OCR Text |
Show 1880.] PROF. WESTWOOD ON THE GENUS PER 'A. 361 tion of the cross veinlet at its extremity, which is sometimes quite straight, in others much curved ; in one species it is sharply angulated in the middle (P. walkeri); and in another species (P. schiodtei) the female has occasionally a small supplemental spur, extending from the middle of this angulated cross veinlet. The closed cells vary in their extent, sometimes scarcely extending beyond the stigma and sometimes reaching nearly to the hind margin of the wings. The legs are generally rather short, especially in the males, in which sex they are thickened. The tarsi vary considerably in length, being generally shorter than the tibiae ; but in the females of P. lewisii, as well as in other species, the tarsi are more elongated, with the joints flattened and the cushion on the underside more developed. Dr. Leach divided the genus into as many sections as the species with which he was acquainted, employing the antenna? and wing-cells as characteristic of his groups, which were as follows : - A. Alis anticis anteareolam marginalem non proniinenti-bus (antennis articulo tertio duobus sequentibus longiore). a. Areolis submarginalibus duabus primis confluen-tibus, ultima ad basin superne subacuminata; areola marginali elongata, antice et postice acuminata Sp. 1. P. polita. b. Areolis submarginalibus perfectis, ultima basi ar-cuato- emarginata; areola marginali elongata, antice et postice acuminata Sp. 2. P. bicolor. c. Areolis submarginalibus perfectis, ultima basi recta; areola marginali ovata Sp. 3. P. latreillii. B. Alas anticas ante areolam marginalem prominens (areola submarginali ultima basi superne acuminata). a. Areola marginali ovata; antennis articulo tertio duobus sequentibus longiore Sp. 4. P. dorsalis. b. Areola marginali elongata angusta utrinque (postice prresertim) acuminata ; antennis articulis tertia et quarto subtequalibus, tertio longiore, articulo quinto precedente breviore Sp. 5. P. kirbii. c. Areola marginali fere lineari, antice obtusa postice acutiuscula, antennis articulis tertio, quarto, et quinto fere asqualibus Sp. 6. P. ferruginea. I have not thought it necessary to carry out this principle of subdivision into the numerous species now known of the genus, which would have required a formidable tabulation of the specific distinctions of the insects with their sectional characters. Neither have I thought it necessary to adopt the subgenus Pseudoperga, proposed by M . Guerin-Meneviile (in the text of the ' Iconographie du Regne Animal, Ins.,' p. 395) for P. lewisii on account of the first and second submarginal cells being confluent by the almost obsolete condition of the transverse veinlet separating them in the ordinary species. Details of the natural history of two of the species, P. dorsalis and P. lewisii, have been recorded, condensed abstracts of which will |