Scott Powell’s comment on my post about ant-like jumping spiders provokes me to take a break from our current field trip in Mexico to write a post about one of the most stunning cases of mimic-model matching I’ve seen in salticid spiders. On a trip to the Dominican Republic in 2009 we found a fair diversity of jumping spiders of the genus Peckhamia. In one locality we found this ant and this species of Peckhamia.
In another locality we found this ant and this species of Peckhamia. Notice that the front legs of the spider are tipped in red, just as are the sides of the face and the mandibles of the ant. Wow.
In yet another locality we found this beautiful species of Peckhamia. We didn’t see a correspondingly red ant, but perhaps a reader can advise us if such exists in the Dominican Republic?
Reflections on a Spider's Eyes 
Wow, is right! The mimic of the Cephalotes unimaculatus worker is just astonishing. I suddenly have a huge urge to know how many Cephalotes-mimicking spiders are out there, and where they fall on the Cephalotes tree.
I’m afraid I don’t have any general knowledge of the ants of the Dominican Republic, but I can’t help get excited by the last spider. The red coloration is exceptionally rare in ants. There is a strong possibility that this spider is copying another Cephalotes, but this time one that is very poorly known. Cephalotes vinosus is known only from the type series (collected in Haiti) and is characterized by “a dark red gasteral dorsum” with the rest of body black. It all seems to fit very well. To top it off, Cephalotes vinosus is thought to be sister to C. unimaculatus, your second example here!
Wouldn’t it have been a great story if Cephalotes vinosus had not been known, and its mimicking spider provoked us to look for it! The red and black Peckhamia was collected by G.B.Edwards (DOMINICAN REPUBLIC: Pedernales: Rio Mulito. N 18.155° W 71.758° elev.270m 16 Jul.2009)
The story is still pretty great for me! The extant Cephalotes species on Hispaniola are very important because they are a clade that does not have a soldier (contrasting almost every other member of the genus). But, they are very poorly known and collected. Even the most common couple of species are usually collected as lone workers, not colony series. Having a recent location in the Dominican Republic (instead of the old and only known locality in Haiti) where we might be able to find and collect a colony or two of C. vinosus in the future is incredibly exciting! Thanks so much for the post and the collection info. I have saved the collection info for a future mission.
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I expect that, like the domestication of animals in general, evolution of this kind can proceed quickly in an isolated population. This assumes that there are specific agents of selection that are looking directly at the appearance of these ants, in some detail. This hypothesis predicts that you should be able to find these agents. They might be the ants, but perhaps they are ant eating birds that look closely at a group of ants for interlopers or out of place (non matching). My first question would be, why are these ants so colored?
Cephalotes flavigaster, maybe?
http://www.antwiki.org/wiki/Cephalotes_flavigaster
Hi Alex. C. flavigaster would be fun too, but I think the gaster is too orange to be the model for the last spider. Kempf saw flavigaster as an intermediate between the bright yellow gaster of unimaculatus and the redder vinosus. Admittedly, the red gaster of the existing vinosus specimens (e.g. http://www.antwiki.org/wiki/Cephalotes_vinosus) is not as vivid as the live spider, but the colors obviously dull substantially with drying and aging. I think there is still even the possibility that this is a mimic of an undescribed Dominican Cephalotes, as Wayne wondered about. I think the sampling has been light enough for this to be possible. Either way, this spider is a great excuse to plan a trip!
I’m really in tune with David Hills question here – who is the selecting agent? Ant mimikry is so frequent in salticidae and this is just one more quite extreme example, where the mimikry is taken to such a high level, that one needs to assume, that whoever the agent is, he must have pretty good eyesight. I have always been a proponent of the ants-do-also-often-have-pretty-good-eyesight group (if that group existed, otherwise its a group of 1), but they do most of the time not seem to care too much, as long as the chemical camouflage is right. Birds would have the eyesight we are talking here. But how would it increase the spiders fitness to look like such a Cephalotes?
Yes, the question of what is the selecting agent is the subject of our comments in the previous post (https://waynemaddison.wordpress.com/2014/02/23/the-sincerest-form-of-flattery/#comments): Birds? Specialist spider predators? Ants seem unlikely as the agent — as you say, chemicals would matter more to most ants.
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