OF THE INTELLIGENCE AND OF INSTINCT. 155 



322. With the instinct, nature of course gives the ability 

 to gratify it. 



Thus the larva of the ant-lion (Fig. 98), a small insect re- 

 sembling an ephemera, preys on ants and other insects, of 

 which it sucks the juices ; but being slow of foot, it is 

 forced to spread traps for the capture of its prey. It digs in 

 the sand a small pit, in the form of a funnel (Fig. 99), in the 

 bottom of which it conceals itself, watching the moment 

 when its prey may fall unawares into it. Should the fall not 

 be effectual, it stuns its victim by throwing grains of sand 

 at it, by means of its mandibles. Its mode of procedure in 

 digging the pitfall is equally curious. After having examined 

 the ground, it traces a circle ; placing itself within this circle, 

 it commences digging, throwing out the sand from the 

 excavation as it is being formed ; this is done by means of 

 the head. Thus he continues turning himself round within 

 the circle traced, untilhe returns to the point from which he 

 started, where, changing sides, he repeats his labour until the 

 pitfall be complete. Should he meet with a stone difficult to 

 move, he leaves it for a while, to return to it when the rest of 

 his work has been accomplished ; his whole efforts are now 

 directed to remove the stone, but, should these fail, he aban- 

 dons the entire enterprise, proceeding elsewhere to break up 

 fresh ground. Lastly, he repairs carefully any damage done 

 to the walls of the pitfall by accident. 



Fig. 99. Pitfall of the Ant-lion. 



Certain spiders, as is well known, spread nets still more 



curious, to catch flies and small insects. The disposition of 



the thread of the web in some is without regularity; in 



others, as in the web of the Epeira Biadema,* it presents the 



* Aranea Diadema, Lin. 



