20 INSECTS 



or leathery fore-wings, beneath which the membranous 

 secondaries are transversely folded. They gain their 

 food by chewing, in all stages, although the early or 

 larval forms are usually altogether unlike the adults. 



The Lepidoptera include the butterflies and moths, 

 known by the scaly covering of the wings. The scales 

 appear as fine, dust-like particles that are easily rubbed 

 off; but under the microscope show great differences 

 in form and color. In this order the mouth parts of the 

 adult are modified into a coiled tongue capable of sipping 

 liquids only ; but in the larval stage the caterpillars are 

 voracious devourers of plant and other tissue. 



Bees, ants, wasps and the like belong to the order 

 Hymenoptera, in which the wings are transparent, with 

 few and often no veins; never reticulated. Many of 

 the species are of extreme interest because of their 

 social habits and organizations, and the honey bee is of 

 direct benefit to man in. more ways than one. 



Finally come the flies ; differing from all other insects 

 by having only one pair of wings, whence their ordinal 

 name Diptera. We shall have more to say concerning 

 some of their species and development elsewhere. 



The insects as a whole are at the top of the line of 

 development in the Articulata: they diverged early 

 from the worm-like ancestors and their remains, already 

 well developed, are found in the earliest fossil-bearing 

 strata. At the present time there are more species of 

 insects than there are of all other species of animals 

 taken together, and in number of individuals they are 

 unapproachable. The class as a whole is yet a growing 

 one and both genera and species are in some orders 

 unfixed and in process of formation. There is no better 

 field for the study of animal variation, and the problems 

 imposed upon us by them have scarcely begun to be 

 appreciated. 



