Diario de arnim

This is the species which instigated this series of articles on the special species in the dunes of our region. It is also the species that kicked off my dunes ecology habit, more than a decade ago. What's the big deal?

Firstly, almost everyone born here and many who have made this land their home, at least know what a katipō is. Most have never seen one, except in photos. In some circles, perhaps because it is the only species endemic to New Zealand which is regarded as venomous, it has achieved iconic status. The flashy markings on an adult female serve to elevate that status too. Here is one fine example:
https://inaturalist.nz/observations/103864584
Katipō males look quite diminutive beside the female, ref.
https://inaturalist.nz/calendar/arnim/2011/2/12

So you have a taste of how small spiderlings can be, ref.
https://inaturalist.nz/observations/5050491

As that observation infers, it is common for katipō spiderlings, when they break out of the eggsac, to scamper immediately to the top of the nearest tall plant to balloon away - a spectacular sight I have witnessed a few times. To get an idea of how effective spider ballooning is, read for instance
https://arxiv.org/abs/1309.4731
which is (AFAIK) the original work citing electrostatic fields as the key enabler.
The sexual dimorphism in katipō is not so extreme as with the Australian redback - that female is larger than a katipō, and the redback male is smaller than the katipō male. No wonder the redback male is lunch for the female - that is not the case with katipō.

Secondly, katipō is listed by the Department of Conservation as an 'at risk' species. It is absolutely protected under the Wildlife Act. But, it goes further than that. Quite some years ago DoC correctly decided that it could not have a programme for every species on the threatened species list. Instead signature species were nominated for varying types of ecology. Katipō was nominated for dunes environments. In my opinion, this was an excellent choice. I have observed that there's a pretty useful correlation between the katipō population in an area of dunes, and the general ecological health of those dunes, ie. there's a parallel to the coal miners' canary.

Katipō live in the dunes, and only in the dunes. If you find a look-alike spider in your backyard, I'd suggest with something greater than 99% certainty, that what you're looking at is a false katipō, (Steatoda capensis), which not only lives in more habitat types than katipō, but can look superficially like katipō too, as specimens may be very dark with a fine red-orange stripe, eg.
https://inaturalist.nz/observations/13066015

There's plenty of good material on the InterNet if you want to learn about katipō. Some I can recommend are Phil Sirvid's fine pieces for Te Papa, ref.
https://collections.tepapa.govt.nz/topic/9431
and some excellent related articles:
https://blog.tepapa.govt.nz/2009/02/10/1743/
Phil's reference in the above article is for my money, the definitive work on katipō
https://blog.tepapa.govt.nz/2009/02/13/latrodectus-love-bites/

Phil's material wasn't written recently so it doesn't include some of the things I learned in the decade I've been studying katipō. Here's some of what you won't learn from the above, or any other sources I'm aware of:

1) depending on where you're looking, katipō can produce eggsacs almost all year round. I've found new ones here, and in Hawkes Bay from August through June. Further north that may be right through the year. That doesn't say that all of them produce vast amounts of new katipō - there's a known strong correlation between katipō fecundity and temperature.

2) I had the pleasure of learning about katipō at Ocean Beach south of Cape Kidnappers, which is the only place I'm aware of where katipō of both colour morphs have been studied together. Although only 1% of those were black katipō, another 5% or so appeared to be 'hybrids' of both red and black katipō. That doesn't happen here in the dunes of the West Coast of the lower North Island, since black katipō don't find their way here. Hawkes Bay is about as far south as you can find black katipō, perhaps slightly further north on the West coast, since there is a distinct correlation to temperature for black katipo to thrive.

3) Occasionally experienced katipō viewers find katipō with a distinct brown tone to the abdomen. What is not widely known is that this is a very short phase in an adult female katipō's life, just before she produces another eggsac. The abdomen has stretched so far during this 'gravid' phase, that the light reflects differently from the abdomen. Immediately after she's laid her eggs, she's back to quite black again, and for a short period, quite wrinkly too. The second katipō observation from the top illustrates a gravid female about to add to her first eggsac.

4) Habitat loss, ie. human intervention, has doubtless been a major factor in the decline of the national population of katipō, but it is not the only reason. Earlier studies indicated that the false katipō, Steatoda capensis, which hails from South Africa, is displacing our native katipō in its ecological niche, but the story goes further. My work has included photographing instances of false katipō preying on a katipō - the colonists are killing off the natives, ref. for instance
https://inaturalist.nz/observations/102063519
The false katipō in this first case had mortally wounded the katipō, which stopped all motion a minute or two later. What makes this worse, is that false katipō and real katipō often coexist in the same web structure, from juvenile ages through adulthood, but at some point, the false katipō might turn on the native host, making a meal of it. ref. eg.
https://inaturalist.nz/observations/13065845

Further, I've fingerpointed another three exotic spider species which prey on katipō. The worst offender seems to be an Australian crab spider which in it's native Australia is not known to prey on spiders at all. Here I've observed Sidymella trapezia preying on half a dozen species of spider, including katipō and other native spider species. The following depict S.trapezia killing off a false katipō, a katipō and a native seashore wolf spider (Anoteropsis litoralis).

Sidymella eats Steatoda
a) https://inaturalist.nz/observations/6970072
Sidymella eats katipo
b) https://inaturalist.nz/observations/7152143
Sidymella eats seashore wolf spider
c) https://inaturalist.nz/observations/7152319

A third species, Australomimetus hartleyensis, colloquially known as a 'pirate spider', is well known for preying on spiders in its native Australia. These Mimetid spiders are often smaller than their prey, ie. these pirate spiders are very good at what they do. ref.
https://inaturalist.nz/observations/19039648

All three of these species are common on this coast. Any time you come across them, don't be shy. Nixing one of these is an invertebrate equivalent of bumping off a stoat. A fourth katipō-predating spider, the Australian import Nyssus coloripes, is common in Hawkes Bay, but in almost 6 years I have yet to meet it here on the West Coast.

There really is nothing to fear from katipo - they're much more afraid of you than you are of them. A male or juvenile would struggle to break your skin, and even an adult female cannot do so without real effort, so if you don't entrap an adult female, envenomation won't happen. If you get brash and provoke this, appropriate antivenin is available in hospitals, which can save you considerable discomfort for weeks. Previous generations were taught to fear the katipo, but as my friend Ruud Kleinpaste will tell you, if we educate our children to treat them with respect, then the fear gets put into perspective.

Lastly, I'm pleased to report that most of the active members of our Dune Garden team have learned how and where to find katipo in our fortnightly sessions. If you're so inclined, don't be shy about joining us. It isn't a bug, it's a feature.