CHERMES H1MALAYENSIS ON THE SPEUCE AND SILVER FIR. 107 



" The gall growth continues its outward course until it reaches the bases of the needles, and these in 

 their turn begin to swell up. As the growth proceeds up them the needles assume a tapering shape, 

 very much thickened at the base and gradually diminishing in size until about halfway up, where they 

 still remain normal. The gall is now visible to the naked eye as soon as the bud-scales are removed, 

 being rendered evident not only on account of its swollen nature, but also by reason of its bleached 

 appearance due to the absence of chlorophyll. 



" The needles at first increase evenly in thickness on every side, but before long the swelling becomes 

 confined on the inner (ventral) side, since this faces the main axis, which is also swelling, and the two 

 soon meet. When this happens any further growth goes on chiefly on the dorsal side, and the leaf 

 becomes asymmetrical in transverse section. The outer (dorsal) side of the needles soon comes in 

 contact with the inner surface of the bud-scales, but as these are gradually unfolding all the time, they 

 do not offer much resistance to the swelling, and the dorsal side of each gall-needle consequently 

 becomes convex in shape. 



" Owing to the erect position of the needles at this stage and their crowded spiral arrangement 

 round the main axis, this eulargement of their bases quickly results in adjacent needles coming into 

 contact with each other, and grooves are formed on the surface of each needle, where other needles 

 have pressed upon it. The phyllotaxis is such that the base of any one needle must on swelling come 

 in contact with the swollen bases of no less than four other needles, two belonging to the spiral above 

 it, two to the spiral below. 



"Each needle-base is consequently marked with four grooves. Of these, the two on the inner side 

 are much deeper than the two on the outer side, owing to the pressure being greater in the former case, 

 and between these grooves a slight ridge is formed which corresponds with the space between the 

 needles of the spiral above, or below as the case may be. 



" As the stem gradually elongates the needles are carried slightly apart, and the resulting space 

 above each needle forms a chamber which is later on taken possession of by the young offspring of the 

 Chermes mother. The deeply grooved inner (ventral) side of the needle forms the floor of this chamber, 

 whilst the two needles of the spiral above each contribute a half towards the formation of the roof. It 

 will thus be seen that each individual leaf participates in the formation of three distinct chambers, its 

 ventral side forming the floor of the chamber above it, and the grooves on its dorsal side each forming 

 one-half of the roofs of the two chambers below it to right and left. 



"At a later stage these chambers become closed in by the development of thick tumid lips around 

 their mouths. 



" About the beginning of May the shoots begin to emerge from the bud-scales, but the galls are not 

 at once visible, since the base of the shoot is still concealed in the persistent basal bud-scales. They 

 soon, however, make their appearance and the galls then enter on the second stage of their existence, 

 the history of which must be left at present as my examination is not yet completed. 



" But to return to the insect. Whilst the changes described above have been proceeding in the bud, 

 the Chermes larva has been steadily sucking and increasing in size. She has secreted a quantity of 

 white wool-like wax, which, while it entirely conceals her, renders her position most conspicuous. She 

 undergoes three ecdyses before reaching maturity, and the cast skins may be found lying beside her 

 in the ' wool.' As soon as she reaches maturity she commences to lay eggs, and continues the 

 process through May and on into June, until a heap of some hundreds of eggs accumulates beside 

 her. Each egg is attached to the stem by a delicate hair-like stalk. The first eggs begin to hatch 

 soon after the gall has emerged from the bud-scales, and the minute larvte at once creep up 

 the shoot and establish themselves in the gall-chambers, where they find a fleshy succulent tissue 

 already prepared for them. They at once commence sucking and become entirely enclosed within the 

 chambers by the development of the tumid lips previously referred to, and here they remain until the 

 galls open. 



SECOND SERIES. — ZOOLOGY, VOL. XI. 16 



