Maratus nimbus, Otto & Hill, 2017

Otto, Jürgen C. & Hill, David E., 2017, Two new peacock spiders from southeastern Australia (Araneae: Salticidae: Euophryini: Maratus Karsch 1878), Peckhamia 153 (1), pp. 1-34 : 2-16

Maratus nimbus , new species

Type specimens. The holotype male (♂ #1) and one paratype male (♂ #2), were collected on sedges in a garden near an artificial body of water at Moama, New South Wales (36.075846°S, 144.722619°E, 23 APR 2015, coll. J. Otto). Two paratype males (♂ #3-4) and one paratype female (♀ #1) were collected in a garden near Tatiara Creek at Bordertown , South Australia (36.317417°S, 140.772611°E, coll. A. Lance), ♂ #3 on 20 DEC 2014, and ♂ #4 and ♀ #1 on 8 FEB 2015 . All types will be deposited in the Australian Museum, Sydney. We also identified four males, from Sturt National Park, New South Wales (KS85477, estimated location 29.13°S, 141.50°E, 29 SEP 1997, coll. M. Gillings, pitfall trap; KS79525, 29.282222°S, 142.155278°E, 25 SEP 1997, coll. M. Streulens, pitfall trap) and Coleambally irrigation area (KS109818 and KS109865, 34.873889°S, 145.942778°E, 2-16 MAY 2004, coll. L. Wilkie and M. Elliot, pitfall trap), in the collection of the Australian Museum, Sydney .

Etymology. The species group name ( nimbus, Latin , m., noun in apposition, English translation cloud) is a reference to the image on the male fan that looks much like a group of clouds across the sky at dusk.

Diagnosis. The apex of the embolus of the male pedipalp of M. nimbus ( Figure 9 ) supports placement in the Maratus spicatus group ( Otto & Hill 2017a). As in M. spicatus Otto & Hill 2012 ( Otto & Hill 2012b, 2012c) legs III are not ornamented and resemble the other legs in colouration. Both species have banded legs and pedipalps, and long bristles fringing the fan with no lateral flaps. However a distinctive pastel picture of "cirrus clouds in the sky at dusk" drawn on the front of a wider fan (dorsal opisthosoma) and the larger number of bristles in the surrounding fringe distinguishes the male M. nimbus (Figure 2).

Description of male (Figures 2-9). Males are 2.9-3.1 mm in length (n=8).

The clypeus and chelicerae are dark brown to black and mostly glabrous, with a thin covering of scattered setae ( Figure 4 :11). The eye region is covered with uniform brown setae, and a band of off-white setae runs beneath the PME and PLE, extending on either side half-way to the rear of the carapace behind the eye region. Unless worn, a middorsal tract of off-white scales also extends to the rear behind the eye region. The sides of the carapace are black with a thin covering of off-white setae, and there is a thin white marginal band of white or off-white setae on either side. The PME are closer to the PLE than to the ALE.

The opisthosoma is rounded and surrounded by a prominent fringe of mostly black bristles (stout setae) that are extended when the fan is elevated and flattened during courtship display. There are no lateral flaps. To the front a tuft of stout white setae extends over the pedicel toward the carapace. The pattern of scales on the dorsal opisthosomal plate (fan) is distinctive, with off-white to light orange patches of pigmented scales that resemble cirrus clouds on a background of light-blue iridescent scales (Figures 2:6, 5:9, 7:5). Below, the opisthosoma is brown, covered with white to off-white setae, surrounded by wide black margins. The coxae, trochanters, and sternum are brown with scattered white setae. The labium and endites are brown and glabrous.

All legs and the pedipalps are brown with scattered setae below, and brown interrupted by prominent segmental bands of off-white setae above. Legs I and II are shorter, legs III and IV longer, and legs III the longest. The pedipalps (Figures 8:5-6, 9) have a relatively large, circular embolus. The apex of the embolus is pointed, with dark inner and outer margins converging at the tip. From above, each cymbium is banded, covered with long off-white setae proximally, and dark brown distally.

Description of female ( Figures 10-11 ). The paratype female (♀ #1) is 4.0 mm in length. The lower clypeus and chelicerae are mostly glabrous, light brown and translucent. White setae below the anterior eye row extend to the level of the chelicerae at the midline, and a few smaller, scattered white setae are also present on the anterior face of each paturon. Two larger, off-white spines project upwards at the midline between the AME. The eye region is covered with mixed off-white and light brown scales and many small black or dark brown projecting setae. The sides of the carapace are covered with longer off-white setae. There are only a few off-white setae along each lateral margin, but above this margin there is a regular row of short off-white setae oriented vertically. Each dark lateral margin is accompanied by a second line of dark pigment just below it, associated with the coxae. A dark band of exposed cuticle extends toward the rear of each PLE, bordering a middorsal tract of off-white setae. The PME are closer to the PLE than to the ALE.

The dorsal opisthosoma has a symmetrical pattern of dark brown areas with indistinct chevrons toward the midline, on an off-white background. Less distinct dark markings, including a pair of lateral lines, are visible on the venter ( Figure 10 :12). Above and below the opisthosoma is uniformly covered with short, off-white setae. Pedipalps and legs are fairly uniform in colour with a cover of off-white setae, banded with a dark ring of pigment around each joint. Legs I and II are shorter, legs III and IV longer, and legs III are the longest.

The epigynum ( Figure 11 :5) has a large pair of fossae and an even larger pair of posterior spermathecae typical of Maratus . In the single specimen that was examined heavily sclerotized ducts extend from each spermatheca to the posterior third of the corresponding fossa.

Immatures. Immature Maratus nimbus resemble the adult females, but have a darker and more distinct band on either side of the dorsal opisthosoma ( Figure 12 ).

Courtship display ( Figures 13-16 ). When facing a female, the male Maratus nimbus may wave the elevated and expanded fan almost continuously through an amplitude of ~20° at a rate of 2-5 cycles/s, with frequent and assymetrical raising and lowering of the pedipalps. This display may not include movement of legs III ( Figure 15 ), or it may include almost continuous and mostly symmetrical waving of the extended legs III at a rate of ~2/s ( Figure 16 ).

of the female before mounting. 10, Detail of elevated and expanded fan.

Mating. Mating positions of a male and female Maratus nimbus are shown in Figure 17 . Habitat ( Figure 18 ). At Moama (New South Wales) Maratus nimbus was found on planted sedges in the garden of a residential area near an artificial body of water. At Bordertown (South Australia) M. nimbus hunt on densely tangled dry vegetation and are thought to use the base of these plants or broken earth on the ground for shelter (A. Lance, pers. comm.). Sturt National Park lies in the arid interior of New South Wales and represents a very different habitat from the well-watered gardens of Bordertown and Moama.

Figures

Figure 4. Two male Maratus nimbus. 3, 6, 10, Elevation and expansion of fan during courtship display.

Figure 9. Medial to lateral views of the left pedipalp of four male Maratus nimbus in alcohol.

Figure 10. Paratype female Maratus nimbus (♀ #1) from Bordertown, South Australia. 11, Note the pair of spines between the AME. These are present in many Maratus species. 12, Ventral view of opisthosoma.

Figure 11. Paratype female Maratus nimbus (♀ #1) in alcohol. 5, Ventral view of epigynum.

Figure 12. Emergent or second instar (1-2) and older (3-6) juvenile Maratus nimbus.

Figure 13. Courtship display by two male Maratus nimbus.

Figure 14. Courtship display by two male Maratus nimbus. 4, 6, This male raised legs I to touch the dorsal carapace

Figure 15. Sequential video frames (25 FPS) showing display by a male Maratus nimbus without extension of legs III. Arrows indicate rotation of the fan (~3.5 cycles/s) or movement of the pedipalps relative to each preceding frame. Elevation of the fan axis (yellow line) is shown in degrees at the upper right corner of each frame.

Figure 16 (continued on next page). Sequential video frames (25 FPS) showing display by a male Maratus nimbus accompanied by extension and waving of legs III. Arrows indicate rotation of the fan (2-5 cycles/s), movement of legs III (~2 cycles/s), or movement of the pedipalps relative to each preceding frame. Elevation of the fan axis (yellow line) is shown in degrees at the upper right corner of each frame.

Figure 17. Mating male and female Maratus nimbus. This male was from Moama and the female from Bordertown.

Figure 18. Habitat of Maratus nimbus. 1, At Moama M. nimbus was found on dried blades at the base of sedges near an artificial body of water. 2-3, At Bordertown M. nimbus was found in a tangle of dry vegetation at the base of irises in this garden. They were also found in the dry creekbed of nearby Tatiara Creek (courtesy Alan Lance). 4, Habitat of M. nimbus in the Coleambally irrigation area, New South Wales.