Megadrymus brigalow, Cassis, Gerasimos & Symonds, Celia L., 2014

Cassis, Gerasimos & Symonds, Celia L., 2014, Megadrymus brigalow n. sp. (Insecta: Hemiptera: Heteroptera: Rhyparochromidae: Drymini), a diminutive new species of seed bug from semi-evergreen vine thicket of the Queensland Brigalow Belt, Zootaxa 3774 (6), pp. 596-600 : 597-599

Megadrymus brigalow n. sp.

( Figs 1 & 2 )

Holotype: ♀, AUSTRALIA: Queensland: 3 km S of Pine Mt, 21.77133°S 148.8393°E, 230 m, 24 Mar 2000, G. Monteith, ex. Malaise trap in vine scrub ( AMNH _PBI 00399811) (QM).

Diagnosis. Megadrymus brigalow n. sp. is distinguished by the following characters: very small size, <3.5 mm, ovate, robust body, general colour reddish brown, entire forefemora and apical three quarters of meso- and metafemora orange-brown, remainder of legs pale cream brown; corium with distinct patches of light cream and darker reddish brown; inner corium without distinct distal pale spot, only diffusely pale; posterior pronotal lobe pale overall; transparent (colourless) wing membrane; sparse distribution of very short simple setae on abdominal venter, denser laterally; middle of posterior pronotal lobe with v-shaped depression; tricarinate keel of pronotum removed from anterior margin of scutellum, scutellum strongly inclined anteriorly, keel without thickened anterior arms; prosternum slightly elevated but without longitudinal ridge between forecoxae; posterior lobe of metapleuron punctate; forefemur weakly incrassate, only with anteroventral row of spines, hind tarsi with 1st tarsomere less than twice 2nd and 3rd together.

Description. Female. COLOURATION. Head: dark reddish brown; labium cream, labial segment orangish. Antennae: orange-brown. Pronotum: explanate pronotal margins cream; anterior pronotal lobe uniformly redbrown; posterior pronotal lobe cream, with prominent red-brown v-shaped marking medially from anterior margin and two diffuse semi-circular orangey patches from posterior margin, punctations red-brown, posterolateral corners orange-brown. Scutellum: mostly red-brown, anterolateral corners slightly darker, lighter cream markings along posterolateral margins adjacent to clavus. Hemelytra: punctations red-brown; clavus orange-brown, cream dash posteriorly; corium banded, orange-brown basally, red-brown medially and apically, cream brown in between; inner third of corium without distal cream spot, just diffusely lightened; embolium cream basally, orangey distally; membrane transparent, no colour. Thoracic pleura and sterna: red-brown; posterior margins of pro- and metapleuron and supracoxal lobes slightly lighter orange-brown; scent gland evaporative area and peritreme dark brown. Legs: trochanters yellowish; coxae orange-brown; forefemur entirely orange-brown; mid and metafemora yellowish at base, apical three quarters orange-brown; tibiae and tarsi yellowish. Abdomen: red-brown. SURFACE AND VESTITURE. Punctation present over entire inner third of corium and most of outer third of corium, outer third with three rows of punctuations; antennal segments with moderate distribution of semi-erect setae, apical half of AIII+AIV also with short adpressed simple setae; abdominal venter with sparse distribution of short simple setae, denser laterally.

STRUCTURE. Very small size, body length 3.37 mm; body shape ovate, robust. Head: length 0. 36 mm; width 0.75 mm; without bent or stepped gula; clypeus prominently elevated above mandibular plate; interoccular distance 0.47 mm. Pronotum: anterior pronotal lobe 0.47 mm long, 1.07 mm wide; posterior pronotal 0.40 mm long, 1.38 mm wide; anterior pronotal lobe a half longer than posterior pronotal lobe; latter 0.47 mm; anterior pronotal lobe moderately elevated; posterior pronotal lobe with medial depression from anterior margin. Scutellum: length 0.77 mm; tricarinate keel over posterior two thirds of scutellum, strongly elevated, anterior arms not thickened. Hemelytra: macropterous. Thoracic pleura and sterna: prosternum elevated medially; posterior section of metapleuron with row of punctations along posterior margin and on lateral margin. Forefemora: weakly incrassate; with one row of spines on ventral surface; anteroventral row of spines straight, major spine small, much shorter than width of tibia, directed straight; anteroventral margin not apically excavated/concave between major spine and apex; posteroventral swollen spine absent. Hind tarsi: 1st tarsomere less than twice length of 2nd and 3rd tarsomeres combined.

Remarks. We did not place this new species in Megadrymus ( Cassis & Symonds 2012) based on its lack of a stepped gula; transparent wing membrane; scutellar keel being more weakly defined, without thickened anterior arms; presence of a v-shaped impression medially on the posterior pronotal lobe; forefemora with only one (anteroventral) row of spines and only very weakly incrassate; contrasting colouration on corium with very distinct patches of light and dark (whereas in other Megadrymus spp. edges between light and dark patches are more diffuse); lack of distinct and relatively large pale spot distally on inner corium; posterior pronotal lobe pale overall; clypeus prominently elevated above mandibular plate; hind tarsi with 1st tarsomere less than twice 2nd and 3rd together. As a consequence M. brigalow n. sp. was placed sister to the clade of Paradrymus exilirostris Gross + Megadrymus , in our phylogenetic analysis ( Cassis & Symonds 2012, see Figure 1 ).

However, on re-examination of the specimen and more extensive study of Australian Drymini in collections, we have determined this species to be a member of Megadrymus . We have observed that within other Drymini , that with very small species many characters seem to be reduced in expression or absent compared to other seemingly congeneric morphospecies (i.e. shape of the head, pronotum and scutellum and structure of the forefemora), as seen also in Megadrymus brigalow n. sp.

Megadrymus brigalow n. sp. is the smallest species in the genus and most atypical with respect to the pronotal and scutellar colouration and structure, and colouration of corium as described. In particular, colouration of the tricarinate keel of the scutellum is for the most part the same as the ground colour of the scutellum, as opposed to most other species of Megadrymus where the keel colouration is contrasting, being lighter in colouration.

Megadrymus tenuicornis (Gross) is also very small (Female = 3.76 mm) and also more pale in colour but can be differentiated most easily by the shape of the pronotum and scutellum structure.

Megadrymus brigalow n. sp. is similar to M. kakadu Cassis and Symonds , but differs by being smaller, and by having a more ovate and robust body shape (rather than the more slender shape of M. kakadu ), and again the pronotal and scutellar structure. Setae on the abdominal venter of M. brigalow n. sp. are slightly shorter than in M. kakadu but with same distribution. In addition, M. brigalow n. sp. has the forefemora only weakly incrassate and without any outer swelling or spine, which we refer to as the posteroventral basal tumescence (see Figure 7, Cassis and Symonds 2012).

Distribution. Megadrymus brigalow n. sp. is known from a single locality on the Great Dividing Range, southwest of Mackay on the mid coast of Queensland (See Figure 2 ). The specimen was collected from semievergreen vine thicket, a scattered dry rainforest habitat found in the Brigalow Belt (North and South) and Nandewar IBRA Bioregions (mapped in Figure 2 ), and nationally listed as an endangered ecological community, mainly due to loss and fragmentation from clearing and degradation of remnants (Department of the Environment 2013). Pine Mountain is located within the Brigalow Belt North IBRA Bioregion.

Etymology. After the biogeographic region of the type locality. Noun in apposition.

Figures

FIGURE 1. Habitus photo of Megadrymus brigalow n. sp., holotype specimen, female. Scale = 1 mm.

FIGURE 2. Distribution map showing locality of Megadrymus brigalow n. sp. and the boundaries of the Brigalow Belt (North and South) and Nandewar IBRA Bioregions, where the endangered semi-evergreen vine thicket habitat occurs.