J^ 1)1 AN DRAG ON FLIES. 4r,9 



retaining the long s]>ociiic utinies for each of the olevou main ncrvuros, the 

 expedient of uuniboring them in order fnmi apex to base, has been adopted 

 as one more easy to work with when deseribing the species.) 



The ]\'in;/!i. 



The wings are h>ug. narrow, membranous organs, built on a system of 

 main sectors or nervures and a secondary reticulation or network of minor 

 nervures. The wings of the Anisoptericho (I'lates 3, 4 and o), are 

 iniequal, the hind being broader than the fore and dilated at the base, 

 that is, the part nearest the attachment of the wings. In the Zygopteridie, 

 (Plates (3 and 7) the fore and hind wings are usually equal and never 

 dilated at the base, although there may be a broadening at their middle. 

 (Plate (1, tig. 4. Euphcea.) 



The anterior border of the wing is knowai as the " costa," and presents 

 somewhere near its middle, the site varying in the two wings and markedly 

 in the various species, a stout, transverse nervure, the " node,"' at which 

 point, the costa is generally slightly angulated. Posterior to and running 

 parallel to the costa, from apex to base, is a second nervure, the " sub- 

 costal." (The " median ■' of French authors and " 1{-M " of the German.) 

 Between the costa and subcostal nervures, running from the base to the 

 node, is an intermediate nervure, the " intercostal."' (The " subcostal" of 

 French and German writers.) The space above this is called the " superior 

 costal held" and the space below it, the " inferior costal field." A series 

 of transverse nervures running between the costa and subcostal nervures, 

 on either side of the node, are called the "ante — and post-nodal nervures,'' 

 respectively. Traversing the wing, posterior to the subcostal nervure, are 

 a series of main nervures, the " iJrd, 4th, 5th, 6th, 7th, 8th, and 9th " and 

 in addition to these will be found, in many species, lying immediately 

 posterior to the oth and 7th, two supplementary nervures, the " oa " and 

 " 7a."' Near the base, the 3rd nervure meets a small, curved n,ervure spring- 

 ing from the anterior border of the 7th and fusing with it over a varying 

 distance, to form the " sectors of the arc "', the "arc" being a small, transverse 

 nervure running back from the basal end of the subcostal. The space 

 between the sectors of the arc and the 7th nervure is the " hypertrigone." 

 The outer extremity of the wing, is its "apex," and the posterior border, its 

 " termen." In the hind wings of the Anisopteridie, the termen 

 meets the basal border at a sharp or rounded angle, the "tornus."' A 

 tornus is not a marked feature in the fore wing and is never present in the 

 Zygopterid;e. In the Anisopteridie, posterior to the hypertrigone, will be 

 seen a triangle, the " trigone"", with its apex directed towards the termen. 

 According to the species, the trigone may be equilateral, acute or obtuse 

 and may or may not be traversed by one or more nervures or again, may 

 be filled with a network of fine nervures. Its outer angle corresponds to 

 the point at which the sectors of the arc cuts the 7th nervure. In the fore 

 wing there is often a third triangular area Ij'ing immediately internal to 

 the trigone, in the angle formed between it and the 7th nervure and this 

 when present is called the " subtriangle." The space posterior to the 

 basal part of the 7th, limited outwardly by the trigone and inwardly by 

 the base of the wiug, is called the "cubitus"": the space above the same 

 part of the 7th, limited outwardly by the arc and inwardly by the base, 

 is the '•' svibcostal space." The space between the 7th and 8th nervures, 

 limited inwardly by the outer border of the trigone, is the " discoidal 

 held" and may hold one, two or more rows of cells, thus forming a useful 

 point for classification purposes. The base of the wings in the Anisopter- 

 dte, is strengthened by a rudimentary, opaque membrane, more or less 

 extensive, which is known as the " accessory membrane"' and which is more 

 evident in the hind than in the fore wings. The angle formed between 



