176 INDIRECT INJURIES CAUSED BY INSECTS. 



same instinct. It was a pleasant spectacle, he observes, to 

 behold this army of ants marching constantly in the same 

 direction, and each individual with its bit of green leaf in its 

 mouth. ^ The insects injurious to deciduous trees mostly 

 leave the fir and pine tribes untouched ; but these, on the 

 other hand, are subject to have their foliage ravaged by a 

 great variety of insect enemies peculiar to themselves, to some 

 extent in this country, but far more on the Continent, as by 

 the larvae of various moths {Dendrolimus pini, Psilura mo- 

 nacha, Achatia piniperda, Bupalus piniarius, OrtliotcBnia 

 turionana and resinella, &c.) ; and of not fewer than three 

 species of saw-fly {Lophyrus pini and rufus and Pamphilius 

 erythrocepliala)?' The injury thus caused to trees by insects 

 is not confined to the mere loss of their leaves for one season ; 

 for it occasions them to draw upon the funds of another, by 

 sending forth premature shoots and making gems unfold, 

 that, in the ordinary course, would not have put forth their 

 foliage till the following year. 



Other insects, though they do not entirely devour the 

 leaves of trees and plants, yet considerably diminish their 

 beauty. Thus, for instance, sometimes the subcutaneous 

 larvae undermine them, when the leaf exhibits the whole 

 course of their labyrinth in a pallid, tortuous, gradually 

 dilating line — at others, the Tortrices disfigure them by 

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

 of them, or certain Tinece again by eating their under surface, 

 and so causing them to wither either partially 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 ! I ^ Perhaps you 

 may not be aware that it is a secretion of Aphides, whose 

 excrement has the privilege of emulating sugar and honey in 

 sweetness and purity. It however often tarnishes the lustre 

 of those trees in which these insects are numerous, and is the 



1 Stedman, ii. 142. 



2 KoUar, on Ins. inj. to Gardeners, &c. 323 — 356. 



3 Hist. Nat. 1. xi. c. 12. 



