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Archive for the ‘Paraguay’ Category

Feeling nostalgic this afternoon for my Peace Corps days, I did a Google Earth fly-by of my adoptive community, Colónia Once de Setiembre. Not only does Google show the site in high-resolution, the images are clear enough to see a patch of trees I planted with my neighbor in 1997. Judging from the shadows, our token attempt at reforestation must be at least 10 meters tall now.

The miracle of the internet also allows me to confirm that the economy of Once de Setiembre hasn’t changed much since I left.

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Platythyrea pilosula - Image by April Nobile/Antweb

Yesterday, the above photograph was uploaded to Antweb’s databases.   Platythyrea pilosula is the final species to be imaged for the Ants of Paraguay project, marking the end of a sporadic and meandering study that I started in 1995 as a hobby during my stint in the Peace Corps.  After combining several years’ worth of my field collections with the holdings at 19 entomological museums, I tallied 541 species for the country.  This turns out to be too many species to keep track of in my head (I max out at about 300 or so), so I’ve found Antweb’s ready access to Paraguayan ant images very helpful.

An unexpected result of the survey was an unusual imbalance between the number of non-native ants present in Paraguay with the number of native species that are trampy or invasive elsewhere in the world:

This is precisely the opposite pattern than that shown by most regions.  Consider California.  With a land area equivalent to Paraguay, the state hosts 25 non-native species and perhaps only one or two natives that have established elsewhere.

Here’s something for the invasion biologists to chew on: Paraguay may be the only place in the world that is a net exporter of invasive ant species.  I’m not volunteering to figure out why this is, but I do hope that having the regional ant fauna catalogued and imaged will make the job easier for those who do tackle it.

source: Wild, A. L. 2007. A Catalogue of the Ants of Paraguay (Hymenoptera: Formicidae). Zootaxa 1622: 1–55.

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Dinoponera grooming

Back in 2002 when I used the Nikon Coolpix 995 for everything, I would occasionally play around with the camera’s very basic video mode. The 995 made small, grainy movies without sound, and most of the videos I took are, well, pretty bad. But the camera had impressive macro abilities, which meant it could shoot ants close-in. Here’s a movie of a Dinoponera from the Mbaracayú Forest Reserve in Paraguay:

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My lovely wife Jo-anne has been in South America the last couple weeks doing field research on Argentine ants while I tend the home fires here in Tucson. I hope she finds it in her to forgive me for the post I am about to write.

Earlier today I got an email explaining why I’m not getting my much-awaited phone call:

I’d call but there aren’t any phones at this locutorio and we’re on our way out to look for social spiders.”

Excuse me? Social spiders? More important than me, your needy hubby?

Ok, I grant that social spiders are pretty cool, if a bit creepy. I remember those things from when I lived in South America. They spun massive webs that spanned tree-tops, anchored to the ground with tow lines as strong as steel cables. I nearly died from shock the first time I saw them. I had accidently walked under their tree, a large Enterolobium, and looked up to find the sky speckled with thousands of grape-sized spiders, all sharing a web tens of meters across. It still gives me the willies to think about.

A few years later I had a camera handy when a Paraguayan friend and I drove past what looked like a small body caught up in Shelob’s web. We stopped.

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Turned out not to be a single body, but hundreds of little hairy bodies that had fastened several branches into a little cradle. Social spiders!

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From close in:

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Social spiders are something of a mystery. They don’t share all the traits that have tipped the more famously social ants, bees, wasps, and termites into cooperative living. Yet it appears that nearly a dozen independent lineages of spiders have converged on a cooperative lifestyle. There must be something advantageous in it for the spiders, and that question continues to attract inquisitive scientists like Jo-anne.

Still, which do you think is better? Me? Or that twitching arachnoid mass of legs? And anyway, wouldn’t calling me be *safer* than going out looking for those things?

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So you like insects, but can’t be bothered to get up from your computer to go look for some? Google earth to the rescue!

South of Tucson, Arizona (31°38.097’N 111°03.797’W) I found this lovely aerial image. Visualized from an elevation of about a kilometer and a half, it shows a hill just west of I-19 covered in freshly-sprouted grass. Except, there’s this strange pattern of evenly-spaced polka-dots:

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What could account for the speckles? Alien crop-circles? Bizarre gardening accidents?

Why no, those are the nest discs of one of our most conspicuous insects in the Sonoran desert, the red harvester ant Pogonomyrmex barbatus. Down on the ground it is harder to get a sense of the even spacing of the nests, but the discs are plenty obvious. The ants keep the large area around their nest entrance free of vegetation and other unwanted debris. Below is a photo I took south of the Huachuca mountains, not far from the google earth image above:

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Even closer-up, here are the engineers:

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North American Pogonomyrmex aren’t the only ants whose engineering prowess is visible from low-earth orbit. Some of the more spectacular leafcutter ants in South America make even larger mounds. The image below the fold is also from Google Earth, 1 km over the Paraguayan Chaco (24°06.914’S 57°22.240’W).

(more…)

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Camponotus personatus

Paraguay may be the world’s most important country. Never mind that it is economically isolated and geopolitically forgettable. Rather, I measure importance by less trivial metrics, and by that of course I mean ants.

Paraguayan ants have changed the world. Many of the world’s worst pest species evolved on the broad plains of the Paraná river before hitchhiking with human commerce to points abroad. The infamous fire ants in the southern U.S. originated on the Paraná, as did the Argentine Ants that plague California and Europe, along with a rogue’s gallery of other trampy and invasive species. These invasives transform ecosystems and drive native species to extinction. Not to mention that some of them are champion stingers and are very good at getting into houses, greenhouses, and wherever else they can stir up trouble.

We do not know why ants from this region are so potent, but perhaps something about the Paraná acts as a cradle for pestilence. Sadly, we’re a pretty long way from finding out, as the ant fauna in that part of the world has been among the most poorly-documented anywhere. We know a fair bit about what happens to these ants after they arrive in Europe, Hawaii, Florida, and other places frequented by scientists, but what goes on in the native range is largely a black box. I’ve been slowly been chipping away at the problem by cataloging the ant species that live in Paraguay. You can check out the progress- accompanied by April Nobile’s amazing ant images- here:

The Ants of Paraguay

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For more details, the full catalog is here (full text is subscription only, sorry):

Wild, A. L. 2007. A Catalogue of the Ants of Paraguay (Hymenoptera: Formicidae). Zootaxa 1622: 1-55.

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