WING-VENATION OF PHYSEMACRIS VARIOLOSA 199

On the wing-venation of Physemacris variolosa (Linn.) (Insecta : Pneunioridae) .

JOHN SMART, M.A., D.Sc., F.Z.S. Department of Zoology, University of Cambridge.

[Received 10th March 1952.1

(With Plate 1 and 2 figures in the text.)

CONTENTS. Page

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199 Notes on the wings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201 References ............................................ 202 Explanation of the Plate ................................ 202

INTRODUCTION. Physemacris variolosa ( =Pneumora variolosa (Linn.) of authors, =Bulla

variolosa Linn. of authors) is a short-horned grasshopper from South Africa ; it, and its relatives, are not common in collections. In older classifications (e.g. Kirby, 1910) it, and a few other related species, all from South Africa, were placed in a subfamily, Pneumorinae, of the family Acridiidae. More recently, however, i t has been recognized that their uniqueness entitles them to family rank of status equal to that accorded to the Acridiidae as now more usually restricted (e.g. Chopard, 1949).* The males produce sound by stridulating the rather weak hind legs, which are furnished with a stridulatory rasp on the inner surface, against a rasp on each side of the much inflated abdomen and not on the thickened fore-wings in the manner usually associated with the stridulating Acridiidae. Compared with other Saltatoria, the wings of the males are remarkably primitive, and have an almost diagrammatic venation ; a t no point in their phylogenetic history can they have been used as stridulatory organs. This venation is important in developing an inter- pretation of the wing-venation of the Acridiidae as that family is now usually restricted. The photograph on the plate is of the wings of a male Physemacris variolosa (Linn.); text-figs. 1 and 2 show the venation with the Comstock-Needham notation, as developed by Snodgrass (1935) in his " Principles of Insect Morphology ", applied.

NOTES ON THE WINGS.

If, keeping in mind the wings of a familiar acridiid such as Locusta migratoria Linn., one examines the wings of Physemacris, a number of points become evident (see Smart, 1953).

* A recent revision of the Pneumoridae will be found in Rehn (1941), who recognized eleven species distributed amongst four genera.

The generic name Physemacris was proposed by Roberts (1941) for reasons explained in that paper. BuZZa Linn. is the name of a genus of gastropod molluscs ; see Hemming (1950) for decision by the International Commission of Zoological Nomenclature to place BuZZu (Gasteropoda, Mollusca) on Official List, of Generic Names.

200 JOHN SMART

Figures 1-2.

Physemacris variolosa (Linn.),

1. Fore-wing x 2-8 (appx.). 2. Hind-wing x 2.8 (appx.).

Fore- and hind-wings. (a) General texture rather alike (primitive). (b) Venation of both from Sc to Pcu very similar (primitive), but this

venation showing a tendency towards the acridiid pattern in that stem of M close to (but not yet fused with) stem of R ; R branching into simple R, and postero-pectinate Rs ; M is 2-branched*, and these branches are simple ; Cu is 8-branched, and these branches are simple; primary forks of R, M and Cu in same relative positions in fore- and hind-wing fields as in Acridiidae.

(c) R and its branches occupy a relatively large area (primitive). (a) Primary fork of Cu still in wing-field (primitive), very near but not yet

Tendency for Cu,,and Cu, to diverge and then incorporated in wing-base. converge towards wing-margin.

( e ) Pcu almost straight. Cu, weaker than Cu,.

(f) Cross-veins (primitive) ; poor formation of intercalary veins, proximally not reaching the forks of the main those formed

veins (primitive). * I n some wings examined the anterior branch of M has become detached from M

and attached to R. Zeuner (1942) suggests that M '' often lends one or two branches to R (not to Rs !), a feature unknown in other Acridodea". This statement appears to rely on a presumption that the furcation of R into R, and Rs must take place proximal to the place a t which any branches spring from Rs. I consider that R, is to be regarded as having migrated distally along the stem'of Rs, thus bringing the apparent furcation of R, and Rs distal to the most proximal of the postero-pectinate branches of Rs. M can then be regarded as being in a comparatively primitive condition, with two simple branches and not, as Zwner mggests, as " a specialised vein ".

WING-VENATION OF PHYSEMACklS VARTOLOSA 20 1

Fore-wing only. (a ) Relatively wide area between C and Sc and well-developed pre-costal

area both with irregular system of cross-veins, though some give appearance of small antero-pectinate branches of C and Sc (primitive).

(6) Cu, a distinct longitudinal vein (trachea seen in specimen) (primitive) but beginning to weaken, approach, and become associated with PCU.

Hind-wing only. (a) Vannus about same area as remigium, with relatively small number of

vannal veins (primitive). ( b ) Trachea present (seen in specimen) in Cu, (primitive) but vein itself

weakening. (c) Tips of posterior branch of M and Pcu tending to converge towards

wing-margin and " prevent ') either Cu, or Cu, from reaching the wing-margin. (d) Concave intercalary veins between convex vannal veins irregular

and incomplete, not reaching the wing-base (primitive). (e) 1V and 2V joining a t fork towards wing-base and not as widely separated

from each other as remaining vannal veins ; 2V concave towards base. The most interesting feature is the condition of Cu, with its strong anterior

branch Cu, and its rather weaker posterior branch Cu2, in both fore- and hind-wings, and especially the fa.ct that the latter vein has a trachea in it. I n an acridiid such as Locusta, Cu, in the fore-wing is extremely weak, and no homologous trachea exists in the nymphal wing-pad, while in the hind-wing it is a very weak though distinct vein, without a full-length homologous trachea in the nymphal wing-pad (see Smart, 1953) It is worth also noting that 1V and 2V in the hind-wing are separate from the remaining veins of the vannal series, that they join together towards the base, that they have a slight but very incomplete intercalary vein between them, and that, while both are convex veins for the greater part of their length, 2V becomes concave just before it joins 1V towards the wing-base. In the hind-wing of Locusta 1V and 2V run almost parallel with each other, separated only by a single row of cells formed by a series of simple cross-veins, and 2V is concave throughout its

In the Pneumoridae the females ar 4 all apterous or brachypterous. The length (see Smart, 1953).

wing-venations of the males of other genera and species are all very similar to that of Physemacris variobsa. In a solitary specimen appearing over the name Bullacris consorbina (Peringuey) in the British Museum (Natural History) the stem of Cu was rather longer than in any of the other species.

The material examined in detail consisted of five males of Physemacris variolosa Linn. (some incomplete) in the Insect Room of the Museum of Zoology of the University of Cambridge. Specimens belonging to this and other genera of Pneumoridae were seen in the Department of Entomology, British Museum (Natural History) by the courtesy of Mr. R. B. Benson.

AURNOWLEDCMENTS. I am indebted to Mr. D. K. McE. Kevan for helpful discussion. Figures 1 and 2

were drawn by my assistant,, Miss M. E. Haslop, from photographs and specimens.

SUMMARY. The wing-venation is described and discussed.

WmG-VENA!CIO'N OF PHYSEMACRIS VARIOLOS i" 202

REFERENCES. CHOPARD, L. (1949). Ordre des Orthopttzes, in Grass6 : Trait4 de Zoologie 9, 617-722.

Paris : Masson. HEMMING, F. (editor) (1950). " Bulla " Linnaeus, 1758 (Class Gastropoda) : designation

of type species of, under the plenary powers. KIRBY, W. F. (1910). A synonymic catalogue of Orthoptera 3, 62-65. London:

Brit. Mus. (Nat. Hist.). REHN, J. A. G. (1941). On new and previously-known species of Pneumoridae (Orthoptera,

Acridoidea). ROBERTS, H. R. (1941). Nomenclature in the Orthoptera concerning genotype designations.

Trans. Amer. ent. Soe. 67, 1-34. SMART, J. (1963). On the wing venation of the migratory locust Locusta migratoria Linn.

(Insecta : Acridiidae). Proc. zool. SOC. Lond. 123, 207. ZEUNER, B. E. (1942). The Locustopsidae and the phylogeny of the Acridoidea (Ortho-

ptera). Proc. R. ent. 8oc. (B) 11 ( l ) , 1-18.

Bull. 2001. Nomen. 4, 305.

Trans. Amer. ent. Soc. 67, 137-159.

EXPLANATION OF THE PLATE.

Fore- and hind-wings of Physemacris variolosa (Linn.). The dark patches in the middIe of cells in fore-wing are not pigment spots but opaque patches that appeared in the membrane in the course of preparation and mounting in Canada Balsam. x 3-7 (appx.).