38 



HA RD WICKE'S SCIENCE- G OS SIP. 



so around the body, on the insects being relaxed, that it 

 is almost impossible to separate them without doing 

 considerable damage to their delicate membranes. 



Having now given the above general information, 

 and as it will be necessary to explain the application 

 of the technical names given to the various portions 

 of the wings of the Perlina, I cannot do better than 

 reproduce, at this place, the note on the subject given 

 in Mr. F. Walker's " Catalogue of Neuroptera in the 

 British Museum." This will enable the intending 

 student to understand the synopsis and descriptions of 

 genera that follow. 



" The five principal veins of each wing are : — I, the 

 costa, which forms the fore-border ; 2, the sub-costa, 

 which is parallel to the costa and not far from it ; (3), 

 the medius, which springs directly from the side of 

 the sub-costa, is in juxtaposition with it for a small 

 space, then diverging, divides the wing into two 

 almost equal parts, and is bifurcate at two-thirds of 

 its length ; (4), the sub-medius, which springs near the 

 internal angle of the wing, and terminates in the 

 middle of the hind-border, and is bifurcated very 

 near its beginning, its fore-branch forming the anterior 

 sub-medius, and its hind-branch the posterior sub- 

 medius ; (5), the anal vein, 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 

 principal regions, which are thus named: (1), the 

 marginal region, comprised between the costal and 

 sub-costal veins ; (2), the sub-marginal region, 

 between the medius and the anterior sub-medius ; 

 (3), the median region, between the medius and the 

 anterior sub-medius ; (4), the anal region, which 

 contains all the internal part of the wing between 

 the lower sub-median vein and the anal angle, and in 

 which the vein of the same name ramifies. There is, 

 besides, the sub-median areolet, between the branches 

 of the sub-median vein. The principal line of trans- 

 verse veins, or Parastigma, divides the first, second, 

 and third regions into two parts, the basal and ter- 

 minal part. The basal part of the marginal region is 

 divided longitudinally into parts by the vein accessory 

 to the costal, and thus contains three principal 

 areolets, the external basal areolet, the internal basal 

 areolet, and the terminal areolet. In the hind-wings 

 the sub-marginal region is divided longitudinally by 

 a vein accessory to the median-vein, not by one 

 accessory to the sub-costal." This description is 

 a general one, including all the members of the 

 group. The several generic variations are shown in 

 the accompanying illustrations, a reference to which 

 will greatly assist a right understanding of the text. 

 The venation is perhaps the most useful character 

 upon which to base a classification of the Perlid:e, 

 notwithstanding individual variations, but a closer 

 comparison than has yet been made of the anal and 

 other appendages might possibly afford sure points 

 for the identification of species. Mr. McLachlan 



considers Pictet's terminology defective, and holds 

 that "the nervure accessory to ,the costal" is the 

 true sub-costal. As, however, Pictet's nomenclature 

 amply serves my purpose in the present paper, I 

 merely note the disparity and pass on. 



The following synopsis of sub-families, genera, and 

 species, although of course not absolutely perfect, is, 

 I venture to think, sufficiently reliable for the purpose 

 of enabling the student to identify with certainty, 

 and with but little trouble, any of our native stone- 

 flies of which descriptions have been published. 

 Although I am confident of there being several 

 undescribed British species in collections to which 

 I have access, and elsewhere, I prefer not to publish 

 descriptions of them until my knowledge of the group 

 is augmented. 



In the following table capitals refer to sub-families 

 and genera ; italics indicate species, which follow 

 under their respective generic heads. 



General Characters. — Eody depressed, elongated ; sides 

 parallel, or nearly so ; prothorax large ; antennas long, seta- 

 ceous ; wings unequal, posterior ones broader than the 

 anterior ; tarsi three-jointed ; two abdominal setae usually 

 present : Perlid^e. 



Characters of Families, Genera, and Species. 



A. Tail bristles present. 



B. ,, „ long. 



C. Palpi setaceous : Sub-Fam. 1, PERLINA. 



D. Anal region of hind-wings large. 



E. Terminal part of submarginal region divided by cross 



veins: Dictyopteryx. 

 Veins of submarginal region very regular, forming 



square cells : Rcctangula. 

 Veins of submarginal region irregular ; cells seldom 



square : Microcephalci. 

 EE. Terminal part of submarginal region not divided by 



cross veins. 



F. Marginal terminal areolet with at least two cross 



veins. 

 • G. Accessory veiniof sub costa much branched and very 

 irregular: Isogenus. 

 Front wholly black : a brown costal cloud above 

 middle of wings : Nubecula. 

 GG. Accessory vein of subcosta without branches or with 

 one or two regular bifurcations: Perla. 

 Prothorax spotted with black : Maxima. 

 „ unicolorous brown. 



„ large, wider than the head : Marginata. 



„ small, narrower than the head: Cepkalotes 



FF. Marginal terminal areolet with but one cross- vein, 



beyond which the accessory vein terminates at the 



costal vein : Chloroperla. 



V-mark on head with a transverse band behind : 



Rivulonim. 

 V-mark on head isolated, without band: Grammatica. 

 DD. Anal region of hind-wings almost wanting: Isopteryx 

 No spots between the ocelli : Torre?itium. 

 Small black spots between the ocelli : Burmeisteri. 

 Prothorax small, wholly yellow : Apkalis. 



,, medium-sized, caudal setae entirely yellow: 



Tripitnctata. 

 CC. Palpi filiform. 



BB. Tail bristles long: Sub-Fam. CAPNIINjE. 

 Tips of wings without cross veins : Capnia. 

 Dark shining brown, with middle of abdomen yellow : 

 Nigra. 

 AA. Tail bristles rudimentary or wanting : Sub-Fam. 

 NEMOURIN^E. 

 I. Veins of parastigma not forming an X. 

 BBB. Tail bristles rudimentary : T.eniopteryx. 



Wing fasciae indistinct, or less in number than three. 

 Femora brown ; wings opaque : Nebulosa. 

 Wing fasciae never less than three ; distinct in female, 

 faint in male: Trijasciata. 

 H. Labial palpi very short, placed far apart : Leuctra. 

 Prothorax long, constricted in front and behind ; 



abdomen pale, yellow above: Geniculata. 

 Prothorax with three elevated longitudinal lines; an- 

 tennae wholly blackish, feet and wings brown: 

 Fitsciventris. 

 BBBB. Tail bristles wanting. 



