GALLS INDUCED BY PLANT-LICE 83 



gall is a small pale green thing, about the size of a pea, with 

 a whitish, waxy bloom (Fig'. 2). It ripens very early, and 

 usually opens in the middle of June. The Alatae migrate 

 to the Larch, and deposit their eggs on the needles. The 

 resulting Colonici hibernate on the bark of the branches, 

 and deposit numerous greenish-brown eggs at the base of 

 the buds in spring. Fig. 3 shows a third-year Larch shoot 

 at the end of March, with Colonici and their eggs, and Fig. 4 

 presents an enlarged view of one with its eggs ; there is no 

 wool. The generation which hatches from these eggs in 

 May and June departs from the sequence observed in the 

 life-cycle oiCk. wn'rfw, and, instead of winged Sexuparae only, 

 which migrate to the Spruce, we find that the generation 

 usually spUts into two parallel series — wingless insects known 

 as Exules and the winged Sexuparae. The larval stages of 

 both are spent on the Larch needles, which often bend at 

 right angles at the point attacked. Figs. 5 and 6 show 

 eggs of Exules and Sexuparae on bent Larch needles. The 

 afflicted needles are often slightly swollen at the affected 

 part (Fig. 5), and become yellow. The winged sexuparae 

 (Figs, g, 10) fly back to the Spruce and deposit their eggs 

 on the needles. Fig. 7 depicts a Larch shoot with Colonici, 

 Exules, and winged Sexuparae, some of the latter starting 

 on their migration to the Spruce. The eggs are said to vary 

 in colour according to the sex, the yellowish-green ones pro- 

 ducing male, the reddish ones female, sexuales. The female 

 deposits her single egg on the shoot, and this egg yields the 

 Fundatrix. The wingless Exules remain on the Larch, and 

 lay greenish-brown eggs on the needles. There may be two 

 generations during the summer. Fig. 8 shows an Exule 

 with its pupal skin on a Larch needle. With the approach 

 of winter they withdraw to the branches to hibernate, and 

 are then identical with the Colonici. 



The double of Ch. strobilobius Kalt. is Ch. lapponicus Cholod., 

 which in its life-cycle resembles Ch. dbietis. The Fundatrices 

 are seated on the bud, never below it, and differ from those 

 of Ch. strobibbius in the larger size, more copious excretion of 



