INDIRECT INJURIES CAUSED BY INSECTS. 169 



created no small alarm amongst agriculturists lest it should 

 prove to be the Hessian fly, so notorious for its depreda- 

 tions in North America; but Mr. Marsham, by tracing 

 out the species, proved the alarm to be unfounded a . That 

 there was sufficient cause for apprehension, should it have 

 so turned out, what I have formerly stated concerning the 

 latter insect, and the additional facts which I shall now 

 adduce, will amply show. 



The ravages of the animal just alluded to, which was 

 first noticed in 1776, and received its name from an er- 

 roneous idea that it was carried by the Hessian troops in 

 their straw from Germany, were at one time so universal 

 as to threaten, where it appeared, the total abolition of 

 the culture of wheat; though, by recent accounts, the in- 

 jury which it now occasions is much less than at first. It 

 commences its depredations in autumn, as soon as the 

 plant begins to appear above ground, when it devours 

 the leaf and stem with equal voracity until stopped by 

 the frost. When the return of spring brings a milder 

 temperature the fly appears again, and deposits its eggs 

 in the heart of the main stems, which it perforates and 

 so weakens, that when the ear begins to grow heavy, and 

 is about to go into the milky state, they break down and 

 perish. All the crops, as far as it extended its flight, fell 

 before this ravager. It first showed itself in Long Island, 

 from whence it proceeded inland at about the rate of fif- 

 teen or twenty miles annually, and by the year 1789 had 

 reached 200 miles from its original station. I must ob- 

 serve, however, that some accounts state its progress at 

 first to have been very slow, at the rate only of seven 

 miles per annum, and the damage inconsiderable ; and 

 a Linn. Trans, ii. 76-80, 



