THE WINGS OF SISYRIDM 177 



wings, and does not fall within the scope of this essay. Until this is done, 

 I suggest the inclusion in this family provisionally of another remarkable 

 insect; this is Rapisma viridipennis . 



The genus Rapisma was established by McLachlan to receive a species 

 from the East Indies that had been described by Walker under the name 

 H enter ohius viridipennis. Dr. Needham has obtained this species from the 

 East Himalayas and I give here a figure of its wings (Fig. 171). 



In Rapisma the costal area of the fore wings is more expanded than in 

 Ithone; but the courses of the terminal portions of veins Sc and Ri are 

 similar in the two genera, as are also most of the other more general features 

 of the wings. 



The chief reason for giving a figure of the wings of Rapisma in this dis- 

 cussion of the wings of the Neuroptera is to call attention to one feature of 

 the structure of the radial sector. This is the fact that the primitive 

 dichotomy of this sector appears to have been retained although the 

 development of its other pectinate features has progressed far. This 

 appearance is especially striking in the fore wing where what appears to be 

 the forks of veins R2+3 and R4+5 are opposite. 



A little consideration will suggest that it is not probable that the 

 position of the fork of the first branch of the radial sector, vein R4+5, would 

 remain so nearly in its primitive position while the other features of the 

 pectinate vein were being developed. 



The explanation of the condition in question is that in each of the wings 

 of Rapisma there has been developed a radial cuneate area; and that in the 

 fore wing the first fork of vein Ro has extended nearly to its base. In the 

 hind wing this forking of vein Rj has not extended so far. 



The extent to which the development of a radial cuneate area has 

 progressed in the wings of Rapisma and the transverse position of the first 

 radio-medial cross-vein of the hind wings are the most striking didercnces 

 between these wings and those of Ithone. 



(g) THE WINGS OF THE SISYRID.^ 



Until quite recently the members of this family have been included in 

 the family Hemerobiida ; but several recent writers have separated them as a 

 distinct family. The structure of their wings warrants this separation, as the 

 distinctive characteristic of the hemerobiid wings is not exhibited by them. 



The type of wing-venation characteristic of the Sisyridae is well illus- 

 trated by the wings of Sisyra fiavicornis, a species found in British India 

 (Fig. 172). The more striking characteristics of these wings are the follow- 

 ing: The costal area of the fore wings is not greatly broadened. The 

 humeral vein is not recurrent and is not branched. Veins Sc and Ri 

 coalesce near the apex of the wing. The dichotomy'of the radial sector has 



