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Taxonomy.
The New Zealand Orsillini are so peculiar that no relatives of the endemic genera are known from elsewhere. Nysius huttoni Buchanan-White, however, is allied to the Hawaiian blackburni Buchanan-White and to Nysius baeckstroemi Bergroth from Juan Fernandez. The new genus, Brachynysius, is apparently a remarkable off-shoot from typical Nysius. Stäl originally separated Rhypodes as a subgenus because of the sublateral lobes on the posterior margin of the pronotum. It now appears doubtful if this character is even of specific value, but I have retained the generic name for its type, clavicornis (Fabr.), which is obviously of a different stock from typical Nysius. The other species described below, e.g., myersi, stewartensis, chinai, and sericatus, differ so considerably from the genotype that, according to standards elsewhere in the world, each should perhaps be made the type of a new genus. However, I have chosen to lump these together with zealandicus into a single, possibly unnatural genus, until further material is at hand and more extensive field work has been done.
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| 1. Hemelytra reduced to short pads which reach only a short distance on to base of abdomen, nearly as broad apically as long, 13: : 15, the corium definitely delimited, subtriangular, with veins distinct; membrane very short, one-tenth as long as hemelytra. Antero-lateral angles of pronotum produced laterally as small tubercles. | Hudsona anceps (Buch.-White) | |
| Hemelytra larger, usually exceeding tip of abdomen. Pronotum without minute antero-lateral tubercles | 2 | |
| 2. Hemelytra distinctly convex, costal margins strongly rounded beyond basal fourth. Membrane small, exceeding level of apices of coria by less than one-fourth the total length of membrane, without apparent veins | Brachynysius convexus n.gen. and sp. | |
| Hemelytra subflattened, the costal margins not strongly rounded. Membrane much larger, extending beyond level of apices of coria for a distance almost half the total length of membrane, veins distinct | 3 |
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| 3. Bucculae decreasing only slightly in height posteriorly, reaching to base of head. Size small, less than 4 mm. | Nysius huttoni Buch.-White | |
| Bucculae decreasing in height at level of antenniferous tubercles, not reaching base of head. Size larger, over 5 mm. | Genus Rhypodes | 4 |
| 4. Ground colour ferrugineous with black markings. Head and pronotum very coarsely punctured, the punctures of pronotal disk less than one puncture width apart. Hind margin of pronotum more or less distinctly produced sublaterally into rounded or subtriangular plate-like lobes | Rhypodes clavicornis (Fabr.) | |
| Ground colour pale, ochraceous, marked with fuscous or black. Head and pronotum less coarsely punctate, the punctures either shallow or separated by more than one puncture width. Hind margin of pronotum without sublateral lobes | 5 | |
| 5. Last two antennal segments subequal in length. Sides of pronotum straight | Rhypodes sericatus n.sp. | |
| Fourth antennal segment distinctly longer than third. Sides of pronotum swollen at level of callosities | 6 | |
| 6. Antennae short and thick, the second segment about four-fifths as thick at middle as front tibiae basally. Body subflattened above, the head and pronotum only feebly declivous. Clavus and corium in great part pale, ochraceous | Rhypodes myersi n.sp. | |
| Antennae more slender, the second segment scarcely more than half as thick at middle as front tibiae basally. Body not noticeably flattened above, the head and pronotum more strongly declivous. Clavus and corium extensively marked with brown | 7 | |
| 7. Body nearly three times as long as broad. Head and pronotum moderately declivous. Female genital cleft deep, the fourth and fifth visible ventral segments concealed beneath third at middle | Rhypodes chinai n.sp. | |
| Body shorter and very robust, about two and one-half times as long as broad. Head and pronotum strongly declivous. Female genital cleft shallow, both fourth and fifth ventral segments exposed at middle | Rhypodes stewartensis n.sp. |
Hudsona anceps (Buchanan-White).
Nysius anceps Buch.-White, Ent. Month. Mag., 15: 32–33, 1878.
Hudsona anceps, Evans, Bull. Ent. Res., 19: 353, 1929.
One male is at hand from the British Museum, Otago, New Zealand, Pascoe Coll., determined by Buchanan-White. Five other specimens are from the collection of H. G. Barber as follows: one male, Darfield, New Zealand, August 15, 1923, J. G. Myers; two females, Taitapu, September 2, 1921, J. W. C.; one female, Governor's' Bay, New Zealand, November 8, 1922, on grass, J. G. Myers; and one female, Methven, November, 1911. The series is remarkably uniform in size and coloration except for the usual sex differences.