elusive, like the cockroaches and earwigs, and have little or no special costume- 

 development. Monochrome blackish, and unmarked, are also certain aquatic 

 forms which live exposed to the daylight, such as some of the Water Boatmen 

 (Notonecdidce). It is likely that, for one reason or another, such insects are 

 little sought as prey by the higher animals. But many of the larger sub- 

 aquatic bugs are mud-colored, and some of them are decidedly pale-bellied. 



Three important insect orders remain to be glanced at in this chapter, 

 namely, the Hymenoptera (bees, wasps, borers, etc.), Diptera (flies, mos- 

 quitoes, etc.), and Neuroptera (dragon-flies, ephemera, etc.). In these orders 

 obliterative shading does not play a uniformly dominant part. The insects 

 comprising them are for the most part winged, and not only winged but ac- 

 tively aerial, and depend much on their powers of flight for escape from enemies. 

 Some of them (dragon-flies, wasps, etc.) are themselves ferocious hunters, 

 and too big and active to be eaten by the smaller insectivorous birds; while 

 most of the flying Hymenoptera are terribly armed for offense and defense 

 with poison-injecting stings, so that they are avoided by the general run of 

 insectivores. Again, many of the Diptera and most of the Hymenoptera have 

 no fixed perching postures relative to the prevailing light, but sit both above 

 and under twigs and leaves, etc. This last fact alone is a sufficient reason 

 why these insects, as a class, cannot greatly profit by obliterative shading. 

 Some of them have it, to be sure; and it does work, more or less, when they 

 cling to the undersides of things, or sit on a surface perpendicular to the earth, 

 — provided, in both cases, that the surface belongs to an opaque substance, 

 and is of sufficient extent to cut off much light from the insect's ' underside.' 

 But since they also cling beneath slender twigs and translucent leaves, the 

 obliterative effect of their counter shading, when they have it, must often be 

 wholly upset, and this alone, as we have said, is reason enough why many of 

 these insects should be nearly or quite as dark below as above.* 



*In this book the term counter shading, when unqualified, means shading from dark above 

 to light below. Insects like many Diptera that have their darkest details on their under side may profit 

 by this in situations we do not understand. In general, it is not safe to deny to any coloration what- 

 ever, concealing functions under circumstances not yet recognized. — A. H. T. 



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