Kobber 3ly 



In less than an hour on a hot fall day, I can find perhaps fifty 

 varieties of insect life around the old apple tree. Some are 

 friendly, some are not. 



I number among the friendly a certain big, two-winged fly 

 the indispensable robber fly who feeds on the gnats, flies, and 

 mosquitoes humming around my head while I rest in the shade 

 of the tree. 



Among the thousands of related species of two-winged flies 

 that swarm over the earth, the robber fly is one of the largest 

 and most interesting. This close-up shows the two great com- 

 pound eyes that practically cover the upper part of his head. 

 Each of these contains several thousand separate lenses, making 

 it possible for him to spot an insect a dozen feet away. A long, 

 streamlined body, two fast-moving wings and strong, spiked legs 

 further equip him for catching flying insects. Occasionally he'll 

 capture a large insect, such as a honeybee. After he snatches it 

 out of the air he stabs it into helplessness with a stout beak car- 

 ried underneath his bushy red beard; then the robber fly carries 

 his paralyzed victim to some convenient perch, where it will be 

 sucked dry of its juices. Often a mound of empty skins is found 

 under the robber fly's favorite perch. 



A robber fly resting on a twig isn't readily frightened away by 

 the approach of a human. In fact, you can usually touch him 

 with your finger. Often I've scratched him gently on his side 

 with the tip of a blade of grass. Sometimes he turns his body 

 toward me as if he enjoyed the scratchings; at other times he 

 seems to resent it, and will kick. 



18 



