THE WINGS OF HEMEROBIIDM 



181 



stem of the radial sector has resulted, in the fore wings, in the separate 

 origin of from three to many branches of the radial sector from what appears 

 to be the main stem of radius, but what is really the coalesced vein Ri and 

 the stem of the radial sector. 



A comparatively simple example of this condition is exhibited by 

 Hemerohiiis humiili; in the fore wings of this species (Fig. 175), veins R5, 

 R4, and R2+3 arise separately from what appears to be the main stem of 

 radius. 



In systematic works treating of the Hemerobiidas, a radius like that of 

 the fore wing of Hemerobius humuli is described as possessing three radial 

 sectors; such a statement suggests that the two branches that arise 

 separately are not a part of the primitive radial sector, as is maintained by 

 a recent writer, which is unfortunate. 



This usage is so firmly fixed, however, and is withal so convenient, as 

 the number of the branches that arise separately is an important taxonomic 



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Fig. 175. — Wings of Hemerobius humuli. 



character, that it is not probable that it will be abandoned; and no harm 

 will be done by following it if the origin of the various "sectors" be kept 

 in mind. 



