Mayriella occidua new species

(Figs 5-8)

Description: Holotype worker. CI 88; HL 0.50; HTL 0.27; HW 0.44; ML 0.50; PW 0.32; SI 61; SL 0.27. Sculpturing in posterior section of antennal scrobe well developed and distinct. Sculpturing on dorsal surface of mesosoma consisting of large, closely spaced pits. Propodeal spines short, triangular. Dorsal surface of petiole in lateral profile with distinct dorsal and posterior faces which are separated by an obtuse angle, dorsal face much longer than posterior face. Lateral margins of postpetiole in dorsal view essentially parallel. Dorsum of postpetiole and gaster lacking erect hairs (excluding row along posterior margin of gastral tergite).

Material examined: Holotype worker from Western Australia, Nuyts Wilderness (approx. 35°04'S 116°38'E), Walpole, December 2003 (P. F. Van Heurck) (ANIC, No. 32-009464).

Comments: Mayriella occidua can be separated from other Australian species of Mayriella by the presence of a cylindrical or slightly barrel-shaped postpetiole which lacks lateral expansions when viewed dorsally, the well developed and distinct sculpturing in the posterior sections of the antennal scrobes and in having the dorsum of the petiole with distinct dorsal and posterior faces which are separated by an obtuse angle. It is most similar to M. abstinens but can be separated from it by the shape of the petiolar node (the node lacks distinct dorsal and posterior faces in M. abstinens).

This is the only species of Mayriella known from Western Australia, and extends the range of this genus in Australia westward by nearly 2,000km. Morphologically this species is most similar to M. abstinens, a species found along the Queensland and New South Wales coasts (Shattuck and Barnett, 2007) and not M. ebbei, the species which occurs in the Adelaide region and is geographically closest to M. occidua. The only known specimen of this species was collected during a survey in an area with pines.

Key to Australian species of Mayriella (workers)

The following key, modified from Shattuck and Barnett (2007), can be used to identify the Australian species of Mayriella.

1. In dorsal view, anterior region of outer margin of postpetiole expanded laterally compared to posterior regions so its overall outline is trapezoidal ................................................................................................. 2

In dorsal view, outer margins of postpetiole approximately the same width anteriorly as posteriorly so its overall outline is cylindrical or slightly barrel-shaped ............................................................................... 3

2. Dorsum of postpetiole with more than four erect hairs and dorsum of gaster with numerous erect hairs; dorsum of petiole in lateral profile uniformly convex and without distinct, separate dorsal and posterior faces ..................................................................................................................................................... ebbei

Dorsum of postpetiole with at most four erect hairs and dorsum of gaster generally lacking erect hairs (rarely hairs present); dorsum of petiole in lateral profile angular and with distinct, separate dorsal and posterior faces ................................................................................................................................ spinosior

3. Sculpturing in posterior section of antennal scrobe at most weakly developed and always indistinct; sculpturing on dorsal mesosoma consisting of small, widely spaced pits (separated by greater than their diameter) .................................................................................................................................................. overbecki

Sculpturing in posterior section of antennal scrobe well developed and distinct; sculpturing on dorsal surface of mesosoma consisting of large, closely spaced pits (separated by less than their diameter) .......... 4

4. Dorsum of petiole in lateral profile strongly angular, the dorsal and posterior faces indistinguishable ....... ....................................................................................................................................................... abstinens

Dorsum of petiole in lateral profile with an obtuse angle, the dorsal and posterior faces separated by an angle ................................................................................................................................................... occidua