INSECTA. 



927 



The anterior margin is that portion which is 

 situated anteriorly upon its expansion in flight, 

 extending from its base to its distinctly visible 

 extremity of the costal nervure, a little beyond 

 the marginal cell; at its termination the apical 

 margin commences, and extends to the sinus 

 of the wing, which is the incision at the apex 

 of the posterior margin, which latter extends 

 from this sinus back to the base, and it is by 

 this margin that the upper and under wings 

 are connected in flight. The costal nervure is 

 the first longitudinal nervure of the wing 

 (fg. 393, ), and, as we have seen, extends 



Fig. 393. 



i 



Wing of Hymenopterous insect {Shuckard). 



a, costal nervure; d, post-costal; S, stigma; 

 e, exteruo medial ; f, anal ; g, transverso-medial ; 

 1, costal cell -, 2, medial ; 3, interno-medial ; 4, 

 anal ; h, radial nervure ; 5, marginal cell ; 6, 

 cubital nervure. 



upon the anterior margin to just beyond the 

 extremity of the marginal cell. The second 

 longitudinal nervure is the post-costal (d); this 

 extends to the stigma (s), which is that thick- 

 ened point or spot upon the wing placed upon 

 its anterior margin at about two-thirds the dis- 

 tance of its base and extreme apex, and ap- 

 pears to me to be a dilatation of the costal 

 nervure. The third longitudinal nervure is the 

 externo-medial (e\ which proceeds in a direct 

 line nearly parallel with the preceding for a 

 little more than half the length of the post- 

 costal, or about one-third of the entire length 

 of the wing, and then leads off at an obtuse 

 angle to join the post-costal just before its 

 junction with the stigma. The anal (f) is the 

 fourth longitudinal nervure, which also extends 

 from the base to the sinus at the apical ex- 

 tremity of its posterior margin: a transverse 

 nervure unites the externo-medial and anal, 

 and which I purpose calling the transverso- 

 medial (g). These nervures, which I consider 

 the primary nervures of the wing, severally 

 inclose what have hitherto been called collec- 

 tively the basal or humeral cells, but to which 

 I purpose applying different names (derived 

 from the nervures which inclose them), that 

 they may be more readily distinguished from 

 each other. The first, or that very narrow one 

 between the costal and post-costal nervures, is 

 the costal cell (1) ; the second is that placed 

 between the post-costal and externo-medial 

 nervures, and which I call the externo-medial 

 cell (2): that inclosed between the externo- 

 medial and anal nervures parallelly, and ter- 

 minated at its apex by the transverso-medial, 

 is the interno-medial cell (3); and the cell 



seated between the anal nervure and the pos- 

 terior margin of the wing is the anal cell (4). 



" From the interior margin of the stigma 

 arises the radial nervure (A), which makes a 

 curve and then joins the costal upon the mar- 

 gin of the wing : the lanceolate space thus in- 

 closed forms what is called the radial or mar- 

 ginal cell (5). The cubital nervure (6) is 

 nearly parallel with the radial and originates 

 from the externo-medial near its junction with 

 the post-costal ; this extends to the apical 

 margin of the wing just below its extreme 

 apex (6 i). The space thus inclosed is divided 

 by three transverse nervures, which I propose 

 calling the transverso-cubitals (m, m, m, m), 

 inclosing as many spaces forming so many 

 cubital or sub-marginal cells, a fourth being 

 formed in consequence of the nervure extend- 

 ing to and joining the apical margin (g}. The 

 third nervure, originating from the primaiy 

 nervures of the wing, is what I call the dis- 

 coidal nervure (/c), (it is from this that I anti- 

 cipate the chief results), and which, commenc- 

 ing at the transverso-medial, extends in a di- 

 rect line to the disc of the wing directly be- 

 tween the stigma and the sinus, when it makes 

 a sudden curve at a right angle backwards and 

 joins the anal nervure close to the sinus (/c). 

 From this discoidal nervure at the centre of its 

 apical return another springs, forming what I 

 call the sub-discoidal nervure (/), and which 

 here extends to the posterior margin of the 

 wing. From the cubital nervure two others 

 originate ; these are called the recurrent ner- 

 vures, the first of which always inosculates at 

 the angle of the discoidal nervure, and the 

 second just beyond the centre of the sub- 

 discoidal. By the reticulation of these four 

 nervures several cells are formed upon the disc 

 of the wing ; the first of these, which is in- 

 closed between the discoidal and anal nervures, 

 I call the first discoidal cell^lO). The second 

 is that placed between the externo-medial cubi- 

 tal, first recurrent, and discoidal nervures (11). 

 The third discoidal cell is that inclosed by the 

 second recurrent, sub-discoidal, discoidal, and 

 first recurrent nervures (12). The space in- 

 closed between the second recurrent, sub-dis- 

 coidal, and cubital nervures, and the pical mar- 

 gin of the wing, forms the first apical cell (13), 

 and there is a second only when the sub-dis- 

 coidal nervure extends to the apical margin, 

 by which and a portion of the discoidal cell 

 it is inclosed." 



The distribution of the nervures in the wings 

 of the males of some of the Orthoptera affords 

 some curious peculiarities, by which the pteri- 

 gostia become instrumental in the production 

 of sounds. At the base of the superior pair 

 of wings in Acrida; at the inner angle of each 

 wing, is an oval or nearly circular space 

 (fig. 394, o), in which the membrane is more 

 transparent and free from ramifications of ner- 

 vures than in any other part of the wing. 

 These spaces have long been known to be con- 

 nected with the production of sound. The 

 membrane itself appears to be thinner than in 

 other places, and more tense, and the nervures 

 by which it is inclosed are thick and strong. 



