position until 

 the middle to the end of the third week in June or even until the end of the month, 

 the period apparently depending almost entirely, if not entirely, on the nature of the 

 season experienced. If a hot dry spring followed by a late monsoon is experienced, the 

 Aphids may be found in the corkscrew masses up to the end of June. If a wet spring is 

 followed by an early monsoon (as in 1909), an examination of the corkscrew masses in 

 the third week of June will show them to be dried up, open and empty. 



At whatever time the yellow larvae mature, it will be found that just before this 

 period the insects apparently cease feeding or cease exuding sugary material. The 

 corkscrew needles now dry and shrink apart slightly, and the small apertures so left 

 enable the yellow larvae, or nymphs as they now r truly are, to crawl through. They creep 

 out onto one of the lower needles or onto the stem, moult their skin, the skin splitting 

 down anteriorly to the metathorax, and the winged insect with the small bunches of 

 wings on the dorsal anterior surface crawls out, much in the same manner as the winged 

 insect of the Spruce gall leaves its larval skin, and as the first generation of winged 

 insects on the Silver Fir leave their nymph-skins. 



The numerous white paper-like skins on the twigs and the untwisted needles in the 

 neighbourhood of the large " bud " are easily visible. 



The winged generation of flies resulting from these yellow nymphs act in two ways. 

 Some remain on the Silver Fir and lay eggs covered with cottony masses on the branches 

 and bark of the main stems of young trees and on the branches and. upper part of the 

 main stems of old trees. The remainder leave the Silver Fir and migrate to the Spruce, 

 where I have found them fixed to the needles of the tree. Here they probably lay 

 the eggs which give rise to the sexual generation (Sexuales) on the Spruce. This 

 generation I have not yet found. 



The apterous females arising from the madder-brown larvse move from the interior of 

 the corkscrew mass down onto the untwisted needles and shoots below before egg- 

 laying. The greater bulk of the eggs laid beneath the cottony masses are always to be 

 found here outside and below the corkscrew mass; and there is a good reason for this, 

 for the needles of the corkscrew, together with the portion of the shoot bearing them, 

 as I have said, shrivel up and fall off. The other needles of the year, below those which 

 actually formed the corkscrew, turn yellow in colour or have numerous spots and dots all 

 up them, and in their turn wither and die, but at a later stage. 



The eggs, within a week or a couple of weeks of being laid, hatch out into tiny grul s, 



