ZOOLOGICAL SOCIETY BULLETIN 



1407 







DEAD INSECTS AROUND A CRATER 

 The bodies indicate the cliaracter of the feeding ground. 



settling down to wait for its prey, by a lateral 

 movement of the head, the insect accumulates 

 a heap of sand upon it, and this is held in instant 

 readiness — perhaps for hours — until the help- 

 less prey topples over the edge of the fateful 

 crater. If, by active scrambling, the victim 

 gains a foothold upon the crater's brink, the 

 heap of sand upon the ant-lion's head is hurled 

 at it to bring it down. 



With smaller insects, a stumble over the edge 

 of the pit-fall brings a certain slide to destruc- 

 tion. The fine sand yields to the struggling 

 feet, and an ingenious movement of the destroy- 

 er causes the walls of the inclined plane to shift 

 and give way. More powerful insects are so 

 bombarded by jets of sand from the head of the 

 larva, that they are partially overcome b}^ the 

 dusty medium, and are quickly dispatched by 

 its long mandibles. 



From the methods of construction and opera- 

 tion of the ensnaring crater, it will be under- 

 stood that the ant-lion requires sand that is 

 dry at all times. Hence the necessity of pro- 

 tecting the crater colonies from rain. In trav- 

 eling over the extensive areas of the sandy 

 regions, the writer observed very few ant-lion 

 pits in exposed places, and these were in small 

 groups of seldom more than three to four. The 

 colonies of great numbers were sheltered under 

 trees with particularly heavy foliage or under 

 shelving banks. The largest colonies were ob- 

 served in deserted sheds where in the times past 

 cattle or horses had softened the sandy floor to 

 a considerable depth. An old house occupied 

 by us as a collecting base was supported upon 

 posts set in fine sand, and under this house was 

 a series of flourishing craters, to the number pf 

 several hundred. 



Observations of the feeding habits of the ant- 

 lion were made in the crater colony under the 



house. While ants form a considerable portion 

 of the food, man}^ other kinds of insects are 

 trapped and devoured in the snares. Aside 

 from ants, the larvae were catching small grass- 

 hoppers, minute beetles, various grubs, and oc- 

 casionally flies that alighted in the pit and were 

 instantly rendered unable to fly by a sand bom- 

 bardment. 



A heavy-bodied beetle, a furry caterpillar or 

 some insect larva with tough integument, is an 

 intruder in the crater. When a creature of 

 that kind falls in, the ant-lion may make a 

 herculean effort to get its head under the tumb- 

 ling victim to cast him out. If this fails, he 

 backs off through the sand and constructs a 

 new crater a few inches away, leaving the strug- 

 gling insect to viltimately scramble its way out 

 of the funnel. 



The ant-lion's prey does not appear actually 

 to be masticated and devoured, but the body 

 juices are sucked from it in much the same 

 manner as a spider feeds. This explains the 

 preference for insects with bodies that are eas- 

 ily crushed by the mandibles. Spiders are a 

 favorite prey, and the writer's collection of cap- 

 tive specimens thrived and developed best upon 

 them as a diet. After the completion of the 

 meal, the ant-lion thrusts its head beneath the 

 empty insect shell, and with an upward jerk 

 throws the victim several inches from the funnel. 



The dead insects about the craters clearly in- 

 dicate the character of the feeding ground, and 

 in the accompanying photograph will be seen 

 the surprising number of slain about a pit-fall. 

 This particular funnel was near a deca3ring post 

 inhabited by ants, and the carcases themselves 

 appeared to act as decoys. The ants were ob- 

 served to wander excitedly among them, exam- 

 ining each one with tremulous antennae as 

 though searching for missing companions. Sev- 



AN ANT-LION MAGNIFIED 



