146 TRANSACTIONS OF ROVAL SCOTTISH ARBORICULTURAL SOCIETY. 



(4) Sexicpara Generation. — The Sexuparae hatch out and 

 develop on the needles of the silver fir as described under 

 Colonici {b i.). The fourth moult gives the adult, winged 

 Sexuparae. These deep red Sexuparge migrate to the needles 

 of Picea orientalis and P. excelsa. Each secretes coarse strands 

 of wool and lays about ten reddish eggs. The development is 

 very rarely completed on common spruce {P. excelsa). 



(5) Sexuales Generation. — The eggs laid by the Sexuparae on 

 the needles of Picea orientalis hatch in about three weeks. The 

 reddish larvae of the males and females first feed under their 

 mother, but later openly on the needles. They moult four times 

 and become adult at the beginning of August. Each female 

 lays a single, fertilised reddish-orange &gg, near a bud, under 

 a little " wool." This tgg hatches in three to four weeks and 

 gives a first-stage larva of a Fundatrix. 



The following is a diagram of the life-history of Dreyfusia 

 Niisslini, according to Marchal : — 



Fig. 3. — Diagram illustrating the Life-History of Dreyfusia Nusslini, 

 according to Marchal. 



Dreyfusia picecR (Ratz.), Borner. 



This species appears to be indigenous in Western Europe. 

 It, no doubt, originally was present only on Abies pectinata, 

 but now is found on most silver firs. In this species the cycle 

 on spruce has been completely obliterated, so that it carries on 

 entirely on the intermediate host. Marchal has worked out 

 the life-history, and I have been able to confirm some of his 

 observations for this country. 



(i) Fundatrix Generation. — None. 



(2) Gallicola Generation. — None. 



(3) Colonici Generation. — The winter is passed as first-stage 



