CHERMES HIMALAYENSIS ON THE SPRUCE AND SILVER FIR. 101 



treating of the subject iu a most able manner. Burdon' s interesting papers * will be 

 alluded to later on. 



As has been stated, the fact that the Himalayan form lives upon two host-plants was 

 unknown before 1901. 



In order to present the somewhat complicated stages of life passed through by this 

 insect in a form intelligible to the reader, I propose to give a brief description of the 

 various generations at present known to live upon the two trees and which give rise 

 to the parallel series. 



To the generations of the European forms of Chermes the names I. Fundatrices, 

 II. Alat^e, III. Colonici, IV. Sexupar.e, and V. Sextjales have been given f , and I 

 propose, as far as possible, to retain these names in the following account. 



In the early spring dead apterous females, "stem-mothers" (Generation I. Funda- 

 trices), are to be found upon the Spruce trees, these having most probably hibernated 

 through the winter. These females are merely shrivelled skins covering the masses of 

 eggs similar to those shown in PI. 22. fig. 5. These dead females are found at the 

 base of small pinkish cone-shaped swellings which are galled buds, the females by 

 their sucking-operations having already caused the tissues of the stem in their close 

 neighbourhood to swell to an appreciable extent. 



The larvae hatching out from these eggs (Generation II. Alat.e) feed at the base of 

 the young developing Spruce-needles, the part of the stem below and the needles 

 gradually swelling up and coalescing into a gall within which the young Aphids become 

 enclosed (cf. PL 20. tig. 1). 



This gall resembles a small fir-cone and gradually increases in size, until during July 

 it opens by a contraction of its parts (cf. PI. 21. fig. 1) and the now mature larvae or 

 nymphs crawl out, moult their skins, and appear as winged insects. 



A portion of these winged insects remain upon the Spruce, and lay the eggs from 

 which the stem-mothers of Generation I. Ftjndatrices develop, whilst the others 

 fly to the Silver Fir, where they may be found upon the needles of the tree. 

 These are the Migrantes-Alatje of Burdon (see Table, p. 120). They there secrete a 

 cottony mass, which wholly or partially covers them, and lay eggs upon the needles. 

 Some of these eggs at least give rise to apterous parthenogenetic females, forming 

 Generation III. Coeonici. 



In the case of the Silver Fir an examination of the branches of old trees and the masses 

 of saplings and poles in the early spring (May) will show minute white cottony specks 

 on the bark. These cottony masses at times may be seen thickly dotting the whole of 



* Burdon : •' The Pine-apple Gall of the Spruce. — A Note on the Early Stages of its Development," Proc. Camb. 

 Phil. Soc. xiii. pt. 1 (1906), p. 12 ; " The Spruce Gall and Larch Blight Diseases caused by Chermes and Suggestions 

 lor their Prevention," Journ. Econ. Biol. Lond. vol. ii. (1907) pt. 1, p. 1; "Some Critical Observations on the 

 European Species of the Genus Chermes," ibid. pt. i (1908), p. 119. 



t Cholodkovsky, op. cit. ; Burdon, " Spruce Gall and Larch Blight Diseases," Journ. Econ. Biol. Lond. vol. ii. 

 pt. 1 , p. 5. 



15* 



