BEHAVIOR OF THE ANT-LION. 



283 



differ much in size, and this is true even in the early spring. 

 Certain writers attribute these differences in size to the fact that 

 some obtain more food than others. The following simple 

 experiment lends support to this view. From a certain well- 

 circumscribed area, containing about fifty ant-lion pits, a dozen 

 larvse were removed, on June 22, and placed in my insectary. 

 A portion of these were well fed daily, the remainder were fed 

 only occasionally. A few were lost by accidents. By August 

 8 all of the survivors of the well-fed lot had formed cocoons and a 

 few imagoes had emerged. The poorly fed individuals were 

 still larvae. The majority of those left in the field were still 

 larvse. 



Morphologically the ant-lion (Figs. 1-3) is well adapted to 

 this pit-building behavior. The flat head, which, with the stout 

 mandibles, forms an excellent shovel, is so articulated to the rest 



Fig. 3 



Larval ant-lion. Lateral view. 



of the body that it is possible to give it a powerful upward jerk. 

 The abdomen is flat on the ventral and convex on the dorsal 

 side, the whole tapering toward the tip in such a manner as to 

 form an excellent burrowing instrument. From the sides of the 

 body clusters of stiff bristles project outward and forward in 

 such a manner that the body is prevented from slipping forward 

 after it once has penetrated the earth. Then, too, the terminal 

 claws on the legs (Fig. 12) make efficient anchors. The front of 

 the dorsal portion of the prothorax is so rounded that dirt easily 



