Long, cryptic spiders

Iona beach, near the Vancouver International Airport in Richmond, BC, is fantastic place to go looking for spiders and other arthropods, and there always seems to be something new to discover on the dunes. So it was an unusual situation when last Friday evening, just before the park gates were about to close, Sean was lamenting not having found anything very interesting to photograph. We decided to spend our last minutes on the beach in an effort to turn up some sleeping hymenopterans in the vegetation bordering a walking path. After closely inspecting a couple of plants, instead of a sleeping bee or wasp, I found what at first glance looked like a tiny twig hanging in the middle of a spider’s orb web. Meet Tetragnatha caudata, the longest, most cryptic orb-weaver I have ever met!


This slender female was not easy to spot among the grasses, even though she was hanging right in the middle of her web. Her body is only about 1cm long from tip to tail.

Tetragnathidae is the family of the longjawed orb-weavers. You can see where the name comes from in the photo of a male below. During mating, the male and female interlock their large chelicerae in toothy embrace. This is where the male’s exceptionally long pedipalps come in handy, allowing him to reach the female’s epigynum while maintaining his hold on his partner’s fangs.


You can see this male’s large, powerful jaws sticking out to the sides underneath his very long, slender pedipalps.

Spiders in the genus Tetragnatha are sometimes called ‘stretch spiders’ because of their elongated bodies. They often rest with their first two pairs of legs stretched out in front. They can be very cryptic in this posture, especially if they cling to twigs or stems that are similar in colour to their bodies. Although they normally use their webs for hunting, sometime Tetragnatha will also snap up unsuspecting prey when lying low like this on vegetation.


A male Tetragnatha in camouflage mode. This works better on dry grasses or twigs, I would think. But still pretty stealthy here.

Most species in the genus Tetragnatha are difficult to tell apart, but I got lucky with this one (it keys out in the second couplet of the key to the Canadian species in this genus). Tetragnatha caudata is so named because of its strange looking abdomen (caudata means ‘tailed’ in Latin). While I would expect the spinnerets to sit at the tip of a spider’s abdomen, in this species there is a slight kink where the spinnerets sit on the underside of the abdomen, and a pointy tail sticks out behind them.


If you look closely you can see a strand of silk coming out of this female’s spinnerets, located on the underside of her abdomen just before it bends into a pointy tail.

The orb webs of Tetragnatha are usually horizontal or angled (unlike the vertical webs of spiders in the more familiar orbweaver family Araneidae) and have a hole in the centre where the spider sits waiting for prey.


We found several of these tiny Tetragnatha caudata among tall grasses, but larger members of the genus typically build their horizontal orbwebs over water, allowing them to capture insects such as mosquitoes as they emerge.


So let this be a lesson: next time you’re out looking for wildlife, stop and take a careful look in some seemingly boring vegetation! You never know what wonders you might turn up.

Thanks to Sean, as usual, for the great photos!

Adams, R.J. (2014) Field Guide to the Spiders of California and the Pacific Coast States. University of California Press, Berkeley and Los Angeles.

Bradley, R. (2013) Common Spiders of North America. University of California Press, University of California Press, Berkeley and Los Angeles.

Dondale, C. D., Redner, J. H., Paquin, P., & Levi, H. W. (2003). The Insects and Arachnids of Canada. Part 23. The Orb-weaving Spiders of Canada and Alaska (Araneae: Uloboridae, Tetragnathidae, Araneidae, Theridiosomatidae)Ottawa, NRC Research Press.

The mystery of the burrow-dwelling sand dune spider

On a walk at Iona Beach a couple of weeks ago with Sean (who kindly provided all the photos that follow) I came upon a small hole in the sand, and after poking at it a bit, realized it was a silk-lined burrow with what looked like a trap door. We tried to figure out who lived there, but didn’t find anyone inside.


The mystery burrow where this natural history adventure all began!

I went home puzzling about the mysterious burrow-dweller, and emailed our local spider expert Robb Bennett to see if he had any idea what kind of spider the owner might be. His response that it was probably a wolf spider burrow came as a surprise to me. I don’t know a lot about wolf spiders (family Lycosidae), and although I have occasionally seen them hunkered down in shallow depressions under stones and logs, I wasn’t aware that many species build quite elaborate silk-lined burrows. As it turns out, some lycosids overwinter or oviposit in burrows, or hunt by waiting just inside the burrow entrance for prey. One genus, Geolycosa, spends almost its entire life underground, in burrows up to 17cm deep (Dondale & Redner 1990)!


Before this mystery began, I had only seen lycosids associated with shallow burrows, like this one we found on Mt. Tolmie.

A few days later, we returned to the beach to look for more spiders and other arthropods. We encountered several jumping spiders, including this one.


 A Sitticus male?

After a while, Sean spotted this beautiful and well-camouflaged male wolf spider.


After being disturbed, this spider alternated between lightning-fast sprints and freezing with its legs splayed out against the sand. It takes full advantage of its banded legs and mottled body coloration, which allow it to all but disappear against the background!

Next we encountered two females of the same species carrying their spiderlings on their abdomens. Lycosid females have special abdominal hairs onto which the inner layer of spiderlings cling (Rovner et al. 1973).


The second female we found had a smaller brood of larger spiderlings hanging on mainly to the underside of her abdomen.



Here’s a portrait of the same female as the previous photo, this time showing the characteristic lycosid eye arrangement.

A little while later, much to my excitement, I came across another silk-lined burrow!


Another mystery burrow, very similar to the original!

Using a bit of dry grass to scratch at the sand-covered silk surrounding the burrow entrance, I was able to entice the resident spider towards the opening. And just like that, the mystery was solved! The burrow belonged to a female of the same wolf spider species we had been running into all evening as we explored the beach.


The spider soon approached the entrance of her burrow to investigate the source of the disturbance.


After some more serious disturbance resulting in the opening of the burrow now looking a lot more like the (also disturbed) entrance of the original mystery burrow, the spider was persuaded to come out entirely.

After a successful evening of sleuthing, we went home and identified our cryptic burrow-dwelling spider as Arctosa perita. This species is typically found on sand dunes or sandy heathland, and only the females construct silk-lined burrows (Dondale & Redner 1990). It is introduced to North America, and is apparently only present in certain areas of southern British Columbia. The similarly coloured beach wolf spider Arctosa littoralis (beautifully photographed by Ted MacRae here) is native to North America.

The burrow entrance can be cinched up and made effectively invisible to humans, but this does not prevent some predators from detecting the spiders inside. In Britain, Arctosa perita is the preferred prey of the spider wasp Pompilus plumbeus, which uses a combination of smell and touch to locate the spiders within their burrows (Bristowe 1948). This spider (and other lycosids) can detect polarized light, and this species is somewhat famous for being able to navigate using the sun or the moon (references in Dondale & Redner 1983).

Arctosa perita doesn’t seem to have a well established common name, but I found it referred to as the ‘sand bear-spider’ by Steven Falk on Flickr (check out his lovely photo set), which I quite like. The genus name Arctosa is based on the Greek word for bear, ἄρκτος (arctos). The species name ‘perita‘ means ‘mountain dweller’ in Greek which doesn’t make a whole lot of sense unless you consider the sand dunes that are apparently the preferred habitat of this species to be very small mountains. I will now always think of it as the mysterious burrow-dwelling tiny sandy mountain bear-spider! Catchy, right?

Bonus fun fact about wolf spider names:

The type genus is Lycosa, which of course means ‘wolf’. Several other genera were subsequently named to rhyme with Lycosa, with the names based on other carnivorous animals: Alopecosa (fox), Crocodilosa, Dingosa, Hyaenosa, Lynxosa, Mustelicosa (weasel), and Pardosa (leopard).


Bristowe, W. S. (1948). NOTES ON THE HABITS AND PREY OF TWENTY SPECIES OF BRITISH HUNTING WASPS. Proceedings of the Linnean Society of London, 160: 12–37. doi: 10.1111/j.1095-8312.1948.tb00502.x

Dondale, C. D., & Redner, J. H. (1983). Revision of the wolf spiders of the genus Arctosa CL Koch in North and Central America (Araneae: Lycosidae)Journal of Arachnology, 11: 130.

Dondale, C. D., & Redner, J. H. (1990). The insects and arachnids of Canada. Part 17. The wolf spiders, nurseryweb spiders, and lynx spiders of Canada and Alaska. Araneae: Lycosidae, Pisauridae, and Oxyopidae. Publication-Agriculture Canada (English ; 1856).

Rovner, J. S., Higashi, G. A., & Foelix, R. F. (1973). Maternal behavior in wolf spiders: the role of abdominal hairs. Science, 182: 11531155. doi: 10.1126/science.182.4117.1153

Spiders of Mount Tolmie

Spring is springing in Victoria, and it’s a great time to see spiders. Sean insisted that I take a break from the intense data-wrangling I was working on yesterday afternoon to take a walk at Mount Tolmie. We were rewarded with an amazing abundance and diversity of spiders, just by flipping over a few rocks. Here is a selection of our most exciting finds, by family.

(All photos by Sean McCann)

Our adventure began with another observation of spider-on-spider predation. This lovely reddish jumping spider’s victim is unknown – perhaps a sac spider (family Clubionidae).IMG_1898

Pimoa altioculata. Pimoidae is a family of spiders that is closely related to the Linyphiidae, and one I have never before encountered. The name Pimoa comes from the Gosiute language, and means ‘big legs’. An rather apt description for this leggy spider, found hanging out near a couple of egg sacs.IMG_1996

Alopecosa – named for a fox. We found several of these gravid (pregnant) wolf spiders under the stones. IMG_1951

This one was hiding out in a burrow.IMG_2001

A ground spider with its characteristic cylindrical spinnerets visible. IMG_1892

The western black widow, Latrodectus hesperus, can usually be found under the rocks at Mount Tolmie. They are not nearly as abundant there as at Island View Beach, however.

The prize of the day was Phrurotimpus borealis. Phrurotimpus means ‘guarder of stones’, in reference to their habit of dwelling under rocks. These tiny spiders are ant-mimics, with the first pair of legs held forward like antennae (ants are also abundant under the rocks at Mount Tolmie). This one is a mature male.IMG_1906


Dictynidae or Cybaeidae (?)
Finally, a mystery spider that we initially mistook for an amaurobiid. IMG_1903

Not shown, but also encountered, were many Tegenaria (some of which are now Eratigena) (Agelenidae) and a pair of Dysdera crocata (Dysderidae). At least nine families is not too shabby for an impromptu afternoon stroll!

Many thanks to Robb Bennett for his kind help with identification.

Phidippus and Salticus

Two spiders, both alike in family,

Phidippus johnsoni, the red-backed jumping spider. (Photo: Sean McCann)

Salticus scenicus, the zebra jumper. (Photo: Sean McCann)

In fair Victoria, where we lay our scene,


Uplands park, Victoria, BC, is among the many homes of these common jumping spiders (family Salticidae). (Photo: Colin McCann)

From ancient grudge break to new animosity,

Where spider blood makes spider fangs unclean.

Jumping spiders (like all spiders) are generally predators of insects and other arthropods. Spiders are the second most common prey items of Phidippus johnsoni (27% of their diet, just after dipterans, coming in at 30% of the total count), and comprise 5% of the diet of Salticus scenicus.

Jackson, R. R. 1977. Prey of the jumping spider Phidippus johnsoni (Araneae: Salticidae). J. Arachnol. 5 :145-149.
Okuyama, T. 2007. Prey of two species of jumping spiders in the field. Appl. Entomol. Zool. 42 (4): 663–668.

The zebra jumper’s stripes may serve as camouflage in many settings, but in this case they were no match for the excellent visual hunting abilities of a fellow salticid. (Photo: Sean McCann)


Oxyopidae: sharp, cat-like spiders

The family Oxyopidae contains 448 species of spiders in 9 genera. They have a worldwide distribution but are (like so many groups) most speciose in the tropics. I had never encountered one personally before traveling in Central and South America, but it turns out we have two species in the genus Oxyopes in Canada!

Oxyopids (also known as lynx spiders) all have 8 eyes, and can be easily distinguished from spiders in other families by their characteristic hexagonal eye arrangement, as well as the often dagger-like spines (called macrosetae) on their legs. The family name Oxyopidae is derived from the genus name Oxyopes, which is a combination of the Greek word for ‘sharp’ (ὀξύς), and the Latin word for ‘foot’ (pes). Sharp-legged is a rather apt description for many members of this family. (Update: according to Spiders of North America it means sharp-eyed, which is also an accurate, but slightly less obvious, descriptor.)


A female Oxyopes salticus (one of the two lynx spider species found in Canada) sporting impressive (sharp-looking!) spines on her legs and the characteristic hexagonal oxyopid eye arrangement. Photo by Thomas Shahan, licensed under CC BY-NC-ND 2.0.

Members of this family are generally diurnal hunters, with keen eyesight (for spiders) and great agility. Like the cats they are named after, lynx spiders often stalk and pounce on their prey. They are proficient jumpers, and some might even be mistaken for a salticid at first glance. This one (click the link, it’s worth it!) looks like it might actually mimic a jumping spider.

This cryptic oxyopid (a Hamataliwa species) we found in Honduras fooled me twice: at first glance it looked like a bump on a twig, and on my second look, after realizing it was a spider, the size and posture had me thinking it was a salticid. Photo: Sean McCann

Some oxyopids are ambush predators, staking out flowers and waiting for unsuspecting insect visitors. Like crab spiders (Thomisidae) with similar behaviour, green lynx spiders have the ability to slowly change colour (the process takes several days) to match the background they are sitting on – usually flowers.

A green lynx spider (Peucetia viridans) from Fort Pierce, Florida. This species can change its colour to match the background it sits on (see some examples of better background-matching here under ‘identification’). Photo: Sean McCann

Like the disparate forms these spiders take – compare the Peucetia viridans above with the Hamataliwa grisea below – they also have fascinating variety in their habits. 

A Hamataliwa grisea found in Gainesville Florida. Photo: Sean McCann

While most lynx spiders are cursorial hunters that don’t use silk for prey capture, there is one web-building genus (Tapinillus), including a social spider species that engages in communal web building and cooperative prey-capture!

Peucetia tranquillini is a wanderer that invades the orb-webs of female Nephila clavipes, locating and preying on courting males by responding to their vibrations, and sometimes vibrating the web themselves, apparently to attract a resident spider (a possible example of aggressive mimicry). One individual was also found residing in the tangle-web of a brown widow (Latrodectus geometricus) for several days, capturing prey caught in the web, and even stealing prey captured by the web owner (kleptoparasitism).

Spiders in the genera Oxyopes and Peucetia are members of what I like to call the centimetres high club: they mate in the air, hanging from a silken thread spun by the female. In one species, the male wraps the female in a silk ‘bridal veil‘ before copulation.

scalaris kyron basu

Oxyopes scalaris, the other lynx spider that can be found in Canada. Photo by Kyron Basu, licensed under CC BY-ND-NC 1.0.

Mother green lynx spiders guard their egg sacs and newly emerged spiderlings, and will fiercely defend them by spitting venom. While the spitting spiders (Scytodidae) shoot a deadly combination of venom and silk out of their fangs to capture prey, this seems to be the only spider with venom-spraying defensive behaviour.


A gravid female green lynx spider (Peucetita viridans), capable of forcibly ejecting irritating venom from her fangs. Photo: Sean McCann

Check out the following posts for even more information about awesome oxyopids:

Kids and Spiders in Honduras

Here in Honduras, Sean and I have happily taken the opportunity to interact with some great local kids who seem almost as excited about spiders as we are!

We lent them some plastic tubes for collecting, and they headed off to search for cool spiders around town. In no time at all, they brought back an impressive collection, from tiny jumping spiders to massive wandering spiders.


These kids are totally fearless, casually picking up spiders that are about half the length of their hands! Sometimes they were a bit too enthusiastic in their efforts to capture a speedy specimen, and one brought back a partly crushed spider and a bite on his finger to show for his efforts. (Spiders do occasionally bite, but only as a last resort if they are in a life-threatening situation!) He seemed more proud than upset by this result, but we tried our best to encourage gentler handling from then on!

Here’s a selection of the best shots from one afternoon of collecting (all photos by Sean McCann).


A large wandering spider (family Ctenidae). I’m not sure about the identification, but she looks similar to the Ancylometes bogotensis I wrote about in a post on ‘bridal veils‘.


A lovely female grey wall jumper, Menemerus bivittatus. This species can also be found in the southern U.S.


A male grey wall jumper (I’m guessing he was caught in close proximity to the female), doing what wall jumpers do, hanging out on a wall.


A tiny tarantula spiderling! Notice that the back end of the abdomen is bald… most likely in response to a kid trying to capture it, this spider has shed its defensive urticating hairs (more about tarantula defenses here).

The real house spiders of Vancouver

(and other West Coast cities)

UPDATE (28 July, 2018): The scientific names used in this post are out of date. The giant house spider is now Eratigena duellica, and the hobo spider is Eratigena agrestis. Tegenaria domestica remains the same!

Living in Vancouver, I frequently hear about a HUGE hairy spider that was trapped in the bath or lurking in the bedroom or scuttling across the kitchen floor. More often than not, it’s described as a wolf spider (family Lycosidae). I’m pretty confident that every single time, the spider being referred to is actually a member of the family Agelenidae, and in particular, the genus Tegenaria. I’m almost as certain that the species in question is Tegenaria duellica, commonly called the giant house spider or European house spider.

NOT a wolf spider. Female Tegenaria duellica (Agelenidae) Photo: Sean McCann*

Sometimes the slightly better informed giant-spider-spotter will have taken a closer look at the spider, or photographed it, then done some online research and concluded that it’s the ‘dangerous’ hobo spider, Tegenaria agrestis. 

Female hobo spider, Tegenaria agrestis. These spiders may also be found in houses on the west coast of BC, but are generally not as large as T. duellica.

There is a lot of flat-out wrong information on the internet about hobo spiders and their supposed ability to cause necrotic lesions. Some people mistakenly refer to T. agrestis as aggressive house spiders. (1) They aren’t. And, (2) agrestis means ‘of the field’. As for ‘dangerous’, arachnologists Robb Bennett and Rick Vetter

“know of no authentic Canadian report of hobo spider envenomation.”

See their paper on the misdiagnosis of spider bites in Canada for more reasons not to fear hobo spiders. Having done a bit of work with Tegenaria agrestis, both in the field (on Vancouver Island) and in the lab, I can personally confirm that they are far more likely to be running away from humans than attempting to bite them (just like other Tegenaria species).


A charming female Tegenaria. Neither aggressive nor at all interested in human flesh.

Both hobo spiders and giant house spiders can be found living alongside humans on the west coast. They are not easy to tell apart, but Rick Vetter and Art Antonelli have prepared an excellent identification guide that will tell you at the very least if it’s NOT a hobo spider (not that there would be any cause for alarm if it was one). In a house in southern BC, that leaves you with T. duellica (larger) or T. domestica (smaller).

male T duellica palps

If it has long pointy palps like this guy, it’s NOT a hobo spider, but either T. duellica or T. domestica.

Even without the (fairly recent) hype about the ‘medically significant’ hobo spider, humans seem to generally fear and despise Tegenaria. In The World of Spidersa delightful book in which the author’s passion for his subjects fairly leaps off every page–W.S. Bristowe admitted that he had no affection for house spiders. In their defence, however, he wrote that,

“A Tegenaria cannot deliver a painful bite. Its unpopularity arises from its leg span, its rapid movements and general creepyness.”

Male Tegenaria duellica

Male Tegenaria duellica. Long-legged and disposed to ‘general creepyness’. 

The movement of these spiders is indeed disconcerting. Males are pretty much all leg, and they can run FAST. Bristowe noted that Tegenaria atrica can run a distance equivalent to 330 times her body length in 10 seconds. This means a human-length (let’s say 5’9″, or 1.75 m) Tegenaria could run the 100-metre dash in 1.73 seconds. Pretty speedy.

But apart from their occasionally-startling dashing to-and-fro (mainly in the fall when males go on the prowl, abandoning their webs to search for females), house spiders in general are fabulous to have around. They are great at taking care of all manner of arthropod home-invaders and are really fun to observe.

House spiders, like this Tegenaria that set up shop just inside the door of our lab, help out by snacking on any bugs that might also enjoy living inside buildings.

If you really can’t stand having them in your home, relocate them outside, and with luck they’ll find a nearby crevice in which to build the retreat of their funnel-shaped webs. You probably won’t often catch them out on their silk sheets, as they will run and hide in their retreats at the slightest disturbance.


Usually house spiders wait for prey just inside their tube-like silk retreat. We enjoy attempting to entice this Tegenaria (who lives just outside our lab) to come out and say hi by dropping small insects onto her sheet web. The speed with which she can dart out and snag prey is quite stunning!

If you’re still not convinced that house spiders are good neighbours rather than enemies, you could always try Bristowe’s method for curing fear of Tegenaria: eat one**.

*Sean McCann, a house spider enthusiast, provided all the photographs for this post. He’d like it to be noted that in addition to being incredibly fast, house spiders also *sound* creepy (if you’re lying on the floor and one runs past your head).

**It didn’t actually end up curing his fear of house spiders, but he did win a lot of money as a result.

Meet the Mygalomorphae!

Mating behaviour and silk use in (some) mygalomorphs

So in my ‘intro to spider systematics’ post, I wrote that most of the Mygalomorphae are tarantulas. This is not actually true when you consider total numbers of species. Of the 2775 mygalomorph species (in 16 families), 950 species are in the family Theraphosidae (tarantulas), so that’s actually only about 34%. I probably should have said that the tarantulas are the most common mygalomorphs (and the ones people are generally most familiar with). Theraphosidae definitely wins the prize for the largest mygalomorph family, though. The next most speciose family is Nemesiidae, with 364 species.

I also implied that the Mygalomorphae aren’t all that sophisticated when it comes to silk use. Whereas the Araneomorphae have the ability to spin several different kinds silk specialized for particular functions, the Mygalomorphae produce only one general purpose silk. This is not to say, however, that they have not come up with some marvellous silk-based innovations!

turret M Hedin http://www.flickr.com/photos/23660854@N07/4485414016/sizes/z/in/photolist-7QmVjq-hBLdXo-7L4ijK-7L8h9G-bsNAPc-bsNArZ-bsNBLK/

In the centre of the vegetation in the foreground, you may spy the mouth of a well camouflaged silk-lined ‘turret’ built by a mygalomorph in the family Antrodiaetidae. (Photo by M. Hedin, licensed under CC BY 2.0)

Mygalomorphs have poor vision, so they must rely on chemical (smell or taste), vibratory, and tactile senses. It was traditionally thought that these relatively ‘primitive’ spiders had simple sexual communication systems. However, in their recent review in the Journal of Arachnology, Ferretti and coauthors argue that the sexual behaviour of mygalomorphs actually involves some quite elaborate courtship displays and complex mechanisms of communication. This post will highlight the 6 mygalomorph families described in the paper, most of which use silk in various ways for both prey capture and sexual communication.

Now, as a general rule, spiders are predatory, and mygalomorphs are no exception. They’re pretty keen to snap up anything that blunders into their field of vibratory perception, even if it’s another spider. The main functions of courtship behaviour in mygalomoprhs are mate recognition, orientation and synchronization of sexual behaviour, and suppression of non-sexual responses. Females must advertise their location and receptivity, and males must somehow signal “male, not meal!” to their potential partner. This can be tricky when the stage on which the male must show off his desirability as a mate is the same one that the female uses to detect prey. We’ll see what kinds of things these spiders get up to in order to make it to the finish!

Antrodiaetidae: turret mygalomorphs

Antrodiaetids live underground in silk-lined burrows. The burrow entrance is extended with a turret made from silk, soil, and plant material that blends in beautifully with the surrounding substrate. The spider waits for prey just out of sight inside the tube, where she can detect and quickly respond to vibrations produced by insects brushing against the litter encasing the turret. Males detect the female’s location using pheromones – chemicals acting as olfactory personal ads – on the silk that lines her home.

Antrodiaetus riversi (Antrodiaetidae) in feeding position in turret (Photo by M. Hedin, licensed under CC BY 2.0)

Dipluridae: funnel-web mygalomorphs

The diplurid funnel-web is a horizontal silk sheet leading to a tubular retreat in a crevice or perhaps under a stone or log. From this silken hideout, the spider detects vibrations produced by prey passing over her sheet web. The female’s funnel-web also forms the dance-floor for the male’s vibratory courtship display. The male’s courtship signals are transmitted to the female through the silk sheet. Typically, she does not respond, which is great news for the male! Presumably his pedipalp drumming and many legged tap-dancing is quite distinct from prey vibrations, inhibiting the predatory tendencies of the female.

Ischnothele caudata (Dipluridae) female in her funnel web. Note the elongated spinnerets characteristic of this family. (Photo by M. Hedin, licensed under CC BY 2.0)

Mecicobothridae: sheet-web mygalomorphs

Mecicobothriidae is a family containing nine species of small spiders that build sheet-webs on the soil. In Mecicobothrium thorelli, chemical and/or tactile signals on the female’s silk trigger the male’s courtship display. Like in the diplurids, the male’s dance moves transmit vibrations through the silk to the female, who sits passively in judgment. The receptive female apparently enters a cataleptic state, allowing the male to haul her around the web and manoeuvre her into just the right position. It’s not quite as easy as all that for the male, though. In order for a successful copulation to occur, the chelicerae of the spiders must interlock in a very specific way. If the couple is disturbed while in copula, or there are any difficulties disengaging from this toothy embrace, it’s game over for the male, and dinner time for the female. Once the deed is done, a successful male will stick around on the female’s web, attacking any other males attempting to try their luck with the female. This ‘mate guarding’ behaviour is very unusual among mygalomorphs.

Female Mecicobothrium thorelli (Mechicobothriidae) on her sheet-web. (Photo credit: Gabriel Pompozzi)

Theraphosidae: tarantulas

Theraphosids often live in silk-lined underground burrows, or silken retreats under rocks and vegetation. Sometimes they even build their tube-like homes in trees. Pheromones on the silk allow males to find and recognize females, and also trigger courtship behaviour. Males transmit species-specific vibratory courtship signals through the ground, to the female listening in her burrow. These seismic love songs can be detected by females at a distance of more than one metre. In Avicularia avicularia, the female actively responds, tapping her first pair of legs and pedipalps on the substrate. These good vibrations tell the male she is receptive to his advances, and may also help the male orient toward her.

Immature Avicularia avicularia (pinktoe tarantula) (Photo credit: Sean McCann)

Nemesiidae: tube-trapdoor mygalomorphs

Nemesiids generally live in silk-lined burrows, sometimes finished with hinged, camouflaged trap-doors. Male courtship includes scratching and tapping with the legs on the ground, often at a distance from the female’s burrow entrance, suggesting that this is another form of long-distance seismic communication. While most female mygalomorphs remain relatively passive throughout courthship and copulation, Acanthogonatus centralis females jerk violently, twitching all their legs and pedipalps. This enthusiastic behaviour may stimulate the male to begin copulation.

Nemesiidae (M Hedin)

Calisoga longitarsis (Nemesiidae) at burrow entrance (Photo by M. Hedin, licensed under CC BY 2.0)


The family Microstigmatidae contains 16 species of tiny spiders (males are only 1-3 mm long!). This is one family that apparently makes minimal use of silk. Xenonemesia platensis males only begin courtship after making direct contact with the female’s body. The male’s courtship behaviour includes quivering with the first two pairs of legs. The female, if she is receptive, responds by moving into a mating posture with her genital area exposed, allowing the male to clasp her pedipalps and chelicerae with his first legs.

This clasping of the female’s chelicerae by the male is common in mygalomorphs; in many species males have specialized structures on their legs that facilitate the embrace. Some researchers think it may be a way of restraining a potentially lethal female, keeping her fangs at leg’s reach. However, the fact that female catalepsy during copulation is also widespread sheds some doubt on this interpretation. Alternatively, it may be a more ‘symbolic’ form of bondage akin to the bridal veil in some araneomorphs. The tactile stimulation associated with the male’s clasping may in fact cause the female to become quiescent.

Throughout copulation, the Xenonemesia platensis male continues his tactile courtship, tapping and scraping his second pair of legs against the female. It’s possible that this copulatory courtship persuades the female to use his sperm over that of competitors, but more work needs to be done to test this hypothesis.

Mating Xenonemesia platensis (Microstigmatidae). The male has the female’s pedipalps and chelicerae clasped in his first pair of legs, while he uses his second pair of legs to beat and scrape the female’s coxae (leg segments closest to the body) (Photo credit: Gabriel Pompozzi)

The mygalomorphs may all look fairly similar, but they have surprisingly diverse habits, and use their multi-purpose silk in clever ways. Their sexual communication is most certainly not simple, incorporating multiple signaling modalities. Just as with most araneomorphs, good vibrations and sexy scents are the key!

Growing evidence suggests that contact sex pheromones associated with female silk are common in mygalomorphs (as they are in araneomorphs). Sex pheromones have also been implicated in the sexual communication systems of some spiders in the Mesothelae, suggesting that chemical communication was acquired early in the evolutionary history of spiders.

This story of mygalomorph mating also highlights the fact that female spiders in general are not simply passively waiting for marauding males to stumble across their doorsteps. On the contrary, they actively advertise for a mate, sometimes participating in a vibratory signaling ‘conversation’ with courting males, and likely judge a suitor’s quality both before and during copulation.

The private lives of spiders never cease to fascinate!

References, resources, and acknowledgements:

For a wonderful read about the evolution of spiders and their silk, including lots more information that I didn’t include about the fascinating habits of mygalomorphs, I highly recommend Leslie Brunetta and Catherine Craig’s book Spider silk: Evolution and 400 Million Years of Spinning, Waiting, Snagging, and Mating (an excellent gift idea!).

Ferretti, N., Pompozzi, G., Copperi, S., Gonzalez, A., & Pérez-Miles, F. (2013). Sexual behaviour of mygalomorph spiders: when simplicity becomes complex; an update of the last 21 years. Journal of Arachnology, 16(3), 85–93.

Ferretti, N., Pompozzi, G., Copperi, S., Pérez-miles, F., González, A., & Pe, F. (2012). Copulatory behavior of Microstigmatidae (Araneae: Mygalomorphae): a study with Xenonemesia platensis from Argentina. Journal of Arachnology, 40(2), 252–255.

Costa, F. G., & Perez-Miles, F. (1998). Behavior, life cycle, and webs of Mecicobothrium thorelli (Araneae, Mygalomorphae, Mecicobothridae)Journal of Arachnology26, 317–329.

Special thanks to Gabriel Pompozzi for allowing me to use his photographs of Xenonemesia platensis and Mecicobothrium thorelli. Check out more of his fantastic images of mygalomorphs here.

I am also very grateful to Marshal Hedin for generously making his photographs available under creative commons licenses. He has some really wonderful sets of shots of several mygalomorph families on flickr.

Spider Monday: featuring my favourite spider

Hot on the heels of Black FlyDay, today we can celebrate Spider Monday!

In honour of this web-tastic day, I would like to showcase the most awesome spider I have ever personally met: a member of the family Hersiliidae (tree trunk spiders). The beautiful photos that follow were all taken by Sean McCann, in French Guiana.

Um... is there supposed to be a spider in this photograph?

Um… is there supposed to be a spider in this photograph?

The special thing about this spider is her incredible camouflage!

Here’s a closer look:


Aha! There she is. And what’s that she’s guarding so closely?

Not only does the spider’s body blend into the background, but you might not even have noticed that she’s guarding an egg sac. What I find most remarkable is that she has evidently decorated her silken egg sac with lichen and bits of plants to make it blend in with the rest of the tree trunk.


An even closer view. Check out those elongated spinnerets! The hersiliids are also sometimes referred to as two-tailed spiders.

I didn’t even notice the extremely elongated spinnerets characteristic of the Hersiliidae until I looked closely at the photographs, so perfect is the camouflage on all the spider’s appendages. It’s probably because they are so cunningly cryptic that there seems to be very little known about the biology of hersiliids.

For more great photographs and the story of how I met my favourite spider, check out Sean’s blog post here.

A VERY brief introduction to spider systematics (Part 1)

All the information that follows is from Rainer Foelix’s excellent book Biology of Spiders. Photos used with permission from Sean McCann.

Here I will provide a brief orientation to the spiders that I hope will help place future posts that feature spiders in different suborders, orders and families. I will try to add more detailed taxonomy information as I go along. Also, I hope this post will help me to remember some basic information that I am always re-learning (never again will I look up orthognath vs. labidognath!).

There are about 40,000 more than 44,000 identified species of spiders in 110 112 families* (I hope that someday I will have posts highlighting every family!).

The order Araneae includes all the spiders. There are three suborders:

The most ‘primitive’ (phylogenetically oldest) spiders are in the suborder Mesothelae. They have segmented abdomens like other arthropods, and unlike the rest of the spiders. There is only one family in the Mesothelae, the Liphistiidae. I don’t really know anything else about them at this point (I will come back to them in the future).

The rest of the spiders are in the Opisthothelae, which contains the two other suborders, the Mygalomorphae and the Araneomorphae.

Both the Mesothelae and the mygalomorphs have orthognath chelicerae. Spider chelicerae are a large pair of mouthparts tipped with articulated fangs through which venom is injected into prey. Orthognath chelicerae work in parallel. Make ‘air quotes’ with your first two fingers – like that.

The majority of species in the Mygalomorphae are tarantulas, in the family Theraphosidae (in French, a tarantula is called a ‘mygale’, which makes this easy to remember ever since I spent some time in French Guiana).

Female Theraphosa blondi in French Guiana.

Female Theraphosa blondi (Theraphosidae) in French Guiana.

There are several other less well-known families in the Mygalomorphae that I will get to in later posts. Mygalomorphs can produce silk, but most don’t build webs; they lack the pyrifrom silk glands that that araneomorphs use to cement their silk threads together or to a substrate.

Araneomorphs have labidognath (opposing) chelicerae. Touch your thumb and forefinger together repeatedly in pincer-like fashion, so. The Aranaeomorphae includes all the ‘usual’ non-tarantula spiders you might run into, including families such as the

Araneae (orb-web spiders),


A common European Garden Spider, Araneus diadematus (Araneidae), on her orb-web.

Salticidae (jumping spiders),


A gorgeous Salticid. Check out those brightly coloured labidognath chelicerae! The red bits are the opposing articulating fangs.

Thomisidae (crab spiders),

A goldenrod crab spider, Misumena vatia (Thomisidae) doing her thing.

Lycosidae (wolf spiders),


A female Lycosid carrying her spiderlings on her abdomen. Some spiders have highly developed brood care!

Pholcidae (cellar spiders),


A female cellar spider, Pholcus phalangiodes (Pholcidae) carrying her egg sac. I grew up calling these spiders daddy long legs, but that name is also sometimes used to refer to harvestmen (order Opiliones), which are non-spider arachnids.

Theridiidae (the combfooted spiders, also known as cobweb or tangle-web weavers),


Female western black widow, Latrodectus hesperus (Theridiidae), on her tangle-web.

Agelenidae (funnel-web weavers),


Female hobo spider, Tegenaria agrestis (Agelenidae). Her close relatives T. domestica and T. duellica are often found in homes.

and lots of other less common/well-known ones that I intend to make posts about in due time. Although some of them don’t build webs at all, they all produce silk draglines that can be anchored to a substrate (often useful as a sort of ‘safety line’).

To sum up, the relationships and basic differences between the three suborders look like this:


For more about the phylogenetic relationships among the Araneae see the tree of life page.

UPDATE: I learned this morning that the in the latest phylogenies Opisthothelae is considered a suborder, with Mygalomorphae and Araneomorphae as infraorders.

*UPDATE 2: Thanks to Chris Buddle for pointing me to the latest information at the World Spider Catalog!