Announcing a new project: Recluse or Not?

This is just a quick announcement about a new citizen science and education project called Recluse or Not?

A recluse spider (Loxosceles arizonica). Photo: Sean McCann.

Recluse or Not? is a collaboration with North Carolina entomologists Eleanor Spicer Rice (Dr. Eleanor’s Book of Common Spiders) and Matt Bertone that you can read all about on the project page here! Briefly, it is a way for citizens to contribute data about where in North America recluse spiders (genus Loxosceles) occur, and to quickly get suspected recluse spiders identified by an expert. We also aim to correct myths and misinformation by regularly tweeting facts about recluse spiders from our new twitter account, @RecluseOrNot.

Zora & Syspira: wolf-like prowling spiders

Did you ever come across one of the most beautiful wolf spiders you’ve ever seen, only to realize that it’s not a wolf spider at all, because the eyes are all wrong? And if it’s not a wolf spider then what the heck is it because it doesn’t look like a spider from any of the other spider families you’re familiar with? No? Well, I had this experience recently. Twice, actually.

The first time it happened was during our epic journey from Toronto to southern Texas to California and then to Victoria (also known as #SpiderTrip2016 – check out some of the great photos Sean took along the way here). We stopped one morning in Joshua Tree National Park and flipped over some rocks to see if we could find any insects or spiders hiding underneath. Almost immediately, I uncovered this gorgeous spider with perfect desert camouflage.

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Not a wolf spider. Photo: Sean McCann.

The bold markings reminded me a bit of some funnel-web weavers in the family Agelenidae, but this spider didn’t have a web.

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Agelenopsis aperta (family Agelenidae, the funnel-web weavers). Yeah, this spider isn’t on a web either, but that’s because we put it on a rock to get a good photograph of it. Agelenids are usually pretty camera-shy, and they like to hide in their retreats. Photo: Sean McCann.

The sandy camouflage was similar to that of the beach-dwelling wolf spider Arctosa perita, but on closer inspection I realized the eyes were all wrong for it to be a lycosid.

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Arctosa perita, with characteristic wolf spider eye arrangement. Photo: Sean McCann.

The key to figuring out whether or not you’ve got a wolf spider is the eye arrangement. Lycosids are visual hunters that have their eyes arranged in three rows. The first row has four small eyes, the second has two large forward-facing eyes, and the third has another pair of slightly smaller eyes quite far back on the cephalothorax. From straight on, they may appear to have only 6 eyes (the first two rows).

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Wolf spider (family Lycosidae) eye arrangement. Photo: Sean McCann.

Syspira is clearly not a wolf spider – it has two rows of four eyes (or if you like, a smiley face eye arrangement – once you see it, you won’t be able to un-see it!) that are all pretty similar in size.

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From above, the eyes appear to be arranged in two more or less straight rows.

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I never would have guessed by looking at it that this spider is in fact a prowling spider in the family Miturgidae. When I think of miturgids, the first thing that comes to mind are the long-legged sac spiders in the genus Cheiracanthium.

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Cheiracanthium sp. – a yellow sac spider in the family Eutichuridae (formerly placed in Miturgidae, and before that, Clubionidae – spider systematics is complicated and constantly changing). Photo: Sean McCann.

These “yellow sac spiders” are famous for being common in homes, biting people all the time (actually, they rarely bite) and causing necrosis (they don’t, although bites are painful like a bee sting), and causing car trouble. They also aren’t actually in the family Miturgidae. They used to be, but they recently got separated into a new family called Eutichuridae, so I really need to update my mental inventory of spider families! Anyway, because the spider we found didn’t look at all like a long-legged sac spider, I didn’t think of looking in the family Miturgidae. It was only later that I was browsing Marshal Hedin’s wonderful collection of spider photographs on entirely unrelated business that I came across this photograph:

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Immature Syspira sp. (family Miturgidae, also known as the prowling spiders). Photo: Marshal Hedin. Licensed under CC BY-SA 2.0.

That’s it! That’s our spider! Not only does it look pretty much identical, but it was found in the very same desert where we found ours. Syspira! The trail goes cold here, however. I can’t say for sure what species it is because the most recent revision of the genus is an unpublished thesis that I can’t get my hands on at the moment (for what it’s worth, I suspect Syspira tigrina). And very little is known about the natural history of these spiders. They are nocturnal wandering hunters who hunker down under rocks or other objects during the heat of the day. They are a pretty good size – the body length (combined length of the two body segments) of the individual we found is probably about 15 mm.

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Female Syspira sp. Photo: Sean McCann.

Our second wolf-like spider is a much smaller critter (less than 5 mm in body length) that we found wandering the forest floor while we were hiking at Mount Work on southern Vancouver Island this past weekend.

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Wolf-like spider from Mount Work. Photo: Sean McCann.

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This photo shows how tiny this spider is relative to Sean’s thumbnail. Photo: Sean McCann.

This little guy definitely had us thinking he was a wolf spider until we took a closer look at his eyes. The eye pattern is sort of similar to that of a lycosid, but I only see two rows of four eyes rather than three distinct rows, and the middle two eyes in the second row (called the posterior median eyes if you want to be technical) are too close together. This eye arrangement is more similar to that of ctenids (wandering spiders, which we don’t have in Canada) or pisaurids (nursery web spiders and fishing spiders).

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Eye arrangement of our mystery spider. Photo: Sean McCann.

I guessed that this might be Zora hespera (another miturgid!) based on a drawing of a similar tiny spider in our field guide, and our friend and arachnological guru Robb Bennett quickly confirmed the guess. As it turns out, this species was only described in 1991, and Robb first documented its presence in British Columbia in 1996.

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Adult male Zora hespera (Miturgidae). Photo: Sean McCann.

The genus Zora used to be in the family Zoridae, which no longer exists (if you use the excellent Field Guide to the Spiders of California, however, you’ll still find Zora hespera listed as a zorid). The name Zora is also new – the genus was originally called Lycaena (which means female wolf) because of its similarity to wolf spiders, but the name had to be replaced because it was already being used for a butterfly genus. These spiders hunt on the ground and low vegetation during the day and are most often found in open sunny areas of wooded or disturbed habitats.

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Adult male Zora hespera. Note how small he is relative to the pine needles! He was pretty cryptic against the forest floor. Photo: Sean McCann.

The individual we found prowling the forest floor is a male (you can tell by the enlarged pedipalps) who may have been on the hunt for a female. Courtship in this species is brief and includes a leg-waving display on the part of the male. Once mated, the female produces an egg sac that she attaches to the underside of a rock or other object. A flat sheet of silk hides the egg sac and the female stands guard to protect her offspring from predators and parasites.

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Syspira sp. looking cryptic on the desert sand. Photo: Sean McCann.

Spider identification can be tricky! Next time you think you’ve found a wolf spider, take a closer look – it might be a wolf-like prowling spider, or something else altogether! The more time I spend learning about spiders, the more amazed I am by their beauty and diversity.

References

Adams, R. J. (2014). Field Guide to the Spiders of California and the Pacific Coast States (Vol. 108). University of California Press.

Bennett, R. G., & Brumwell, L. J. (1996). Zora hespera in British Columbia: a new spider family record for Canada (Araneae: Zoridae). Journal of the Entomological Society of British Columbia, 93, 105-110. PDF

Bradley, R. A. (2012). Common Spiders of North America. University of California Press.

Corey, D. T., & Mott, D. J. (1991). A revision of the genus Zora (Araneae, Zoridae) in North America. Journal of Arachnology, 55-61. PDF

Ubick, D., Paquin, P., Cushing, P., & Roth, V. (2005). Spiders of North America – an identification manual. American Arachnological Society.

Oecobiidae

Last week a colleague of mine found a tiny spider we didn’t recognize in the biology building at UTSC. We regularly find common house-dwelling spiders in and around the buildings on campus (most often false widows, Steatoda grossa triangulosa). But this spider was different from the ones we usually find in the building – tiny (only a couple of millimetres long), pale in colour, and a very fast runner! I brought it home and asked Sean to take some photos of it, and we soon realized it was a member of the fascinating family Oecobiidae. [note: this paragraph was revised on 7 Dec. 2015]

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Oecobius sp. from Scarborough, Ontario. Photo: Sean McCann (used with permission)

The name Oecobiidae comes from the Greek words oikos (οικος), meaning “house” and bios (βιος), meaning “living”. A name that means “living in the house” is highly appropriate for these synanthropic spiders that are commonly found in human dwellings. The spider we found is most likely one of two species that have a worldwide distribution and can be found in southeastern Canada: Oecobius cellariorium (cellariorium means, unsurprisingly, “of the cellar” in Latin) and Oecobius navus (navus means active or busy, which these little spiders certainly are!).

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Oecobiid next to its sheetweb. Photo: Mark Yokoyama, licensed under CC BY-NC-ND 2.0

Despite their very appropriate scientific names, non-Latin and Greek speakers have come up with a variety of fun common names for members of this family. These include wall spiders, baseboard spiders, stucco spiders, starlegged spiders, disc web spiders, and dwarf round-headed spiders. The official common name for the family is “flatmesh weavers” (at least in North America, according to the American Arachnological Society) because of the flat webs they build.

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Figures 2 and 3 from Glatz 1969, showing the two kinds of webs built by Oecobius navus (previously called Oecobius annulipes). The first is a “star-shaped” web with an upper and lower sheet surrounded by radiating silk lines. These threads allow the spider sitting on the lower sheet to detect vibrations produced by prey. When the spider detects prey outside its web it can rush out in any direction to capture it. The second type of web is similar, but the upper and lower sheets form a tube, with only two entrances.

I quite like the name starlegged spiders for oecobiids though, because it so aptly describes one of the very distinctive characteristics of spiders in this family. Unlike most spiders, which have the first two pairs of legs pointing forward and the last two pointing backward (an exception is the family Segestriidae, which have the first three pairs pointing forward), oecobiids have all 8 legs sticking more or less straight out from their bodies, in a somewhat starburst-like fashion.

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Oecobius sp. (male). In addition to being “star-legged”, oecobiids have their 8 eyes arranged in a characteristic cluster in the centre of a circular cephalothorax. Photo: Sean McCann

The defining characteristic of oecobiids, however, is the extraordinary anal tubercle (that’s exactly how it’s described in this paper, and I assure you it is entirely appropriate). Seriously, these tiny spiders have the most incredible hairy butts! Ahem. Fringed anal tubercles, I mean. Let me explain.

The North American oecobiids are cribellate spiders. What this means is that the spider is equipped with a cribellum (a special silk spinning organ covered with thousands of tiny spigots) near the spinnerets and a calamistrum (a specialized row of bristles) on each of the fourth legs. The calamistrum is used to comb out fine strands of cribellar silk into sheets with a fuzzy texture. The stickiness of this silk comes from its physical structure, as opposed to the glue used by ecribellate (non-cribellate) spiders to make their capture silk sticky. Anyway, instead of combing silk out of the cribellum with the calamistrum like regular cribellate spiders, oecobiids have their own fancy way of doing things. They use the fringe of hairs on their jointed anal tubercles to comb silk directly from arrays of spigots on a pair of enlarged spinnerets.

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Figure 11 from Glatz 1969, showing the extraordinary fringed anal tubercle and spinning apparatus. The long posterior lateral spinnerets (labelled hspw) are covered with spigots (s). The outer fringe of hairs (rh) on the anal tubercle comb silk out of the spinnerets. The anal tubercle is also equipped with sensory hairs (mh) that are used to detect prey movement via vibrations through the silk threads.

This unusual set-up enables oecobiids to produce a sheet of sticky silk without using their legs, which is important for their unusual method of prey capture. Many spiders use their last pair of legs to pull sticky silk out of their spinnerets and throw it onto their prey. Oecobiids, instead, run around and around their prey in circles as they spew out ribbons of silk from their feathery butts. Once the victim (often an ant) is fully encircled and stuck to the substrate, the spider bites it. Here is a video of the behaviour. (Video* by Ahmet Özkan, used with permission.)

As you can see in the video, the spider does occasionally use its last pair of legs while wrapping the ant with silk, but the anal tubercle/spinneret combo does most of the work. Female and juveniles of Oecobius navus can produce cribellar silk, but adult males have a reduced cribellum and don’t have a calamistrum at all. Another oecobiid genus, Uroctea, used to be placed in its own family, the Urocteidae, because they are ecribellate (lacking the cribellum and calamistrum).

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Uroctea durandi, one of the ecribelleate oecobiids. Photo: Siga, licensed under CC BY-SA 3.0

Early work on spiders in the genus Oecobius suggested that they were ant-specialists, but more recent research has shown that they eat a variety of prey types. However, different populations of a single species seem to specialize to some extent on whatever type of prey is most locally abundant. In Portugal, a population of Oecobius navus preys mainly on ants, but another population in Uruguay eats mostly flies.

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Male (right) and female (left) Oecobius sp. Photo: Allan Lance (used with permission). Check out more of Allan’s photos of oecobiids here.

Reproductive behaviour has only been well documented in Oecobius navus. The male spins a tubular silk mating web on top of the female’s retreat and tries to entice her to join him inside. Copulation only occurs if she enters the male’s web, and sometimes the female will cannibalize the male during or after mating. Females are not caring mothers in this species – they spin several egg sacs that each contain only 3 to 10 eggs and then abandon them.

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Oecobius sp. from Scarborough. Photo: Sean McCann

Now that you know all about oecobiids, keep your eyes out for them! They live all over the world, and often on the walls and ceilings of houses. You never know – there might be one in the room with you right now!

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This photo of an Oecobius sp. is one Sean dug up from his archives. We had found the spider in our old lab at SFU in BC, and did not identify it at the time. When Sean showed me the photo recently, and I started trying to ID it, I took a look at the checklist of BC spiders to get an idea of which species it might be. I didn’t see any oecobiids on the list, so I emailed the author, Robb Bennett, and it turns out that this photo is the first record of the family for British Columbia.

*For another cool oecobiid video with a surprise ending, click here.

References

Adams, R. J. (2014). Field Guide to the Spiders of California and the Pacific Coast States (Vol. 108). Univ of California Press.

Glatz, L. (1967). Zur biologie und morphologie von Oecobius annulipes lucas (Araneae, Oecobiidae). Zeitschrift für Morphologie der Tiere, 61(2), 185-214.

Líznarová, E., Sentenská, L., García, L. F., Pekár, S., & Viera, C. (2013). Local trophic specialisation in a cosmopolitan spider (Araneae). Zoology, 116(1), 20-26.

Shear, W. A. (1970). The spider family Oecobiidae in North America, Mexico, and the West Indies. Harvard Univ Mus Compar Zool Bull.

Pirate spiders

Mimetidae are the pirates of the spider world, but their acts of theivery take place on the webs, rather than ships, of other spiders. The name Mimetidae means “imitator” and is thus a very fitting name for these sneaky spiders.

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A mimetid found at Payne’s Prairie in Florida. Photo: Sean McCann (used with permission).

Common names for this family include pirate spiders and cannibal spiders, for reasons that will soon become clear. They have a worldwide distribution, occurring on every continent except Antarctica, and everywhere in North America except the arctic.

What makes mimetids so fascinating is their predatory behaviour. These spiders don’t build their own webs. Instead, they invade the webs of other spiders – most often spiders in the families Araneidae (orb-weavers), Theridiidae (cobweb weavers), and Dictynidae (mesh web weavers). Here’s a series of photographs showing an interaction between a pirate spider and an orb-weaver in Arizona. (Full disclosure: Sean and I introduced the mimetid ourselves, hoping to witness a predation event).

Below is the web of a trashline orbweaver, Cyclosa turbinata (family Araneidae). The vertical “trashline” that bisects the upper half of the orb is made of old prey carcasses.

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This photo and the rest in this series by Sean McCann.

Here’s a closer look at the trashline. The spider is well camouflaged when she sits right in the centre of the orb-web.

CyclosaHere’s a better view of the spider herself.

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And this is another Cyclosa conica female, for a better idea of what these spiders look like.

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Ok, now back to the pirate spider! This is a male Mimetus hesperus that we found nearby, and introduced onto the yucca right next to the orb-web.

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Soon he entered the periphery of the web and assumed the ‘legs cocked’ posture characteristic of hunting mimetids. He then started carefully plucking the threads of the orb-web with his front pair of legs. This plucking makes the web vibrate in very much the same way it would if an insect had been captured, and resulted in the Cyclosa female orienting toward the source of the vibrations, but remaining in the hub of the web.

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Gradually Mimetus began to move toward the hub of the orb-web, plucking and sometimes even snapping spiral threads (much as would happen if a winged insect was struggling to free itself from the sticky threads). At first it seemed the mimetid was going to be successful in luring the female Cyclosa out onto the web and into its deadly embrace, but after a few steps toward the mimetid she suddenly dropped out of the web on a dragline.

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As Cyclosa hung below, the mimetid made his way to the hub of the web and took up residence. Sean and I were impressed by Cyclosa’s ability to recognize the mimetid as as being dangerous rather than dinner, but disappointed not to see Mimetus succeed in securing a meal. So we put the spider back onto her web. (Sorry Cyclosa!)

As soon as she started moving back toward the hub, Mimetus lunged and bit Cyclosa. Mimetids are equipped with a spider-specific venom that paralyzes their prey almost instantly.  

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The successful pirate then carried its meal back to the periphery of the web to feed. Below you can see that he has Cyclosa by the leg. Apparently mimetids almost always bite the legs of their victims, and when they do paralysis occurs within moments. If they bite another spider’s abdomen, however, the venom takes much longer to work. 

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We left the pirate enjoying his meal on the yucca. He may have gone on to find a new web to invade, or taken over Cyclosa’s web for a while. If we hadn’t interfered, he may have remained in the hub of the web and used it to capture insect prey himself. In addition to this sort of takeover, mimetids are also known to steal prey from the webs of other spiders who are much larger (and thus too big to prey on). They also sometimes eat the eggs of other spiders.

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Mimetus sp. from High Park in Toronto, Ontario. Photo: Sean McCann (used with permission).

Notes on identification:

Mimetids look most similar to orb-weavers (araneids) and cobweb weavers (theridiids) but they can be distinguished from spiders in all other families by the unique pattern of spines on their first two pairs of very long legs.

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Nice example of the characteristic spination on the tibiae and tarsi (first two leg segments) of the first two legs of pirate spiders. Photo: Nicky Bay (used with permission). Check out more of Nicky’s awesome pirate spider photos here.

The eye arrangement is not so diagnostic (it’s quite similar to that of araneids and theridiids) but here’s a great portrait courtesy of the Insects Unlocked project.

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Finally, Mimetids build characteristic egg sacs that are easy to identify to genus even in the absence of the mother (who inevitably abandons her offspring). The sac has a long thin stalk and/or a fluffy coating, depending on the genus, and these two features may help protect the eggs within from parasitoids or predators.

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Egg sac of a mimetid in the genus Ero, found hanging inside a hollow stump in Burns Bog, Delta, BC. Photo: Sean McCann (used with permission)

References and further reading:

Eric Eaton’s blog post on pirate spiders.

Africa Gomez’s blog post on pirate spiders.

Bristowe, W. S. (1958). The world of spiders. London: Collins.

Jackson, R. R., & Whitehouse, M. E. (1986). The biology of New Zealand and Queensland pirate spiders (Araneae, Mimetidae): aggressive mimicry, araneophagy and prey specialization. Journal of Zoology, 210(2), 279-303.

Kloock, C. T. (2001). Diet and insectivory in the “araneophagic” spider, Mimetus notius (Araneae: Mimetidae). The American Midland Naturalist, 146(2), 424-428.

Kloock, C. T. (2012). Natural History of the Pirate Spider Mimetus hesperus (Araneae; Mimetidae) in Kern County, California. The Southwestern Naturalist,57(4), 417-420.

Castianeira: ant-like spiders

The spider genus Castianeira (in the family Corinnidae) is one of my favourites. These small spiders are rather elusive, but so beautiful! There are currently 128 known species in the genus, so I will only be able to highlight a small number in this post. This should nonetheless provide a glimpse into the diversity of gorgeous forms they take!

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Castianeira dorsata from Arizona. Photo: Sean McCann

Natural History

Common names for the family Corinnidae include “ground sac spiders” (they used to be included in the sac spider family Clubionidae) and “antmimic spiders”. They are not all antmimics, but many species in the genus Castianeira are rather ant-like and are considered generalized ant-mimics.

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Castianeira longipalpa, found under a rock near a lot of ants at Iona beach in Richmond, British Columbia. This species is thought to be a generalized mimic of myrmecine or ponerine ants. Photo: Sean McCann

The species shown above and below don’t look especially like any particular species of ant, and their mimicry is “imperfect” – besides having fairly elongate bodies and stripes that might give the illusion of a third body segment, they look a lot more like spiders than ants. At first glance, however, they can easily be mistaken for ants (at least by humans). They are fairly ant-like in size and colour (often red or brown and/or black) and they move around a lot like ants, waving their front legs like antennae, and bobbing their abdomens in ant-like fashion. These spiders are often found in close proximity to ants, which provides some support for the idea that they are in fact mimics. They might benefit by looking ant-like to predators who find ants distasteful (and don’t look too closely).

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Castianeira sp. from near the Soutwestern Research Station in Arizona. Photo: Sean McCann

Some species, like the one from Singapore below, are a little more ant-shaped, but their morphology is not as extremely modified as some other kinds of ant-mimicking spiders (like this one photographed by Alex Wild).

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Castianeira sp. from Singapore. Photo: H. K. Tang, licensed under CC BY-NC-ND 2.0.

Some Castianeira species are thought to mimic velvet ants (Mutillidae), rather than ants. Mutillids are not actually ants but wasps, and the females are wingless and brightly coloured, with extremely painful stings. In this case, harmless Castianeira spiders might benefit by looking like the much more dangerous velvet ants, and thus be avoided by predators (this is called Batesian mimicry).

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Castianeira occidens from South Fork, Arizona. This spider was found running (fast!) across a forest path during the day. Photo: Sean McCann

As with the ant-like species, these spiders tend not to look very much like any particular species of velvet ant. They are generally mutillid-like in their movements and in that they have bright markings on their abdomens reminiscent of the warning colouration (aposematism) of velvet ants, like the one below.

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Velvet ant from French Guiana. Photo: Sean McCann.

One of the most gorgeous spiders I have ever seen is the Castianeira dorsata (below, and at the top of this post) that Sean found wandering around by a stream one evening while we were staying at the Southwestern Research Station in Arizona. These spiders are supposed to be active during the day, so it was interesting to find this one running around in the dark while we were out with our headlamps searching for wolf spiders. Obviously, looking like a velvet ant isn’t going to fool anyone if it’s so dark they can’t see how brightly coloured you are.

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Castianeira dorsata from Arizona. Photo: Sean McCann

I don’t know of any velvet ants that look much like this (although many are bright orange), but I just can’t get over how beautiful this spider is with its sunset-like stripes on the abdomen and a bluish iridescence on the carapace. Even more dramatic is what I like to call the “tiger-striped” Castianeira below. The photo below shows the relative size of Castianeira amoena on a human hand. I imagine they would be as fearsome or even more so than a tiger if they were blown up to a comparable size. In reality however, these spiders are extremely shy, and very fast runners when they are disturbed (as by humans!) – so all the photographs in this post are real treasures.

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Castianeira amoena. Photo: promiseminime, licensed under CC BY-NC-ND 2.0.

Finally, the spider below is notCastianeira, but a species in the related genus Graptartia (also in the subfamily Castianeirinae). I couldn’t resist adding it because it shows such a beautiful example of mimicry, and one that’s much more specific than the examples above. The velvet ant model and spider mimic where found within a few metres of another (one of the criteria for Batesian mimicry is that the model and mimic have to be found in the same place!) and the photographer then managed to move them so that he could capture them together in the photo below. Wow!

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Graptartia granulosa mimic and velvet ant model from Tanzania. Photo: Paul Bertner (used with permission).

Notes on Identification

Usually these spiders are pretty recognizable because of their distinctive colouration, but some of the less bold ones can be confused with other ant-like spiders (like Micaria). Spiders in the genus Castianeira have 8 eyes in 2 rows. The posterior eye row (the upper row, in the photo below) is slightly wider than the anterior (lower) row with all four eyes about the same size. Both rows are slightly procurved (curved toward the front end of the spider). The anterior median eyes (front and centre) can be slightly smaller to much larger than the other two in their row.

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Castianeira cingulata portrait, showing the eye arrangement. Photo: sankax, licensed under CC BY-NC 2.0.

The last (hindmost) pair of legs is always longest, followed by the first (frontmost) pair, and the abdomen is often decorated with bands of white scale-like setae (hairs).

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Dorsal veiw of Castianeira longipalpa from BC. Photo: Sean McCann.

 

References:

Dondale, C. D., & Redner, J. H. (1982). The insects and arachnids of Canada. Part 9. The sac spiders of Canada and Alaska. Araneae: Clubionidae and Anyphaenidae (No. 1724).

Reiskind, J. 1969. The spider subfamily Castianeirinae of North and Central America (Araneae, Clubionidae). Bull. Mus. Comp. Zool. 138(5): 163-325.

Segestriidae: tube web spiders

Recently Sean and I took a quick trip down to Bellingham, Washington, to meet up with a friend. While we were wandering around a beachfront park, we encountered this beautiful spider under the loose bark of a tree. I didn’t recognize it, and we didn’t have our field guide with us, so it wasn’t until we got home that we were able to identify it as Segestria pacifica – a member of the tube web spider family Segestriidae.

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Segestria pacifica. This species is the one member of the family Segestriidae that can be found in British Columbia, but we’ve never encountered it before. (Photo: Sean McCann)

Segestriids are closely related to spiders in the family Dysderidae (which includes the common woodlouse hunter, Dysdera crocata). Like dysderids, segestriids have only 6 eyes. You can see the characteristic eye arrangement in the photo below – it looks like the pair of eyes that should be at the front and centre of the spider’s face are missing.

Segestria_pacifica_eye_arrangement_CCBY_Kyron Basu

Nice portrait of Segestria pacifica showing the eye arrangement and hairy chelicerae. (Photo: Kyron Basu, licensed under CC BY-ND-NC 1.0)

Spiders in this family also have the unusual habit of resting with their first three pairs of legs pointing forward and the last pair pointing back (most spiders do two pairs pointing forward and two pairs pointing back).

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Segestria pacifica resting in the characteristic pose with six legs forward, two legs back. (Photo: Sean McCann)

Segestria florentina (sadly not found in North America) has beautiful irridescent green chelicerae. The function of this striking colouration is not clear – it’s unlikely to be for catching the eye of a potential mate, because these spiders have poor vision and rely mainly on vibratory and acoustic communication. What we do know is that this structural colour is produced by parallel layers of chitin that reflect different wavelengths of light (called a multilayer reflector). The mechanism is the same one that gives these beautiful beetles their green irridescence.

Segestria_florentina_CCBY_Luis Miguel Bugallo Sánchez

Segestria florentina female showing off her beautiful irridescent green chelicerae (Photo: Luis Miguel Bugallo Sánchez, licensed under CC BY-SA 2.5 ES)

Segestriids are nocturnal and build their tube webs in crevices, often in the cracks of rock walls, under loose tree bark, or in the ends of broken branches. Several signal threads are arranged radially around the opining of the tube-web. The hunting spider sits near the entrance of the tube, waiting for prey to make contact with one of her trip lines. This contact transmits vibrations through the silk to the spider’s sensitive feet, six of which rest near the opening of the web, allowing her to determine the exact location of the prey.

Segestria_senoculata_02_CCBY_Totodu74

Tube-web of Segestria senoculata (Photo: Totodu74, licensed under CC BY-SA 3.0)

“Corolla spiders” in the genus Ariadna live in the Namib Desert, and have modified their tube webs to include a circle of stones around the entrance. Here the trip lines are very short, and are all attached to the small stones circling the web entrance. The function of the stones is essentially the same as the silk signal lines of a regular tube web, which would not be very effective in the desert because of the constantly shifting sands and gravel. The stone circle solves this problem. When prey brushes against one of stones in the circle, vibrations are transmitted to the spider and it rushes out to dispatch them. The corolla spiders apparently preferentially select quartz crystals for their signal stones – these may direct vibrations from prey more effectively than other kinds of stones.

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Fig. 1 from Henschel (1995) showing the stone circle built by corolla spiders in the Namib desert. The drawing shows the position of the six forward-facing legs of the hunting spider resting just inside the mouth of the burrow.

Females in this family don’t build a traditional egg sac but deposit a mass of eggs in the tube web and then cover them with silk. Very little else seems to be known about the natural history of these spiders, although apparently they are quite easy to keep in captivity, and females can live for several years.

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References:

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

Henschel, J. R. (1995). Tool use by spiders: stone selection and placement by corolla spiders Ariadna (Segestriidae) of the Namib Desert. Ethology, 101(3), 187-199.

Ingram, A. L., Ball, A. D., Parker, A. R., Deparis, O., Boulenguez, J., & Berthier, S. (2009). Characterization of the green iridescence on the chelicerae of the tube web spider, Segestria florentina (Rossi 1790) (Araneae, Segestriidae)Journal of Arachnology, 37(1), 68-71.

 

How to tell if a spider is not a brown recluse

UPDATE (Oct. 2017): We have just launched a new citizen science and education initiative called Recluse or Not? This is a collaboration with Eleanor Spicer Rice and Matt Bertone that will allow us to obtain information about where people are finding recluse spiders inside and outside their native range in North America and help people to learn more about recluse spiders and how to identify them. Please check out the project page here for more details, and send us your photos of suspected recluse spiders on twitter!

This post addresses one of the most common spider identification questions in North America (north of Mexico): is it a brown recluse?*

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A female brown recluse, Loxosceles reclusa. Photo: Alex Wild, used with permission.

The brown recluse spider (Loxosceles reclusa) is arguably the most feared and most misunderstood spider species in North America. So, here we will find out how to tell if a spider is not a brown recluse. But before we do, it’s important to note that even if you do find a brown recluse, it’s not that big a deal.

Arachnologist Rick Vetter is an expert on the brown recluse spider who has done a ton of research on where they are (and aren’t) and how dangerous they really are (hint: not as dangerous as you think), as well as spending a lot of time dispelling myths and misconceptions held by both the public and the medical community. His website is full of excellent resources, and is the source of most of the information here. I encourage you to peruse his website and the articles linked in this post yourself, but I will highlight a few of the more compelling reasons that the brown recluse hysteria is unwarranted.

recluse_infestation_Abstract

Exhibit A: brown recluse bites are rare even where the spiders are abundant.

A family lived in a house full of brown recluses (more than 2000 of them!) for half a year and not a single bite occurred. Even in places where brown recluses are common, bites are very rare. Of those rare bites the vast majority of bites can be effectively treated with RICE (rest, ice, compression, and elevation) without any dire consequences. The small percentage of bites that are very serious are the ones that get all the attention in both the medical literature and the media, which has led to the misconception that recluse bites are always severe, require hospitalization, result in extensive scarring, and so on. Furthermore, misdiagnoses of all manner of other (more serious) conditions as brown recluse bites are rampant throughout North America (even in areas where the spiders do not occur), adding fuel to the already raging fire.

Now that all that’s out of the way, here is a series of questions to determine if a spider is NOT a brown recluse**. (Some of these may seem silly, but many of the spiders below that are not brown recluses are regularly misidentified as brown recluses by non-experts. Many people aren’t aware just how many different kinds of spiders there are, and for some, seeing brown, any marking vaguely reminiscent of a violin, and 8 legs is enough to conclude that a creature as a brown recluse.)

For those who want to skip the fine print, if the answer to question 1a or 1b is “yes”, it’s probably not a brown recluse. If the answer to any one of the remaining questions is “yes”, it’s definitely not a brown recluse. 

1a. Are you in Canada (or Alaska)?

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The range of the brown recluse spider does not extend into Canada. If you are in Canada, you are extremely unlikely to encounter a brown recluse spider. (Also see notes under 1b.)

1b. Are you in a state outside of the range of the brown recluse?

recluse_map_no_text

Here is a map of the known ranges of all of the species in the genus Loxosceles in North America. If you are anywhere outside the red-outlined region, you are very unlikely to encounter a brown recluse.

Brown recluses are occasionally found outside this range – sometimes they hitch a ride with people moving around the country (in boxes that have been stored in basements, for example). But even in these cases they will typically remain in the building into which they are introduced because they are very poor dispersers. Just because one or a few brown recluse spiders have been found in a new area does not mean that their range has expanded or that they are abundant there. (Note: A brown recluse spider bite diagnosis in an area outside their range does NOT mean that brown recluse spiders have been found there. Many doctors erroneously diagnose spider bites in the absence of any evidence, namely a spider that has been identified as the culprit.)

2. Is it on a web out in the open?

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Some brown web-building spiders that are not brown recluses. Clockwise from top left:       common garden spider (Araneus diadematus) on orb-web, dome-web spider male (Neriene radiata) false widow spider (Steatoda grossa) on cobweb giant house spider (Eratigena atrica) on funnel-shaped sheet web. Photos: Sean McCann.

If you find a brown spider on a web out in the open, it is not a brown recluse. Unlike the various brown web-building spiders shown above, each with their different types of web, brown recluse spiders do not use silk for prey capture. They do build small irregular silk retreats in which they hide during the day. These retreats are made low to the ground and out of sight in cracks and crevices or under objects like rocks.

Update (8/06/2015): I should mention that house spiders in the family Agelenidae are probably the most likely spiders to be mistaken for brown recluses in Canada. While females will usually be found on their webs, males are often found out and about when searching for females. They all look pretty similar to the one pictured below, but see this post for more information house spiders and hobo spiders.

Eratigena atrica

Female giant house spider (Eratigena atrica – formerly Tegenaria duellica). These spiders are often mistaken for recluses, but note the pattern on the abdomen. Photo: Sean McCann.

3. Does it have stripy or spiky legs, or more than one colour on its abdomen?

Stripy_legs

Stripy legs + patterned abdomen = not a brown recluse. Photo: Sean McCann.

If you find a spider that has stripes or large spines on its legs, it is not a brown recluse. If it has a patterned abdomen, it is not a brown recluse.

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Stripy legs with large spines + patterned abdomen = not a brown recluse. Photo: Sean McCann.

Brown recluses have plain brown abdomens and plain brown legs with fine hair but no large spines.

4. Does it have extremely long and skinny legs?

Pholcus_phalangiodes

Cellar spider, Pholcus phalangiodes (family Pholcidae). The dark spot on the cephalothorax looks a bit like a violin,  but do not be fooled. This is not a brown recluse. Photo: Sean McCann

If it has extremely long skinny legs like the spider in the image above, it is a cellar spider (or daddy-longlegs), not a brown recluse. Despite looking very dissimilar to brown recluses, these spiders are often mistaken for brown recluses because of the “violin” mark on the back. Having a violin-shaped marking is not, by itself, a good way to determine if a spider is a brown recluse.

4. Is it really big? 

Brown recluses are not huge spiders. If its body length (not including legs) is more than 0.5 inches or about 1.25 cm, it’s definitely not a brown recluse.

5. Does it have 8 eyes? 

This is the dead giveaway, provided you are close enough to the spider to count its eyes. If it has 8 eyes (like most spiders), it is not a brown recluse. Below are some 8-eyed spiders that are sometimes mistaken for brown recluses.

Fishing spider

Fishing spider (family Pisauridae) actually a close relative of fishing spiders in the family Trechaleidae, with 8 eyes. Also see: stripy, spiky legs. Photo: Sean McCann.

 

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A wolf spider (family Lycosidae). Wolf spiders have 8 eyes and spines on the legs. Photo: Sean McCann.

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A sac spider (family Clubionidae) A ground spider (family Gnaphosidae, genus Drassodes). It looks a bit like a brown recluse, but again, has 8 eyes, some larger spines on the legs, and a dark stripe on the abdomen. Photo: Sean McCann.

 

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Huntsman spider (family Sparassidae). These spiders are fairly frequently mistaken for brown recluses. Note the 8 eyes in 2 rows, and spines and darker dots on the legs and abdomen. Photo: Sean McCann.

Update (12/06/2015): Another 8-eyed spider that can easily be mistaken for a brown recluse (and is common in the southern states) is the male southern house spider. It has a similar violin-like marking on the back, but several other features that distinguish it from brown recluses. The 8 eyes are all tightly clumped together, it has conspicuous spines on the legs, and its pedipalps (the two small leg-like appendages at the very front end of the spider) are extremely long and stick straight out in front of its face (compare to a male brown recluse spider here).

Southern_house_spider_Sam_Heck

Male southern house spider (Kukulcania hibernalis). Photo: Sam Heck, licensed under CC BY-NC 2.0.

Some other spiders that are not brown recluses, like the woodlouse hunter Dysdera crocata, also only have only 6 eyes, but they are arranged differently (not to mention D. crocata is red or pinkish or orangish in colour, not brown).

Dysdera crocata on white

Female woodlouse hunter, Dysdera crocata. Her 6 eyes are all in a tight bunch in the centre of the cephalothorax, and her massive fangs are much larger than those of a brown recluse. Also, these spiders are not brown. Photo: Sean McCann.

Brown recluses only have 6 eyes, arranged in 3 pairs.

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This is a brown recluse. It has only six eyes. Also note the fine hairs on the legs, but no spines, and the plain brown abdomen. Photo: Alex Wild, used with permission.

If you answered no to all those questions (or all but questions 1a and 1b and you’re really lucky!) AND the spider looks just like the one in the image above, then you’ve found a brown recluse. If not, then it’s another kind of spider that is totally harmless. (The only other medically significant spiders in North America are black widows). Either way, please remain calm. Spiders are not out to get you, and will leave you alone if you leave them alone. Here are some tips for avoiding brown recluse bites if you do live within their range. Still not sure about any of this? Please feel free to tweet at me (I’m @Cataranea on twitter) or comment here if you have any questions and I’ll be happy to try to answer them.

 

*I’ve also started answering this question on twitter with the hashtag #notabrownrecluse. This campaign, with the goal of educating people about the brown recluse spider, is a blatant ripoff of inspired by wildlife biologist David Steen (he’s @AlongsideWild on twitter), who tweets snake identifications using the hashtags #NotACottonmouth and #NotACopperhead. For more about his awesome twitter outreach, check out this excellent article: ‘This snake scientist is the best biologist on twitter‘.

**This guide is based on the following resources:

Vetter, Rick. (1999). Identifying and Misidentifying the Brown Recluse Spider. Dermatology Online Journal, 5(2). link

Vetter, Rick. (2009). How to Identify and Misidentify a Brown Recluse Spider. Web Resource. link