364 



PROTECTION AGAINST INSECTS. 



troublesome ; the galls if on seedlings may be snipped off, and 

 the experiment may be tried of spraying the young trees in 

 April with kerosene-emulsion. (See the following species.) 



2. Chermes coccineus, Ktzb. 



The winged ? , 1'6 mm. long, are dark red. The galls formed 

 on the spruce by this insect are at first yellowish green, then 

 red, and lastly brown, but are much smaller than those of 

 C. abietis, L. They are also always on side-shoots, and are 

 never topped by a sprig of needles. 

 Isolated and border plants are usually 

 selected. 



The intermediate hosts are the 

 common silver-fir and other firs. The 

 winged emigrants lay their reddish- 

 yellow eggs below the needles of firs. 

 The brown, later blackish, wingless 

 plant-lice, which come from these eggs 

 in 2 3 weeks, suck the needles and 

 lay yellowish or reddish-brown eggs 

 covered with wool, that hibernate. 

 These give rise to other wingless 

 plant-lice in the spring, on the young 

 twigs, from the eggs of which are pro- 

 duced winged and wingless ? . The 

 former fly back to the spruce and the 

 others remain on the silver-fir. From eggs laid by the former 

 the $ and ? arise. 



Those that remain on the silver-fir cover the bark, which 

 looks as if it had been -powdered. Damp places sheltered 

 from the wind are preferred. Young silver-fir may be seriously 

 weakened by this attack, which is very destructive to silver-fir 

 in Scotland. Abies f/randis, Lindl., is said to escape injury. 

 Remedial measures as for C. abietis, L. 



3. Chermes strobilobius, Kltb. 



Galls on the spruce, intermediate in size between those of 

 C. abietis and C. coccineus. It looks like an unripe strawberry, 

 with, or without, a sprig of needles at top. 



Fig. 189. Gall of C. coc- 

 cineus, Rtzb. (Natural 

 size.*) 



