BY R. J. TILL YARD. 747 



used as a generic character. As the description of the formation 

 of this line usually occupies two or three lines of print, and is 

 unwieldy for use in dichotomous tables, generic definitions, and 

 so forth, it seems advisable to give it a definite name. I there- 

 fore propose here the name Banksian Line for it, in honour of 

 Mr. Nathan Banks, who has done so much to advance the study 

 of Neuroptera, and has described an immense number of new 

 species from all parts of the world. 



The Banksian Line should be contrasted phylogenetically with 

 the development of crossveins known as the Gradate Series in 

 Chrysopidce and other families of Neuroptera. Both formations 

 are derived from the typical archaic arrangement of the branches 

 of the radial sector seen in Xymphidce, and still preserved for us 

 in Mynneleon and other genera. In Text-fig. 9, the series A 

 shows the formation of the Banksian Line, the Series B the 

 formation of two Gradate Series. 



Those genera in which the Banksian Line is well-developed 

 must be considered, at any rate in this respect, as the highest 

 developments in their respective subfamilies. Thus, Acanthadisis 

 is evolutionarily at the head of the Myrmeleonince^ Glenoleon at 

 the head of the Dendroleonince. 



(h) The Hypostigmatic Space. (Text-fig;. 6, lis). 



Below the pterostigma in Jlyrmcleonidce, there is a narrow 

 elongate cell devoid of crossveins, and enclosed by R above and 

 Rs below. This space I here designate as the Hypostigmatic 

 »S)^cR'e (Text-fig. 6, hs). Proximally, it is bounded by a more or 

 less slanting crossvein which may be termed the radial brace 

 (Text-fig. 6, rb), distally by an isolated crossvein of unspecialised 

 form. The hypostigmatic space is present in Nymphidce, and is 

 very constant in all Myrmeleonidce. It may, howevei', be used 

 as a convenient basis of reference for stating the position of spots 

 and colouring on and around the pterostigma, the latter organ 

 being merely an assemblage of crowded crossveins, with ill-defined 

 limits. Besides this, for any given species, the number of 

 branches of Rs may conveniently be stated up to the limit of rb, 

 and the position of I'b itself, whether standing directly oxav one 



