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Subfamily Aenictopechinae Usinger, 1932.
Genus Maoristolus gen. nov.
Rather small and slender Aenictopechinae with the head, abdomen and appendages shining. the thoracic segments and the fore wings dull; with a covering of fine hairs. Head less than half as broad across the eyes as long, with a distinct transverse dorsal impression behind the eyes; posterior lobe (excluding granular “neck”) wider than long and subequal to or only slightly wider than anterior lobe across eyes, not strongly globose, disc above nearly flat, only very slightly convex from front to rear, sides only slightly convex, narrowest in front. Eyes relatively small, separated beneath, and as seen from above not strongly prominent and each much less than half as wide as interocular space. Ocelli elevated, conspicuous, placed at anterior margin of posterior lobe near the transverse constriction. Antennae rather shorter than head and pronotum combined, with first segment shortest, the others subequal in length. Rostral segment III nearly three times as long as II, IV considerably longer than II. Pronotum unarmed, nearly flat; the anterior transverse impression well formed at the sides, though not excessively deep, rather weak in the middle; posterior transverse impression obsolescent in middle, not demarcating a definite third lobe; lateral margins as seen from above diverging from front to rear, slightly sinuate; anterior and posterior margins nearly straight; humeral angles cut away at sides to expose the hemelytral articulations. Scutellum scarcely raised, broadly exposed, subtriangular, with apex rounded and not carinate or lobed. Front wings with the claval suture and often the subcostal vein white, the former particularly conspicuous; costal margin towards middle with a distinct transverse fracture extending to subcosta; basal cell present; discal cell usually completely closed, sometimes with the subapical transverse vein incomplete anteriorly; discal and stigmal cells nowhere confluent, with a transverse connecting vein present between them (r-m of Jeannel (1942), m-cu of Usinger (1945)); stigmal cell divided by one or sometimes two transverse veins, and thus with one or sometimes two apical appendicular cells; main part of disc almost devoid of hairs, which are most numerous towards humeral angle; costal and apical margins with a fringe of rather long, pale brown hairs Legs: Fore legs moderately incrassate; front coxae oblong; front coxal cavities open behind (proepimera not meeting behind them); fore tibiae considerably but gradually expanded to apex, which bears a pecten on anterior (inner) margin and ventrally a group of eight long simple spines, without tubercles or plate-like processes. Middle and hind tibiae without pectines, with an apical ventral row of four long spines. All tarsi two-segmented, the first segment extremely short, longest ventrally; the second segment of front tarsi with two pairs of ventral spines, the more basal pair the longer, and with two subequal claws; the second segment of middle and hind tarsi with particularly long hairs but without spines, with two slender claws, the inner rather longer than the outer. Abdomen : Ninth tergum of female a dorsal pygidial
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plate, with an apical pair of especially long dorso-lateral hairs; anal lobe (tenth segment) short; no ovipositor; valvulae vestigial. Male with a pair of hairy claspers; without a ventral apophysis.
Type Species. Gamostolus tonnoiri Bergroth, 1927.
Notes on the Taxonomic Position of Maoristolus:
Usinger (1945: p. 326), after redescribing the genus Gamostolus Bergroth and the type species G. subantarcticus (Berg), from Tierra del Fuego, noted that he had been unable to examine a specimen of G. tonnoiri Bergroth, adding, however, that “Bergroth did not describe the venation of tonnoiri but it seems unlikely, on the bases of other characters, that the New Zealand species and the Fuegian species are congeneric”.
Maoristolus appears rather closely related to Gamostolus, but differs in certain diagnostic features. The apex of the fore tibiae bears long, relatively slender spines and lacks the plate-like expansions and the peg-like and hemispherical spines of Gamostolus. Other differences from the latter genus are the much smaller size, the relatively smaller and less prominent eyes, the differently proportioned antennal segments, the longer third and fourth rostral segments, the stigmal cell divided by one or two transverse veins, the more complete venation of the hind wings, the subequal claws of the front tarsi, and the vestigial valvulae of the female. Maoristolus is readily differentiated from Aenictopechys Breddin by a number of characters, including the much longer and transversely impressed head, the non-tuberculated and much less produced apex of the front tibiae, the presence of a basal cell and of a completely or incompletely closed discal cell on the fore wing, and in the absence of a ventral apophysis in the male. From Cocles Bergroth it differs conspicuously in the much smaller eyes, not occupying the greater part of the head.
Because of the presence of harpagones in the male, and the general affinities shown to Gamostolus, Maoristolus has been placed in the Aenictopechinae. This subfamily, which was established by Usinger in 1932 on the basis of the unlobed or imperfectly lobed pronotum, and included Aenictopechys Breddin, Gamostolus Bergroth and Cocles Bergroth, was shown by Jeannel (1942), from a study of the male genitalia of Aenictopechys necopinatus Breddin (unavailable to Usinger), to be a relatively primitive group. Unlike the Enicocephalinae, the male of the above species possesses undoubted claspers (harpagones), while the ventral apophysis of the pygophor is of a very different form and probably, as regards its unperforated structure only, more primitive. (Its hypertrophied and sucker-like form must, however, almost certainly be regarded as specialised (p. 402 and p. 410).) Wygodzinsky (1949), in his detailed redescription of Gamostolus subantarcticus (Berg), showed that this species not only has claspers in the male but also has a valved ovipositor in the female, likewise lacking in the Enicocephalinae. In the present paper similar genitalic structures are described for both sexes of Nymphocoris maoricus; the female of Aenictocoris powelli has the valvulae much reduced.
The nature of the female terminalia of Aenictopechys and of the terminalia of both sexes of Cocles is unfortunately unknown. The subfamily position of the latter genus thus remains uncertain. The extreme reduction of the valvulae in the female of Maoristolus appears somewhat anomalous, but the related Aenictocoris shows an intermediate condition, and it is not yet known to what extent this discrepancy between the sexes applies within the Aenictopechinae. The condition in Maoristolus and Aenictocoris is perhaps indicative of the way in which the simplified terminalia of the Enicocephalinae could have been derived. Reduction and loss of gonapophyses is more likely to occur first in the female, because of the direct relation between the form of the ovipositor and the egg-laying habits. Modification of the male genitalia, including reduction, is then likely to follow. The harpagones of Maoristolus are short and pad-like rather than clasper-like. This form and their concave inner margins suggest that they may be used to grasp the apex of the female abdomen between them. The male terminalia of Aenictocoris are yet unknown.
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As Usinger (1945) has intimated, the absence or imperfection of the transverse pronotal constrictions can no longer be considered diagnostic in separating the two subfamilies, which stand on the structure of the genitalia, especially of the male. The lobation of the pronotum is too liable to secondary reduction to have a certain and critical systematic value at the suprageneric level, and among undoubted Enicocephalinae there is considerable variation in the degree of distinctness of the constrictions. Notwithstanding this, it is of course possible that in the Aenictopechinae, since these are by other evidence closer to the ancestral Reduvioid stem, the unlobed or imperfectly lobed condition of the pronotum may be a primary one. However, it is difficult to avoid the impression that the peculiar form of the pronotum and the complete absence of the posterior impression in Nymphocoris have been arrived at by reduction associated with a long-established flightless condition.
Maoristolus tonnoiri (Bergroth) New comb. Figs. 11–18.
Gamostolus tonnoiri Bergroth, 1927, Trans. N.Z Inst., 57: 684 Myers and China, 1928, Ann. Mag. nat. Hist., (10) 1: 382 Usinger, 1945, Ann. ent. Soc. Amer., 38°: 326, 340 (considered tonnoiri unlikely to belong to Gamostolus)