Parahyadina bulla, sp. nov.

(Figs. 18, 23–26, Map 5)

Diagnosis. This species is distinguished from congeners by the following combination of characters: Adults. Small to moderately small shore flies, body length 1.75–2.40 mm.

Head (Fig. 18): Lateroclinate fronto-orbital seta well developed, basal diameter comparable or only slightly reduced in comparison to basal diameters of vertical setae.

Thorax (Fig. 18): 2 pairs of posterior dorsocentral setae. Wing hyaline; costal section II greater in length than costal section III; costal vein ratio 0.83–0.85; M vein ratio 0.30–0.32.

Abdomen: Tergites 3–5 with ventrolateral margin shallowly round; male tergite 5 extended posteriorly in same plane as tergite 4. Male terminalia (Figs. 23–26): Epandrium in posterior view (Fig. 23) as inverted, regular U, surstylar arms oriented ventrally, widest a ventral level of cerci, in lateral view (Fig. 24) with dorsal, epandrium linear, narrow, more or less parallel sided, widest at level of fusion with surstyli; surstylar length (from fusion bulge ventrad) subequal to height of cercus, oriented in same plane as epandrial portion, in lateral view (Fig. 24) with slight basal swelling (at fusion with epandrium), thereafter ventrally tapered to narrowly rounded, shallowly recurved apex, posterior margin very shallowly obtusely angled, apex bearing a single, short, curved setula, also bearing 2 larger setulae along anterior margin at midheight, length of setulae twice that of apical setula; cercus in posterior view (Fig. 23) irregularly obovate, generally covered with small setulae, in lateral view (Fig. 24) height greater than twice width with anterior margin somewhat straight, posterior margin almost regularly arched; aedeagus in lateral view (Fig. 26) slipper-like with toe toward base, base shallowly bifurcate with slightly asymmetric, short arms, in ventral view (Fig. 25) with basal margin deeply arched, wide, apical margin with short, wide medial projection, apex truncate; phallapodeme in lateral view (Fig. 26) irregularly triangular, with moderately broad, elongate keel with a broadly rounded apical margin, extension toward aedeagal base digitiform, elongate, hypandrial extension broader and shorter than extension toward aedeagal base, in ventral view (Fig. 25) very as a cross, with base shallowly bifurcate, cross piece at midlength, thereafter toward apex tapered to narrowly rounded apex; gonite and hypandrium broadly fused, in lateral view (Fig. 26) with hypandrial portion longer than gonal portion, with shallow step at midlength, gonal portion short, tapered to point apically, in ventral view (Fig. 25) tubular with lateral extension at 90° angle and with paired apical, digitiform extensions medially that bear 2 apical tubercles.

Type Specimen. The holotype male of Parahyadina bulla is labeled “ NEW ZEALAND. Tennants Lake (43°49.4’S, 176°34’W), 14 Oct 2002, D. and W. N. Mathis/ USNM ENT 00184462 [plastic bar code label]/HO- LOTYPE ♂ Parahyadina bulla Mathis & Zatwarnicki NZAC [red].” The holotype is double mounted (minuten in a plastic block), is in excellent condition, and is deposited in the NZAC. Thirty-two paratypes bear the same label data as the holotype (18♂, 14♀; USNM). Other paratypes are as follows: Chatham Islands. Chatham Island: Cape Young (43°41.7’S, 176°37.5’W; on Cotula coronopifolia L.), 16 Jan 1976, R. P. MacFarlane (1♂; NZAC) ; Kiringe Creek (44°02.8’S, 176°38.3’W), 13 Oct 2002, D. and W. N. Mathis (1♀; USNM) ; Lake Te Roto (43°49.2’S, 176°34.8’W), 12 Feb 1967, J. S. Dugdale (2♂, 2♀; NZAC) ; Mangahu Forest (43°58.6’S, 176°30.2’W), 10 Feb 1967, J. S. Dugdale (1♂; NZAC) ; Ocean Mail Point (2.5 km W; beach on lagoon; 43°45’S, 176°27.6’W), 12 Oct 2002, D. and W. N. Mathis (2♀; USNM) ; Port Hutt (1 km NW; peat and bracken fern; 43°48.1’S, 176°43.3’W), 14 Oct 2002, D. and W. N. Mathis (13♂, 14♀; USNM) ; Rotoparaoa Lake (43°48.7’S, 176°35.3’W), 14 Oct 2002, D. and W. N. Mathis (2♂, 1♀; USNM) ; Tuku River (mouth; 44°03.9’S, 176°39.2’W), 13 Oct 2002, D. and W. N. Mathis (3♂, 3♀; USNM) ; Waitangi Creek (43°47.1’S, 176°48.3’W), 14 Oct 2002, D. and W. N. Mathis (1♂, 1♀; USNM) ; Waterfall Creek (44°03.5’S, 176°38.2’W), 13 Oct 2002, D. and W. N. Mathis (1♂; USNM) ; Wharekuri (field and beach; 43°42.4’S, 176°34.7’W), 12 Oct 2002, D. and W. N. Mathis (6♂, 5♀; USNM) . Pitt Island: Glory Bay (44°19’S, 176°12.1’W), 14 Jan 1990, J. W. Early (1♂, 2♀; LUNZ) .

Type locality. New Zealand. Chatham Islands. Chatham Island. Tennants Lake (43°49.4’S, 176°34’W) .

Distribution (Map 5). Australasian/Oceanian: New Zealand. Chatham Islands (Chatham Island, Pitt Island).

Etymology. The species epithet, bulla, is of Latin derivation and means knob, referring to the swollen, knoblike apex of the shallowly recurved gonite of this species.

Remarks. This species is apparently endemic to the Chatham Islands, occurring on both Chatham Island and Pitt Island. The dozen or so islets of the Chatham Islands were not sampled.

This species is very similar to P. lacustris, including many structures of the male terminalia, such as the surstylus. The gonites of this species, however, differ markedly, as seen by comparing Figs. 26 of this species with those of P. lacustris (Fig. 52). The anterior projections of the gonite are approximate, not widely separated, and the posterior structure is as a very broad and short U-shaped structure. The phallapodeme is T-shaped (Fig. 25) with the comparatively large cross piece located near the midlength and not toward the base. In addition, the surstylus in posterior view (Fig. 23) is sinuous with a slightly expanded, semispatulate apex.