OBJECTIONS ANSWERED. 16 
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 
endeavour to prove at large hereafter ; but for the present, taking this for 
granted, it necessarily follows that the study of them must also be im- 
ortant. 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- 
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 unscientific men, that these destroyers 
of our enemy were its parents, and the original source of all the mischief, 
Middleton, in his “ Agricullure 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 en- 
couraged as friends to man, since no insects are: greater devourers of the 
Aphides. The confounding of the apple Aphis, or American blight 
(A. lanigera*), 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 creature 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 know- 
ledge, 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 
the gardeners and country people, with great industry, gather whole 
baskets full of the caterpillar of the destructive cabbage moth (Mamestra 
Brassice), and then bury them, which, as Roesel well observes®, is just as 
1 Kirby, in Zinn. 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. 2638. Meig. Dipt. i. 94.), yet 
fe corresponds with the characters of Cecidomyia laid down both by Latreille and 
eigen, 
a . 192, 
5 See Latr. Familles Naturelles du Régne Animal, 420. This insect has had 
four generic names given to it.— Lachnus by Mliger, Hriosoma by Leach, Myzoxyle 
by Blot, and Schizoneura by Hartig in Germar’s Zeitschr. f. d. Zntomol. 
+ Collett, in Month. Mag. sxxii. 320. 
5 Roesel, I. iv. 170. 
