In my last post, I showed the Anicius that moulted. In the same area I also collected a juvenile male Mexigonus. Here he is:
He looked unusual enough that I was pretty excited to see what he would look like as an adult, but even though I fed him well, he just hung out as a juvenile. Several days before we left Mexico, I noticed that he seemed a bit lethargic, and then I saw the telltale sign of an impending moult: his legs had fine stripes on them. These stripes are the new hairs all lined up under his old skin, ready to pop out and fluff up. Recalling how my skin itched when it peeled after a sunburn, I wonder: did this young male spider feel terribly itchy when he had a new skin under old?
I made sure his container was humid enough. Moulting is a dangerous time, and dryness can cause them to get stuck in the old skin and die. I waited. A couple of days later, I saw the old skin beside him, and this is what he looked like:
He’s still not quite darkened completely in this picture, but I couldn’t wait. How elegant! I’ve never seen a male jumping spider with first legs ornamented like that. Notice how there are two segments that have dark and shiny swellings, surrounded by a fringe of yellowish hairs.
If we were arthropods and shed our skin periodically as we grew, how would we celebrate the event? Would all of your friends throw a party while you were still soft and pale in your new skin? Would they prop up the old moulted skin and burn it in effigy?
Well, when some of my favourite species moulted recently I didn’t throw a party, but I was pleased as punch. One of the species was the Anicius I’d mentioned in a previous post. Of that, we had found adult females but only juveniles of the males. Identifying species is easiest with adult males, so I kept the juvenile males alive and fed them, in hopes that they would mature. After about a week of keeping them, I found a male was in his little silken retreat beside his newly moulted skin. Here he is soft and fresh beside his skin:
And here’s how he looked after he hardened up, strutting around as a fully adult male. Now that he’s adult, I can see that he is quite similar to a species I’d found 31 years ago near Naupan, Puebla.
Our plane flight was to leave Puerto Vallarta yesterday evening, and yet by yesterday morning we still hadn’t achieved one of the big goals of the trip: to get enough Habronattus aztecanus to do good behavioural observations. This had worried me the whole time we were in Chamela. On our last morning we had planned therefore to go back to the beach in Puerto Vallarta where we had found our lone adult male. However, the evening before, plans changed: we found out that, while we were in Chamela, Isabel Navarro had found H. aztecanus by the CUC* basketball courts in Vallarta. She led us to the spot, and there we found them hopping like popcorn. We got about 20 adults, enough to do what we wanted. What a delight to see this beautiful species abundantly. It was quite a feeling of satisfaction to have found all of our major targets.
Here are a male and female of H. aztecanus. The photo of the female on the right has the focal plane intentionally away from the face, to show the tiger stripes on the femur of the third legs. This is a modest version of the more powerful striping on males. Often, females show faint ghosts of the courtship ornaments of males. In this case, I think it would be a good way to recognize H. aztecanus females. Otherwise, they can be hard to tell from other female Habronattus in the area.
*Centro Universitario de la Costa.
After Chamela we stayed two nights at the colourful, peaceful, and bird-full Rancho Primavera in El Tuito. The diverse birds, rich forest, and Bonnie and Pat’s cooking were more than enough to satisfy, but to my delight we found a population of Habronattus with a face I’d not seen before. It appears to be a geographical variant of the same undescribed species as the one in Chamela that I call informally “Habronattus CHMLA”. Instead of having two thin reddish stripes in the middle of the face, the males from Ranch Primavera have a single broad band. Below at left is the form from Rancho Primavera; at right is the form from Chamela.
In the end, we found six species of Habronattus on the Chamela reserve: Habronattus “ROBRT”, H. “CHMLA”, H. cambridgei, H. mexicanus, H. zapotecanus, and H. huastecanus. I’ve shown photos of the first three of these; here are photos of the last three.
Habronattus mexicanus is common through much of Mexico on lawns and other grassy areas. Here is the male, which like many of its close relatives, has a fringed first leg and a strangely modified and coloured third leg. The last photo shows a close-up of the third leg.
Habronattus zapotecanus is a modest striped species that lives in disturbed areas with tall dry grasses, much like the familiar prairies species H. altanus. I was surprised to notice how red the third femur is in the male.
Habronattus huastecanus was the last for us to find. It usually lives on shaded leaf litter. We had seen babies, but not any adults, until Heather found a female walking on a cement wall. I was surprised to see this female had yellow palps, which I’ve never seen in another Habronattus. I wonder if they are fluorescent…
A few days later, I found a male Habronattus huastecanus hopping by as we were rooting around looking for opilioacarids.
Six is a respectable number of Habronattus for one small area. I expect that there may be other species in microhabitats we didn’t search; those will remain for other trips or other biologists to find.
We’ve left Chamela. We grew fond of the station, its people, and the reserve it’s on. It’s a wonderful place. We are grateful to the station director Jorge Vega and all of the staff for providing a great context in which to work.
I haven’t finished reporting about the spiders we found — more on that in the next few days I hope — but as we go I thought I’d post a few photos of Chamela memories.
Ah, the wonders of picking burs off of shirts and pants and socks. All of these burs were on my shirt. These are from grasses, and there is one variety common on the beaches that has very sharp spines. We do not have fond memories of those burs.
Here in February the dry season is provoking the leaves of most trees to fall, but some trees are in beautiful bloom, dropping their flowers on the ground. In some cases we saw bees visiting these already-amputated flowers for pollen, making one wonder if there are species of plants whose flowers regularly donate pollen posthumously (so to speak).
Heather in the Chamela station museum, maintained as an excellent place to work by Enrique Ramírez García. This served as our place to look at specimens and as a refuge from the heat.
And finally, the sun-touched leaf litter on which Habronattus “ROBRT” lives. To you, it might look like some plants and dead leaves on dry ground, but to me it represents the possibility of an elegant spider hopping suddenly into view, my heart stopping for a moment as a think of how to stalk it.
Being at a field station offers the biologist a chance to be embedded in a natural setting, to do studies in a relatively pristine habitat. But, even at a field station like Chamela that does a good job of leaving the forest in its natural state, nature is not entirely untouched. Particularly right around the field station, there are interactions between human and non-human nature. Army ants raid small treasures that are the byproduct of human presence; leaf litter accumulates more deeply than normal at the edges of swept walkways; ticks find large primates to bite rather than just squirrels and coatis.
The biggest animal that had regular interactions with us was this almost-tame coati that hung about the kitchen. The other coatis were much more timid.
A spooky gecko. The species is an invasive, brought in accidentally by humanas, which does indeed make it a bit scary. However, it is probably harmless to the local forest fauna, as it seems to stay on human structures.
In contrast to the gecko, the jumping spiders on the buildings are indeed local natives (Platycryptus spp.). In most places in the world, the jumping spiders on buildings are foreigners, following humans around. It’s nice to see the local spiders treating the human-altered station area as home.
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?
Back in 1998 when I was last in Chamela, we found two species of Habronattus that were new to science. They are still new, which is to say, we haven’t gotten around to describing them yet formally and giving them proper scientific names. They are two of my biggest targets on this trip, and I’m happy to report that despite it being the middle of the dry season, we’ve found adults of both.
The first was given a code name ROBRT in my paper with Marshal Hedin on molecular phylogeny of Habronattus. It’s a species that seems unclear whether it wants to be in the viridipes group (erect scales between the posterior eyes, courtship behaviour) or the clypeatus group (black central stripe under the abdomen, backward triangle marking on abdomen). What has surprised me is that I now see it has the same strange pattern inside the eyes as I recently posted for H. aztecanus of the clypeatus group. Check out the eyes here:
By the way, in that photo notice the third leg with the bumpy green and red patella. It strikes me that the eye pattern and third leg are usually in focus at the same time when I take the photos. Crazy idea: could the eye pattern actually be a courtship ornament that the male displays to the female in coordination with motions of the third leg?
The second undescribed species was give the code name CHMLA by Marshal and me. It’s a sweet little species from forest leaf litter. The face has a cute little pair of stripes that make them look as if they have a rodent-like grin. For the first time I got photos of the female of CHMLA:
Now that we have both, along with the common H. zapotecanus and H. cambridgei, we have achieved an important goal of this trip: to get fresh specimens of several common Mexican species groups of Habronattus, for future phylogenetic work.
I’ve been quiet for a few days, which is a good sign in field work: many new specimens to process will keep me away from the computer. To break the silence I’ll show two ants, which despite Heather’s gasteropost and subsequent comments, have a certain cuteness to them. But of more interest to me than the two ants (sorry, myrmecologists) are some jumping spiders that look a whole lot like the ants.
First is a cephalotine ant, which I find rather stylish with its grey robotic body. Below are a Bellota and a Peckhamia, both of which have independently evolved a resemblance to it.
Bellota. I like how the head of the spider seems to correspond with the thorax of the ant, with the thickened first legs of the spider corresponding with the head of the ant. (Why the spider’s name comes from the Spanish word for “acorn”, I don’t know.)
Peckhamia. While many antlike jumping spiders wave around the first legs as if they were the antennae of their model ants, Peckhamia belongs to a group that waves around its second pair of legs.
The second ant is a Pseudomyrmex, the long, thin, quick ants common here in Jalisco.
And this is not an ant but Synemosyna. Even after decades of looking at jumping spiders, when I find a Synemosyna I have to look closely to confirm that it’s actually a spider. This particular species has black spots corresponding to the eyes of ant — within the black spot is one of the spider’s eyes, but the eye is much smaller than the spot.
Why is it a good idea for a jumping spider to look like an ant? This hasn’t been well enough studied to answer the question with confidence. For most antlike jumping spiders, the mimicry does not seem to have evolved to fool the ant (e.g. to eat the ants, like a wolf in sheep’s clothing). One possibility is that it’s a good idea to make a predator think you are an ant, as many predators avoid ants because they can sting or bite and are accompanied by many friends who will do the same. Check out Heather’s blog for some insects that have evolved to look like ants.