Arachtober, Part XV!

This year marks the fifteenth anniversary of “Arachtober,” an event initiated on the photosharing website Flickr by my good friends Ashley Bradford and Joseph Connors. Since then, it has extended its silky reach to social media, especially Twitter and Instagram, where searching on #Arachtober will bring up stunning images of spiders, scorpions, solifuges, ticks, and mites, oh my.

© Ashley Bradford & Joseph Connors

The banner shown above was hand drawn by Ashley, and digitized by Joseph. They both have acute powers of observation, and are supremely talented photographers who are constantly experimenting. They have inspired literally thousands of others to focus their lenses on our eight-legged friends, and come together as a global community for at least this one month each year.

You should join in the fun! It is a window on an overlooked, seriously maligned group of organisms, illuminated in a positive light by photographers and scientists. I learn something new almost daily thanks to the stories attached to the photos.

I will forever be indebted to Ashley and Joseph for their supportive friendship, and starting something truly unique, valuable, and enduring. More details about the origin of Arachtober can be found in this livescience.com article.

Pseudoscorpions: The Strangest Arachnids?

Yes, the image below is of a crane fly in the family Limoniidae, but what is that other thing attached to it? The crane fly showed up at our backyard blacklight a few nights ago in Colorado Springs, and by itself would have been interesting. Its hitchhiking companion made it even more spectacular.

Crane fly with pseudoscorpion gripping its leg

Pseudoscorpions are tiny arachnids, most of them under five millimeters in length, that never fail to provoke head-scratching among people unfamiliar with them. They look like they could be baby scorpions that are missing their telson ("tail"), but they are literally in an order unto themselves: Pseudoscorpiones. They are fairly common, but seldom seen because they frequent microhabitats under bark on trees, stumps, and logs, or leaf litter or topsoil, or in mammal nests or caves, or other places that require a dedicated effort to uncover them. It is only those species that occasionally turn up in our "caves" (homes) that catch our attention.

I wrote about pseudoscorpions previously, for Missouri Conservationist magazine, thanks to fantastic photographs by Ashley Bradford and Ted MacRae, but this week's find finally allowed me my own imaging opportunities. It is interesting that the insects favored as transportation by pseudoscorpions are frequently those associated with decaying wood: longhorned wood-boring beetles (Cerambycidae), braconid wasps that are parasites of wood-boring beetles, and in this case a female crane fly which I would bet oviposits (lays eggs) in decaying wood.

Pseudoscorpions are predatory on other small invertebrates such as springtails, barklice, fly larvae, and mites. They seize their prey with the pincer-like chelae at the ends of their "arms." Those heavy, muscular appendages are actually modified mouthparts called pedipalps. Many species of pseudoscorpions have venom glands in the chelae that help subdue struggling victims. From there, the prey is passed to the plier-like chelicerae, or jaws, that puncture the body wall of the prey, or crush it, and allow for the introduction of regurgitated enzymes to begin the extraoral digestive process. The resulting liquified material is then ingested by the pseudoscorpion.

Bizarre? We are just getting started. The chelicerae also house silk glands, and pseudoscorpions spin silk to encase clutches of eggs, for shelter during molting and overwintering, or even as a retreat from which they can wait in ambush for unsuspecting prey to pass within reach.

Using another animal for transportation is a behavior called phoresy, and that appears to be the chief means of dispersal for pseudoscorpions. They do not have wings, after all, and are so tiny that getting from one optimal niche to another under their own power is almost impossible. Also, they do not "balloon" as many spiders do, spinning silken threads that are caught by the wind and waft the spider to a new home.

After the crane fly died, the pseudoscorpion disembarked and I was able to get the images you see here. I discovered they are much more agile than I anticipated. This one could scuttle backwards fairly rapidly, run forward quickly, and it could easily climb the slick walls of our casserole dish "studio." Maneuvering the tiny creature with an artist's paintbrush was challenging since the animal could simply grip a single bristle and refuse to let go.

The social life and love life of pseudoscorpions is surprisingly complicated. Members of some species can live side by side without antagonizing each other, displaying unique and rhythmic movements of their bodies and/or pedipalps to communicate. Meanwhile, courtship between male and female in nearly all species is accomplished through a variety of behaviors. In all cases, the male packages his sperm in a spermatophore. In the most primitive scenario, he simply deposits on the ground or other substrate where he hopes a female encounters it. She will then pick up the spermatophore in her genital opening.

Males of other pseudoscorpion species will only deposit a spermatophore if they encounter a female. These males may then spin a simple or elaborate, three-dimensional silken bower to help funnel the female to the location of the spermatophore. This greatly improves the male's chances of reproductive success.

Mating can be more intimate in the most "advanced" species. This involves what is best described as dancing, the male grasping the female's pedipalps in his, and gently but firmly guiding her over the spermatophore he has just deposited. There may be subtle choreography and pre-programmed body movements involved in that. They may even kiss, if you will, interlocking their chelicerae.

Pseudoscorpion from leaf litter in Massachusetts

Despite the extent of our collective knowledge of pseudoscorpions, new species are discovered with a surprising degree of regularity. Those who study caves and other specialized habitats; and those who study rodents and other vertebrates, would be wise to keep their eyes out for pseudoscorpions. Meanwhile, carefully inspect the insects at your porch light and you might eventually find one of these arachnids on an insect attracted by your beacon.

Sources: Johnson, Elizabeth A., and Kefyn M. Catley. 2002. Life in the Leaf Litter. New York: American Museum of Natural History. 28 pp.
Weygoldt, Peter. 1969. The Biology of Pseudoscorpions. Cambridge, Massachusetts: Harvard University Press. 145 pp.

Book Review: Dr. Eleanor's Book of Common Spiders

One resource that has been missing from the recent explosion of spider-related material coming from various publishers has been a book aimed squarely at the average homeowner or gardener with something other than an all-consuming passion for arachnids. "Dr. Eleanor" to the rescue with Dr. Eleanor's Book of Common Spiders (Chicago: The University of Chicago Press. 2018. 96 pp.).

Eleanor Spicer Rice, who already has several related titles under her belt, mostly about ants, has teamed up with Chris Buddle to deliver a nicely organized, thoroughly researched book on the spider species that the public most often asks about. You know, the eight-legged critter crawling across the kitchen floor, the infamous "shower spider," and the ones you always see in the (insert shed, basement, garage, or other appropriate venue).

The authors treat their subjects with accuracy, clarity, and brevity, while still managing to cultivate the same sense of fascination in the reader that they, as scientists and writers, have already found for themselves. This is no small feat. There is a dash of humor here and there as well, and they are not above poking fun at themselves. Color photographs, mostly by Sean McCann, complement the lively text and enhance the impact of the book. Whether arachnophobes will reach for it on the bookstore shelf, or over the online vendors remains to be seen. I hope they do.

Even if the book were a complete failure otherwise, it would bear recommending for this passage alone:

"Striped lynx spiders prefer biding their time in agricultural fields. When we plant our crops with only one or two types of plant per field, we humans essentially sow arthropod grocery superstores. In nature, any given species of plant is often mixed in with other plant species and so bugs that like a particular plant species may need to search to find the plansts they like. As a result, only a limited number of bugs can live in an area. It's like living in a town with a gas station-sized grocery store. In our human-planted superstores, however, tons of insects that like our crops can move into the giant all-you-can-eat buffet of a farm, filled with only their favorite foods. These insects become agricultural pests, gobbling up billions of dollars' worth of food we grow for ourselves each year."

Exactly. I have said the same thing myself in my own publications, about how humans are responsible for creating their own insect pests. Further, all the crop plants are equally vulnerable because they have identical genetics. Not so in nature. Watch a butterfly laying eggs. She won't oviposit on every plant; only on those a little weaker in their chemical defenses.

My only quibbles with the book stem mostly from the fact that I am a writer, too. There were a couple of bad word choices, but I see worse errors in other books. There was one implied assertion that is incorrect, however. In the Frequently Asked Questions part of the back matter, one FAQ concerns whether all spiders are venomous. The authors indicate they are. This is not true. Spiders in the family Uloboridae, common in North America, lack venom glands. Lastly, there are some common English names for certain spider species or genera that were apparently created just for this book. There is no such thing as a "Ceiling Spider," even though I would endorse that name for Cheiracanthium species because that is exactly where you encounter them.

Enough nit-picking. The "up sides" of this handy volume are much more numerous. It is a paperback, and of a size that is large enough to not lose easily in a stack of other books, and comfortable to handle for those of us who are all thumbs. Again, the text is a joy to read. Spicer and Buddle manage to give each spider a personality that reflects its biology. This style comes close to anthropomorphism, but I am all in favor of whatever it takes to win more arachnophiles. Spiders need all the friends they can get in Humanland.

One of my measures of the goodness of a book like this is whether it teaches me, a longtime naturalist, something new. This book did that, in spades. I love being surprised with new knowledge, and with that I heartily recommend Dr. Eleanor's Book of Common Spiders.

"Arach" is Back!

One of the things I look forward to each autumn is the annual Flickr event known as "Arachtober". It is a Flickr group which slumbers between November and the following September, but remains a tradition among arachnophiles and macro photographers. There are always mesmerizing images posted from all corners of the globe.

Marbled Orbweaver, Kansas

Arachtober manages to recruit several new participants each year through word of mouth, blogs, and sheer curiosity. Not only spiders, but scorpions, ticks, mites, harvestmen, and all other arachnids are eligible for inclusion. Don't forget the artistry of spider webs, too, whether dew-adorned or dry.

Apache Jumping Spider male, Colorado

The only hard and fast rule of Arachtober is that the images you post to the group must not have appeared on your own Flickr photostream previously. Allowed quantity of images per day varies at the discretion of the group administrator.

Banded Garden Spider female, Colorado

Overall, interest in spiders seems to be increasing among the general public, and arachnids are achieving a much higher profile than ever before. This is great news, for there is still a great deal of work to be done to combat myth, superstition, misinformation, and fear.

Wolf spider, Alopecosa sp., Colorado

Please consider contributing to "Arachtober" on Flickr, or find another way to dedicate some time to sharing your spider observations, questions, or images. There are many groups on Facebook devoted to spiders and their identification, for example; and presumably, the same applies to Instagram. There is much you can contribute to our collective knowledge by doing so. Thank you.