Cosmophasis bitaeniata ( Keyserling 1882 )

Hurni-Cranston, Tiziano & Hill, David E., 2021, Three new jumping spiders of the genus Cosmophasis from Wallacea (Araneae: Salticidae: Chrysillini), Peckhamia 228 (1), pp. 1-84 : 24-27

4. Cosmophasis bitaeniata ( Keyserling 1882)

Figures 7 :5, 22-23, Map ( Figure 1 ) #8

Cosmophasis bitaeniata is perhaps the best-known member of the genus, largely based on studies of its apparently obligatory association with the green tree ant, Oecophylla smaragdina ( Figure 21 ), a classic example of myrmecophily (Allan & Edgar 2000). It is only known from tropical Sahul, found from northeastern Australia to Papua ( Figure 1 ).

C. bitaeniata take larvae from ant workers, using colony-specific cuticular hydrocarbons (mono- and dimethylalkanes) taken from these prey to support their colony-specific chemical mimicry ( Allan 1998; Allan et al. 2002; Elgar & Allan 2004, 2006). They appear to avoid unnecessary contact with the ant workers ( Ceccarelli 2006). John (1920) has observed similar behavior by females of an unidentified Cosmophasis species ( cf. bitaeniata , also resemble female C. valerieae ) in the Andaman Islands.

Diagnosis. Unlike the many sexually dimorphic Cosmophasis , male and female C. bitaeniata have essentially the same colour pattern ( Figures 22-23 ). Except for the eye region, the carapace is relatively glabrous and uniform in colour, with a narrow, white dorsomedian stripe behind the eye region. Legs are relatively uniform in colour, with a black stripe on the anterior of each femur. The pattern of scales on the dorsal opisthosoma resembles that of several other Cosmophasis species. but the first transverse white stripe is not interrupted as in C. valerieae and there is a median black blotch just behind the second white stripe. In males and unfed females the opisthosoma tends to be more cylindrical than in related species. The origin of the male embolus is near the proximal end of the tegulum (rotation ~220°), the cymbium is relatively short for the genus, and the female epigynum has two distinctive loops (sclerotized ducts) on either side that are best seen in published photographs ( Żabka & Waldock 2012). Unless new forms of this species are discovered, both sexes are easy to identify.

Figures

Figure 1. Known occurrence of Cosmophasis species in Sunda, Sahul and adjacent oceanic islands. Better-known species are identified in the key at upper right. See Appendix 1 for identification of the other species, most know from a single locality, by number. The new species described here are from Ambon and the Banda Islands within the Wallacean region (small yellow rectangle near the center), shown in more detail in Figure 2. Localities are based on references cited in Appendix 1, as well as reliable photographs posted in iNaturalist and FLICKR. Note that some records of C. thalassina (52, generally found to the south) and C. umbratica (57, generally found to the north) are most likely confused, as separation of these species may not be possible. Background image courtesy of NASA/USGS/Landsat.

Figure 7. Comparative dorsal views of representative male Cosmophasis (drawings not to scale). 1, C. ambonensis, sp.nov., Ambon. 2, Cosmophasis sp. A, found at Warimak, Waigeo Island, West Papua (Baum 2019) and at Pulau Penem, Fam Islands, Indonesia (Smutný 2020). 3, Cosmophasis sp. B, found on Leilei Island (Sustainable Strategies Network 2018), Halmahera Island (Harris 2019), and Ternate Island (Knowles 2021a) in the Bacan Islands, Indonesia. 4, Cosmophasis sp. C, found at Manokwari, West Papua (Knowles 2021b). 5, C. bitaeniata, Queensland. 6, C. valerieae, Bali. 7, C. bandaneira, sp.nov., Banda Neira.

Figure 21. Green tree or weaver ants, Oecophylla smaragdina (Fabricius 1775), photographed at Pachuap Khiri Khan, Thailand. 1, Workers swarming around a captured beetle. 2, Workers tending a colony of treehoppers. O. smaragdina colonies include both major and minor workers, as shown here, and intermediates (Crozier et al. 2010). This is a fiercely aggressive ant species. Photographs © Troup Dresser, used under a CC BY-NC 2.0 license (1, Dresser 2010; 2, Dresser 2012).

Figure 22. Adult Cosmophasis bitaeniata from Queensland. 1-2, Male from vicinity of Cairns. 3, Male from Laura. 4-6, Females from Townsville. Photo credits: 1-2, © Iain Macaulay, used with permission; 3, © Jim McLean, used with permission. 4-5, © Lek Khauv, used under a CC BY-NC 4.0 license (Khauv 2014a, 2014b); 6, © briand79, used under a CC BY-NC 4.0 license (briand79 2017).

Figure 23. Adult female Cosmophasis bitaeniata from Townsville or Cairns, Queensland. Photographs © Iain Macaulay, used with permission.