Category Archives: Arachnids

Notes from the field: Yukon wildlife (Part 1)

Posted on August 20, 2012 | 2 Comments

This is the first of a three-part series that was originally published (as one article) in the McGill Reporter, as part of their “notes from the field” section – it is an account of my research trip to the  Yukon, back in July.  It is reproduced here, with permission.  For a different (yet complementary!) account of this field trip, see The Bug Geek’s blog posts, Part 1 and Part 2.

MSc student Katie Sim searching for wolf spiders in the Yukon, among fields of cottongrass

8 July 2012, 10 PM, The Westmark Hotel, Whitehorse Yukon

Our entomology research team has just arrived in Whitehorse in anticipation of our upcoming fieldwork in the Yukon.  I just returned to my room after enjoying a beer at the hotel bar where we completed our GIANT shopping list this evening. Tomorrow morning we are picking up our RV, and will be driving about 500 km NW of Whitehorse (on paved roads) before turning onto the Dempster Highway – this famous Yukon road is a dusty, gravel road that heads straight up towards the Northwest Territory, crossing the Arctic Circle, and taking you from boreal spruce forests in the south to sub-arctic tundra in the North.  The Dempster crosses the Yukon-Northwest Territory border at about kilometer 465, and then continues on to Inuvik.   It’s a big trip with few opportunities for groceries along the way.  We are all part of the Northern Biodiversity Program - a multi-University collaborative project about the diversity of insects and spiders in Canada’s North.   After months of planning, applying for research permits, and fine-tuning our methods, it is great to finally be here.  That being said, I worry that the excitement and anticipation will keep us too jittery to get a good night’s sleep tonight – too bad since after tonight, we’ll be sleeping in tents rather than hotel rooms!

10 July 2012, 3 PM, Tombstone Campground, km 72 (Dempster Highway), Yukon

We have made it up to the Tombstone mountain range, about 75 km up the Dempster Highway.  Unfortunately, the weather has not been cooperative, so we are stuck in the campground, huddling in a cook-shack with other travelers.  Most of the other campers are on vacation, so we are unusual since our trip is for research.  We are also unusual because unlike most visitors to this part of the world, we are NOT viewing large wildlife (bears, moose) but are instead spending our time searching for the tiny wildlife along the Dempster highway.

PhD student Crystal Ernst installing insect traps on the Yukon Tundra

Our team includes two graduate students from my laboratory, Crystal Ernst and Katie Sim.  Crystal has been setting out “pan traps” (yellow bowls) to collect ground-dwelling arthropods (i.e., insects, spiders).  Part of her PhD is about unraveling some of the complexities of arthropod-based food webs in the Arctic, and she is using these traps to collect critters that live on the tundra.  Thankfully, her work does not require good weather!  Katie is working on the population genetics of a high arctic wolf spider, Pardosa glacialis – and she needs some more specimens.  We know that the species occurs near the Yukon-NWT border (in the Richardson mountains), about 300 km north of us.  A post-doc, Dr. Laura Timms, is part of our team also – she studies plant-insect interactions in the North, and is focusing her research on insects that feed on Willow and Balsam Poplar trees.  Our final team member is Dr. Barb Sharanowski, an entomology professor from the University of Manitoba – she is collecting parasitic wasps, with a goal of better understanding their evolution and diversity in northern environments.  Unfortunately, Barb and Laura’s work is dependent on dry and warm weather, so they are hoping for good conditions!

I am here to find a small (< 4 mm) and curious Arachnid known as the “Arctic pseudoscorpion“.  Pseudoscorpions are relatives of other Arachnids, and resemble scorpions, but without a tail.  They are predators (of other invertebrates) that live in soil, leaf-litter, under bark, and under rocks.  The species Wyochernes asiaticus lives under rocks beside creeks and rivers in the Yukon.  It is a Beringian species, meaning it exists in North America in regions that were unglaciated during the last ice age, including many regions in the Yukon. The Dempster Highway travels directly through a lot of these regions.   I have previously collected this species in the Yukon, and on this trip, I am hoping to gather more specimens to further understand its full distribution, and to collect data about its biology and life-history.

This morning, despite the rain, our team traveled to a half-dozen streams further south from this campground, and we had great success in pseudoscorpion hunting!  Numerous specimens were found under rocks beside creeks, including females with their eggs held under their abdomen.

We are now drying out and I am about to finish preparing a seminar that our team will deliver tomorrow at the campsite.  The Tombstone Park staff are keen to have researchers discuss their work with the general public – it’s a nice opportunity to share our research stories with other people traveling the Dempster.  I am always thrilled that all types of audiences show keen interest and enthusiasm about insects and spiders.

Stay tuned…later this week will be Parts 2 and 3

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Do spiders like to dance? Do spiders like music?

Posted on August 16, 2012 | Leave a comment

A couple of comments on one of my previous posts  piqued my curiosity about Arachnids and sound – one comment talked about how Harvestmen seemed to enjoy the reader’s singing, and another comment suggested a yellow sac spider moved and grooved (danced?) when a record player was playing tunes.

Huh?

So… it is well known that spiders respond to direct vibrations (i.e., through their webs), but what about sound waves that could be produced by singing or other forms of music?  Do spiders like music? Do they like to dance?

A spider that likes music? Araneus cavaticus (photograph (c) by Tom Murray, published here with permission)

Being a good scientist, I looked to the literature.  Behold, I found a paper published in 1966 in the journal Ecology, titled “Reactions of Orb-Weaving Spiders (Argiopidae) to Airborne Sounds” by Frings and Frings. In this paper, the authors used two common orb-web spiders, and asked whether spiders responded to airborne vibrations as well as to vibrations through their webs.  Unlike previous papers at the time, these authors separated the two possible modes of vibration (i.e., direct vibrations versus airborne sounds).   The Introduction of this paper is wonderful, and provides a series of anecdotes about spiders and sound, including a 1928 citation about how the sensory hairs of spiders moved to the sounds of a mandolin played 5 m away.  As a mandolin player, I was very excited to read this – and I will keep an eye out for spiders when playing!

Frings and Frings collected spiders (including the common orb-web species Araneus cavaticus, of “Charlotte’s Web” fame – it is Charlotte A. Cavatica don’t you know!), used a fancy laboratory set-up to make sounds (and vibrations), and measured responses by their study species.  For one species, the responses were the following ‘1) spasmodic extension of the front legs; (2) jerking of all the legs; (3) shaking the web vigorously by flexing and extending the legs’.

Results:  indeed, their study species respond to airborne sounds, and their responses occur between 200 and 3000 cycles per second (Hertz) and between 90 and 110 decibels.

Let’s put that in perspective -

For Hertz (i.e. cycles per second, or pitch):

Strings on a mandolin range from about 196 Hz to 660 Hz; A barking dog has a range between about 400 Hz and 1000 Hz; The range of a typical human voice is between 80 Hz and 1100 Hz.

For Decibels (i.e., “loudness”)

A violin is between 82 and 92 dB; Singing can be up to 100 dB; A really loud rock concert can be up to 150 dB

 So, if you sing loudly to a spider, play the mandolin for it, or take it to a rock concert, the sound waves produced can elicit responses in spiders.

(A  barking dog will also work.  Or, a dog playing a mandolin)

Might spiders like my mandolin playing more than my family?

Caveats:  the results I mention are for two species only, and it would be  interesting to see whether other species responds in a similar fashion.  Also, I am personally very curious about how spiders respond to different styles of music – classical, bluegrass, punk rock?  THIS is a great research question!

Reference:  Fings, H, & Fings, M (1966). Reactions of Orb-Weaving Spiders (Argiopidae) to Airborne Sounds Ecology, 47 (4), 578-588 DOI: 10.2307/1933935

 Thanks to Tom Murray for permission to use his photograph – more of his work can be viewed here. 

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Canada’s largest spider …sittin’ on the dock of the bay

Posted on August 13, 2012 | 10 Comments

I just returned from a week of vacation on beautiful Stony Lake, north of Peterborough, Ontario.  A lot of time was spent sitting on docks (Note: the correct terminology should be Wharf instead of dock i.e. you ‘dock’ at a wharf; however, it is generally more commonplace to use the terminology Dock), at water’s edge.  Where there are docks wharfs, there are spiders.   The most common species on the docks tends to be the (in)famous “dock spiders”.  I am pretty sure that dock spiders are the largest spiders in Canada (if not, please correct me!).  I receive many phone calls and e-mails about dock spiders, and I suspect an impressive amount of arachnophobia can be blamed on this hairy wonder of the Arachnid world.

Dock spider (Family Pisauridae), Dolomedes sp.

Dock spiders belong to the family Pisauridae, which are closely related to wolf spiders (family Lycosidae).  Both of these families of spiders show interesting behaviours towards their young (‘spiderlings’).  Females lay eggs within a silken egg sac, and this sac is carried around by the female until it is time for the young to hatch.  Wolf spiders attach their egg sacs to the end of their abdomen, and when the spiderlings hatch they are carried around on the mother’s abdomen before embarking on a solitary life.  Pisaurid females, however, hold the egg sacs by their fangs, and it is carried underneath the female’s body – it looks like the females are carrying around a big wad of cotton by their mouths.  Pisaurids are commonly known as nursery-web spiders, as females build a silken, tent-like ‘nursery’ for their spiderlings.  Upon hatching, the young spiders live in a protected place, typically spun in and among grasses, low-growing vegetation, or between rocks around the margins of water.

A dock spider (Family Pisauridae), Dolomedes sp., in its favourite habitat

Two species, Dolomedes tenebrosus and Dolomedes scriptus are the common ‘dock spiders’.  Unfortunately it is difficult to tell these two species apart, without a microscope, forceps, and expertise. Both species are brownish-grey in colour, with black and light brown markings (‘chevrons’) on their abdomen. These spiders, especially the full-grown females, are the largest (native) spider species in Canada, and their body (including legs) can almost fill your palm – the body length (i.e., not including legs) of mature females can easily exceed 2 cm.  But do not worry!  These spiders do not bite people, and would rather eat land-dwelling and aquatic insects, and they are known to catch small minnows, which is the reason for their other common name, the fishing spider.  The spider will wait with its front legs resting in the water, and when small tadpoles or fish come near, the vibrations alert the spider to its lunch. An invertebrate eating a vertebrate is not a common occurrence in the animal kingdom!  

Dock spider habitat

Dock spiders, as their name suggests, tend to be associated with the margins of lakes, ponds, swamps and rivers, where they typically sit motionless on tree trunks, rocks, boats, and docks.  However, individuals are known to travel some distance from water, and are the reason for many alarmed people describing hairy monsters in their basements.  This mainly occurs in the autumn months when the spiders are searching for a warm place to spend the winter (under stones, leaves, or bark, or inside buildings).  After spending a winter as an immature spider, dock spiders typically mature and mate in the spring, with females carrying egg sacs for a few weeks, before the young hatch in the nursery.  Females can then go on to produce a second, or sometimes a third egg sac before the end of cottage season.  One egg sac can produce over 1,000 spiderlings.

Without a doubt, dock spiders are impressive animals and although not small and obscure, they are still worthy of study. They should be considered friends of cottagers, boaters and home-owners.  I encourage you to watch them, observe their behaviours, and marvel at their size – it’s especially fun to do this when sitting down at the dock, having a glass of your favourite beverage, watching when the evening comes….

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Why I study obscure and strange little animals

Posted on July 23, 2012 | 17 Comments

I sometimes find myself defending why I study obscure and strange little animals.  Questions such as “what good are they” are asked of me.  I sometimes get weird looks when I describe what it is like discovering new distribution records of a tiny jumping spider, or the thrilling anticipation of turning over a rock to see what hides underneath.  I have to remind myself that not everyone is fascinated by the natural world.  I also think it is worthwhile reminding myself why I study small animals. Here is a list:

The Arctic pseudoscorpion Wyochernes asiaticus (copyright C. Ernst, reproduced here with permission)

I study these animals because they are there even if we can’t always see them.

I study these animals because they are unknown, and stir up a sense of curiosity, wonder and awe; their biology is as amazing as any other species.

I study these animals because they play important roles in their ecosystems; roles that we have yet to fully understand.

I study these animals because they are one piece of a giant biodiversity puzzle – they are as interesting and fascinating as primates, blue whales, oak trees, honey bees, or coral reefs.  

I study small animals because they are giants in their own world; size is relative.

I study these animals because they are beautiful; they are a landscape painting; they are a a Bach Cello Suite; they are millimetres of perfection.

I study these animals because they have a history; a history as great as their larger cousins; they are evolution exemplified.

I study these animals because nobody else does.

The Arctic pseudoscorpion Wyochernes asiaticus (copyright C. Ernst, reproduced here with permission)

What are your reasons for studying small, strange animals?

(thanks to Crystal Ernst for the stunning photographs of Wyochernes asiaticus - these photos were taken on our recent field trip to the Yukon)

 

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Successful Pseudoscorpion Hunting in the Yukon

Posted on July 19, 2012 | 7 Comments

The Arctic Pseudoscorpion Wyochernes asiaticus

I am heading back home after a simply amazing field trip to the Yukon Territory. As mentioned in a previous post, one of the goals of the trip was to collect more specimens of an Arctic pseudoscorpion Wyochernes asiaticus (Family Chernetidae) – a Beringian species known from Siberia, Tibet, and the Yukon. This species survived the last great glaciation event in North America by living in unglaciated regions of the northwest, including parts of the Yukon. In 2008 I had collected this species under rocks beside high elevation and high latitude creeks and rivers in a few locations in the Yukon. On this trip, my goal was to collect more specimens to further assess the distribution of this Beringian species, and to gather more life-history information including estimates of size and fecundity. Because of the relative rarity of pseudoscorpions, few data exist that describe life-history parameters of these arachnids.

Despite some rather wet and cold weather for a lot of the trip, the pseudoscorpion collecting was completely successful – we were able to collect hundreds of specimens, from the south end of the Dempster Highway (approximate latitude 64.3 degrees N) all the way up into the Northwest Territories (>67 degrees N). We collected specimens under rocks in more boreal regions, as well as the upper headwaters of high elevation creeks – some of these less than a metre wide. Here is an example of one of these northern, high elevation creeks in the Northwest Territories, just beyond the Yukon-NWT border:

An Arctic, high-elevation stream in the Northwest Territories: pseudoscorprion country!

To give you some idea of the ease of collecting, here is an example of what you might find when flipping over rocks beside the creeks:

Several Wyochernes asiaticus (Pseudoscorpiones) females (with yellow eggs visible)

I was also able to capture some video of these pseudoscorpions – as far as I am aware, Wyochernes has never before been videotaped, so this is the FIRST EVER movie of this species!

Our larger research goals included more than pseudoscorpion colleting, and I was in the Yukon with a wonderful team of scientists, including my graduate students Crystal Ernst, Katie Sim, a post-doctoral researcher Dr. Laura Timms, and an entomology professor from the University of Manitoba, Dr. Barb Sharanowski. We all had different objectives and goals for the Yukon trip, and over the next couple of weeks. I will post some more research stories from this field-work to give a sense of the scope of our research efforts in the Yukon.

The research team at the Arctic circle (Laura, Katie, Crystal, Barb & Chris)

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A classy canopy-dwelling jumping spider: Hentzia mitrata

Posted on July 17, 2012 | 2 Comments

I have just returned from a week of field work in the Yukon – and will report on that in some detail soon.  However, in the interim here is a short story about a lovely jumping spider (Family Salticidae).  This is a story that started quite a few years ago, with my graduate student at the time, Maxim Larrivée.  Max documented that the spider fauna of canopies of the forests around Montreal hosted fewer spiders than the understorey, and a lower number of species than the understorey (Larrivée & Buddle 2009).  However, he also noticed and documented that there were a handful of specific spider species that were more frequently encountered in the canopy compared to the understorey, including a stunning jumping spider Hentzia mitrata.  Here’s a photo, courtesy of Thomas Shahan .  (you can view more of Thomas’ amazing photographs here):

Hentzia mitrata, copyright T. Shahan, reproduced here with permission

Just recently our laboratory had a publication come out in The Canadian Entomologist on another study of spiders (and beetles) in the canopy of forests at the Morgan Arboretum (Aikens & Buddle 2012). This was work done by my former MSc student Kathleen Aikens.  As one part of her work, Kathleen asked whether there was vertical stratification in beetle and spider assemblages – there was, and in addition to that finding, Kathleen again documented that Hentzia mitrata was more common in the canopy as compared to the understorey – here’s a figure from that paper showing those data:

We have now published this finding three times – in Max’s work on foliage dwelling spiders (Larrivée & Buddle 2009), his work on bark-dwelling canopy spiders (Larrivée & Buddle 2010), and now with Kathleen’s work.  This is a convincing body of evidence: Hentzia mitrata has a strong affinity for tree canopies.  

But why?  Why is this species more common in the canopy compared to the understorey?  What does it eat in the tree-tops?  Where does it overwinter?  (our deciduous forest are bare, cold and snowy in the winter!).  As is typical, I have no idea.  We have yet to embark on any life-history study of Hentzia mitrata in the canopy, but it would be well worth pursuing.  In my experience, this species is not all that common in understorey habitats at our latitude, yet there it is, watching us with its big, curious eyes as we enter its tree-top realm:

Hentzia mitrata, copyright T. Shahan, reproduced here with permission

References

Aikens, K.R. & C.M. Buddle. 2012. Small-scale heterogeneity in temperate forest canopy arthropods: stratification of spider and beetle assemblages. The Canadian Entomologist, in press.  doi:10.4039/tce.2012.51

Larrivée, M.  & C.M. Buddle.  2009. Diversity of canopy and understorey spiders in north-temperate hardwood forests.  Agricultural and Forest Entomology 11: 225–237 DOI: 10.1111/j.1461-9563.2008.00421.x

Larrivée, M.  & C.M. Buddle.  2010. Scale dependence of tree trunk spider diversity patterns in vertical and horizontal space. Ecoscience 17:400-410 DOI 10.2980/17-4-3403

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Hunting Pseudoscorpions in the Yukon

Posted on July 4, 2012 | 6 Comments

In four days I head off for two weeks of field work in the Yukon.  I’ve written about this stunning place before, and my student Crystal also posted about the upcoming adventure.  Our time will be spent doing some final collections as part of the Northern Biodiversity Program, and I will also be hunting pseudoscorpions.

A selection of Pseudoscorpions

Although I have a fondness for harvestmen and spiders, pseudoscropions are truly fascinating,  and the most curious of the Arachnids.  They are small arachnids ( most are < 5 mm in length) that resemble scorpions, minus the ‘tail’.  They are found around the world (except Antarctica), and although only a few thousand described species, globally, they are morphologically diverse, and beautiful.  Pseudoscorpions are predators of other small invertebrates, and they typically live within leaf-little, soil, tundra or other substrates on the ground.  They are also phoretic, and sometimes found hanging onto the legs or bodies of other insects.   To learn all about the biology of pseudoscorpions, I recommend reading  Weygoldt’s book.

C. Buddle venturing towards Sheep Creek, Yukon, to search for pseudoscropions

I have a longstanding interest in Pseudoscopions from Canada, and keen to obtain more records to increase the distribution notes for Canada’s fauna.  My trip to the Yukon next week will include searching for a fascinating species: Wyochernes asiaticus.    In North America, this species was described as W. arcticus by William Muchmore in 1990, and is considered the most northern pseudoscorpion on this continent.  Muchmore’s paper was based on 6 specimens collected under rocks beside Sheep Creek, Yukon.  When I was in the Yukon in 2008, I went to Sheep Creek, looked under rocks beside the creek and there were hundreds of specimens to be found:

A Wyochernes (Chernetidae) pseudoscorpion, under rocks at Sheep Creek

Later, Muchmore determined that W. arcticus is the same as a species from Asia (W. asiaticus).   So… those of you that know your glacial history are aware that sections of the Yukon remained unglaciated during the last ice age. Quite a number of taxa have been found in that region of the Yukon whose closest relatives are from Siberia and other parts of Asia. They are relicts of the past, and labeled ‘Beringian’ species because of the Beringian land bridge that used to join North America to Asia.    That tiny pseudoscorpion is a perfect and stunning example of a Beringian species – it is known only from Siberia, Mongolia, possibly Tibet, and from a few localities in the Yukon.

You can probably anticipate my excitement – when I was last in the Yukon almost all the dry creek beds up the Dempster Highway hosted Wyochernes asiaticus.  I am most eager to collect more.  I will be collecting them to test some life-history theories,  verify distribution records, and see just how far north this species can be found.  NOTE:  IF YOU ARE THINKING OF DOING YOUR OWN COLLECTIONS IN ARCTIC REGIONS, INCLUDING THE YUKON, YOU NEED A SCIENTIFIC PERMIT TO DO SO.  You cannot collect in these parts of the world without authorization.  This makes sense-the beauty of the North cannot be taken for granted and needs to be studied with caution:

The Yukon.

As you can guess, the Dempster highway is a rather isolated and remote region.  I will not likely be posting again until after my return. Later in July, I do hope to share some more research stories with you…and I can pretty much guarantee there will be discussions about pseudoscorpions!

References: 

Buddle, C.M. 2010. Photographic key to the Pseudoscorpions of Canada and the adjacent USA. Canadian Journal of Arthropod Identification No. 10, 03 February 2010, available online at http://www.biology.ualberta.ca/bsc/ejournal/b_10/b_10.html, doi:10.3752/cjai.2010.10.

Muchmore, W.B. (1990). A pseudoscorpion from arctic Canada (Pseudoscorpionida, Chernetidae) Canadian Journal of Zoology, 68 (2), 389-390 DOI: 10.1139/z90-055

Muchmore, W.B. (1996). On the occurrence of Wyochernes in Asia (Pseudoscorpionida: Chernetidae).  Bulletin of the British Arachnological Society 10(6): 215-217.  Link

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You are always within three feet of a spider: Fact or Fiction?

Posted on June 5, 2012 | 9 Comments

A lovely crab spider (Thomisidae).

Last week I wrote a post about the life history of Arctic wolf spiders – and in that post I discussed how some of our recent research results show wolf spider densities in Arctic tundra habitats are just under 0.5 per square metre.  Morgan Jackson commented on that post, and asked about whether it was true that you are always within six feet of a spider.  This is one of those common myths (along with ‘do spiders bite?).

A quick scan on the Internet suggests this myth can be stated in many ways (e.g., within a metre, within six feet, within three feet, etc.)  but you get the point: are you always close to spiders? .  This ‘myth’ has been submitted to Mythbusters  as one that the show should tackle,  and ‘yahoo answers‘ has this question – some of the answers are hilarious (e.g., not when you are swimming).   So…is it fact or fiction?  When in doubt, let’s go look at the scientific evidence.

What does the scientific literature tell us?

As mentioned in my post last week, our laboratory just published a paper in the Canadian Journal of Zoology about wolf spiders in the Arctic.  In this work, wolf spiders occurred at densities of close to 0.5 per square meter.  In some of my own earlier work in Alberta (more shameless self-promotion! see Buddle, 2000), I estimated densities of wolf spiders (in a forest environment) to be between 0.5 and 1 per square meter.   Not long ago, I had a discussion with a PhD student working in Alaska, and she also had densities estimates of wolf spiders within a similar range.  Kiss & Samu published a paper in 2000 that was about densities of wolf spiders in agroecosystems in Europe, and their estimates were at a minimum of three adults per square metre.

A wolf spider (Lycosidae) – they are everywhere!

Those aforementioned estimates are for one family of spiders only (the wolf spiders, Lycosidae), and wolf spiders are active and easy to see.  I would argue that densities of other spider families are likely higher than wolf spiders.  Most spiders are quite small and easy to miss, but they are everywhere.

In a classic and seminal paper by Turnbull (1973) (all Arachnologists should read that paper!) there are a series of estimates of spider densities in a range of habitats – and these are estimates for all spiders, not just a single family.   The lowest estimate he provides is from work in a Polish meadow where densities of 0.64 spiders per square metre were reported.  The highest density was 842 spiders per square metre in an English pasture. Turnbull averaged all previous published estimates and ended with a mean of 130.8 spiders per square meter.  Turnbull does point that it is kind of a meaningless statistic, except that it helps us tackle the question of interest: Is there always a spider within three feet of you…?

So…. in most “natural” habitats, I think it is true that you are always within three feet of a spider.

There are some exceptions, of course.  Here are some:

-spiders are not nearly as common in heavily managed, monoculture habitats (e.g., turf grass, golf courses, some urban greenspaces)

-spiders are not as common in buildings as in natural habitats (although they are there, as I’ve written about in posts about the zebra spider, cellar spider, and ceiling spider)

-in Northern climates, spiders are not active in the winter months- so although you could still be close to them (i.e, they are under the snow, somewhere…), it’s quite a different context

-spiders are terrestrial, so you are not close to spiders when you are swimming!

-on the theme of ridiculous exceptions, spiders don’t tend to be common on trains, in airplanes or in trucks and cars (although have you noticed there is often a spider tucked away in your side-view mirror?)

Spiders: you gotta love them – in natural systems, they are always close to you!

Spiders – they really are everywhere – even as sculpture.

References

Buddle, C. (2000). LIFE HISTORY OF PARDOSA MOESTA AND PARDOSA MACKENZIANA (ARANEAE, LYCOSIDAE) IN CENTRAL ALBERTA, CANADA Journal of Arachnology, 28 (3), 319-328 DOI: 10.1636/0161-8202(2000)028[0319:LHOPMA]2.0.CO;2

Kiss, B., and Samu, F (2000) Evaluation of population densities of the common wolf spider Pardosa agrestis (Araneae : Lycosidae) in Hungarian alfalfa fields using mark-recapture.  European Journal of Entomology 97(2) 191-195  Link

Turnbull, A. (1973). Ecology of the True Spiders (Araneomorphae) Annual Review of Entomology, 18 (1), 305-348 DOI: 10.1146/annurev.en.18.010173.001513

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Life History of Arctic Wolf Spiders: Part 1

Posted on June 1, 2012 | 6 Comments

For those of you who follow my blog, you will notice I’m somewhat obsessed with the Arctic – in part because of our large Northern Biodiversity Program, but also because it’s an ideal  system for studying the ecology of arthropods.    It also doesn’t hurt that the Arctic is a beautiful place to work!

The northern Yukon landscape: spider habitat

I am very excited to write about the latest paper published from our laboratory, titled Life history of tundra-dwelling wolf spiders (Araneae: Lycosidae) from the Yukon Territory, Canada.  This has just recently been published in the Canadian Journal of Zoology, with Dr. Joseph Bowden as the lead author.  Dr. Bowden graduate from my laboratory just over a year ago, and is now living in California with his family.  Although the climate is somewhat warmer in California compared to the Yukon, he’s still actively working on research related to the biology of Arctic arthropods.   Dr. Bowden was a terrific student in my laboratory, and has already published some work about the community ecology of Arctic spiders: he has one paper in the journal Arctic and another in Ecoscience.

Dr. Joseph Bowden, working in the Yukon and ready for the biting flies!

In the CJZ paper, Joseph studied three species of tundra-dwelling  wolf spiders (family Lycosidae) and asked whether body size or condition better explained variation in fecundity and relative reproductive effort (defined as the ratio of female body mass to clutch mass).  He also tested whether  a trade-off exists between investment in offspring size and number.  The field work for this research was really enjoyable, as it involved collecting spiders by visual surveys and dry pitfall traps – after collection, Joseph set up a laboratory in a local campground shelter to do measurements on the species:

Dr. Joseph Bowden in a Northern “laboratory”

One of the main findings was that body size explained well the variation in offspring number.  Stated another way, larger female wolf spiders produced more eggs, a finding well supported in the literature.   A second main finding was that females with a lower condition allocated relatively more to offspring production than did females in better condition. This makes some sense – if the going is tough (i.e., poor condition), the females primary objective (from a fitness perspective) is to invest in offspring.  A third key finding was that  we found a negative relationships between egg size and number.    These trade-offs may in part be because of variation in resource availability at some of the study sites in the Yukon tundra.

An Arctic Pardosa (Lycosidae) female, with egg sac

Joseph also calculated tundra wolf spider densities.  Here’s the text of the CJZ paper that describes the methods (straightforward but time consuming):

Densities of the three focal species were estimated using a ring of hard plastic measuring 1.13 m in diameter (1 m x 1 m area) and about 12 cm high. The ring was haphazardly and firmly placed on the tundra surface in each site and all wolf spiders collected inside the ring were identified and counted. This protocol was adapted from Buddle (2000).

Results? Well… the most common species Pardosa  lapponica averaged about 0.4 spiders per square metre.  Some simple calculations will tell you just how common wolf spiders are on the Tundra:  4000 wolf spiders per hectare.  Don’t forget – wolf spiders are only part of the Arachno-fauna in the Arctic.  With confidence, this estimate of 4000 spiders per hectare represents a minimum.  There are a LOT of Arachnids living on the tundra!

In sum, this paper by Joseph is about studying some good old-fashioned natural history of a fascinating group of animals.  The methods are straightforward, but the findings are significant.  It’s pretty difficult to progress in ecology without a deep understanding of a species’ biology and life-history.  Life-history studies are the cornerstone of biology, and I’m thrilled that Joseph recognized that fact and did this research on Arctic wolf spiders.

    You will see that this post is titled Part 1:  some more work will hopefully be published soon – stay tuned for Part 2…

References

Bowden, J., & Buddle, C. (2012). Life history of tundra-dwelling wolf spiders (Araneae: Lycosidae) from the Yukon Territory, Canada Canadian Journal of Zoology, 90 (6), 714-721 DOI: 10.1139/z2012-038

Bowden, J., & Buddle, C. (2010). Determinants of Ground-Dwelling Spider Assemblages at a Regional Scale in the Yukon Territory, Canada Ecoscience, 17 (3), 287-297 DOI: 10.2980/17-3-3308

Buddle, C. (2000). LIFE HISTORY OF PARDOSA MOESTA AND PARDOSA MACKENZIANA (ARANEAE, LYCOSIDAE) IN CENTRAL ALBERTA, CANADA Journal of Arachnology, 28 (3), 319-328 DOI: 10.1636/0161-8202(2000)028[0319:LHOPMA]2.0.CO;2

Bowden, J. & Buddle, C. (2010). Spider assemblages across elevational and latitudinal gradients in the Yukon Territory, Canada.  Arctic 63(3): 261-272 http://arctic.synergiesprairies.ca/arctic/index.php/arctic/article/view/1490

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Daddy longlegs: spider or harvestmen?

Posted on May 3, 2012 | 3 Comments

I’m about half-way through the “Opiliones Project” – this is a twitter-project devoted to sharing facts about Harvestmen (follow using the hashtag #OpilionesProject).  As I was working through some of the chapters, I gave a lot of attention to the variety of common names given to Harvestmen, including Daddy Longlegs.  This is not a very good common name for Opiliones because the characteristic of ‘long legs’ is not common to all Harvestmen, and many species (especially in tropical regions) are rather stout and don’t have the long, dangly, legs that we often associate with Opiliones in more northern regions.

The other reason to avoid the name daddy longlegs for Harvestmen is because of the confusion it creates with respect to a distant relative of Harvestmen – a spider with the latin name of Pholcus phalangioides.  This species is often referred to as the “Daddy longlegs spider” (and, by the way, the name “Phalangida” has historically been used as a synonym to Opiliones – more confusion!).   The rather obvious similarity between northern Harvestmen and Pholcus phalangioides is that they both have long legs – but it stops there.  Spiders have a narrow waist (i.e., the constriction between the cephalothorax and abdomen) whereas Harvestmen do not.  Pholcus phalangioides is also an enthusiastic web-builder whereas Harvestmen do not live in webs.  Here’s a photo of Pholcus phalangioides, courtesy of Ashley Bradford. (thanks, Ashley, for permission to use your photograph!)

A cellar spider, with prey (c) A. Bradford

Comparing a Spider to a Harvestmen is like comparing a blue whale to a chimpanzee.  Spiders are a different order (Araneae) than Harvestmen (Opiliones), and although both Arachnids, they diverged millions of years ago.  Opiliones are more closely related to Scorpions, Pseudoscorpions, and Solifugids than they are to the Araneae.

The other common name for Pholcus phalangioides is the “cellar spider” and this is much more appropriate – these spiders are synanthropic (see my other posts about spiders that like living in or near your home, the zebra spider & the ceiling spider), and are very commonly found in dark, damp places in and around human structures.  In my own house, the garage and basement are the common habitats.   Pholcus phalangioides is very distinctive – in addition to its long legs, it is a fascinating species from a behavioural perspective – if disturbed, it gyrates and whirls around in an impressive display of arachno-energy.  This is something I encourage you to try with your own populations of the species – it is wonderful to watch.  This behaviour is very well documented on youtube.  For example….

Wikipedia has an interesting entry about Pholcus phalangioides – including mention that one of its other common name is the “skull spider” because of patterning on its abdomen.  I also learned that the television show “Mythbusters” did an episode (in 2004) devoted to this species!   They busted the myth that this species had potent venom, but was unable to to pierce human skin (you can watch some of that episode here).

There has been some high quality research done on Pholcus phalangioides.  A nice overview of the biology of the species was provided by Jackson & Brassington, in 1987 – their paper is a key source for taking you back to the older literature on the species, and they also provide evidence that Pholcus phalangioides is an aggressive mimic of other spiders, and they are araneophagous (i.e., eat other spiders).  More recently,  Schafer and Uhl, in 2002, focused on mating behaviour and the role of male “pedipalp movements” as predictors of paternity in the species.  Bernhard Huber has recently (2011) written about the phylogeny and classification of the family Pholcidae and provided an updated cladistic analysis.

Keep an eye out for these characteristic spiders and don’t confuse them with the Opiliones…and be careful using the common name of Daddy Longlegs – it means different things to different people.

References:

Jackson, R.R. & R.J. Brassington. 1987.  The Biology of Pholcus phalangioides – predatory versatility, araneophagy and aggressive mimicry.  J. Zool. 211: 227-238. http://onlinelibrary.wiley.com/doi/10.1111/j.1469-7998.1987.tb01531.x/abstract

Huber, B. (2011). Phylogeny and classification of Pholcidae (Araneae): an update Journal of Arachnology, 39 (2), 211-222 DOI: 10.1636/CA10-57.1

Schäfer, M., & Uhl, G. (2002). Determinants of paternity success in the spider Pholcus phalangioides (Pholcidae: Araneae): the role of male and female mating behaviour Behavioral Ecology and Sociobiology, 51 (4), 368-377 DOI: 10.1007/s00265-001-0448-9

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