Austrolestes minjerriba, Watson & Moulds, 1979

J. A. L. Watson & M. S. Moulds, 1979, New Species of Australian Lestidae (Odonata), Australian Journal of Entomology 18, pp. 143-155 : 147-149

Austrolestes minjerriba * Watson sp. n. (Figs 2, 9, 10, 15-18, 25-27)

Austrolestes sp. “ m” ; W atson, 1977: 277.

Types.— Holoiype ♂, Queensland: North Stradbroke Island, Brown Lake , 3.i.1976, J. A. L. Watson and A. H. Arthington ( ANIC Type No. 9876) (in ANIC). Paratypes: Queensland: two ♂♂, Fraser Island, Lake Minker , 21. xii. 1975, H. Burton ; two ♂♂, Moreton Island, swamp east of Blue Lagoon , 18.xii. 1975, A. H. Arthington ; seven ♂♂, North Stradbroke Island, perched swamp above Flinders Beach , 7.i.l976, J. A. L. Watson and A. H. Arthington ; two ♂♂, one ♀, North Stradbroke Island, Brown Lake, 3-5.i.l976, J. A. L. Watson and A. H. Arthington ; one ♀, same locality, 23.iii. 1966, D. P. Heenan ( UQ) ; one ♀, same locality, 9.iii. l974, D. Smith ( UQ) ; three ♂♂, one ♀, North Stradbroke Island, Dunwich , 3-4.iv. 1971, R. O. O ’Shea, B. Reville, R. Coles and A. Saul ( UQ) ; 10 ♂♂, two ♀♀, North Stradbroke Island, Tortoise Lagoon , 2.i. 1976, J. A. L. Watson and A. H. Arthington . New South Wales: one ♂, Lake Hiawatha, Wooli , 13.iii.1976, A. F. O’Farrell and P. Brookhouse .

Male

Colour pattern much as in Austrolestes psyche , light blue and black, sometimes partly obscured by whitish pruinescence in mature individuals, yellowish brown and blackish in tenerals.

Head.—Labium yellowish; labrum light blue, edged black; anteclypeus blue; postclypeus, frons, vertex and occiput black; blue spot below each lateral ocellus; antennae black; genae pale blue above, yellowish below; mandibles bluish; back o f head black.

Prothorax (Fig. 2).—Centre half of anterior lobe of pronotum and margin light blue, lateral comers and posterior central spot black; median lobe largely black, with variable,.triangular to squarish blue spot, commonly divided by black middorsal line, on posterior half, and variable blue stripe or spot on lower margin above epimeron, sometimes much reduced; posterior lobe black; upper quarter to third of pleura black, lower parts blue. Coxa and trochanter yellowish; outer surface o f femur black, basal part to all of inner surface yellowish; outer ridge of tibia yellowish brown, rest of tibia black; tarsi black.

Synthorax (Fig. 2).— Front black, with slight greenish sheen; bright blue antehumeral stripe extending from mesostigmatic lamina along approximately 80% of length of upper mesopleural suture, often narrowly crossing it at upper end (Fig. 2); anterior third o f mesokatepisternum and much of mesepimeron black; metapleura blue, yellowish below and behind, with narrow inverted triangular mark in upper third of upper metapleural suture, black subalar ridge, dark shadowing on anterior edge of katepisternum and black spot on either side of yellowish poststernum; sterna yellowish.

Anterior halves of outer surfaces of coxae blackish, posterior halves yellowish; trochanters yellow above, spotted black below; femora black on spinose inner surfaces, yellow outside; outer ridge of tibiae yellowish brown, rest of tibiae black; tarsi black.

Wing dimensions apparently varying with locality (Table); overall range of hind wing length 17.3-20.0 m m(N = 14), offore wing pterostigma 1.34-1.67 x 0.36-0.47 mm (N = 14); membrane hyaline, veins black; pterostigma dark brown.

* minjerriba , the Aboriginal name for North Stradbroke Island, where the species was first discovered; to be treated as an indeclinable noun.

Abdomen (Figs 9, 15-18).—Tergites black with green or bluish sheen, marked with light blue; tergite 1 black above, blue at side, with brown to black trapezium shaped mark extending approximately half of length of segment from upper acrotergite parallel to ventral carina; intersegmental membrane 1-2 light blue; tergite 2 blue with brownish to black rim to genital fossa and variable, dorsal black band narrowest in centre of segment, narrower but generally similar to corresponding mark in A. psyche (cf. Figs 7, 13, 15), often marked with small middorsal blue spot two-thirds of tergite length from base (Fig. 16), or partly or completely divided by blue, V-shaped band (Figs 17, 18); intersegmental membrane 2-3 black; tergites 3-7 with basal blue band occupying, in the midline, a fifth to an eighth of length of segment, relatively wider on tergites 6-7 than on preceding segments, sometimes divided by fine middorsal black line, and expanded along lower part of tergite, terminating in yellowish spot in front of apical black band; intersegmental membranes 7-10 blue; tergite 8 black with or without small, yellowish anterolateral spot; tergites 9-10 black; sternites dark brownish to almost black, darkest in posterior segments.

Anal appendages (Figs 25-27).— Superior appendages black above, inner subterminal surfaces brown; length variable, overall range 1.17-1.31 mm (N = 14) (Table); subapical tooth protuberant, its anterior margin sinuate viewed from above, the tip directed more backwards than transversely; ventrobasal knob almost a third of appendage length from base, 0.69-0.74 x appendage length from apex, 0.40-0.43 x appendage length from tip of subapical spine; inferior appendages pale brownish, variably darkened, their apices strongly concave.

Female

Dimensions apparently slightly larger than those of male; length o f hind wing averaging 19.53 mm (range 18.0- 21.1 mm); fore wing pterostigma averaging 1.653 mm (range 1.50-1.74 mm) x 0.463 mm (range 0.40-0.52 mm) (N = 6).

Head.—Colour pattern as in male, the pale markings duller, brownish; outer upper parts of scape and pedicel pale.

Prothorax. —Pronotum much as in male, the pale brownish to blue m arkings variable, generally more extensive; much of anterior lobe often pale; middorsal pale stripe on median lobe broadening towards posterior lobe, often extending across it, as does variably broad pale band on lateral margin, above epimeron, often leaving isolated black spot on each side of posterior lobe; pleura substantially pale, the epimeron darkened or slightly so above; legs as in male.

Synthorax pattern as in male; dorsal carina and outer part of antealar ridge pale; antehumeral stripe sometimes forked, narrowly extending onto katepistemum along lower part of mesopleural suture; legs as in male.

Abdomen (Fig. 10) shorter than in male, the pattern similar, the blue duller, intersegmental membranes 1-2,7-10 grey; dorsal m ark on tergite 2 similar to that of male illustrated in Fig. 15, lacking blue dorsal spot or V-shaped band.

Distribution and habitat

The distribution and habitat of A. minjerriba strikingly parallel those of the libellulid Orthetrum boumiera Watson and Arthington; both appear to be confined to dune lakes in south-eastern Queensland and north-eastern New South Wales ( Watson and Arthington 1978). O. boumiera has been recorded from Fraser, Moreton and North Stradbroke Islands, and from the Wooli Lakes, east of Grafton in New South Wales. A. minjerriba is also known from all these localities, and fragmentary material of an Austrolestes , collected from the Cooloola lakes system by J. N. Yates, almost certainly belongs to A. minjerriba . There are minor differences between the distributions of O. boumiera and A. minjerriba on North Stradbroke Island; A. minjerriba has been taken from a boggy, perched swamp at the northern end of the island, a swamp from which O. boumiera appears to be absent. On the other hand, neither has been found on any of the stream habitats on North Stradbroke, nor on Blue Lake (Lake Karboora), or any of the more open ponds such as those behind Flinders Beach, or the 18-Mile Swamp ( Watson and Arthington 1978, and unpublished report). The factors that restrict the two species to the dune-lakes are not understood ( Watson and Arthington 1978).