218 LECTURE XTII. 



numerous wire-worms. The grub of the cock- 

 chafer, as has been said, is very destructive to 

 crops of grain. The female of this insect drops 

 her eggs in considerable quantities in the ground. 

 These, the next year, hatch, and become small 

 grubs, and continue to increase in size for two 

 years afterwards, all this time feeding on the 

 roots of grain, or those of potatoes, turnips, &c. 

 These grubs are the favourite food of the rook, 

 who searches for and eats them. It is a curious 

 fact that at the end of the third year, and when 

 they have become perfect insects in the spring, 

 and ready to quit the earth to feed on the leaves 

 of oaks, hazels, &c., they have a sort of in- 

 stinctive knowledge when the leaves are on 

 those trees ; and in a late spring they remain 

 in the ground until the leaves appear. As they 

 settle on them, and begin feeding, you may see 

 numbers of rooks busy in devouring them, thus 

 conferring additional benefit on the farmer. 

 In fact, but for this destruction, cockchafers 

 would become an enormous evil to him. 



Some few years ago the turf in many places 

 in Greenwich Park turned brown, and, in fact, 

 was killed. It then appeared that this was 

 occasioned by myriads of the grubs of an insect 



