NATURE STUDY LESSONS. 220 



wait motionless for hours, and even days. Then, as some 

 insect or other small creature comes near, the queer doub- 

 le-jointed lower jaw is thrust out and as quickly brought 

 back, with the victim secure. 



But the dragon-fly nymph, if very hungry, will go in pur- 

 suit of prey. Our aquarium was once greatly reduced by 

 the larger insects eating the smaller. The may-fly nymphs 

 had disappeared, and, save a few hard-shelled beetles, there 

 remained only a dragon-fly nymph and a large caddis-fly 

 larva, of the kind that makes a tube of the thin covering of 

 water plants, which he rolls up and unites in sections, 

 much as waterpipe is joined. 



We saw the dragon-fly snap at the head of the caddis- 

 fly. He missed, but evidently there was to be a battle, as 

 in real life in the w^ater. We covered the bottom of a deep 

 plate with white sand, filled it with water, and placed the 

 two insects in it, that they might have a fair field and we 

 a clear view. 



The dragon-fly remained still a long time. The caddis- 

 fly put his head out and looked about ; then he put out his 

 six legs and began to draw his long house over the sand. 

 He had hooks at the end of his body, with which he could 

 hold to the silk lining, and he also had a hump with a sharp 

 spine on his back. With this and the hooks to hold by, 

 he was safe from being dragged out. The dragon-fly came 

 and snapped at him, but the jaws slid off the hard, round 

 head. This happened as often as the caddisfly put his 

 head out. At last he resorted ^to strategy. He turned 

 around in his house and, coming partly out at the other 

 end, slowly worked himself and his shelter behind and 

 alongside the dragon-fly. Then there was such commotion 

 in the sand that we could see nothing. When it cleared, 

 the caddis-fly had the dragon-fly fast and had already 

 gnawed a hole in the shell, back of the right fore leg. 

 Pushing his head far in, he ate greedily. In half an hour 

 the empty shell floated to the surface, while the caddis-fly 

 retired to his house and remained perfectly still all day. 



