PERLIDES. 137 



tarsis triarticulatis, articulo lo long^iore obconico. Alap incumbcu- 

 tes ; posticae plenimque loiifjiores, veiiosae, abdominis duplo loni,n- 

 tudiiie, marginc iuieriure jjlicato. 



Phrvganea p., Linn. 

 St'iublis ])., Fair. 

 Perla, Geoff'roy. 

 Planipenues p., Latr. 

 Perlariae p., Latr. 

 PerlidoD, Leach ; Steph. 

 Me<j:aloptera p., MacLeay. 

 IV^rlides, Pictet. 



The five principal veins of each wing are the following : 1st, 

 the rustal, which forms the fore border ; 2nd, the subcostal, which is 

 parallel to the costal and not far from it ; 3rd, the median, which 

 springs immediately from the side of the subcostal, is in juxtaposi- 

 tion with it fur a short space, then diverging divides the wing into 

 two almost equal parts, and is bifurc.ile at two-thirds of its length ; 

 Ith, the mhmedian, which springs near the internal angle of the 

 wing, and terminates in the middle of the hind border, and is bifur- 

 cate very near its beginning, its fore branch forming the anterior 

 snhmedian vein, and its hind branch the posterior suhnedian vein : 

 .3tli, the anal, which is near the base, has a short course, and of 

 which it is often difficult to distinguish between the principal and 

 secondary branches. These veins divide the wing into four princi- 

 pal regions, which are thus named: l9,t, the marginal rei/ ion, com- 

 l)rised between the costal vein and the subcostal vein ; 2nd, the 

 subtnarijinal region, between the subcostal and the median vein : 

 .'3rd, the median region, between the median vein and the anterior 

 submedian vein ; 4lh, the anal region, which contains all the internal 

 l)art of the wing between the lower submedian vein and the anal 

 angle, and in which the vein of the same name ramifies. There is 

 l)esides the submedian areolet, between the branches of the sultme- 

 dian vein. The principal line of transverse veins divides the 1st. 

 2nd and 3rd regions into two jtarls, the basilar part and the termi- 

 nal part. The basilar jiarl of the marginal rei;ion is divided longi- 

 tudinally into two parts by the vein accessory to the costal, and thus 

 cuntains three principal areolets, the external basilar are(dct, the 

 internal basilar areolet and the terminal areolet. In the hind-wings 

 the sul)marginal region is divided longitudinally by a »ein accc^vniy 

 to the median vein, not by one accessorv to the subcostal. 



N 3 



