282 C. H. TURNER. 



ing manner. When it had tossed up a few loads of dirt, the larva 

 would back away from the obstacle in a straight or a curved line; 

 then turning, it would back through the furrow thus made and 

 proceed as described above. When the stone is too heavy for 

 the insect to handle in the manner mentioned above, it either 

 deepens the pit on one side of the obstacle, or buries the obstacle 

 by mining under it, or else abandons the pit. In several impor- 

 tant respects the behavior observed by me differs from that 

 described by Bingley; (i) never once did I see the stone fall from 

 the insect's back and roll to the bottom of the pit, (2) obstacles 

 encountered in constructing the pit were usually removed at 

 once, (3) such bodies were usually deposited just beyond the rim 

 of the pit, (4) occasionally they were left on the side of the pit. 



On rare occasions I have seen pits constructed in a different 

 manner. Instead of beginning by striking out a circle, the ant- 

 lion burrowed downward into the ground and began at once 

 casting out the soil, thus making a pit of small diameter. Usually 

 such pits were afterwards enlarged by burrowing into the walls 

 and proceeding about as described above. 



Thus my experience with the pit-building behavior of the ant- 

 lion harmonizes with McCook's account (10) ; but is not in accord 

 with that of Mrs. Comstock (5) who writes: "Wonderful stories 

 are told about the way ant-lions dig their pits, marking out the 

 outer margin in a circle and working inward. However, our 

 common ant-lion of the East simply digs down into the sand and 

 flips the sand out until it makes a pit." 



The magnitude of the pit and the slope of the sides depend 

 upon the size of the larva and the nature of the soil ; the coarser 

 the individual particles and the greater their specific gravity the 

 more gentle the slope. In the loess about here the pits vary in 

 diameter from less than half an inch to about two inches; the 

 latter being the more abundant. Often the depth of the pit is 

 almost as great as the diameter. Although a small ant-lion 

 usually excavates a small pit, a small pit does not necessarily 

 contain a small larva; for large larvae sometimes construct small 

 pits which they afterwards enlarge. 



Occasionally one finds an isolated ant-lion pit; usually they 

 occur in groups (Figs. 10, n). In the same cluster the ant-lions 



