Saratus hesperus, Otto & Hill, 2017

Otto, Jürgen C. & Hill, David E., 2017, Five new peacock spiders from eastern Australia (Araneae: Salticidae: Euophryini: Maratus Karsch 1878 and Saratus, new genus), Peckhamia 147 (1), pp. 1-86 : 70-84

Saratus hesperus , new species

Type specimens. The holotype male (♂ #1) was collected at Canberra, ACT (S35.22818°, E149.19309°, 22 OCT 2013, coll. S. Harris). Paratypes include one male (♂ #2) from Canberra , ACT (S35.22836°, E149.19315°, 21 OCT 2013, coll. S. Harris), two males (♂ #3-4) and one female (♀ #2) from the Namadgi National Park gate south of Canberra, ACT (S35.68806°, E149.08194°, 27 OCT 2013, coll. S. Harris), one female from Canberra, ACT (♀ #5) (S35.22675°, E149.19198°, 29 OCT 2013, coll. S. Harris, M. Girard), and one female (♀ #4) reared from eggs deposited by one of the other two females (♀ # 2 or ♀ #5). All types will be deposited in the Australian Museum, Sydney .

Etymology. Hesperus (noun in apposition, m.) is the Latin name for the planet Venus as the Morning Star, corresponding to the white to light yellow spot at the centre of the dorsal opisthosoma of this species.

Diagnosis. Saratus hesperus is the only known representative of the genus Saratus . Colouration of the adult male ( Figures 79-80 ) is distinctive, with a bright white or light yellow spot at the centre of a dark purple to dark blue or black background ( Figure 82 ), flanked on either side by a light blue margin of the dorsal opisthosoma (fan), in turn flanked on either side by a broad black band. The carapace is black, but the legs are all light yellow. The dorsal opisthosoma of the female is brown, with lateral marginal bands of lighter brown setae outlined with darker brown setae ( Figures 86-87 ).

Description of male ( Figures 79 -85). Males are 3.4-3.5 mm in length (n=4). The chelicerae, clypeus, and lower carapace, on the sides and to the rear, are black and glabrous. The carapace has no marginal band. The top of the carapace is also black, but bears a cover of scales along the anterior and lateral margins. A band of white scales extends from the top of the carapace behind each PLE to the front of the eye region, but the centre of the eye region is black and glabrous. Below this band there is a band of dull-red scales running below the posterior eyes on either side and through the lower part of the anterior eyes in front ( Figure 79 : 6). The PME are closer to the PLE than to the AME. The dorsal opisthosoma has a spot comprised of white to light yellow pigmented scales at the centre of a large, nearly rectangular dark purple to dark blue or black figure ( Figure 82 ). The margins are covered with light blue to blue-green iridescent scales. At the front is a wide band of white setae, truncated at each side of the dorsum. Below the dorsum there is a wide black band flanked by a wide white band on either side of the opisthosoma. The ventral opisthosoma has a cover of off-white setae flanked on either side by a black stripe ( Figure 81 ). The posterior lateral spinnerets are white and can be extended during display. The other spinnerets are black.

Viewed from below, the coxae of the legs are black and translucent, and the sternum, labium and endites are black. Distal to the coxae the legs are uniform light-yellow in colour, and somewhat translucent. Legs I and II are shorter and about the same length, legs III and IV are longer, and legs III are the longest. Except for the cymbium, which is dark brown, each pedipalp has a dorsal cover of long, bright white setae. The tegulum and RTA of the pedipalp resemble those of Maratus , but the embolus appears only as a short, curved spike above a small process of sclerotized cuticle (Figure 85).

Description of female ( Figures 86-90 ). Females are 3.4-4.5 mm in length (n=3). They resemble female Maratus species and when viewed from above they have a uniform brown colouration marked only by a lighter, off-white marginal band that circles the dorsal opisthosoma.

The pedipalps are mostly glabrous, light-brown, and translucent with scattered off-white setae. The chelicerae, clypeus, sides, and rear of the carapace are light brown, translucent and mostly glabrous. Longer off-white setae extend anteromedially below the front eyes. The thick lateral rims of the carapace are clearly visible and there are no marginal bands. The dorsal carapace including the eye region and the cuticle underlying the lateral eyes is dark with a relatively uniform cover of light-brown to brown or redbrown setae. This cover is dense in the eye region and sparse behind this. The PME are closer to the PLE than to the ALE.

The dorsal opisthosoma is covered with dense light to dark-brown scales or setae, flanked at the front and sides by a more-or-less distinct band of light brown scales or setae. The sides and underside of the opisthosoma are light brown with a covering of off-white scales or setae. The sides of the opisthosoma are mottled with dark brown spots, a feature that is more evident in specimens under alcohol. Below the opisthosoma is mottled with a pair of more-or-less distinct lateral lines, all dark brown ( Figure 88 ). The coxae, sternum, labium and endites are all light-brown and translucent. The legs are uniform in colouration, light-brown to brown and translucent with relatively few setae above and on the sides. Isolated black spots may be present under the proximal or distal ends of each femur. Legs I and II are shorter and about the same length, and legs III-IV are longer, also about the same length.

The epigynum of the Saratus hesperus female ( Figure 89 ) differs from Maratus in that the fossae (windows or fenestrae) are poorly defined and the large posterior spermathecae lie almost directly above these (below in the ventral view shown here). Heavily sclerotized ducts can be seen above the anteromedial corners of the spermathecae.

Immatures. Emergent (second instar) juveniles have a distinctive set of eight black spots on the dorsal opisthosoma ( Figure 91 : 1-6). As they mature, these spots gradually disappear or coalesce ( Figure 91 : 7- 18). The mother of an emergent juvenile pounced on it as if capturing prey, held it for several seconds, and then released it unharmed ( Figure 91 : 2). This suggests that a female can discriminate between prey and emergent conspecifics, or is able to recognise her own young.

Courtship display ( Figures 92-96 ). When courting a female, the male Saratus hesperus alternates between elevation of the fan with extended spinnerets, and sudden extension and vibration of legs III accompanied by depression of the opisthosoma ( Figure 94 ). When the fan is elevated the male may make sudden, interrupted steps to either side, and the pedipalps are raised and held to the side to expose the chelicerae to view from the front. This is "staccato" (not smooth) movement. During the final approach to a female, the male bobs his depressed opisthosoma and rapidly vibrates the outstretched legs I ( Figure 95 ).

Females raise and wave their opisthosoma after turning away from a courting male ( Figure 96 ), a display that has been observed in a number of Maratus species (e.g. M. elephans , Figure 14 in Otto & Hill 2015).

Distribution and habitat. In addition to the type and paratype localities in the vicinity of Canberra, ACT, Saratus hesperus is widely distributed, ranging from eastern Victoria through eastern New South Wales to the southern border of Queensland ( Figure 97 ). Habitats where this species has been found vary greatly ( Figure 98 ).

Figures

Figure 14. Display positions of the holotype male M. aurantius, showing elevation and flexion of a leg III.

Figure 79. Living holotype (1-6) and paratype (7-9) male Saratus hesperus.

Figure 80. Living paratype male Saratus hesperus.

Figure 81. Ventral view of living holotype (1) and paratype (2) male Saratus hesperus.

Figure 82. Opisthosoma of holotype (1-3) and paratype (4) male Saratus hesperus. At the centre is a distinctive patch of white or light yellow pigmented scales. Surrounding this patch the saturated dark purple to dark blue or black (based on illumination) colouration of the dorsum is associated with structure of the underlying cuticle, and this has a cover of scattered, long black scales. On the lateral margins are many iridescent or transparent blue-green to blue scales, the colour of which appears to originate with the underlying cuticle. Flanking the margins of the dorsum is a wide dark grey lateral band covered with many black scales and setae, and below this the opisthosoma has a dense cover of bright white setae (3).

Figure 86. Two living female Saratus hesperus (1-5, 6-12).

Figure 87. Three living female Saratus hesperus (1-5, 6-7, 8-9).

Figure 88. Ventral view of three living female Saratus hesperus.

Figure 89. Ventral view of the epigynum of three female Saratus hesperus. 2, If visible, the anterior margins of the relatively small fossae (arrows) are indistinct. Note the sclerotized duct at the anteromedial corner of each large posterior spermatheca.

Figure 90. Three female Saratus hesperus fixed in alcohol (1-2 & 9, 3-4 & 11, 5-8 & 10).

Figure 91. Immature Saratus hesperus. 1-2, Emergent (second instar) juvenile with mother. 3-6, Emergent (second instar) juveniles. 7-18, Dated series of photos showing stages of development of three juveniles (7-12, 13-14, 15-18).

Figure 92. Display positions of three different male Saratus hesperus (1, 2, 3-10). Note how the pedipalps are raised and held to the sides of the AME. 9, Bilateral extension of legs III.

Figure 93. Display positions of a male Saratus hesperus. 4-9, Sequential positions with white posterior lateral spinnerets extended. During this display the male pivots from one position to the next very quickly (staccato or interrupted movement). Note elevation and separation of the pedipalps. 11, 14, Rapid extension and vibration of legs III with the opisthosoma depressed. 12-13, Posterolateral and posterior views showing extension of the pedicel. 15, Lateral view.

Figure 94. Sequential but not consecutive frames from a 25fps video of a male Saratus hesperus displaying in front of a female. 1-2, Sudden movement or pivot to one side with the fan elevated. 3-4, Bobbing the depressed opisthosoma, followed by extension of legs III. 5-10, Consecutive frames (0.04s/frame) showing rapid, continuous up-and-down vibration of the extended legs III as the opisthosoma was depressed. 12-19, Successive positions assumed during intermittent (staccato or interrupted) pivoting and stepping to one side (12-17) and then to the other side (18-19) with the fan elevated.

Figure 95. Consecutive video frames (25fps) showing vibration of legs I and bobbing of the depressed opisthosoma (arrows) during the final approach of a male Saratus hesperus to a female that may be a Maratus volans (O. Pickard-Cambridge 1874).

Figure 96. Sequential photographs showing "coy" or rejection behaviour of a female Saratus hesperus (at right), after turning aways from a courting male. Movement of the opisthosoma from side to side by females in this situation has also been observed in a number of different Maratus species.

Figure 97. Distribution of S. hesperus in southeastern Australia. Locations (4) and (5) (See Figure 98) and unnumbered circles represent records of Project Maratus (Michael Doe, Michael Duncan & Adam Fletcher, pers. comm.). S. hesperus has also been found at four locations in Victoria (6-8, Bowerbird 2016; 9, Jacqui Wilson, pers. comm.). Maps based on NASA Visible Earth.

Figure 98. Four localities where Saratus hesperus has been found. 1, Fence near Canberra. 2, Vineyard near Canberra. 3, Enfield, NSW. 4, Girraween National Park, QLD. Photos 1-2 by Stuart Harris, 3-4 by Michael Doe.