182 APHIS. 



insects, which are the chief agents in the hands of 

 Nature for keeping the Aphides within their pro- 

 per limits, we may add a few others, which act a 

 subordinate part in this necessary business of de- 

 struction. The larva of the Hemerobius feeds on 

 them in the same manner as that of the Musca aphi- 

 divora, and deposits its eggs also on the leaves of 

 such plants as are beset with Aphides. The eggs 

 of this Hemerobius stand on long filaments, which 

 are attached by a base to the leaf, and have more 

 the appearance of filaments of flowers with their 

 antherae than the eggs of an animal. The number 

 of these insects being comparatively small, they 

 may be considered rather as the casual invaders 

 of their existence than the main host of their de- 

 stroyers. The Earwig, which is itself no con- 

 temptible enemy to plants, makes some atonement 

 for its depredations by destroying the Aphides, 

 especially such as reside in the curled-up leaves 

 of fruit-trees, and the purses formed by certain 

 Aphides on the poplars and other trees. Lastly, 

 we may add as the enemies of these creatures, 

 some of the smaller soft-billed birds, which gene- 

 rally feed on insects, and which may be frequently 

 seen busily employed in picking them from the 

 plants." 



" When plants assume a sickly appearance, or 

 are disguised by disease, from whatever cause the 

 disease may arise, they are said to be blighted. 

 Blights originate from a variety of causes, the 

 chief of which are unfortunate weather, and in- 

 sects. Two opinions prevail very generally in 



