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the enemy of our enemy is our friend

Posted on June 14, 2016 by richardbradleyJune 14, 2016

Some of you will know, and possibly be plagued by a newly introduced pest insect, the Brown Marmorated Stink Bug (Halyomorpha halys). This animal was accidentally introduced in to the United States from Asia in 1998. They are an agricultural pest, and when they mass for overwintering, they can be also be really annoying. Often hundreds concentrate in and around buildings. When annoyed they produce a foul smell that probably evolved as a defense against predators.

Brown Marmorated Stink Bug (Halyomorpha halys) crawling along the baseboard.

Today’s blog entry is the story of how having spiders around the house can help. Several of the most common household and yard spiders in Ohio are known to eat Brown Marmorated Stink Bugs. Here are photos of just a few that I’ve caught in the act.

Long-bodied Cellar Spider (Pholcus phalangioides) feasting on a Brown Marmorated Stink bug that it found in our basement.

Bold Jumper (Phidippus audax) feeding on a Brown Marmorated Stink Bug on our back porch.

Common House Spider (Parasteatoda tepidariorum) with a Brown Marmorated Stink Bug prey found on our back porch this spring.

So at least three good reasons to keep those spiders around the house! It reminds me of the Machiavellian-like statecraft statement “the enemy of our enemy is our friend.”

Spiders in Winter

Posted on April 4, 2016 by richardbradleyApril 4, 2016

It is spring as I write this, so I’m a bit behind with this blog entry. You may have been wondering about where all those spiders that you saw in the autumn went during the winter. Many of them came to the end of their annual life cycle and died. The species with this lifestyle have already laid their eggs; the future generation will pass the winter in an egg case.

unknown spider egg case found under the leaf litter

Trachelas tranquillus with her egg case

Phururotimpus sp? egg case

Steatoda triangulosa with egg cases hidden under a wooden shelf

Philodromus imbecillus female guarding an egg case, also with previous cases (now empty)

Enoplognatha ovata with her egg case under a leaf

common house spider (Parasteatoda tepidariorum) with her egg case

These tiny spiderlings which emerge in the early spring are so small and inconspicuous that we hardly notice them. Other spiders that emerged from eggs laid earlier in the season may survive the winter as immatures or subadults. When they start moving around in the spring they are large enough to be noticeable.

Bold jumper (Phidippus audax) an immature emerging in early spring

Orchard Orbweaver (Leucauge venusta) immature in early spring

Drassyllus sp? subadult male that was found in a shed in early spring

Yellow Sac Spider (Cheiracanthium mildei) subadult male found indoors in December

The eggs, early-state spiderlings inside the egg case, emerged young spiders, and sometimes overwintering adult spiders often have cryoprotectant compounds in their cells and hemolymph (blood). These compounds either act like anti-freeze (lower the freezing point), or prevent the formation of large ice crystals that would damage cell membranes.

Some species of spiders may live several years and can survive the winter in a retreat or burrow. Retreats are usually silk cocoons hidden under bark, logs, rocks, or leaf litter. Very often these are near the ground where temperatures are moderate. Even under just a few inches of soil and debris, winter temperatures are much milder than above the surface. If there is a layer of snow on the ground, it can act as additional insulation from cold air. Water and ice are excellent buffers against extreme cold.

A few species can tolerate cold so well that even full-sized adults just find a nook or cranny and freeze in place. When the weather warms, they thaw and emerge.

Perhaps most remarkably, some spiders are “active” during the winter. They may take advantage of a warm winter day to wander over the snow. It isn’t clear what they are doing, but very few prey are active, so they may just be dispersing.

a small wolf spider (Allocosa funerea) female found walking on the snow

a long-jawed orbweaver (Tetragnatha viridis) subadult male found and photographed by David Hughes at Clear Creek Metropark (Fairfield County, Ohio) in late January 2016

The most famous “winter active” spiders are the tiny denizens of the leaf litter. These animals may even molt into mature adults during the winter months. They take advantage of the relative “warmth” under layers of dead leaves and other debris on the ground. It there is snow cover, so much the better. The epigeal (soil surface) environment is actually quite hospitable to them. In Ohio deciduous forests the leaves that fell during the autumn have been decomposing by the action of fungi and bacteria. Tiny animals that feed on the decomposing leaves, or on the decomposer organisms, become quite abundant by mid-winter. Other small creatures feed on these, including many species of spiders.

Many of these winter spiders are members of the sheetweaver family (Linyphiidae). They come in a variety of sombre browns and blacks, but quite a large proportion have bright orange coloration. I’d love to know why orange is such a common color. Here is a gallery of tiny sheetweavers, none larger than 2.5mm (~1/8 inch) long. These sheetweavers often find mates and reproduce during the winter.

Origanates rostratus male

Lepthyphantes leprosus male

Hypselistes florens female

Grammonota inornata female

Centromerus denticulatus male

Bathyphantes pallidus male

Gonatium crassipalpum male

Some of the “larger” sheetweavers of the family Linyphiidae will emerge, build webs, and hunt as soon as the early spring weather permits. Below is an subadult male Neriene variabilis. As an adult he will be only about 4 to 4.5 mm (< 1/4 inch) total body length, but this is still twice as large as the dwarf sheetweaver spiders shown above.

Neriene variabilis subadult male in his web in mid March

In addition to the sheetweavers, there are a number of other small spiders that are active on the ground surface under leaf litter.

A tiny immature combtailed spider (Family Hahniidae), possibly Neoantistea that I found in leaf litter in the late autumn. It was probably disturbed from a tiny web among the leaves.

A tiny ground-active spider in the dwarf antmimic family, (Phrurotimpus borealis) immature, found running among the leaves in autumn and winter in Ohio. This may be one of the most common spiders in these situations

Castianeira probably longipalpa immature posed on a piece of slate for this photo. These spiders have often been found among the leaf litter in Ohio woodlands and forests during winter

One last note about large spiders in winter, sometimes they do come out of hiding. When the weather is unusually nice they may show up right on the surface. Late last year I found the beautiful wolf spider, shown in the photo below, out in the tall grass next to a road while I was out “scouting” for an upcoming Christmas Bird Count. She was presumably hunting. There were other small wolf spiders in the area, great prey for a big one like this.

A wolf spider (Rabidosa punctulata) adult Female, this photo is of her “posed” on a piece of wood but she was found out in the grass in early December 2015.

spidering on Gibraltar Island

Posted on January 15, 2016 by richardbradleyJanuary 16, 2016

For the past few summers I’ve taught a Spider Biology course (EEOB 5210) at The Ohio State University’s F.T. Stone Laboratory on Gibraltar Island in Lake Erie. The course will be offered again this summer (2016), from July 31 through August 6. This is a regular Ohio State University course, providing two semester hours of credit for upper division or graduate students. With permission, the course can also be taken as a non-credit workshop for those not currently enrolled at OSU.

Gibraltar Island, Lake Erie, Ohio

main Stone Laboratory building

Now is the time to investigate signing up for the course. One reason is that many students can benefit from scholarships that provide partial support for the course costs. These scholarships are supported by the Friends of the Stone Laboratory. The deadline for a scholarship application this year is March 3, 2016.

welcome sign, F.T. Stone Laboratory

This is an intensive, residential, one week course that introduces spiders and spider research to college students. Past classes have included undergraduates, graduate students, as well as teachers and other interested naturalists. We all live and breathe spiders for seven days, beginning, after introductions, with an evening spider walk around the grounds of the laboratory on Gibraltar Island on Sunday night. Most of the students have little experience with spiders; but some have been keen spider enthusiasts, even a few academic arachnologists.

Larinioides patagiatus female hanging from a web on the outside of the laboratory building

Observing some species of spiders requires a bit of encouragement. One simple method is to gently wiggle a brush in the silk “signal” lines running out from the retreat. For viewing the tubeweb weaver (Ariadna bicolor) this technique can be very successful. Below you can see her attacking the brush. Eventually we managed to lure one completely out of her tube.

luring a tubweb spider (Ariadna bicolor) from her tube retreat

eventually she leaves her tube and bites the brush

another Ariadna leaves her tube and bites the brush

Others are found out wandering on the walls of the buildings or other structures. These include the day-active jumping spiders. Here are a couple of photos of the Zebra Jumper, a common harmless jumper found on Gibraltar Island.

zebra jumper (Salticus scenicus) female

Each day begins with morning lectures followed by afternoon laboratory and field work. During the evenings early in the week, we often convene to search for nocturnal spiders around the island. As the week progresses the students begin to focus on their individual research projects, and much of this work is done in the late afternoon and into the night. Of course, many spiders are nocturnal, so this necessitates field work at that time of day.
Monday’s first afternoon laboratory is an intensive introduction to spider anatomy with way-too-many unfamiliar anatomical terms. By the end of the week, the students all eventually master these, and are conversing in phrases like “median ocular area” and “retromarginal teeth” or “long posterior spinnerets.”

students working in the lab

Christopher Klemm working with spider identification key

Christopher Klemm working with a spider identification key

The course is an exploration of the biology of spiders (Order Araneae), but I try to create a relaxed informal environment for learning. Topics include functional anatomy, senses and perception, behavior, webs and web-building, identification, classification and relationships, field techniques, and ecology.

Michael Chips installs a pitfall trap as the class looks on

Sarah Rose checking a pitfall trap

collecting spiders from a beating sheet

Lectures are profusely illustrated with photos and videos of spiders and spider behavior. There is a tradition of an evening “movie night” with silly commercial hits such as the John Goodman classic: Arachnophobia (1990). Even watching this movie can be a spider-nerd challenge. For example: there several different families of spiders represented as one species in the film. It is difficult to identify them from their brief furtive appearance on the big screen.

Theatrical release poster by John Alvin

Spider identification is a tricky skill to master. We begin in the field “spidering” similar to beginning birding, focus on the large and conspicuous species. The big orbweavers, which are so very common on Gibraltar, such as the Furrow Orbweaver (Larinioides cornutus) and its relative Larinioides patagiatus are among the first ones we find. These big spiders are the “Great Blue Herons” of arachnology.

furrow orbweaver (Larinioides cornutus) female

furrow orbweaver (Larinioides cornutus) male searching for a female

We usually see plenty of the abundant introduced “House Sparrow” of spiders, Common House Spider (Parasteatoda tepidariorum).

common house spider (Parasteatoda tepidariorum) with a bug prey item in the corner of the lab

Students quickly learn that color and pattern aren’t often useful for spider ID; shape & behavior are better clues. With practice, subtle features like eye-arrangement and spinneret structure are recognizable. For some groups, a quick look at the “face” can be distinctive.

wolf spider face and jumping spider face

Field work in this course includes work around Gibraltar island, as well as a field trip to sites on South Bass Island. We observe, and sometimes collect spiders on these trips. Some of the specimens are incorporated into the individual student collections, others are used in individual projects.

Agelenopsis, the grass spider after being lured out of her retreat

Agelenopsis, the grass spider poses in the open after being lured out of her retreat

One of the first lessons in a course such as this one is that “daddy-long-legs” aren’t spiders at all. They are sort of cousins to spiders, members of another group, the harvestman (Order Opiliones). Being arachnids, they share many features with spiders, for example they have four pairs of legs.

Harvestman, not a spider, but a related arachnid in the Order Opiliones

Along the cobbles of the shoreline in the evenings it is often relatively easy to find larger wolf spiders, such as this Pardosa.

wolf spider (Pardosa lapidicina)

immature hammock spider (Pityohyphantes costatus) with a midge prey

The spider below looks similar, but students learn to use a magnifying glass to examine distinctive features such as the high clypeus of Pityohyphantes compared to the low one of Tetragnatha.

Tetragnatha laboriosa female

Some spiders do well in the laboratory and make good captive study subjects. One example is the fishing spider (Dolomedes tenebrosus), below in the field, and then a close up of the same gal feasting on a mayfly in captivity.

fishing spider (Dolomedes tenebrosus)

captive fishing spider (Dolomedes tenebrosus) eating a mayfly

Some of our finds are common introduced species, such as this female Enoplognatha ovata with her large egg case.

Enoplognatha ovata with her egg case

Others are quite rare, like this female running crab spider (Philodromus imbecillus) which represented the third locality record for the state when we found it on the field trip along the Jane Coates Wildflower trail. This site is maintained by the Lake Erie Islands Conservancy.

Philodromus imbecillus female guarding an egg case, also with previous cases (now empty)

One key component of the course are the individual projects. Each student chooses a topic of interest and investigates it in some detail. They collect data and conduct analysis. At the end of the course each student summarizes their results in a brief presentation to the class. For many students, the individual project is the highlight of the course. It is a chance for them to delve deeply into a particular topic suited to their personal interests. Past topics have included census work around windows on the research building, courtship behavior of jumping spiders, and variation in web structure. One of last year’s students, Zachary Diehl focused on spider heart rates.

from Twineline Fall/Winter 2015 p 17

The perennial stars of the course are the often charismatic jumping spiders (family Salticidae). They are the “Blue Jays” of arachnology, conspicuous, colorful, active, and overall fascinating predators.

Sara Klips observing jumping spider behavior as part of her research project

jumping spider (Phidippus putnami) female

jumping spider (Colonus sylvanus) female

jumping spider (Phidippus clarus) female

dimorphic jumper (Maevia inclemens) female

By the end of the week students have achieved the goals of this course and will have:

• learned to appreciate the diversity and relationships among spiders
• learned the functional anatomy of spiders
• become proficient in advanced spider identification
• learned to conduct field study of spiders using standard techniques
• learned to recognize and understand common spider behaviors
• experienced the micro and macro habitat preferences of spiders
• designed and conducted a small research project

Here are a few “group portraits” of our last few Spider Biology courses.

class group portraits, clockwise, 2007, 2012, 2013, 2015

class group portraits, clockwise from the upper left, 2007, 2012, 2013, 2015

Naturally, the impact of any summer course at the F.T. Stone Laboratory on Gibraltar is due to the unique learning atmosphere there. The small classes and intense format mix to create a very special experience for all involved. It doesn’t hurt that the scenery is spectacular.

sunset viewed from Gibraltar Island

For more details about this course consult the Stone Laboratory course information page. Anyone with a specific question about this course is welcome to contact me directly.

color shifts

Posted on December 9, 2015 by richardbradleyJanuary 30, 2016

Some of our most common spiders are extremely variable in color. A few spiders can actually change color to match the background. The “flower spider” group of crab spiders are the most famous of these here in Ohio. They get this name from their behavior of waiting in flowers, where they ambush visiting pollinators. For example, the whitebanded crab spiders (Misumenoides formosipes) in flowers sometimes match the color of their ambush site.

white banded crab spider (Misumenoides formosipes) waiting in ambush

white banded crab spider (Misumenoides formosipes) with a bee fly prey

In a study of the influence of color on movement between flowers, and success at capturing prey, Alissa Anderson and Gary Dodson demonstrated that crab spiders which matched their background did capture more prey.

By the way, just in case you were wondering, the white band in the name “whitebanded crab spider” refers to the light-colored ridge (carina) that runs across the face below the eyes. The carina is the best way to tell this spider from our other common color-shifter, the goldenrod crab spider (Misumena vatia). The goldenrod crab spider shown below has adopted white coloration to blend in (quite well) well with the queen Anne’s lace in this view.

goldenrod crab spider (Misumena vatia) waiting in ambush on flowerhead of Queen Anne’s Lace

Other spiders have discrete “color forms” where there is discontinuous variation in color from one form to another. One example of this type of color variation is the triangulate orbweaver (Verrucosa arenata). In this species the cephalothorax, legs, and most of the abdomen are either red, or black. On the abdomen there is a bright triangle-shaped mark that is either white or yellow. Individuals of this spider come in many combinations of these colors.

triangulate orbweaver (Verrucosa arenata) black&white color form

triangulate orbweaver (Verrucosa arenata) black&yellow color form

triangulate orbweaver (Verrucosa arenata) red&white color form

triangulate orbweaver (Verrucosa arenata) red&yellow color form

Other spiders seem to have more continuous variation in color. One candidate for the most common spider in the world is the aptly named “common house spider” (Parasteatoda tepidariorum). This cosmopolitan spider can be found around buildings nearly everywhere. It was just as common outside my office at the University of Sydney in Australia during the 1980’s as it is around the Ohio State University. Here in Ohio, the cephalothorax and legs are usually a deep brown, sometimes reddish brown. The abdomen has a variegated pattern with a base-color that may be pale tan or yellow, or very dark, nearly black.

common house spider (Parasteatoda tepidariorum) dark female

common house spider (Parasteatoda tepidariorum) pale female

Some individuals have a more red-orange tinge to their dark markings. The brown teardrop-shaped egg cases of these spiders are often found in the webs of adult females.

common house spider (Parasteatoda tepidariorum) with her egg case

We have many of these spiders on the walls of our house in central Ohio. They capture a wide variety of prey. On July 27^th 2014 I photographed this female who had just captured a harvestman (aka daddy-long-legs). Note that she has only one egg case in this photo (one with a distinct pointed end).

common house spider with harvestman prey

Evidently it was a good meal, because by the next day she had two egg cases, having constructed a second one overnight. Amy noticed that she had captured one of the bright green stink bugs that are common in our yard. Here are two of Amy’s photos of her with this prey item.

common house spider capturing green stink bug

common house spider with green stink bug prey

After eating this green bug, she made a remarkable color change. She had evidently absorbed enough of the green pigment from her prey to tint her abdomen green. These photos were taken the very next day.

common house spider with remains of green stink bug prey

Notice that that green stink bug is only a pale lime shadow of its former self… but ms spider has definitely gained some color! (below)

common house spider with green abdomen after eating green stink bug

This diet-related color change has been noticed by many spider workers. Back in 1989 Rosemary Gillespie also demonstrated that diet had a profound effect on the color of the famous “Happy Face” spider of Hawaii. She published a study of this phenomenon in the Journal of Arachnology. You can read this paper here.

In 1998 Theodore Evans and Patrick Gleeson published a paper on a method of exploiting this by feeding dyed termites to captive spiders. The termites were fed paper stained with non-toxic stains. The color was transferred to the spiders when they ate the termites. They used this technique to “mark” the long-bodied cellar spiders (Pholcus phalangioides) with distinctive colors.

Rick Vetter has pointed out in his recent book The Brown Recluse Spider that the abdominal coloration of brown recluse (Loxosceles reclusa) can change dramatically after meals of heavily pigmented prey. In the pictures below, the left photo is what the spider looked like after eating crickets. The photo on the right shows how the same spider appeared after eating two house flies.

Reprinted from The Brown Recluse Spider, by Richard S. Vetter. Copyright © 2015 by Cornell University. Used by permission of the author, Richard S. Vetter. All rights reserved.

Rick’s book describes the biology of the brown recluse and its relatives. He carefully separates myth from reality, and provides useful information about this most notorious American spider. It can be purchased here.

These examples of diet-influenced color change are most obvious in spiders with pale or generally lightly-pigmented abdomens. Often the cephalothorax and legs remain the same because they have a thicker, opaque exoskeleton.

So the moral of this little story is that sometimes “you are what you eat”, or at least you might look like it.

Sources:

Anderson, A.G. and G.N. Dodson. 2015. Colour change ability and its effect on prey capture success in female Misumenoides formosipes crab spiders. Ecological Entomology, 40(2): 106-113.

Evans, T.A. and P.V. Gleeson. 1998. A new method of marking spiders. The Journal of Arachnology, 26: 382-384.

Gillespie, R. G. 1989. Diet-induced color change in the Hawaiian happy-face spider Theridion grallator (Araneae, Theridiidae). J. Arachno!., 17:171-177.

Vetter, R. 2015. The Brown Recluse Spider. Cornell Univ. Press, Ithaca. 186p.

Bolas spiders!

Posted on November 13, 2015 by richardbradleyNovember 17, 2015

Bolas spiders are among the most remarkable spiders in the world. These odd animals are in the family Araneidae, the orb weavers. But unlike the majority of species in this large family, they do not build an orb web. Instead, they hang in a very simple trapeze of silk just below a branch in a tree or shrub. They prepare for their hunt by spinning one silk line with a droplet of glue at the tip. This is their bolas. After preparing the bolas, they wait, hanging in mid air below the branch for a moth to come by, holding their bolas line in one of their front legs. When a moth approaches, they toss the bolas to snare the moth.

bolas spider (Mastophora hutchinsoni) hunting with her bolas

The name “bolas spiders” is a reference to the Argentinean gaucho’s bolas, a line with heavy balls at the end which are used in hunting guanacos (a South American relative of the camel) or rheas (a large flightless bird). If skillfully thrown the line with its balls wraps around the legs of the prey, hobbling them. There is evidence that this unusual hunting tool was invented by the Inca civilization prior to the arrival of the Spanish.

The bolas spider employs her line to catch flying moths. Mark Stowe and Tonia Hsieh have shown that the ball of glue actually has a long thin silk line coiled within. When the spider tosses her bolas the line unwinds and wraps around the moth. This is a very strong line with adhesive glue, and if successfully deployed, it will hold a large moth desperately trying to fly away.

Watching a bolas spider hanging motionless below her branch, waiting for a moth to fly by close enough to snag, one could be excused for being skeptical that this could ever work. The key to the hunting technique was revealed when Bill Eberhard discovered in 1977 that these spiders catch only male moths. Why males? Because Dr. Eberhard determined that the spider produces a chemical perfume that mimics the sex pheromone of a female moth. The males home in on the odor and fly directly up to the waiting spider. Even after she tosses and misses, the sex-starved male moths continue to approach, presumably still searching for the elusive female moth who isn’t there.

During the day bolas spiders glue themselves to a leaf. Here they sit, with their legs curled up around them. They are fat globular-shaped spiders with subdued colors. Some are brown and white, others with a slight greenish tone. The globular pose and colors make them resemble bird droppings. When disturbed while resting they employ a “stink” defense, the emit an unpleasant odor. This is thought to deter predators.

bolas spider (Mastophora hutchinsoni) resting pose

bolas spider (Mastophora phrynosoma) resting on a leaf

bolas spider at rest (Mastophora timuqua)

an actual bird dropping, looking a bit like a resting bolas spider

We have been very lucky to have found bolas spiders in our rural Ohio yard. Back in 2001 we found females of the cornfield bolas spider, Mastophora hutchinsoni. Since that time we have found this species hunting in our yard on a number of different years.

bolas spider (Mastophora hutchinsoni) hunting with her bolas

This August I went out hunting with my headlamp for spiders. I was really hoping to find a bolas spider, because we had not seen one the past few years. I was rewarded with a beautiful adult female hanging from a low branch of a crab apple tree. As I approached, I realized that she didn’t look like the familiar M. hutchinsoni, it was actually a different species of bolas spider! After consulting Herbert Levi’s monograph on this genus, I identified her as an adult female of Mastophora timuqua. This was a very surprising find, the species had been previously known only from Florida and North Carolina, a very long way from Ohio.

bolas spider (Mastophora timuqua) hunting with her bolas

As the summer progressed into autumn I was able to observe the spider hunting on many occasions. Several times I saw moths approach, and observed the spider fling her bolas. Most of these attempts were failures, but once while I was watching she managed to snag a moth. The moth flew in a circle, round and round, held by the silk line until it reached part of the branch and landed. He pulled himself free from the line and escaped.

On one evening I was able to take a photo of the bolas spider before she had completely wrapped her prey. It turned out that this photo was sufficient for John Gilligan to provide me with an identification of the moth (Greater Black-lettered Dart, Xestia dolosa).

bolas spider with fresh capture of Greater Black-lettered Dart (Xestia dolosa)

Experimental work has shown that bolas spiders can vary the odor lure that they use to capture moths. They evidently choose from an arsenal of chemical attractants the one that is appropriate for the particular moth species flying that night.

I even tried to shoot video of the hunting bolas spider. My efforts were rewarded with a few short video segments of her hunting. The first video shows her spinning her bolas, pulling out silk and glue to fashion her bolas. This part takes quite a while, if you stick with it she eventually re-positions herself, holding the completed bolas below. Near the end of this segment she tosses it at a moth, but misses.

Finally after many fruitless evening video shoots, I secured a segment with a successful capture and wrap. This is a five minute video, so you will have to hang in there to see the whole show. At first she misses, but then… success! Beware this is a very violent capture. It is a real testament to the strength of the silk snare. Eventually you will see her approach the wildly spinning moth, deliver a bite, and back off. Soon you can see the venom take its effect and the moth stops struggling. Finally she returns to wrap her prize.

For the next few weeks she would fatten up on moths each night. Sometimes I was able to find the empty husk of a moth, wrapped mummy-like in a silken shroud, below the spider on the ground.

Mastophora timuqua wrapping a moth prey

“mummy” of a moth, having been wrapped and discarded by bolas spider

On a few nights I saw the bolas spider hanging with her legs spread, but without a bolas. Perhaps she was still emitting her pheromone lure because on at least two occasions I saw moths approach her in this pose. I never saw her capture a moth without a bolas, so I don’t know for sure if this is what she was doing.

bolas spider Mastophora timuqua hanging in mid air

The bolas spider stayed on the same branch for weeks. Even after very heavy rain and wind, she remained. On the early morning of the 9^th of September, Amy noticed that she was building an egg case. She carefully attached it to the branch, walking around the case and branch laying down many layers of silk to form a sort of strap.

bolas spider (Mastophora timuqua) egg case

After laying eggs and constructing the silken case, the spider appeared shrunken. The next night she was hunting again. After a couple of weeks of meals she was back to her plump self. After her third egg case, she was visibly wrinkled.

Mastophora timuqua completing her third egg case, she’s looking pretty wrinkled

After laying this third egg case, the spider appeared very gaunt. She hung from the end of her branch, listless. This is the end of her annual cycle, and like most orb-weaving spiders, she would not survive the hard frosts to come. She was remarkably successful to grow to adulthood and produce three egg cases. We can only hope that these will yield a little army of bolas spiderlings next spring.

Bolas spiders have lots of other interesting tricks. For example, sometimes they use a passive bolas technique, spinning a horizontal line and hanging several bolas’ below it.

bolas spider (Mastophora hutchinsoni) with silk line and four hanging bolas lines

As if all of this wasn’t peculiar enough, adult male bolas spiders are dwarfs. They are very tiny compared to the female. The males mature very early, some even mature while in the egg case and emerge as adults. In other species they molt to maturity very soon after leaving the egg case. As a result they are tiny, like most young spiderlings. In contrast, the females must grow and molt many times to achieve adult size. In the illustration below a female of Mastophora cornigera is shown with a male to the same scale. This illustration is by Steve Buchanan.

Mastophora cornigera, female on left, male on right, painting by Steve Buchanan

Recently I was perusing images of bolas spiders (Mastophora) on one of my favorite web sites (bugguide.net). I found a series of remarkable images of a female Mastophora phrynosoma accompanied by an entourage of little males. The photos were posted by one of the many volunteer contributors to the bugguide site, Matt Coors. Matt found the spider in August of 2014 near Cincinnati, Ohio. Matt is an artist and you can see some more of his photos and samples of his art here.

These photos of adult males with a female of any species of Mastophora are quite rare.

Mastophora phrynosoma with an entourage of little males, photo courtesy of Matt Coors

Mastophora phrynosoma close-up view of a male, photo courtesy of Matt Coors

There are a total of 50 species in the genus Mastophora, currently known only from the new world. Other spiders, classified in different genera, with similar pheromone mimicry hunting behavior are found around the world. Of the members of Mastophora, only 15 species have been found in North America north of Mexico, and only 5 are known for Ohio.

For more information about bolas spiders and Steve’s illustrations of a few other species and their distinctive egg cases, you can consult Common Spiders of North America, plate 7 and pp. 94-96.

References:

Eberhard, W. 1977. Aggressive chemical mimicry by a bolas spider. Science, 198: 1173-1175.

Levi, H.W. 2003. The bolas spiders of the genus Mastophora (Araneae: Araneidae). Bulletin of the Museum of Comparative Zoology, 157(5): 309-382.