HOP-FLY. 77 



evident signs of being uneasy, continually crawling about 

 on the upper as well as the under side of the leaves, and 

 leaving no deposit whatever. The direction of the wind 

 has nothing whatever to do with their first appearance, but 

 in a warm, westerly wind they will take flight most readi- 

 ly, and be thus distributed. The lice, when half grown, 

 change the skins; and I have often found the skins of 

 very large ones stuck to the leaves, and yet showing no 

 opening where the insect could have got out. I believe 

 these are the prey of a little parasitic fly, whose history I 

 don't know enough of at present to attempt to give it you 

 here ; they have, however, other enemies ; and as these 

 seem to offer the only hope of checking the increase of 

 these destructive wretches, I shall give you a little account 

 of them. 



You will never find a plant of any kind infested with 

 the Aphis, without also observing a number of ants and 

 lady-birds among them, and also a queer-looking insect, 

 like a fat lizard, which is, in fact, the caterpillar of the 

 lady-bird. The connexion of the ants and the Aphis is of 

 the most peaceful kind that can be conceived ; their object 

 is the honey-dew which the Aphis emits ; and, far from 

 hurting the animal which affords them this pleasant food, 

 they show it the greatest possible attention and kind- 

 ness, licking it all over with their little tongues, and 

 fondling it, and patting it, and caressing it with their an- 

 tennae in the kindest, prettiest way imaginable : not so 

 the lady-bird, or its lizard-like caterpillar ; these feed on 

 the blights most voraciously, a single grub clearing a leaf, 

 on which were forty or more, in the course of a day. The 

 perfect lady -bird is a decided enemy to them, but not so 

 formidable a one as the grub. The eggs of the lady-bird 



