Reaching 700 species for Ohio

Research on spider diversity (the number of spider species) in Ohio has been limited. The first major effort was conducted by William M. Barrows (1883-1946) of the Ohio State University, culminating in publications from 1918 to 1924.  Barrows listed 306 species of spiders known from Ohio at that time.

Between 1924 and the beginning of the Ohio Spider Survey, several published projects as well as unpublished masters’ theses and PhD dissertations increased our known list up to 410 species.  The work of the Ohio Spider Survey (1994-2014) increased the list of species known from our state to 682 species.  Of course this doesn’t mean that several hundred spider species have recently moved into Ohio, it is merely an increase in our knowledge about our spider fauna.  There have been a few species “introduced” by the actions of humans, mostly through accidental importation with stored materials, garden and landscape shipments, and incidental transport into Ohio. Some have established populations here. These number about 12 species (there is debate about the status of a few of these).

There are quite a few species which have not been detected recently.  Examining the verified records (supported by a voucher specimen), 104 species have not been recorded since 1994. Many of these species are small, inconspicuous, or difficult to find.  Some may have disappeared from the state, but it seems likely that others have just gone undetected.

A current project involves the identification of specimens held in the Ohio Spider Collection, housed at the Museum of Biological Diversity of the Ohio State University, Columbus, Ohio. This work is attempting to examine, identify, and catalog, a large backlog of unidentified specimens there. Many of these were collected by researchers doing other field work, and captured spiders by accident (bycatch). Others were donated by spider researchers. As a result of this work, the list of species known from Ohio has increased to 700 species.

Tod and Suzan Jervey working on curation of the spider collection

Lauren Blyth working on curation of the spider collection

The current check-list is available here.

I thank Suzan & Tod Jervey, Lauren Blyth for their many hours of volunteer curatorial work. I also thank Mark Milne (Indianapolis University) Mike Draney (University of Wisconsin, Green Bay) and Nina Sandlin (Field Museum) for their help with the challenging identification of dwarf sheetweb weavers (Linyphiidae, Erigoninae).

Hyptiotes the triangle weaver

In a woods near you there may be an amazing little spider called Hyptiotes.  This spider (and relatives in the same genus around the world) are famous for constructing a triangle-shaped web, hence their common name “triangle weaver.”

photo of Hyptiotes cavatus (the triangle spider) in her hunting pose, holding her web under tension.

Hyptiotes cavatus (the triangle spider) in her hunting pose, holding her web under tension.

photo of Hyptiotes tending to her web among the dead branches of a shrub.

Hyptiotes tending to her web among the dead branches of a shrub.

The web is unusual for many reasons but most folks look at it and see what appears to be a pie-slice out of an orb web.  There are radial lines converging on a point, and there are parallel spaced silk lines forming a pattern that does look like part of a typical orb.  But these webs are different. They have been built by a spider that uses cribellate silk, not glue-laden silk to entrap prey.  The cribellate silk is sticky in a completely different way. It has tiny fluffy silk lines surrounding central lines. The fluff is so fine that when an insect or other potential prey brushes against it, they adhere to the hairs and spines on the prey in a way similar to the function of a Velcro © strip.

Here is a photo of the triangular sticky portion of a Hyptiotes web, made visible by a dark cardboard background after I misted it with water.

photo of the triangular portion of Hyptiotes web.

The triangular portion of Hyptiotes web.

That isn’t the most amazing feature of the triangle weaver’s web.  This tiny spider (they are only about the size of a grain of rice) holds the entire web structure under tension, pulling her line taut with her back legs and gathering the slack in a small ball of silk that lies on top of her legs.  If a fly, or other potential prey, strikes the web and is caught in the sticky cribellar line, the spider rapidly releases the tension. This causes the spider to jerk forward as the web partly collapses.  The collapsing web further entangles the prey. She may use this technique several times to effectively snare the victim.

Here is a close-up view of Hyptiotes as she is holding her web under tension, you can notice the little pile of slack silk line near her back legs.  In this case there is also a small ball of slack near her front legs. I’ve added arrows to highlight these little bundles.

photo of Hyptiotes holding web under tension with extra line in bundles near rear and front legs

Hyptiotes holding web under tension with extra line in bundles near rear and front legs.

A couple of weeks ago I noticed that one Hyptiotes had built her snare between a thin dry twig I had laid across the arms of a lawn chair and the body of the chair.  This is the first time I’ve found Hyptiotes in my yard, and also the first time I’ve ever seen one build a web away from a woods or forest.

photo of Hyptiotes holding her triangular-shaped web under tension.

Hyptiotes holding her triangular-shaped web under tension.

photo of Hyptiotes holding web under tension with extra line in bundles near rear and front legs

Hyptiotes holding web under tension with extra line in bundles near rear and front legs

This presented an opportunity too good to miss.  I decided to take some close-up photos and also see if I might be able to shoot some video of her in action.  The photos were much easier to get.  Here are two that feature this amazing little spider.

photo of Hyptiotes holding her web under tension.

Hyptiotes holding her web under tension.

photo of Hyptiotes holding web under tension with extra line in bundles near rear and front legs.

Hyptiotes holding web under tension with extra line in bundles near rear and front legs.

Now for trying to shoot video.  The capture rate for this little gal in my lawn chair was much too low for me to just set up and wait. I needed to “feed” her prey.  So I captured a house fly and anesthetized the fly with CO2 to immobilize it.  Then I dropped the fly into the web.  I was thrilled when the fly actually “stuck” in the cribellate threads.  This stimulated the Hyptiotes, she quickly released the tension in a jerk, then repeated it a couple of times.  This collapsed the web on the fly as she moved in for her meal.  Remember the spider is really small and positioned in the extreme upper right of the field-of-view at the beginning.

There are a few problems with this video, but it is the best one I’m managed to get so far.  The web is very difficult to see through the viewfinder of the camera, so I didn’t aim perfectly so for a moment the spider-and-fly disappear at the bottom edge of the view. Eventually I noticed this and shifted the camera on the tripod to reveal the action.

You may have noticed that the “jerks” as she released the web, early in the video, are very fast. It turns out that Hyptiotes are now famous for their ability to harness the potential energy of the tense web very efficiently.  A recent paper by Sarah Han and colleagues, she demonstrated that this spider employs what physicists call power amplification. Here is how they describe the action:

Both spider and web spring forward 2 to 3 cm with a peak acceleration of up to 772.85 m/s2  (Han, et al. 2019)

Other animals that employ elastic-energy storage and recoil usually have anatomical structures, like triggers or catches, associated with this behavior.  Hyptiotes manages this feat with pure muscle power.  Remarkably they hold the line under tension for hours at a time, waiting for the right moment to release the web and snare dinner.

After the capture, like any good uloborid, Hyptiotes wraps the prey, but does not bite.  Members of the family Uloboridae lack venom, they don’t even retain venom glands.  So they cannot subdue their prey that way.  What they do is wrap the prey tightly in silk, then they engage in external digestion by spitting a mixture of digestive fluids onto the prey ball. This gradually dissolves the prey into a mush that they can suck in.  Here is a photo of my resident Hyptiotes with the remains of prey that has been reduced to a wet ball of goo.

photo of Hyptiotes with her meal, the wrapped prey is swathed in digestive fluids. It will eventually be liquified and ingested.

Hyptiotes with her meal, the wrapped prey is swathed in digestive fluids. It will eventually be completely liquified and ingested.

Read more about Hyptiotes power amplification:

S. I. Han, H. C. Astley, D. D. Maksuta, and T. A. Blackledge. 2019. External power amplification drives prey capture in a spider web. PNAS, vol 116 (24) June 11, 2019.


American Arachnological Society 2021 virtual meeting

This year the American Arachnological Society (the leading scientific society of arachnid biologists in the Americas) is going to be hosting a virtual annual meeting. The meeting events are from 24 June through 1 July 2021.  One consequence of a “virtual” meeting is the cost is dramatically lower. You can register for this meeting for $20, which admits you to all events and programs.  If that is more than you can afford, you can request financial assistance. To participate, you need to register by Monday 14 June 2021!

AAS 2021 virtual meeting logo

Check out the full schedule here.

The meeting will feature a number of fun events for arachnid enthusiasts in addition to a full scientific program.  These events include:

  1. An Equity, Diversity, and Inclusion Panel Discussion & Workshop
  2. Workshops on Arachnid Collection, Photography, and Identification
  3. Movie nights (Maratus, Sixteen Legs)
  4. Free public talk by Jillian Cowles “THE THIEF IN THE WEB & OTHER STORIES”  Jillian is a clinical microbiologist, naturalist, and photographer and the author of the fabulous and lavishly illustrated book Amazing Arachnids (Princeton University Press, 2018).
  5. A virtual bioblitz incorporating the iNaturalist platform
  6. Arachnid phototography and art contests
  7. An arachnid Q&A livestream

The scientific program will feature:

Keynote speaker: Maydianne Andrade, University of Toronto Scarborough “Widows as Windows on Adaptive Plasticity”

Announcement of the Norman Platnick Award

Research Poster Sessions & Student Poster Competition

Daily Plenary speakers: Mercedes Burns, Ivan Magalhães, and Lauren Esposito

Submitted Research Talks (featuring research on arachnids from around the world)

Student Presentation Competition

For more information about this meeting and how to register follow this link.

But there is very little time. Registration closes on Monday 14 June 2021!

The Asterisk Spider; Ocrepeira

One of our strangest-looking spiders is Ocrepeira, the asterisk spider. She has an amazing camouflaged color pattern complete with little lumps on her abdomen.  She is actually related to our more common orb-weaving spiders, but has a very unusual web.

There are 68 species in the genus Ocrepeira (sometimes known as Wixia). All but three of these are found in the tropics (Central or South America). Of the three northern species, two are known from Ohio. During the Ohio Spider Survey (1994-2014) ten individuals of Ocrepeira ectypa were found, two of Ocrepeira georgia, and four immatures that could not be determined. So this spider isn’t encountered very often. One reason is that they really do an excellent job of hiding, they look just like a broken branch or bud on the stem of a shrub or tree.

Ocrepeira resting on a twig in Adams County, Ohio

Ocrepeira resting on a twig in Adams County, Ohio

Ocrepeira posed front view

Ocrepeira posed front view

Ocrepeira posed side view

Ocrepeira posed side view

This spider is known as the “asterisk spider” because of its web. The web consists of an orb like array of radial threads connected to a loose hub where the spider sits when she is hunting. Because the web does not contain any sticky silk, and because the radial threads spread from the central hub in a star-like pattern, the web is thought to resemble an asterisk mark (*).

The Asterisk Web of Ocrepeira (photo from Stowe, 1986)

The Asterisk Web of Ocrepeira (photo from Stowe, 1986)

Ocrepeira next to her asterisk web

Ocrepeira next to her asterisk web

Ocrepeira at the hub of her asterisk

Ocrepeira at the hub of her asterisk

In his 1976 monograph, Herb Levi describes the natural history of these spiders thus:

“All three species are rarely collected but are found in wasp nests (Levi, 1973). They probably make their unknown orbs in trees and rest at daytime appressed to twigs.”

Now we know that Levi was partly correct, the web is built at night, but it is not a complete orb. The first accurate description of the web of this species was made by Mark Stowe (1978). Mark mentions that it was extremely difficult to observe the construction of the web which is built by the spider very quickly at dusk. When hunting the spider sits at the hub of the web and waits. Prey are detected as they walk on the branches supporting the web, or bumping into one or more of the silk threads. The spider then rushes to the branch and captures the walking prey on the branch. Stowe describes this sequence in his 1978 paper.

“Usually the spider first ties down the prey by rapidly circling the branch and the prey while laying down swathing silk. This prevents the prey from escaping and facilitates subsequent biting. When the venom takes effect, they prey is freed from the branch by biting the restraining threads and after more wrapping the prey is eaten at the capture site or at the hub.”

When Laura Hughes told me about finding a female Ocrepeira she had located in Adams county, we agreed to meet there and observe the spider. We were hoping to see her hunting technique. Thanks to Laura’s great notes and memory we were able to re-locate the spider. When we arrived at the small Eastern Redbud tree at 7:30 pm on 25 September, 2019, she had already built her web.

Ocrepeira in her web in Adams County, Ohio

Ocrepeira in her web in Adams County, Ohio

The weather in early September last year had been very dry, and there were few insects or spiders active in the area. We had hoped to capture some local insects as potential prey and offer them to the spider. Unfortunately, we couldn’t really find suitable prey. Most of the potential prey that we caught refused to walk on the branches. We did get one grasshopper nymph to walk near the spider, but it was evidently too large. The spider did not take the bait.  She eventually retreated to the branch and assumed her cryptic posture.

Ocrepeira ignoring a grasshopper

Ocrepeira ignoring a grasshopper (above spider on branch)

So our quest to observe and photograph the hunting technique in the wild was foiled. I captured the spider to see if I could get her to hunt in captivity. I set up a small branch from one of our redbud trees that had about the same sized branches and an arrangement angles similar to the situation were she was captured. To minimize disturbance she was housed in a windowless room at my home. I put a light on a timer coordinated with the light/dark cycle. At night the room was lighted with a dim red light (so I could observe and navigate). Past work with spiders has indicated that many species cannot see red light, and will continue their nocturnal behavior without disturbance.  Remarkably, she was quite cooperative and built her asterisk web on her new home.

captive Ocrepeira in her web

captive Ocrepeira in her web (flash photo)

I tried several potential prey, including handsome trig (a common bush cricket), moths, small beetles, small crickets, mealworm beetles, and small cockroaches. She did not take the bait.  I continued to offer prey each night. The spider built a web every evening then removed it and retreated to a resting position in the morning. All my attempts to get her to feed, failed.

Ocrepeira on branch

Ocrepeira on branch

I continued the next few nights without success, then on the 2nd of October, she produced an egg sac. Maybe that is why she wasn’t feeding? I don’t really know. But the very next day I fed her a small walkingstick, and she took it. Everything happened so fast, it was very difficult to see in the dim red light. The spider whipped around the walkingstick in an instant, presumably trailing a silk line to tie it down. Then she moved in and bit near the end of the abdomen.

Ocrepeira bites walkingstick prey

Ocrepeira bites walkingstick prey (flash photo)

I never saw her use “swathing” silk the way I had expected from Mark Stowe’s description.

After the Ocrepeira began feeding on the walkingstick, I left her in peace. When I checked after the lights were back on in the morning, she was in her typical resting position and there were no remains of the walkingstick.

It was getting late in the season, and I was having difficulty finding prey for the spider. The most abundant insects were large craneflies. They seemed to be good potential prey, and she did take them. Unfortunately it was extremely difficult to photograph captures. Here is one photo of the remains of her cranefly prey, wrapped with silk to the branch near where she hunted. Later in the month she died.

asterisk spider prey; wrapped craneflies

asterisk spider prey; wrapped craneflies

We don’t know how rare Ocrepeira is, there are so few records for Ohio, but it is also a very cryptic spider. It is possible that they are far more common than these records indicate. The records are scattered across the southern half of the state. In Herb Levi’s 1976 monograph there were none from Ohio, the records were scattered along the Atlantic coast from Massachusetts to Florida, with additional records in Georgia, Missouri and Arkansas. Given this paucity of information, it seemed best to return the egg mass laid in captivity back to the location where the female had been found. So Laura returned it to the original site in Adams county.

Ocrepeira egg case

Ocrepeira egg case in folded redbud leaf

So I’m still hoping to witness an Ocrepeira natural prey capture event, but that will need to wait for another opportunity.

Levi, H.W. 1976. The Orb-weaver General Verrucosa, Acanthepeira, Wagneriana, Acacesia, Wixia, Scoloderus and Alpaida North of Mexico (Araneae: Araneidae). Bulletin of the Museum of Comparative Zoology, 147(8): 378-384.

Stowe, M.K. 1978. Observations of two nocturnal orbweavers that build specialized webs: Scoloderus cordatus and Wixia ectypa (Araneae: Araneidae). J. Arachnol. 6: 141-146.

Stowe, M.K. 1986. Prey Specialization in the Araneidae. pp 101-131 IN Shear, W.A. (editor) Spiders Webs, Behavior, and Evolution. Stanford University Press, Stanford CA.

There is a kleptoparasite in your web!

Up against a window and near the edge of our back deck I found a beautiful orb web and one of my favorite spiders in residence.  It was a Orchard Orbweaver (Leucauge venusta).  She is one of the few green spiders in Ohio, and is also famous for the iridescent silver reflective patches on her abdomen.

An Orchard Orbweaver (Leucauge venusta) in her web

An Orchard Orbweaver (Leucauge venusta) in her web

As I leaned over to admire her, I noticed that there was a second spider hanging in among a few strands of slik slung below the orb of the Orchard Spider’s web. I recognized this spider by her distinctive triangular body shape.  It was an adult female Neospintharus trigonum (aka Argyrodes trigonum).

I felt like yelling to the Orchard Orbweaver the warning “There is a kleptoparasite in your web!” but she probably wouldn’t have understood.  Neospintharus is infamous as a “web invader.”  They add a few strands of silk to, or near an occupied spider web.  Then they wait until the resident spider captures prey.  If the resident is already busy with another prey item, or for some reason doesn’t notice the new potential prey, the Neospintharus sneaks into the web, cuts the prey free, and consumes it herself.  This is a mooch behavior given the technical name “kleptoparasitism” based on parasitic theft.

Here are a couple of views of the thief, inches away from the resident.

A Neospintharus trigonum female in a silk tangle below the web of an orchard orbweaver (Leucauge venusta).

A Neospintharus trigonum female in a silk tangle below the web of an orchard orbweaver (Leucauge venusta).

A Neospintharus trigonum female in a silk tangle below the web of an orchard orbweaver (Leucauge venusta).

A Neospintharus trigonum female in a silk tangle below the web of an orchard orbweaver (Leucauge venusta).

In this case crime did pay, because the Neospintharus had evidently captured enough prey to develop and lay a clutch of eggs.  Her beautiful inverted-urn shaped egg case was attached to the lower end of her little tangle near the window screen.

An egg case of Neospintharus trigonum

An egg case of Neospintharus trigonum

Here is another photo of the distinctive egg case of another Neospintharus trigonum.

photo of egg cases of Neospintharus trigonum

Neospintharus trigonum egg cases

Sometimes Neospintharus isn’t so passive.  They occasionally attack the resident spider, eat her, and then take possession of the web.  When they do this they eventually replace the original web with a three-dimensional tangle of their own making.

When they are inactive, Neospintharus trigonum can look very un-spiderlike. They fold up their legs agains their body and hang in the web looking more like a triangular bit of leaf or seed pod.

photo of Neospintharus trigonum

Neospintharus trigonum female

Here is a different female with her egg case.

Neospintharus trigonum with her egg case

In the current case, either the Orchard Orbweaver was too big to attack, or perhaps there was enough prey for both.