by Joseph DeSisto
So, it turns out a lot of other people think whip-spiders are awesome as well. This is good! Recently I’ve been looking at a lot of them, and I thought I’d share some of the pictures I’ve taken, since I think they’re pretty cool.
The only whip-spider found in the eastern United States is Phrynus marginemaculatus, found in southern Florida and the eastern part of the Caribbean. These also happen to have been the first whip-spiders I ever identified, and one is pictured below.
A few things to notice. First, there are three sets of eyes, one right in the front and one on each side, immediately behind the base of the pedipalps or “grabby claws of death.” Second, between the pedipalps and just in front of the eyes is a pair of structures that resemble a spider’s fangs. Like spider fangs, these are a pair of chelicerae or mouthparts. Unlike spiders, however, whip-spiders have chelicerae that cannot inject venom — they can only tear apart prey after it has been captured.
Here’s the same whip-spider, but viewed from beneath:
The whip-spiders of the Americas mostly belong to the family Phrynidae, and within the Phrynidae, the four New World genera are Phrynus, Paraphrynus, Acanthophrynus and Heterophrynus. I have cited documents with keys to Phrynus (Quintero 1981), Paraphrynus (Mullinex 1975), and Heterophrynus (Adis 2002), although these may be slightly out of date. Acanthophrynus has only one known species, and that’s A. coronatus. A key to the genera of Phrynidae can be found in Quintero (1981).
Most important in the identification of whip-spiders is the pattern of spines on the prey-impaling pedipalps. In fact, there are some species that can be identified even if the pedipalps are all you have to look at! This probably isn’t the way it should be, and it leaves open the possibility of many cryptic species, identifiable by less conspicuous, but just as informative, characteristics — more on that another time. The segments of the pedipalps are labelled in the photo below, the same P. marginemaculatus from before.
Below I have photographed the major components of the left pedipalp of a Phrynus specimen. This is not P. marginemaculatus — it is an unidentified species, perhaps even undescribed. So, I don’t want to give too much away, but I will say that it was collected in Central America, where Phrynus is one of the most widespread and abundant groups of whip-spiders.
This is the pedipalp’s tibia, viewed from above. In case you don’t believe me that this specimen belongs to the genus Phrynus, all you have to do is look at the spines: between the two longest spines is only one shorter spine. In Paraphrynus, there are two shorter spines between the two longest. And the tibiae of Acanthophrynus and Heterophrynus are completely different — maybe we’ll see them at some point.
Anyway, the same structure, viewed from below:
Pretty scary, huh? And just because I like showing off my pictures, here’s a look at the femur from above:
And from below:
There’s a lot more to the whip-spider’s “grabby claws of death,” but I eventually got bored and started taking pictures of other things. In particular, I am interested in the chelicerae of these animals. The mouthparts, although used by Quintero (1981) in his key to Phrynus, have gone relatively ignored by whip-spider taxonomists. This is probably mostly due to the fact that the pedipalps are more accessible — you pretty much have to dissect/rip out the mouthparts to get a look at anything interesting.
But on a whim I did dissect them, and boy, are they interesting. It turns out that taking them out is actually pretty straightforward: just take a pair of fine tweezers and pull. First impressions: they are super hairy. To get a look at the teeth on the mouthparts I had to try and get around all this hair, which ended up being pretty dense.
So I did what anyone would do — I borrowed/stole/liberated a scalpel from the vertebrate specimen preparation room and gave them a good shave! After about ten minutes of shaving, this was the result:
Not bad — I think I’m getting to be a regular Figaro of arachnids! Anyway, the mouthparts or chelicerae are used to tear apart prey after it has been captured with the larger and more impressive pedipalps. The pattern of teeth, especially on the lower part, is important in identifying members of the genus Phrynus.
On the whole, the mouthparts are similar to those of spiders but different in much the same way whip-spiders themselves are different: they are non-venomous, and loaded with teeth. And they are awesome — but spiders are pretty awesome too, which is why if things go according to plan, they will be the subject of the next post.
Mullinex, C.L. 1975. Revision of Paraphrynus Moreno (Amblypygida: Phrynidae) from North America and the Antilles. Occasional Papers of the California Academy of Sciences 116: 1-80.
Quintero, D. 1981. The amblypygid genus Phrynus in the Americas (Amblypygi, Phrynidae). The Journal of Arachnology 9: 117-166.
Weygoldt, P. 2002. Amblypygi. In J. Adis (ed.). Amazonian Arachnida and Myriapoda (293-302). Bulgaria: Pensoft Publishers.