BEHAVIOR OF THE ANT-LION. 



291 



constructing its burrow the larva crosses the light at every possible 

 angle, and that, at times, it moves toward the light. 



This insect invariably moves backward; never under any 

 conditions does it move forward; yet it is capable of performing 

 all the ambulatory feats possible to an insect that progresses in 

 the orthodox way. It can move in a straight line, it can describe 

 simple or s-shaped curves to either the right or the left, and it 

 can ascend or descend rough surfaces inclined at any angle from 

 zero to ninety degrees. By means of w r hat structures does it 

 perform these movements? Are they produced entirely by 

 flexing the abdomen and trusting to the body bristles to prevent 



Fig. 9 





Photograph showing the comparative size of cocoon, chrysalis and imago. 

 They belong to the same ant-lion and are photographed to the same scale. A, 

 cocoon; B, chrysalis skin; C, imago. 



forward movements? Do the legs take any part in the move- 

 ments? Do the mandibles assist? To answer these questions 

 the following experiments were devised. 



Experiment I. An ant-lion was placed on a glass plate arranged 

 horizontally. By means of a hand magnifying glass every movement 



