THE WINGS. 



23 



called, beginuii.g at the costa, ov front edge, the co.sfa/, subcostah 

 median, tdnnedi<n<, and internal, and sometimes the median 

 divides into two, making six *'^--^- 



veins. The costal vein is un- 

 divided ; the subcostal and me- 

 dian are divided into several 

 branches, while the submedian 

 and internal are usualty simple. 

 The venation of the fore- 

 wings affords excellent marks 



in separating genera, but that 



of the hind wings varies less, 



and is consequently of less use. 

 The wings of many insects 



are divided by the veins into 



three well-marked areas; the 



costal, median, and internal. 



The costal area (Fig. 31 b) forms 



the front edge of the wing and 



is the strongest, 



since the veins are 



nearer together than 



elsewhere, and thus 



aftbrd the greatest 



resistance to the air 



Fig. 28. Fore and hiiul win^s of a Butterfly, showing the venation. I. fore wing : 

 a, costal vein; b, subcostal vein; 6i, h^-, b?; hi, bs, five subcostal veinlets; c, inde- 

 pendent vein (it is sometimes a branch of the subcostal, and sometimes of the me- 

 dian vein) ; </, median vein ; rfi, rf2, ,/;?, ,/4, four median veinlets ; e, submedian vem ; 

 /, intenial vein ; /(, mterno-median veinlet (rarely found, according to Doubleday. 

 except in Papilio and Morpho) ; b and d are situated m the " discal cell ; " i^ '. .(/2, .'/•". 

 the upper, middle, and lower discal veinlets. In the Bombycidre and manyotlier 

 moths (/I and r/-' are thrown off from the subcostal and median veins respectively, 

 meeting in the middle of the cell at r/-'. They are sometimes wholly absent. 



II. The hind wing; the lettering and names of the veins and veinlets the same 

 as in the fore wing. — SlU/htlij clumgcdfrom Doiibleday. 



Fiu. 29. Fore wing of a Ilymenopterous insect, c, costal vein; sc, subcostal 

 vein, m, median vein; sm, submedian vein; (, internal vein; c, 1,2, . 'J, the first, 

 second, and third costal cells; the second fre.iuently opaque an<l then called the 

 pteroxfigmu. sr, 1, 2, 3, 4, the four subcostal cells; m, 1, 2, 3, 4, the median cells; 

 sm, 1,2, 3, tlie three submedian cells; a, the internal cell; this is sometimes divided 

 into two cells, and the number of all but the costal cells is inconstant, the outer 

 row of cells (4, 4, 3) being the first to disappear. 



The costal edr,e extends from c to <• ; the outer c, the apex ; the outer edge extends 

 from the apex (c) to a, and the imier edge extends from a, the inner ang'e, to the 

 insertion of the wing at i.— Originul. Figs. 30-32 //•<)« Scudder. 



