This species appears to be well camouflaged in its natural habitat – high elevation tropical wet forest with an abundance of mosses and ferns at Las Brisas Nature Reserve, Límon province, Costa Rica. Luckily I snapped some photos of this species before preserving a few individuals in ethanol to examine later in the lab because, unfortunately, the gorgeous color faded quickly! Upon closer inspection our research team discovered that the harvestman does not produce the green pigment, but rather, the pigment is produced by epizoic cyanobacteria that lives on the dorsal scute of the harvestman. This is an extraordinary example of the evolution of symbiosis. Although it is unclear whether this relationship is mutualistic (one would have to determine whether the cyanobacteria is actually benefiting), the green coloration does appear to provide camouflage for this harvestman within the very lush, green habitat in which it was observed.
I’ve been so busy writing other stuff (proposals and manuscripts) that I haven’t had time to post many pictures lately. That also means I haven’t been out much to take new pictures. So here are some photos from a couple weeks ago – a caterpillar that belongs to one of the species of swallowtail butterfly – probably the Eastern Tiger Swallowtail (I also posted a photo of the adult for this species below).
The “eyes” that you see are not actually eyes at all. Instead this is a type of cryptic coloration (specifically mimicry) that has evolved to look like eyes as a defense mechanism.
I was out hiking the other day looking for harvestmen and spiders, but almost every large rock I turned yielded a salamander! Here’s one of the little guys hiding in some leaves.
The above image is actually a stack of two photos to get the depth of field I wanted on the face of this salamander.
During the arachnologist field trip to Toft Point in Wisconsin a couple weeks back, I was in the field collecting with opilionologist Jeff Shultz and arachnid photographer Joe Warfel. Jeff collected Caddo pepperella, a rare species of harvestman. Previously this species has only been collected in pitfall traps so this was the first time anyone has ever collected and photographed this species alive! I thank Jeff and Joe for giving me a chance to photograph the specimen.
Caddo pepperella is a tiny litter dwelling harvestman that very few people will ever observe out in the wild! The length of its body is less than ONE millimeter!!! And its legs are not much longer than a couple millimeters. But small as it is, relative to its body size, the eyes are huge!
Updated on 4/2/13 – species is Caddo pepperella, ID by J. Shultz.
The ubiquitous species of harvestman Phalangium opilio was named by Carl Linnaeus in 1758. P. opilio is now distributed all over North America, where it has been introduced from Europe (thankfully it is not a pest!). The species range has also apparently spread into parts of Asia and Africa. This species thrives in a number of different habitats, including natural habitats, such as forests, as well as anthropogenic habitats/structures, such as under bridges, in gardens or green spaces.
Males of P. opilio have large horns on their chelicerae (pointing outward, away from the anterior end). These structures are used as weapons in male-male contests which most often results in the loser fleeing and the winner having a chance to mate with a nearby female.
Below are a few more photos from a field trip to Toft Point, WI during the 2012 meeting of the American Arachnological Society at UWGB.
Notes on image below: The cheliceral horns are the long pointed cones sticking off of the first pair of appendages (the chelicerae). The chelicerae bend downward, each terminating in a movable, pincer-like claw that is not visible here. Note that the male pedipalps are very long, unarmed, and appear as if they are an additional pair of legs (here the pedipalps are more gold in color, while the legs are black). This male is also missing the second walking leg on the near side of the body.
Image below: Same male, dors0lateral view.
Image below: Female from a dorsal view. The pedipalps are shorter and are held close to the body partially covering the smaller chelicerae of the female.
Harvestmen: The Biology of Opiliones. 2007. R. Pinto-da-Rocha, G. Machado & G. Giribet (Eds.). Harvard University Press.
Willemart RH, Farine J-P, Peretti AV, Gnaspini P. 2006. Behavioral roles of the sexually dimorphic structures in the male harvestman, Phalangium opilio (Opiliones, Phalangiidae). Can. J. Zool. 84: 1763-1774.
At most academic meetings the arachnologists often get lumped into an entomology section. Or they might find themselves mixed in with general invertebrates. But not this time! Two weeks ago, in Green Bay, Wisconsin, more than 100 arachnologists from all over the world met for the annual meeting of the American Arachnological Society hosted by University of Wisconsin at Green Bay. The meeting took place over the course of four days and included all kinds of arachnid-based talks, posters, social events and an auction with all kinds of spider paraphernalia (books, t-shirts, toothbrushes, old photos, jewelry and more)! It was a great opportunity for many enthusiastic arachnologists to share their exciting research regarding the charming little animals that strike fear into the hearts of most people!
After the official meeting concluded there was a field trip to visit Toft Point State Natural Area, on a peninsula along the western shore of Lake Michigan. About 40 arachnologists jumped on a bus, headed up to Toft Point, and collected specimens in hopes of adding to the list of known arachnids from this site. Here are a few spider photos from the field trip.
Longlegs fact #4: Harvestmen have repugnatorial glands that produce compounds used in chemical defense.
These repugnatorial glands are also known as defensive glands, scent glands, stink glands or odoriferous glands. The repugnatorial glands are a major synapomorphic character of Opiliones. This means that the glands are a derived character, shared among all Opiliones (and their most recent common ancestor), but not among other arachnid groups (though other arachnids may have different chemical defense mechanisms). The glands produce chemical compounds that are meant to deter predators. The chemical compounds produced are very diverse but many are forms of quinones and phenols. The openings of the glands are on the body near the second pair of legs. The harvestmen usually release this secretion when threatened or disturbed.
The chemical compounds produced by some species can actually be detected by our own senses. When I collect harvestmen by hand I will sometimes smell them just out of curiosity (despite the crazy looks I get). The chemical compounds produced by some species are surprisingly potent! If I were a natural predator of harvestmen I would think twice about consuming them after getting a whiff of this. And no, I have not tried tasting them! Yet.
Although there will be many more interesting stories and facts that I will share about harvestmen in future posts, this post will conclude my series on the introduction to the biology of harvestmen.