22 FLASHLIGHTS ON NATURE 



grub of the lace-wing fly, a sort of insect old-clothes 

 man, which covers its back with the cast-off skins 

 of its discarded victims. This is a clever device to 

 enable it to escape observation. The larva, which 

 is a fat and juicy morsel, catches aphides wholesale, 

 and sucks their life-blood ; when he has drained 

 them dry, he hoists up their skins on to his back 

 with his jaws, by way of overcoat. Then the hooks 

 or spines on his back (shown above) hold them in 

 place for a time, while the larva bends over and 

 spins a few threads of web across them, to weave 

 them into a neat and compact garment. Thus 

 securely clad, he is hidden from view : he looks 

 much like a twig covered with aphides, and avoids 

 to some extent the too pressing attentions of his 

 own enemies. Observe in this sketch the charac- 

 teristic unconcern of the aphis who is destined to 

 be his next victim. 



Birds also destroy large numbers of aphides. 

 You can see them picking them off in the bean- 

 fields in summer. 



It is lucky for us that these insect pi->ts have so 

 abundant a supply of natural enemies ; for man, by 

 himself, is almost powerless against them. Strange 

 to say, and paradoxical as it sounds, it is the smallest 

 enemies that we always find most difficult to extir- 

 pate. Lions and tigers we can kill off without diffi- 

 culty ; they can be shot and exterminated. Wolves 

 and hyenas give us a little more trouble ; while 

 against rabbits, our resources are taxed to the 

 utmost. A plague of rats and mice, or of tiny 



