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 Hemerohius 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 
