UHERMES HIMALAYENSIS ON THE SPEUCE AND SILVER EIR, 



115 



(4) A much larger continuous mass of cottony filaments completely covering the 

 dorsal surface of the ahdomen. 



On the 26th the cottony mass had increased and egg-laying commenced. The fly died 

 on 27th or 28th. 



This fly was drawn on the 25th May and is shown in PL 22. fig. 7. 



We thus see that from the spring generation of larvae two forms develop, one apterous 

 and the other winged. 



The whole of the apterous forms and a portion (or all ?) of the winged forms at once 

 oviposit on the Silver Fir needles, laying masses of eggs which resemble the spring ones 

 and are covered with very visible white cottony filamentous masses. PI. 22. fig. 1 

 shows a portion of a Silver Fir branch exhibiting these white cottony masses on the 

 needles, which cover either females still egg-laying or masses of eggs partially shielded 

 by the dead skin of the female insect. This figure was painted from life, the branch 

 having been just previously plucked from a tree. 



The eggs of this second generation of the Aphid hatch out in from two to three days 

 after being laid, and the young larvae spread out over the under surfaces of the still 

 young and soft light green needles, insert their proboscides into the leaf-structure, and 

 remain feeding either in one place for the rest of their lives or more usually shift their 

 feeding-spots later on in their development. At times the under surfaces of the needles 

 are quite black with numbers of the dark madder-brown coloured larvae attached to 

 them, which appear to the naked eye as tiny black dots on the needles. If the needle is 

 closely inspected it will be seen that it is always bent upwards a little on either side at 

 the point at which the larva has been feeding. 



Observations have shown that some of these larvae develop into apterous females about 

 the middle of June and lay eggs, at least a portion of which also produce another 

 generation of the apterous females. 



At the beginning of June it will be noticed that the greater proportion of the larvae 

 feeding on the needles of the upper or terminal portion of the new shoot have collected 

 towards the bases of the needles and on the needle-bearing stalks, and this results in a 

 curious malformation of the Silver Fir shoot (cf. PI. 22. fig. 1). The irritation set up by 

 the feeding larvae causes each individual needle to cockle and twist over in a spiral 

 direction from right to left. The needles so affected appear to lose their chlorophyll and 

 turn a dirty yellow, either all over, or have numerous small yellow blotches amongst the 

 green all up them. As the green needles of the whole of the upper half of the shoot of 

 the year are affected in this manner, it results in this portion of the shoot becoming 

 twisted up into a corkscrew mass, as shown in Plate 23. fig. 1. The tightness of the 

 twist varies, but it is such that the needles so affected remain in this position and finally 

 drop off. During the insects' presence the heavy exudation of sugary liquid from them 

 covers the corkscrew mass and binds the needles yet more firmly together, giving the 

 shoot the appearance of being terminated by a giant bud. I have noticed also that 

 this excretion is added to by an exudation of turpentine from the Silver Fir, round 

 nodules of resin being formed in the axils of the aifected needles. 



An examination of the corkscrew masses at the end of the first to the second week in 



SECOND SERIES. — ZOOLOGY, VOL. XI. 17 





