The Monkey Orb of Asia

Just a quick entry for this week. And for the second week in a row, today's post will somehow involve monkeys.

Female monkey orb-weaving spider Neoscona punctigera, copyright Akio Tanikawa.

The orb-weavers of the family Araneidae are a highly diverse group of spiders, with well over 3000 known species. They are also one of the most familiar spider groups, often being relatively large as well as visible due to their construction of exposed and characteristic webs. The lady in the picture above represents one of the more moderately sized species, being about a centimetre in length (Tikader & Bal 1981). Neoscona punctigera is a widespread species in Asia, with a range extending from Madagascar and surrounding islands to Japan, as well as south into New Guinea and northernmost Australia. Vernacular names for the species include ghost spider or monkey orb-weaver. Like many other orb-weavers, N. punctigera only puts up its web at night; it sits in the web head downwards. When morning comes, the spider consumes the previous night's web and finds a concealed spot to hide until evening. On the underside of the body, N. punctigera has one or two pairs of bright white spots. When the spider is hunkered down for the day, these spots are concealed but when the spider is out on its web at night they are very visible; Chuang et al. (2008) found that these bright spots appear to attract prey, as spiders who had had their spots painted over caught less moths than usual.

Male Neoscona punctigera, copyright Suresh Kumar.

The name 'monkey orb-weaver' refers to the appearance of the male, which like the males of other orb-weavers is quite a bit smaller than the female (I have no idea where the name 'ghost spider' comes from; perhaps something to do with the spider's appearance on a web?) Resting males tend to adopt a pose with the front legs bent close together and the rear legs crossed behind the abdomen (as in the photo just above). Combined with eye-like spots on the abdomen, the overall effect has been compared to a monkey lying back with its legs crossed and its hands behind its head.

Orb-weaver taxonomy can often be confusing. Early authors tended to dump a large number of orb-weavers in a broad genus Araneus; though this genus is now used in a much narrower sense, many orb-weaver genera are difficult to distinguish without examining the genitalia. Individual species can also be quite variable in superficial appearance with a lot of variation in colour pattern, so many species were initially described under a number of names. Female Neoscona differ from Araneus in the presence of a longitudinal groove on the cephalothorax, as well as the presence of one or two lateral lobes at the base of the scape (a projecting process over the epigyne, the sclerotised structure around the female genital openings). Distingushing N. punctigera from other species of Neoscona requires even closer inspection of the genitalia. In a number of older sources the species now generally referred to as Neoscona punctigera (including in the World Spider Catalog) is commonly referred to as 'Araneus lugubris'. Confusingly enough, the latter name actually has priority (it dates to 1841 whereas the name pectinigera was only published in 1857) but has fallen out of disuse since Grasshoff (1986) stated that it was preoccupied in a review of African Neoscona. I'm not sure if he was correct—I suspect that he thought it was antedated by Aranea lugubris, published in 1802 for what is now a species of wolf spider, but as the 1841 species was originally placed in the now-obsolete genus Epeira I don't think they actually conflict. Nevertheless, the rules governing how preoccupation affects the use of older names can be complicated and if N. pectinigera has been settled as standard then it may be best to let it be.

REFERENCES

Grasshoff, M. 1986. Die Radnetzspinnen-Gattung Neoscona in Afrika (Arachnida: Araneae). Annalen Zoologische Wetenschappen 250: 1–123.

Chuang, C-Y., E.-C. Yang & I.-M. Tso. 2008. Deceptive color signaling in the night: a nocturnal predator attracts prey with visual lures. Behavioral Ecology 19 (2): 237–244.

Tikader, B. K., & A. Bal. 1981. Studies on some orb-weaving spiders of the genera Neoscona Simon and Araneus Clerck of the family Araneidae (=Argiopidae) from India. Records of the Zoological Survey of India, Occasional Paper 24: 1–60.