28 OBJECTIONS ANSWERED. 



ceed 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 necessai'y 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 endeavour to prove at large hereafter ; but 

 for the present, taking this for granted, it necessarily fol- 

 lows that the study of them must also be important. For 

 when we suffer from them, if we do not know the cause, 

 how are we to apply a remedy that may diminish or pre- 

 vent their ravages? Ignorance in this respect often occa- 

 sions 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-coloured 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 unscien- 

 tific men, that these destroyers of our enemy were its 

 parents, and the original source of all the mischief'. 

 Middleton, in his " Agrknliia-e 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 



" Kirby, in Linn. Trans, iv. 232. 235. See also a lettei' signed C. 

 in the Gent. Mag. for August 1 795. This little insect produces no 

 galls like the other species of the genus (Latr. Gen. Crust, et Ins. iv. 

 253. Mcig. Dipt. i. 94.;, yet it corresponds with the characters of 

 Cecidomyiu laid down both by Latrcillcand Meigen. *> P. 192. 



