Spiders from the Chickens Islands, New Zealand, by D.J. Court, P 125
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TANE 30, 1984 SPIDERS FROM THE CHICKENS ISLANDS, NEW ZEALAND by D.J. Court Port Moresby International High School, P.O. Box 276, Boroko, Papua New Guinea SUMMARY Sixty four spider species have been collected from Mauitaha, Lady Alice, Middle Rock, Whatupuke, Coppermine and Pupuha Islands which form most of the Chickens Group lying east of Whangarei, Northland. The list includes 20 unidentified species and the majority of these are probably undescribed. Nearly all the named species are native forms expected from Northland coastal forest and seashore. The recently-arrived Australian two-spined (Poecilopachys australasia (Griffith and Pigeon) ) is a most interesting exception; at least one spider ling seems to have ballooned its way to Mauitaha Island; a distance of at least 10 km from the mainland. INTRODUCTION The study of spiders in New Zealand native communities is still in its infancy. While there has been great progress by Dr R.R. Forster (Director, Otago Museum) in working through the overall fauna, little is known of spider assemblages on offshore islands and one has to glean records from hundreds of distribution lists for taxa given in Forster's Bulletins (1968—1979). Marples (1956) and Court (1982) have published initial working lists for the Three Kings and Poor Knights Groups respectively. The Chickens Islands (35°85' S, 174°80' E) lie 20-25 km east of Bream Bay, which is to the south of Whangarei Harbour. They are reserves within the Hauraki Gulf Maritime Park and were visited from 30 December, 1981 to 8 January, 1982 by members of the Offshore Islands Research Group (O.I.R.G.). Of the spiders collected during this trip, only two species have previously been recorded from the Chickens. Forster (1973) notes that an unnamed collector gathered the large sheet- weaver Cambridgea foliata and Hexathele kohua from Lady Alice Island (Big Chicken) in December 1953. A number of species have been collected from the nearby Hen Island (Taranga) by E.G. Turbott and other workers. Spiders were obtained directly from webs or retreats, beating foliage, pitfall and malaise traps and sieving of leaf litter. Much of the collecting was carried out at night. The specimens were preserved in 70% ethanol and identified at the Otago Museum by the author (D.J. C.) or by Dr R.R. Forster. They are now lodged in the Otago Museum, Great King Street, Dunedin. 125 A GENERAL ACCOUNT OF THE SPIDERS OBVIOUS ON LADY ALICE ISLAND As spiders are not well known to most biologists, the following account is given in an effort to familiarise field workers with some of this most interesting group. [It is suggested it be read in conjunction with 'New Zealand Spiders - an Introduction' by R.R. and L.M. Forster (1973)]. On landing on the island, the first place to search is the rocky shore, just at the top of the Nerita zone. Bright white silken retreats in rock crevices are soon obvious. These are constructed of tough silk by the medium-sized Amaurobioides, a brown-black spider with chevron markings on the abdomen and with powerful chelicerae. During the night at low tide the spider waits at the entrance to the retreat with legs extending outwards. It preys on any small invertebrates such as kelp flies and isopods. This spider is often inundated by high tides and so seals itself in with a waterproof silken screen at the retreat entrance. One or two metres above, in much finer, double-entranced silken tubes is Otagoa. This is a smaller, pale-brown coloured spider which runs out at slight disturbances to its web. Both Otagoa and Amaurobioides tend to dwell on rocky cliffs or overhanging branches. These are shaded for at least part of the day and so remain cool and less obvious to predators. Further up, towards the white lichen zone, are the large black Ixeuticus (= Badumna) robustus. These require deep retreats. Because they live in rock or other crevices exposed to bright sun they must be somewhat resistant to high temperatures and dehydration. On extremely hot days, they move right out onto the web lattice and probably avoid the heat conducted through the rock to the inside of the retreat. In and out of the lichens moves the camouflaged, lichen-coloured unnamed jumping spider. Widely distributed around the seashore, and elsewhere, is the cobweb spider Achaearanea. It is found in a wide variety of situations - rock crevices, pohutukawa roots and trunks and clay banks. The web, about 10 cm across, has guy-lines with viscid silk on the base of strands where they are attached to the substrate. Small animals crawling along bump into and become attached to the strands. The spider on detecting the disturbance arrives and combs wrapping silk onto the prey. Insects much larger than the spider itself may be captured even though the fangs are small. Steatoda, a relative of Achaearanea, lives in more inaccessible, damper positions above the shore. It is a shiny chocolate- black and juveniles may have pairs of white dorsal abdominal spots, but is often mistaken for a katipo which shows similar prey-catching behaviour. Katipos were searched for in the drier central parts of Spinifex hirsutus growing above West Bay but only old webs were found. This species can be regarded as present on Lady Alice Island but in small numbers. 126 As the ascent of the shore progresses to the first woody vegetation, the large orb weaver Araneus pustulosus becomes obvious, its webs spun on guy-lines that stretch a metre or more. During the day the adults are usually hidden, their colours camouflaging them with bark, stone or whatever substrate their retreat. The ground colour of the dorsal abdominal 'folium' may range from black to 'lichen white'. At night it gains access to the hub of the web either by a silk thread to the edge of the web or by a guy-line directly leading to the centre of the hub. Whilst in the retreat it normally holds the guy-line with a hind claw and by this means it may be alerted to the arrival of prey. Younger spiders may remain in the orb during the day and as they grow, slowly develop a reddish colouring on the inside of the forelegs. In the karaka scrub just above the shore the first of the forest species are seen. Native spiders such as Araneus subcomptus (another well- camouflaged orb weaver) and Hexathele kohua spin their webs. Hexathele may grow very large and constructs bright white funnel-webs in crevices and holes in larger trunks. This species is related to the trapdoors but is in the family Dipluridae and does not actually build a 'door'. Old puriri moth tunnels are often occupied, with the spider 10 cm or more inside, below or above the entrance hole. The spider itself is medium brown, with distinctive light brown chevron markings on the abdomen. In the Utter under coastal forest there are at least 20 species, the most obvious being the speckled brown wolf spiders (Lycosa hilaris ?) and the fast-running Miturga. These two spiders run out from areas being cleared for campsites. The remainder of the litter species are mainly minute, and blend in with disturbed Utter until a few minutes have passed when they start moving around. On low vegetation at night, crab spiders, Sidymella species, move out from their daytime shelters. They take up positions at the bases of branchlets and at the ends of leaves and extend their two anterior pairs of legs in a raptorial pose; they simply wait for prey in this manner, which is seized immediately it comes into contact with the spider. Sidymella is particularly common in the small Uncinia and Carex sedges. Also at night, Clubiona itself may be captured by theridiid spiders. Often at night, the jumping spiders, Trite and other genera, may be seen hanging on 10 cm-long threads attached to the edges of leaves. This group hunts by day with the use of excellent vision and becomes quiescent at night - the hanging behaviour is probably protective against nocturnal invertebrate predators, including other spider species. In the foliage, two medium to small greenish species are very common. Both the crab spider Diaea albolimbata and the small, fast- running dictynid Paradictyna rufoflava may be found on packs and clothing after one has been pushing through vegetation. Diaea appears 127 to have moderate acuity of sight, though nowhere near that of the salticids, and moves below leaves when disturbed. Paradictyna lives in small webs spun under leaves between the leaf edge and midrib. They run out rapidly all over the plant's surface when they are disturbed and are hard to capture. The most distinctive webs in the forest are constructed by Cambridgea foliata. Large silk sheets with a lattice of threads above, extend out from holes in trunks and banks. The spider emerges at night and hangs 'upside down' below the sheet. The silk is so tough that the web 'catches' leaves and heavy twigs from the canopy above without itself being damaged. In these webs (and in those of Araneus pustulosus) may be found the quicksilver spider, Argyrodes antipodiana. This theridiid is much smaller than the host spider and is quite distinctive with its beautiful downward-hanging silvery abdomen. It moves 'stealthily' at one side of the host's web and cuts out small prey such as midges and sandflies without alerting the larger spider. It is therefore termed a kleptoparasite. ANNOTATED SPECIES LIST The list of species and notes below, are given firstly, in the sequence of families as found in Part II of Forster (1968) and later bulletins.