window may. Sometimes they are merely translucent, being clouded with 

 color, — such color, usually, as continues the background-picturing of the 

 head and thorax when the wings are folded. In some cases, again, the 

 wings are barred or spotted, and these markings have of course an oblitera- 

 tive tendency. 



Iridescence is fairly common among Hymenoptera, and there are some — 

 chiefly small kinds — ^which are equipped with uniforms of intensely vivid 

 changeable color, ranging sometimes from bronze-red to blue-green or green- 

 blue — like the back of the jacamar* among birds, but still more brilliant. 

 Green is the dominant color of almost all such costumes, which are in the 

 highest degree obliterative amidst vegetation, as we have already seen. 



Some flies, too, have obliterative uniforms of iridescent green and blue, 

 as everybody knows. They are, I believe, rarely or never as brilliant as the 

 very finest of those worn by Hymenoptera, though often veiy rich and beauti- 

 ful. The coloration of the Diptera in general difl[ers but little, in essentials, 

 from that of the Hymenoptera. [The bolder patterns and colors of the 

 Hymenoptera fit their more energetic lives, which bring them against bolder 

 background differences.] f But as the dipterous insects are softer and more 

 defenseless, so are their concealing equipments somewhat more elaborately 

 developed. Many are counter shaded, and habitually perch on the tops of 

 things. Some of the more aerial, flower- and foliage-haunting kinds, have 

 bright, transversely 'secant' patterns of yellow and dark brown or black; but 

 this coloration is less characteristic of them than of the Hymenoptera. The 

 close likeness in color and pattern between certain stinging wasps or bees and 

 stingless flies has led naturalists to suppose that the flies are mimics of the 

 bees. This resemblance, however, is quite in keeping with the similarity in the 

 insects' forms, habits, and environments, and less remarkable than many other 

 kindred cases which cannot possibly be connected with mimicry. 



Flies are often dingily colored, and — especially those which have counter 

 shading and more or less finely mottled patterns — ^fitted for "lying close" on 



* See p. 90, Chapter XVI. t Interpolation by A. H. T. 



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