208 INDIRECT INJURIES CAUSED BY INSECTS. 



rollino- them up, or the leaf-cutter bees by taking a piece 

 out of them, or certain Tineas again by eating their 

 under surface, and so causing them to wither either par- 

 tially or totally. You have doubtless observed what is 

 called the honey-dew upon the maple and other trees, 

 concerning which the learned Roman naturalist Pliny 

 gravely hesitates whether he shall call it the sweat of the 

 heavens, the saliva of the stars, or a liquid produced by 

 the purgation of the air a ! ! Perhaps you may not be 

 aware that it is a secretion of Aphides, whose excrement 

 has the privilege of emulating sugar and honey in sweet- 

 ness and purity. It however often tarnishes the lustre 

 of those trees in which these insects are numerous, and 

 is the lure that attracts the swarms of ants which you 

 may often see travelling up and down the trunk of the 

 oak and other trees. The larch in particular is inhabited 

 by an Aphis transpiring a waxy substance like filaments 

 of cotton : this is sometimes so infinitely multiplied upon 

 it as to whiten the whole tree, which often perishes in- 

 consequence of its attack. The beech is infested by a 

 similar one. Some animals also of this genus inhabitinor 

 the poplar, elm, lime, and willow, reside in galls they 

 have produced, that disfigure the leaves or their foot- 

 stalks. Perhaps those resembling fruit, or flowers, or 

 moss, produed by the Aphis of the fir {Aphis Abietis, L.), 

 the different species of gall-gnats (Cecidomyia, Latr.), or 

 occasioned by the puncture and oviposition of the various 

 kinds of gall-flies {Cynips, L.), may be regarded rather 

 as an ornament than as an injury to a tree or shrub ; yet 

 when too numerous they must deprive it of its proper 

 nutriment, and so occasion some defect. And probably 

 a Hist. Xat. 1. xi. c. 1& 



