NATURK STUDY LESSONS. 219 



while on the wing. The robber-flies may be distinguished 

 by their size, by their long, pointed proboscis, and by the 

 fact that the space between the eyes is "excavated," or 

 hollowed out. They should be pinned by themselves and 

 labeled Asilidse. 



Most boys and girls know the crane-flies, with their six 

 long, straggling legs that come oif so easily as to make it 

 difficult to secure and preserve a perfect specimen. The 

 crane-flies have slender bodies and long, narrow wings. 

 They are common in the fields, and there are many spe- 

 cies, of different sizes and colors, but they all have a fam- 

 ily likeness and are easily recognized. They comprise the 

 famil}^ Tipulidse. 



There are many flies commonly found about flowers and 

 shrubs that bear a close resemblance to some other insect 

 which can sting. Some look almost exactly like the hon- 

 ey-bee, others like bumble-bees, and others again like 

 wasps. Some are striped with yellow or white and look 

 like the wasps that are commonly called hornets. Some 

 fly with a humming sound that makes the mimicry all the 

 more complete. 



Of course they are entirely harmless and may safely be 

 handled like other flies, if only one can be sure that they 

 are only make-believe bees and wasps and not the real 

 thing. But it is quite easy to be mistaken, so long as the 

 insects are on the wing, and it is a severe test of one's 

 keenness of observation to decide whether to venture to 

 catch one in the hand. There was once a bright boy who 

 thought it great sport to ' ' dare ' ' his father to make the 

 trial. Even a fairly good entomologist may sometimes 

 be deceived. 



Most of the flies which mimic other insects for their own 

 protection belong to the great family Syrphidse, of which 

 there are known to be nearly two thousand species in the 



