CHERMESID/E IN RELATION TO BRITISH FORESTRY. 147 



larvae of the Sistens type. They are anchored in the crevices of 

 the bark of the trunk and older branches of large trees, and at 

 the base of the buds or shoots of small trees. These larvae may 

 moult once or twice before spring, or may remain undeveloped 

 until spring, according to weather conditions. After three 

 moults each female lays a very large number of reddish eggs, 

 generally during the second half of April. Only a little " wool " 

 is secreted. Two kinds of larvae hatch from these eggs. 



(a) Progrediens Type. — These larvae migrate to the needles 

 or the axils of the needles. They moult four times, 

 and during their development two forms are differ- 

 entiated. 



(i.) Nymphs, later adult winged Colonici alatce. These 

 winged females settle on a needle of the silver 

 fir and lay a few eggs from which issue Sistens 

 larvae. 



(ii.) Adult wingless females each of which lays 10-12 

 orange coloured eggs under copious "wool." 

 From these eggs issue Sistens larvae. 



{b) Sistens lat-vce. — These larvae settle in excavations left by 

 the fallen needles, and in other sheltered parts of the 

 branches and trunks. These larvae develop after a 

 resting period, and become adult at the beginning of 

 July. Each female lays a number of eggs under 

 " wool." Sistens larvae hatch from these eggs. Some 

 of these larvae remain undeveloped until the following 

 spring. 

 The Sistens larvae, hatching from the ^ggs laid by the 

 Colonici alatce {a i.), the Progredientes [a ii.), and 

 the majority of those hatching from the eggs laid by 

 the first summer Sistens generation I. {b), develop in 

 August and September. When adult, these wingless 

 female Sistentes (summer Sistens generation II.) each 

 lay a number of eggs under the protection of " wool." 

 From these eggs issue Sistens larvae, which pass the 

 winter together with the progeny of the first summer 

 Sistens generation I., which remained undeveloped. 



(4) Sexupara Generation. — None. 



(5) Sexuales Ge?ieration. — None. 



