144 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



been confirmed by my observations and experiments in this 



country. 



Genus Dreyfusia (Borner). 

 Dreyfusia JVuss/ini (Borner). 



The spruce host of this species is Ptcea orientalis, and the 

 silver-fir host, Abies nordftiajmiana and A. pectiiiata. The natural 

 habitat of both A. nordmanniana — on which silver fir this 

 Chermes first appeared — and Picea orientalis is the south-east 

 of Europe and Asia Minor. It is, therefore, probable that 

 Dreyfusia Niisslini was originally confined to that region, and 

 that it was introduced to middle and western Europe on Abies 

 nord?nanniatia. Later it established itself on the indigenous 

 silver fir, A. pectinata. In some parts of Normandy, Marchal 

 only found the indigenous species, Drey, picece, but both species 

 appear to be widely distributed in Britain. When Picea orientalis 

 is absent this species carries on indefinitely on silver fir, and this 

 is the normal life-cycle in this country. 



(i) Fundatrix Generation. — The fertilised egg hatches on 

 Picea orientalis in August. The first-stage larva passes the 

 winter on a bud of that spruce. It is black in colour, and 

 surrounding it and along its crest are bands of "wool." In 

 spring the larvae wake up, feed, moult three times, and become 

 adult in April. Each female lays a large number of reddish eggs 

 under some " wool." The feeding of the Fundatrix in this 

 species, as in the genus Cnaphalodes, plays an important part in 

 the formation of the gall. 



(2) Gallicola Generation. — The larvae hatch out in the second 

 half of May and crowd amongst the deformed needles. As a 

 result of their feeding a compact, spherical gall is formed. In 

 most cases the growing point is killed. At first the gall is 

 reddish in colour, later green with deep-crimson bands along the 

 lines of fusion of the needles. The third moult gives the nymph 

 stage. When the nymphs are full-fed the chambers of the gall 

 open and the nymphs climb out. They moult, becoming 

 crimson-winged Gallicolae. In Scotland the galls open in mid- 

 July. The Gallicolae migrantes migrate to the needles of silver 

 fir and lay a number of reddish eggs, generally on the under side 

 of the needles. Short, coarse, curled strands of "wool" are 

 secreted by the Gallicolae. 



