530 PITFALL OF ANT-LION : WEB OF SPIDER. 
the Ant-lion digs this pit is extremely curious. After having 
examined the spot where it purposes to establish itself, it 
traces a circle of the dimensions of the mouth of its pit; then, 
placing itself within this line, and making use of one of its 
legs as a spade, it digs out a quantity of sand, which it heaps 
upon its head, and then, by a sudden jerk, throws this some 
inches beyond its circle. In this manner it digs a trench, 
which serves as the border of its intended excavation, moving 
backwards along the circle, until it comes to the same point 
again; it then changes sides, and moves in the contrary 
direction, and so continues until its work is completed. If, 
in the course of its labours, it meets with a little stone, the 
presence of which would injure the perfection of its snare, it 
neglects it at first, but returns to it after finishing the rest of 
its work, and uses all its efforts to get this upon its back, and 
carry it out of the excavation; but if it cannot succeed in 
doing so, it abandons its work and commences anew else¬ 
where. "When the inclination of the walls of the pit has 
been altered by any slip, as almost always happens when 
an insect has fallen-in, the Ant-lion hastens to repair the 
damage. 
698. Snares of a still more singular character are con¬ 
structed by many Spiders, which spin webs of the finest silk, 
for the purpose of entrapping their prey. The arrangement 
of these toils varies according to the species, and sometimes 
does not present any regularity; but in several instances it is 
