CHAPTER XIII 

 THE TWO-WINGED FLIES (Order Diptera) 



EXT to the name "bug" there is no other name so 

 popular in point of miscellaneous application to insects 

 as "fly." This looseness of popular nomenclature 

 may be largely due to the fact that entomologists them- 

 selves apply the term "fly " in several compound words, 

 as butterfly, alder-fly, caddis-fly, May-fly, saw-fly, and 

 the like, to widely differing kinds of insects. Used as 

 a simple word, however, by fly an entomologist means 

 some species of the order Diptera. The various kinds of 

 true flies have of course special names, as mosquitoes, 

 midges, punkies, gnats, or as in the compounds 

 horse-flies, bee-flies, flower-flies, robber-flies, etc. 

 The order Diptera is so large and includes insects of such widely differing 

 form and habit that it is difficult to formulate any general account of it. The 



name itself is derived from the most conspicuous 

 structural condition of flies, namely, their two- 

 winged state. All Diptera have but a single 

 pair of wings, if any; a few are wingless. The 



FIG. 409. FIG. 410. 



FlG. 409. Mouth -parts of a female mosquito, Culex sp. lep., labrum-epipharynx; md., 

 mandible; mx.l., maxillary lobe; mx.p., maxillary palpus; hyp., hypopharynx; li., 

 labium; gl., glossa; pg., paraglossa. 



FlG. 410. Mouth-parts of the house-fly, Musca domestica. lb., labrum; mx.p., maxil- 

 lary palpi; /*'., labium; la., labellum. 



hind wings of other forms are replaced by a pair of strange little structures 



301 



