For many years, I've been staring hard at little pieces of shit in the forest, learning not to casually dismiss any piles of excrement as they could actually turn out to be devious little dung spiders, sometimes also known as bird dropping spiders.
Living its life as a pile of poop may sound shitty, but the facade is actually an ingenious predatory and defensive tactic.
** Predatory tactic
Excrement from birds, lizards and other vertebrates are an excellent source of food and nutrients for some insects, especially flies and some bugs. Dung spiders capitalize on this attraction with its crap-like exterior and reinforces its deception by remaining motionless for hours just like a true piece of poop.
It had been popularly spread on the internet that these bird dung spiders not only looked like shit, but they smelt like shit as well. The scent may not be easily detected by a human, and there had not been any real evidence of such a notion. Hence in 2015, a group of scientists from Hubei University, China performed a series of experiments to prove that volatile chemical cues helped the spider to repel predators and to attract prey.
** Defence tactic
The crappy disguise also protects the spider from birds and other predators that normally would not consider eating its own poop.
In this photo series, I have consolidated some of the common poop-like genera of spiders from Southeast Asia (mostly Singapore): Pasilobus and Phrynarachne. Cyrtarachne had traditionally been called bird-dropping spiders, so there would be a brief mention at the end of the post. Spiders from these genera are mimics of poop / faeces / dung / excrement / shit / bird dropping to various degrees.
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Interestingly, the abdominal warts and muscular depressions appeared to fluoresce brightly under ultraviolet. It might have served as an additional attractant for unsuspecting prey!
This dung mimic crab spider does not weave any web, and relies heavily on attracting prey to it. Ambush predation is typical for spiders in the crab spider family, Thomisidae. Locally, we have been calling this the peanut dung spider because of its resemblance to sticky peanut bars.
Anterior view shows the face of the predator where the legs are more obvious while the poop illusion is less convincing.
This dung spider specializes in creating a "splatter" of silk, and sits on it, simulating the white stain caused by the bird-droppings when splashed on a leaf. This species is probably Phrynarachne decipiens or one close to it. We found this species in Borneo Bootcamp 2015, and hope to see it again in the next Bootcamp!
A distinctive species, this is probably Phrynarachne ceylonica. It doesn't really look like bird dung on its own, but the disguise is more believable when it sits on its radiating nest which looked like a bird dropping splatter.
Most dung-mimics sport a wet and lumpy surface to resemble fresh bird excrement. At rest, they draw their legs close to their bodies to conceal its shape and would lie motionless for hours in the day. This is probably the best poop-mimic, hence the title "King of Poop".
Younger specimens may come in various shades of brown. The easiest way to differentiate real poop from a spider, is that real poop would never be symmetrical while spiders should show distinct symmetry.
This shit is real. Not a spider. Just to highlight the knobbly, wet appearance of fresh poop!
This dung spider was found in Singapore, and looks superficially like the previous peanut dung spider. It lacks the extreme lumpy surface on its abdomen, but bears numerous tubercles, most notably the two posterior projections.
Another different color morph of this species.
Another piece of poop for comparison. Unfortunately I kept forgetting to take photos of the poop splatter.
Beautiful colors for a poop-mimic! Locally, some of us called this the bak-zhang (rice dumpling) spider.
Not all species of Pasilobus are as lumpy as the one described earlier. Some are smoother but there is little doubt that they are dung-mimics.