By Alison Ballance
Only a few specimens of the Bounty Island endemic spider Pacificana cockayni have ever been collected, including this female in the Te Papa spider collection, held by Phil Sirvid. Photo: RNZ / Alison Ballance
There are more than 1100 described species of native spider in New Zealand, and more than 95% of them are found nowhere else in the world. Among them is a little known spider that is found only on the remote subantarctic Bounty Islands, which are just bare rocks covered in seabirds.
When Te Papa spider expert Phil Sirvid heard that Alison Ballance might have an opportunity to visit the Bounty Islands he quickly enlisted her to look for a rare spider that is endemic to the islands. The species is called Pacificana cockayni and it was first described in 1904. Only a handful of specimens – all females or immature males – have been collected, and no one has ever seen an adult male. And until the scientists have an adult male they can’t be exactly sure that the spider has been classified in the correct family.
Illustration of a female Pacificana cockayni, from Spiders of New Zealand drawn by Nadine Duperre Photo: Nadine Duperre
Phil says the female has a lovely chevron pattern on the abdomen, but he doesn’t know if the male has the same, although he suspects it will. In general male spiders are smaller bodied and leggier than females. He also suspects the spiders are nocturnal hunters, and says that the best way to look for such spiders is to either dig a small pitfall trap into the ground, fill it with preservative and wait for wandering invertebrates to fall in it, or to turn over logs and boulders, looking on the underside for spiders or their webs.
Phil explains that you sex spiders from the appearance of the palps, or pedipalps, which are small leg-like appendages at the front of the spider.
“In male spiders the final segment of the palps, furthest from the body, swells up and develops some structures that the male uses to inseminate the female,” says Phil. “Palps on a male often look like icecream scoops or tiny boxing gloves, whereas on a female they’re just straight and narrow.”
Cor Vink from Canterbury Museum featured in an earlier Our Changing World story talking about introduced spiders that are commonly found around houses.
BOUNTY ISLAND SPIDER AUDIO
