THE WINGS OF MYRMELEONID.E 203 



In the hind wing of Symmatheies conirariiis (Fig. 199), vein Cuo is well- 

 preserved, being about one-half as long as vein Ctti. There is also in this 

 wing a prominent vein Cui^. 



In the hind wing of Brachynemiirus longipalpus (Fig. 198), veins Cuo 

 and I St A anastomose and the basal part of vein Cuo appear like an un- 

 usually stout cross-vein. 



In concluding this discussion of the veins M and Cu of the myrmel- 

 eonids, I wish to call attention to a ver\^ interesting feattire of the wings of 

 these insects, which has doubtless been an important factor in delaying the 

 determination of the homologies of the wing-veins. 



Examine the figure of the wings of Brachynemurus longipalpus (Fig. 

 198) and note the similarity in structure of the fore and hind wings. If we 

 omit in each case a study of the base of the wijig, the venation of the two 

 wings appear to be almost identical except that in the fore wing there is an 

 oblique vein. Behind the radius and the radial sector there is in each case 

 an apparently unbranched vein, formerly regarded as an unbranched media; 

 behind this simple vein there is a forked vein, formerly regarded in each 

 case as the cubitus. It is not strange that the similarity in form of these 

 two veins should have led to the belief that they are homologous. But it 

 has been shown above that the forked vein in the fore wing is vein Cui and 

 the forked vein in the hind wing is vein M3+4. There has been developed 

 in these two wings a similar bracing of each by the use of very different 

 material in the two wings. 



Generalizations and definitions of special terms. — In the descriptions of 

 wings in which peculiar methods of specialization have arisen, it becomes 

 necessary to make use of special terms in referring to the resulting struc- 

 tures. Several such terms have been proposed by Dr. Needham, who has 

 prepared an extensive monograph on the wing-venation of the Myrmeleon- 

 idre. As the publication of this monograph has been delayed it seems 

 desirable to introduce these terms here, so that they may become available. 

 I also include some generalizations kindly handed to me by Dr. Needham. 



MvRMEi.EOMu Venation- 

 "The more striking cliaraeters of the venation of the Myrmeleonidae are: 

 "i. The apical fusion of veins Sc and Ri and the clearing out of all cross-veins 

 from the inclosed space. 



"2. The development behind the ])oinl of fusion of an elongate truss cell of variable 

 form but constant position. 



"3. The extensiv^e development of branches upon the radial sector, pectinately 

 arranged, and diminishing in length from the base outward. The basal branch is 

 much more extensively forked and more deeply forked at its tip than are any of the 

 others. In the subfamily Palparina: and in a few scattering genera {Myrmecalurus, etc.) 

 that portion of the radial sector distal to the base of the truss cell, becomes switched 

 upon a cross-vein, and attached to Vein R\, so as to stimulate a second sector [see Figure 

 200I. 



