Vol. 1.] 



Woodwortli. — Wing Veins of Insects. 



125 



wing is the same in its maximum condition of venation as the 

 maximum of the hind wing of Aphidfe, and the hind wing the 

 same as its minimum. (See Fig. 64.) 



The Coccidffi have the hind wing almost suppressed, and the 



FIG. 63. Diagram of the venation of the 

 Aphidse. Dotted lines represent veins that 

 are sometimes absent. 



FIG. 64. Diagram of the vena- 

 tion of the Aleurodida>. Dotted 

 lines indicate veins that are 

 sometimes absent. 



FIG. 65. Venation of the Coccidse. 



venation of the front wing the same as the minimum of the 

 front wing of Aleurodidie. (See Fig. 65.) 



The venation of the Phytophthires has a nomenclature of its 

 own, not relating it to any other groups, the only investigator 

 who has attempted to homologize the veins being Redten- 

 bacher. This author admits 

 only two branches as belonging 

 to vein V (corresponding to my 

 independents) in the Psyllidse, 

 and sees none at all in the 

 Aphidse. The posterior he con- 

 siders to be vein IX, apparently on the ground that the fold 

 represented by the fine dotted line is uniformly considered as 

 vein VIII. The unsoundness of this view has already been 

 shown. 



PHYSOPODA. 



The thrips are uniformly small insects with very simple 

 venation. Both pairs of wings are narrow and fringed with 

 long hairs, as is not uncommon in very small insects. The 

 function of these hairs is to extend the amount of available 

 wing surface, since they are close enough together not to comb 

 the air, but to press upon it as though forming a tiat mem- 

 brane. Such an arrangement would be an impossibility in a 

 larger wing. Hairs beyond a certain length would not be stiff 

 enough. The fringe that exists on the wings of some of the 

 higher insects may be nearly, or quite, as wide as in the thrips, 



