OBJECTIONS ANSWERED. 51 



connected with sublunary interests, and promote our present welfare, I 

 shall proceed further to prove that the study of insects may be productive 

 of considerable utility, even in this view, and may be regarded in some 

 , sort as a necessary or at least a very useful concomitant of many arts 

 and sciences. 



The importance of insects to us both as sources of good or evil, I shall 

 endeavor to prove at large hereafter ; but for the present, taking this for 

 granted, it necessarily follows that the study of them must also be impor- 

 tant. For when we suffer from them, if we do not know the cause, how 

 are we to apply a remedy that may diminish or prevent their ravages ? 

 Ignorance in this respect often occasions us to mistake our enemies for our 

 friends, and our friends for our enemies ; so that when we think to do 

 good we only do harm, destroying the innocent and letting the guilty 

 escape. Many such instances have occurred. You know the orange-col- 

 ored fly of the wheat, and have read the account of the damage done by 

 this little insect to that important grain ; you are aware also that it is given 

 in charge to three little parasites to keep it within due limits ; yet at first 

 it was the general opinion of unscientific men, that these destroyers of our 

 enemy were its parents, and the original source of all the mischief.^ Mid- 

 dleton, in his ^'■Agriculture of Middlesex,^'' speaking of the Plant-louse 

 that is so injurious to the bean, tells us that the lady-birds are supposed 

 either to generate or to feed upon them.^ Had he been an entomologist, 

 he would have been in no doubt whether they were beneficial or injurious : 

 on the contrary, he would have recommended that they should be encour- 

 aged as friends to man, since no insects are greater devourers of the 

 Aphides. The confounding of the apple Aphis, or American blight {A. lan- 

 igera^,) that has done such extensive injury to our orchards, with others, 

 has led to proceedings still more injurious. This is one of those species 

 from the skin of which transpires a white cottony secretion. Some of the 

 proprietors of orchards about Evesham, observing an insect which secreted 

 a similar substance upon the poplar, imagined that from this tree the crea- 

 ture which they had found so'noxious was generated ; and in consequence 

 of this mistaken notion cut down all their poplars.^ The same indistinct 

 ideas might have induced them to fell all their larches and beeches, since 

 they also are infested by Aphides which transpire a similar substance. 

 Had these persons possessed any entomological knowledge, they would 

 have examined and compared the insects before they had formed their 

 opinions, and being convinced that the poplar and apple Aphis are distinct 

 species, would have saved their trees. 



But could an entomological observer even ascertain the species of any 

 noxious insect, still in many cases, without further information, he may fall 

 short of his purpose of prevention. Thus we are told that in Germany 



> Kirby, in Linn. Trans, iv. 232. 235. See also a letter signed C. in the Gent. Mag. for 

 August, 1795. This little insect produces no galls like many of the species of the genus, 

 (Latr. Gen. Crust, et Ins. iv. 253. Meig. Dipt. i. 94.) yet it corresponds with the characters 

 of Cecidomyia laid down both by Latreille and Meigen. 



2 P. 192. 



3 See Latr. Families Naturelles du Ehgne Animal, 429. This insect has had four generic 

 names given to it, Lachnus by lUiger, Eriosoma by Leach, Myzoxyle by Blot, and Schizoneura 

 by Hartig in Germar's Zeitschr. f. d. Entomol. 



* Collet, in Month. Mag.x^n. 320, 



