SciBlogs

Posts Tagged arachnophilia

Sunday Spinelessness – Cannibalism in the garden David Winter Feb 03

No Comments

The most common jumping spider in our garden, Trite auricoma, with the remains of it most recent meal… a smaller T. auricoma:


Cannibalism,  animals eating members of their own species, is a pretty common and widespread behavior. Species in almost every phylum have been shown to occasionally (or frequently) eat members of their own species. Even herbivores like monarch butterfly caterpillars will eat any monarch eggs they encounter.

In spiders, the most well-studied form of cannibalism relates to mating. In a very few species male spiders will offer themselves as a meal to their mate. In so doing, males make sure their offspring get the best start in life, by providing their mother with a nutrition meal. They are often also posthumously rewarded by female, who reject other suitors and ensure the sacrificial male’s legacy. The best example of this behaviour comes from the Australian red back spider (Latrodectus hasseltii). In this species males actually pirouette their way into their mate’s fangs, and females take up the offer about 65% of the time. New Zealand’s endemic red back relative, the katipo, does not exhibit this behavior (nor does the North American black widow, despite the name).

Such sexual cannibalism isn’t known from jumping spiders (although females will certainly eat unwary males), and a wider (and earlier) shot lets you see that this was a case of a mature spider taking a younger one (males and females are about equally sized in Tauricoma).



Sunday Spinelessness – The other monster David Winter Oct 09

6 Comments

I’ve never taken a good photo of an ant. I’ve tried plenty of times, but even when I’ve happened across queens, whose size should give the point’n'shooter the best chance to capture a passable shot, I’ve failed. I haven’t given up though, and that’s why I was spent about 15 minutes of this morning on my hands and knees pointing my camera at the little red, and slightly larger black, ants that patrol the paving stones in front of our house. I failed again, but if you spend 15 minutes contemplating the little creatures that run our world you are pretty much guaranteed to run into something interesting. Today I saw something I’ve never seen before

.

A baby harvestman! I’ve written about harvestmen before, they are spider-relatives which are mainly scavengers rather than hunters and don’t have poison-delivering fangs. I don’t know if this one is a native or the introduced European harvestman (Phalangium opilio), but New Zealand has a surprisingly large number of native harvestmen (several hundred, and likely more awaiting description) and a suprisingly large number of those are truly weird looking. Arachnids like harvestmen and spiders have two sets of appendeges associated with their head. The chelicerae are use to grasp food and direct it towards their mouths whereas the pedipalps are strangely dual-purpose organs, used almost like an extra set of legs and also to deliver sperm during mating. Earlier this year I ran across a native Palpatores which amazingly giant chelicerae:

Today, while I was lining up the baby harvestman another misshapen harvestmen ran across the paving stones:

This one has considerably shorter legs than than the Palpatores, and when you zoom in on that mouth-gear you can see it’s the pedipals and not the chelicerae which are out-sized.

It’s not clear why the pedipalps are so spikey. They might help males to fight to fight off challangers and secure mates, but they probably also contribute to these creature’s excellent camouflage. The three forward spacing spikes on the carapace place this guy in the genus Aligidia. I took a few more photos before I let him go about his business:

Sunday Spinelessness – The little guy David Winter May 15

2 Comments

I seem to have run out of week. I had a great idea for a Sunday post this week, but I’m not going to have time to write that one. Instead, here’s a recent discovery from the backyard.

Recognise the eyes? This must be a male of the same Cycloctenid (scuttling spider) species I uncovered a couple of weeks ago. He’s a good deal smaller, and a good deal slimmer than his female counterpart:

If I knew I was going to compare the male and the female I would have tried to get a better comparison shot… male on the left, female on the right

Whenever you see males and females of the same species that look conspicuously different from each other you know that each sex is subjected to different evolutionary pressures. In mammals, if there is a difference in size, males are usually the larger sex. That disparity arises because males fight with each other for access to females and big males do better than small.

In invertebrates (and fish, for what it’s worth), the tables are usually turned, with females being larger than males. This pattern probably arises from the different costs that each sex has to bear in creating the next generation – eggs are expensive and sperms are cheap. That bias might be amplified in ‘sit and wait’ predators like these Cycloctenid spiders. Fritz Vollrath and Geoff A. Parker looked across a host of spider species and found those with relatively sedentary females tend to have smaller males, then set about trying to build a model to understand how that size difference might evolve. It turns out, if females are few and far between then the success of males has more to with the time they spend searching for females than their ability to fight off other males. So, the best bet for a male Cycloctenid that wants to leave descendants might be early maturation, even if the extra searching time that results from it comes at the cost of extra growth.

This male’s search seems to be over. I found him about 5 metres from the log that the female in this first post was living under and she hasn’t moved since.


Vollrath, F. & Parker, G. A. 1992 Sexual dimorphism and distorted sex ratios in spiders. Nature, 360, p.156-159. (doi:10.1038/360156a0)

Sunday Spinelessness – All in the eyes David Winter May 01

No Comments

Can you guess what these patterns represent?

Well, having read the title of the post you may have guessed that each black dot is an eye. In fact, these pictures all represent the way a particular family of spiders arrange their eyes. For spiders, the eyes are a window into evolutionary history: the ancestor from which all spider species descent had eight eyes, and, although most modern spiders have kept all eight, they arrange them in an astounding number of patterns. Very often, the eyes are the best way of placing an unidentified spider into at family. (These pictures are from Lynette Schimming’s article on BugGuide, they represent the families Ctenizidae (trapdoor spiders), Oxyopidae (lynx spiders) and Scytodidae (spitting spiders) and are Creative Commons by-nd-nc licensed).

So, when I found this spider lurking under a log, and couldn’t place it into my (admittedly scant) knowledge of spider taxonomy I was very keen to get at least one photo of its eyes (as it turned out, it was also by far the best photo I took of this spider before turning its log back over):

There are a couple of families of relatively large ground dwelling spiders in New Zealand, and and first glance I thought this might be a vagrant spider but the eyes are just all wrong for that placement. I had to dig a little deeper for the answer, but between google and Flickr I found it. You are looking at a member of the family Cycloctenidae.

The drive many naturalists have to call each thing by its right name might seem oddly obsessive, but learning a creature’s place in nature isn’t the same as placing a stamp in the right section of an album. A taxonomic name can be a key to data collected by hundreds of people. In this case, Ray and Lyn Forster wrote about the Cycloctenidae in Spiders of New Zealand. It seems the family is restricted to New Zealand and Australia and has only a few known genera. They are commonly called “scuttlng spiders” because the arrangement of their legs allows them to run sideways as well as forwards and backwards, which means than can rapidly hide from a would-be predator. That’s no-doubt a predator avoiding adaptation, but this particular spider was very happy for me to rest a camera directly in front of and get the shot that let me know what I was looking at.

Sunday Spinelessness – Vanuatu jumping spiders David Winter Mar 06

3 Comments

So, last week my little old blog found itself in the middle of a national discussion abuot Ken Ring and his claimed ability to predict earthquakes. In this space of two days that post recieved a good deal more than a year’s worth of The Atavism’s normal traffic.

And now I have to tell anyone that subscribed to this blog in the wake of that article, hoping perhaps that I’d follow the news of the day and provide analysis of the key claims, that I mainly blog about bugs. I’m an invertebrate fan boy, and dedicate a post a week here to celebrating some creature from that ignored majority. Ninety five precent of animal species don’t have a backbone, and the spineless multitude contains some of the most amazing creatures on earth.

Today, I’m going back to photos I took in Vanuatu over christmas and looking at my very favourite group of spiders – the jumping spiders (family Salticidae). Spiders get a bad rap generally, almost none of them pose any threat to us*, and absolutely none of them are going to go out of their way to get us. Some spiders, like the long-legged big-fanged Cambridgea in this post, seem to set of a revuslion somwhere deep within our brains, but others are just down right charasmatic. Jumping spiders are the puppies of the arachnid world: cute inquisitive and apparently unaware of how small they are. I’ve written about the group before, so lets skip right to the photos:

The big round forward-facing eyes are one of the charactersitc traits of the jumpers, because they are active hunters these spiders need to be able to cast a finely-focused image of their prey. Obviously, this one has used its eyes to good effect, I can’t tell what it has clamped between its jaws (or chelicerae, if you want to be accurate). It has eight legs, which makes it a fellow arachnid, the body looks a little mite-like but the legs seem too long for that identification so I’m afraid I can’t tell you anything more.

As much as it pains me to put up photos with zero taxonomic information, here’s a another jumping spider of unknown affinity. This one was truly tiny, perhaps 3mm across the body, but quite happy to have it’s host plant bent out of shape to allow a camera to intrude

That’s it from me today. You should know that people much more skilled than I am have taken some terrific photos of jumping spiders. Alex Wild has a stunning ant-mimicking spider here, and Thomas Shahan is the acknowledged master in this field. Here’s one example of his focus stacked images:

Sub-Adult Female Phidippus putnami (With Video!)


*In New Zealand it’s only the katipo and the (introduced) redback

Sunday Spinelessness – Updates David Winter Dec 19

1 Comment

I’m going to round out Sunday Spinelessness for 2010 with a few updates from the creatures that have featured here over the year. But, since this is going to be last post here till the first week of January or so, I’m going to start by taking just a moment to wish everyone who has commented on, linked to, tweeted about or just read The Atavism this year a merry Christmas and an enjoyable break over the new year. I enjoy writing these posts for their own sake, but it’s much more satisfying to be part of a community (no matter how small a part!) of people that are interested in the same ideas I am. Thanks.

Right, now own with the spinelessness. The little green spiders I’ve been following, and sacrificing in the name of science are still going strong. Since the last time I wrote about them I’ve seen them grab prey for the first time (confirming the suspicion that they are ambush predators) and seen males fight for the right to mate with a female. Sadly, I didn’t photograph either of these events (well, not in a way that I’d want to show other people, but there are descriptions of each tucked away in my notebook). I can, however, show you the result of those matings. About three weeks after the first one I started spotting these across the agapanthus:

At last count there were about five separate leaves sporting one of these egg sacs and a watchful mother. One very dedicated mum-to-be actually has three on the go at the moment!

I’ll have to wait a while to see the next generation of the little green spiders, but the leaf-veined slugs that featured along side them here have already moved into the next stage

I haven’t seen a full-sized slug in a long time. But these immature ones are out and about every evening, I’ll have a little more to say about them in the new year.

The pittasporum “pysllids” are still dancing, but no longer at plague proportions. There’s no respite for the pittasporum though, now it’s being devoured by leaf roller moths. If I cared more about the tree I might spray it with insecticide but while its pests are feeding animals as wonderful as this spider (anyone have a clue on an ID?) I’m happy to let them have it:

Finally, the bumblebee nest at the bottom of the garden appears to be enjoying the run of hot weather we’ve had here. Some of the bees in our backyard (no necessarily the ones that live at the bottom, since bumble bees can forage several kilometres from their base) have taken up a slightly odd habit. On a couple of warm evenings I’ve popped outside and found bumblee bees asleep inside foxglove flowers:

No doubt the little tubes make a nice warm place for a worker to spend the night if they are caught out too late to make it home. Apparently males, which are only produced towards the end of summer, will often do the same trick once they’ve left the nest and are spending their daytime waiting for a virgin queen to pass by. I think we really have to end with a bumble bee bum sticking out of a flower:

Sunday Spinelessness – Wolf spiders David Winter Nov 28

No Comments

Lately I’ve been trying to reclaim a little of our garden from the weeds that claimed it for themselves over the winter. My dedication to weeding is not absolute, and instead of diligently tugging each weed out seperately I almost end up plucking the big ones then driving my hander und the soil to disturb the roots of the smaller ones. That method is bad news for the wolf spiders that live in and around the bark we use as mulch in the garden.

Wolf spiders are reasonably large hunting spiders, and at this time you can see one of their defining characteristics. Female wolf spiders carry their egg sacs around with them. I’m not sure how many times I’ve knocked over a piece of bark and seen a few legs and an abdomen ducking for cover:

But I’ve only managed to start a fight once. Last weekend I upset a piece of bark with two wolf spiders hiding under it, and in the commotion that followed one of them lost her egg sac. For the next five or so minutes, a fierce fight broke out between the two spiders. Guilty as I was about having started this fight, I managed to record a little of it:

Sunday Spinelessness – A missed opportunity David Winter Jul 25

4 Comments

I hate agapanthus. Really, district councils’ and home gardeners’ obsession with those dull plants must put them alongside geraniums as the most over-planted under-interesting plant in the country. So it’s with some chagrin that I tell you that a clump of these banal flowers is the abosolutley favourite hangout for spineless creatures in our garden. The ichneumon in this post is poised on an agapanthus leaf, and I’ve seen several others wasps, aphips, leaf hoppers, three species of jumping spider, lots of moths and a few beetles among those green swords. But the most interesting creatures to make their home among the agapanthus are these tiny green spiders.

At different times over the summer I could find five or six different imdividuals like that one, living on the the tip of agapanthus leaves. So I started sticking my head into the agapanthus plants a bit more often, and even keeping few notes to track what these guys were up to. In that time I managed to record a few interesting behaviours. Males and females cohabitate (the male is the one in focus here):

They eat aphids and small flies:

They spin a silk “retreat” to hang out in (though, this doesn’t appear to be associated with moulting as they are in some other spiders):

And they lay their eggs in in disc-shaped egg sacks with raised edges.

On one rainy day I saw a female running down to the water pooling inside her leaf, collecting a mouthful of the rain then scurrying back to her egg sack. Once there, she deposited the water around the outside of her egg sack before heading back for another mouthful and repeating the process.

All those observations are tiny little data points that might, if there were written up for a little journal like Weta, help anyone who decided to seriously take up the study of these spiders, or the distribution of these behaviours among spiders as a group. To be really useful those observations need to be tied to a name, after all, species are the fundamental units of biodiversity and each of the observations above are the property of a species. I just don’t know which species. These spiders are definitely from the family Dictynidae, and they fall into either the genus Paradictyna or Viridictyna. That’s where things get a bit interesting.

Both Paradictyna and Viridictyna were described by New Zealand’s preeminent arcahnologist, Ray Forster, who lived right here in Dunedin. The two genera are actually pretty easy to differentiate, “virid” means green and Viridictyna are green with white chevrons on the top while Paradictyna can have purple markings on their abdomen (Forster actually calls them “one of New Zealand’s most handsome spiders”). If you look up there you’ll see “my” spiders have purple on their abdomen, so they must be Paradictyna right? Well it’s not quite so simple, Paradictyna hasn’t been recorded south of about Christchurch (close to 400 km away). New Zealand spiders might be chronically under studied but remember Forster lived in Dunedin, the original descriptions of these spiders include collections from all over the city and if they’d been common in Dunedin gardens at that time surely he would have found them!

So, what are these spiders? They might be one of the Viridictyna species Forster described, in which case the simple rule (purple = Paradictyna) will have to be updated, it’s probably more likely that Paradictyna have moved south to Dunedin, it’s even conceivable these guys are undescribed species. To really work out which of these cases is true you’d have to look at internal and microscopic anatomy of spiders, and I’m certainly not qualified to do that. This is the bit where a dedicated scientist, as opposed to someone poking his head in a bush once a week, would say he took a couple of these spiders dropped them in 70% ethanol and sent them to someone who knows there way around the inside of a spider. Taxonomists are sometimes criticised for their willingness to kill the creatures they study and fill museum shelves with specimens that might never be looked at again. But the major pieces of research I’ve been involved have relied utterly on being able to go to collections that were dealt with by pioneering systematists like HB Baker and JT Salmon (you can tell they’re old because they have initials for names) and apply tools those scientists couldn’t have dreamed off to their samples. Even if I’d simply put my spiders in ethanol with a descriptive tag and sent them to museum the location, date and behaviours of these spiders would be linked to a specimen that could be inspected by anyone who was interested. Who knows, maybe it would help someone PhD student in 60 years time!

But of course I didn’t sacrifice any of these spiders. It was too much fun for a geneticist like me to be playing field biologist for a while and I kept thinking, “I’ll just keep watching them a bit longer”. And now they’re gone, I don’t know if the wasps that hang out in the agapanthus did for them if they’d just done their job, seen their eggs will hatch, and shuffled off. The eggs have hatched now, so I’ll keep sticking my head in those boring leaves, but for now it’s an opportunity lost.

Sunday Spinelessness – Protecting the katipo David Winter Jun 13

7 Comments

New Zealand has a pretty benign fauna. We have no snakes, no carnivorous mammals bigger than our little bats and, ever since Haast’s Eagle was the driven to extinction, the apex of our natural food webs has been occupied by the karearea. The karearea is the native falcon, and a fierce predator, but it holds no threat to humans. In fact, we only have one native animal capable of doing people any harm, a venomous spider known as the katipō. So, some people were a little surprised to hear the katipo had been added to list of “absolutely protected” animals included in the wildlife act, the same level or protection offered to kiwis and the tuatara.

A female katipō, photograph is CC 2.0 from Jon Sullivan


The katipō’s name is a testament to the punch its bite packs, it translates as “night stinger”. Actually, the fact the species has a māori name at all sets it apart from our other spider species, the rest of them fall under the name pÅ«ngāwerewere. The katipō certainly deserves special recognition, it’s a cousin to the black widow and the redback and its neurotoxic venom can produce the same suite of symptoms that make those spiders feared the world over.

Although the katipō’s bite is excruciatingly painful, the spider’s unique ecology means they seldom bite humans. The katipō is very closely related to the Australian redback (the two can still hybridise) but whereas the Australian species is a generalist that lives in amongst rocks and logs and human debris, the katipō has become a specialist. It builds its web in driftwood and grass on sand dunes. That specialised lifestyle has been the katipō’s undoing. In the last hundred years the total area of sand dunes in New Zealand’s coastline has decreased by 70%. Not only has most of the katipō’s habitat been destroyed in the last hundred years, most of the the remainder has been degraded. We introduced marram grass to sure up dunes that have been disturbed by agricultural and urban development. While that grass does a great job of collecting sand and holding up dunes, it’s also very invasive and the katipō doesn’t much care for it (preferring the relatively sparse growing native sedge pingao).

Marram grass isn’t the only invasive species driving the katipō’s decline, a distantly related South African spider called Steatoda capensis has become widespread in New Zealand. S. capensis is another generalist which has not trouble getting by in marram filled dunes and breeds more quickly than the katipō. Add the damage done by recreational activities like quad bike riding to the pressures already listed and you start to realise why there are eight populations of katipō left it the South Island.

There is no doubt that the katipō is threatened with extinction. Adding it to the list of species protected under the Wildlife Act* gives DoC the ability to post scary sounding warnings around remaining habitat, and to prosecute people who willfully damage that habitat. But it’s clear from a few comments around the web that not everyone is on board with saving the katipō. Why should we try and hold on to our only dangerous animal? The risk posed by the katipō is really infinitesimal, they aren’t living on your downpipes or your living rooms. Even if you wander into the sand dunes you’ll have to go out of your way to find a katipō and get it scared enough to bite you. New Zealand’s biota is already so depleted by human enduced extinctions, it really would be shamefull to lose another species because of ill informed fear.


* Reading the actual law really does my head in, I think it means for the purposes of that act terrestrial vertebrates are protected unless other wise noted, and inverts are not unless specially picked out.

And a wee note for all the spineless fans (there are some, right?..), next Sunday I will be in a series of airports on my way to the USA for the Evolution meetings in Portland. So, Sunday Spinelessness will take a break ’till early July.

Sunday Spinelessness – Jump! David Winter May 09

6 Comments

jump4

Surely that’s a face that will find its way into even the most hardened arachnophobes heart? The owner of those big round eyes is a female Helpis minitabunda, the Australian Bronze Jumping Spider. Last week I mentioned that the jumping spiders (family Salticidae) where my absolute favourite group of spiders, but the photos I used in that post didn’t do much to show just how endearing these spiders can be (even when they are in the process of chomping down on a blowfly!)

Jumping spiders stand apart from most of their kin by being active during the daytime. Like the lynx spiders that have featured here before, they are active hunters which rely on good sight and surprise attacks to keep themselves fed. That lifestyle has led to features that make the jumping spiders so cute, huge forward facing eyes and a head that swivels around to follow you. Most spiders will react to an intrusion from some lumbering fool sticking a camera lens in their face by running away. Not jumping spiders, they’ll eye you up in much the same way they would a passing beetle:

jump5
jump1

I managed to take a few photos of jumping spiders while I had all that fancy camera gear to play with. These photos don’t do justice to the gear or their subjects, but here’s a closer look at a couple of tropical jumpers (probably a female and then a male from a Menemerus species):

jump6

jump3

If my hunch about those two photos representing one species is right, then I’ve shown you photos of two species here. Hardly a fair sampling of the 5 000 currently described species of jumping spiders (about as many species as all the mammals put together). Those two species are relatively drab, but jumpers come in some amazing colors. Thankfully, photographers with much more skill than I have recorded some of that diversity. Ted MacRae recently linked to Thomas Shaha’s focus stacked invertebrate photos which include some of the most amazing jumping spider photos I’ve ever seen and Ugly Overload wronged the group by including a montage of jumping spiders on their pages.

A wee update: Another local blogger has been talking about jumping spiders lately, Alan Macdougall had a Trite auricoma pay him a visit, check out his neat photos here.

Network-wide options by YD - Freelance Wordpress Developer