Ants

Ant Science Goes Orwellian

The media is carrying stories of a study in Science showing that Camponotus workers specialize into three behavioral classes, and that workers tend to move through these roles as they age. This result is interesting, but not terribly surprising as a similar pattern is known in the better-studied honey bees.

The reason the paper appears in Science, rather than a more specialized journal, is methodological. Danielle Mersch, Laurent Keller, and Alessandro Crespi have automated the observation of an ant colony. Basically, they built the perfect Orwellian ant-watching machine.

Each ant is labelled to be recognized by high-resolution video, and her position and social interactions are recorded continuously for the length of the experiment. The technique produces a staggering amount of data from relatively little effort once the initial tedious bits of gluing barcodes on ants are out of the way.

Check out just one short clip:

After extending this recording to six colonies for 41 days, Big Brother crunched the numbers:

Network analyses of over 9 million interactions revealed three distinct groups that differ in behavioral repertoires. Each group represents a functional behavioral unit with workers moving from one group to the next as they age. The rate of interactions was much higher within than between groups. The precise information on spatial and temporal distribution of all individuals permitted calculation of the expected rates of within- and between-group interactions. These values suggest that the network of interaction within colonies is primarily mediated by age-induced changes in the spatial location of workers.

The really interesting bits will come later, in my opinion, when the method is harnessed across other species. Assuming the ants don’t first figure out what we’re up to, that is.


source: Mersch, Crespi, Keller (2013) Tracking Individuals Shows Spatial Fidelity Is a Key Regulator of Ant Social Organization. Science, Published online 18 April 2013 [DOI:10.1126/science.1234316]

See also Ed Yong’s “Tracking whole colonies shows ants make career moves” commentary in Nature.

Anting in Gainesville, April 2013

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Oak tree leafing out at Paynes Prairie State Park.

Earlier this month I gave a pair of talks at the University of Florida. The trip was fabulous! In addition to meeting a pile of exceptionally friendly people, I spent time with my myrmecologist friends Andrea Lucky and Lloyd Davis, hunting ants at Paynes Prairie State Park, Austin Cary Forest, and elsewhere around Gainesville.

Below, as promised, are a few of my photos from the visit. I’ve posted a larger set to this gallery.

Andrea2
Andrea Lucky and Lloyd Davis spot a Cyphomyrmex worker walking across a fire ant mound. Paynes Prairie.

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Don’t worry about the leafcutter ants


(clip from Ants- Nature’s Secret Power)

Leafcutters are the ant stars of many nature documentaries. Their most spectacular film appearances, including the nest excavation above, and the relocation of a full colony to a lab for the BBC’s upcoming Planet Ant, involve the destruction and removal of an established colony. Since leafcutters are such dominant players in tropical ecosystems, this practice of destructive filming raises the question of whether we ought be concerned about ant conservation when filming.

The short answer is: No.

Most Atta leafcutter species are not only not endangered, they may even be more numerous now than before our species intruded on their territory.

texana20s

Leafcutters, you see, are beneficiaries of human activity. They are a buggy, neotropical analog of North America’s ubiquitous whitetail deer, a species that thrives along forest edges, farm fields, and other places where weedy, disturbance-associated vegetative regrowth provides an abundance of their favorite foods. Cleared soil may also help leafcutters start new colonies. When humans make field from a forest, or build a road, they also make leafcutter habitat. The leafcutters thrive.

Don’t take my word for it, though. Have a look at these aerial images from rural Paraguay:

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[location]

Atta_aerial2

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Atta vollenweideri nests- the white dots- are denser in old farm fields than in the undisturbed adjacent scrub. We humans have been good to leafcutters. They, in turn, have repaid us by becoming the most economically damaging pest insect in the region.

So enjoy your leafcutter ant documentaries, and don’t worry about the fate of the ants. Our environment is faced with far more serious troubles.


sources:
Wirth et al (2007) Increasing densities of leaf-cutting ants (Atta spp.) with proximity to the edge in a Brazilian Atlantic forest. Journal of Tropical Ecology 23: 501-505. DOI: http://dx.doi.org/10.1017/S0266467407004221

Vasconcelos et al (2006) Roads Alter the Colonization Dynamics of a Keystone Herbivore in Neotropical Savannas. Biotropica 38: 1744-7429. http://dx.doi.org/10.1111/j.1744-7429.2006.00180.x

An insect with only four legs

This is unusual:

image: Douglas Booher/antmuseum.com

It’s an Aphaenogaster worker missing the metathorax and the propodeum. The mid-thorax is fused directly to the second abdominal segment, with the effect that the hind legs are just… gone. For comparison, have a look at a normal Aphaenogaster.

Myrmecologist Douglas Booher pulled her from a litter sample in Georgia. You’d think a major pair of walking legs would be indispensable, but this ant apparently was collected alive.

Thaw yourself a custom ant nest, in the field

ice_nestWalt Tschinkel is a genius:

In this paper, I describe a method based on the burial of a nest constructed of ice. The hollow space that remains after the ice melts is a facsimile of the ant nest as designed by the experimenter.

Want to see, in the field, how a colony of ants reacts when introduced to an alien architecture designed by a different species? Or, perhaps you’d like to establish lab-altered colonies in a field experiment without wasting energy on nest construction. Or, maybe you’re just looking for a kinder, gentler way to release pet ants back to their original habitat. Either way, the field-melted ice nest is an elegant technique.

 


source: 2013. Tschinkel WR (2013) A method for using ice to construct subterranean ant nests (Hymenoptera: Formicidae) and other soil cavitiesMyrmecological News 18: 99-102.

The Ants of China

Aenictus laeviceps

Benoit Guenárd and Rob Dunn have combed the technical literature to make a list of all the ant species known from China (pdf):

China is one of the largest countries in the world and offers an incredible diversity of ecosystems and species. However the distribution of many insect species in China is still poorly known. Here, through a bibliographical review, we synthesize a species list of native and exotic ants (Hymenoptera: Formicidae) for 23 provinces of the People’s Republic of China  and eight surrounding regions. To date, no fewer than 939 valid named species and subspecies within 103 genera are listed from China. However, comparisons with other regions suggest that this list is still incomplete at both provincial and national scales based on the diversity of surrounding regions and the number of undescribed species reported in the literature. Although the species list generated here is not and cannot be exhaustive, we hope that it will facilitate future discovery, revision and conservation of Chinese ants.

The list comes in just shy of 1,000 species, which is surely a gross underestimate given the immense size of China and the diversity of habitats. I’d bet a final accounting will amount to more than twice that.

Plus, hooray for open access! You don’t need a subscription to read the paper.


source: Guenárd, B., Dunn, R. R. 2012. A Checklist of the Ants of China. Zootaxa 3558: 1-77.

The Ants of Fiji, and the relative caution of modern taxonomic practice

Eli Sarnat and Evan Economo have a beautiful new paper out on the Ants of Fiji. It’s open-access, too:

Plate 105 from Sarnat & Economo 2012, just one of many clean, clear illustrations.

This study is not the first to cover the myrmecofauna of the Fijian islands. Worth reading, for contrast, is William M. Mann’s 1921 classic paper on the same topic:

http://gap.entclub.org/taxonomists/Mann/1921.pdf

In particular, notice that the 1921 paper is full of new species descriptions, while the newer monograph refrains from describing a single new ant. It’s tempting to think the earlier work cleared most of the descriptions out of the way, accounting for the difference. But chronology is not it at all. Sarnat & Economo include a stack of undescribed ants (see the Poecilomyrmex, for example), so they had ample opportunity to follow Mann’s lead.

Instead, this modern taxonomic caution has become the norm. It’s a cultural change in the intervening 90 years as taxonomists adopted the Darwinian synthesis. Biologists as a group are more focused on underlying evolutionary processes, rather than simply describing observed diversity.

Increasingly, taxonomists leave descriptions of new species to more detailed studies of particular lineages on a global scale, often in conjunction with a phylogeny. Thus, species are described in global monographs focused on particular genera or species groups. We see new species in revisions of the Ants of Genus X, rather than in papers on the Ants of Region Y.


source: Sarnat, E.M. & Economo, E.P. (2012) Ants of Fiji. University of California Publications in Entomology, 132, 1-398. [pdf]

Late season anting in New York

The deciduous forests of New York's finger lakes region turn brilliant in mid-October. Canandaigua lake runs north-south in the background.

On Monday we dropped by a favorite childhood insect collecting spot, a woodlot atop a hill in upstate New York. The habitat is a mix of mature oak and second growth maple forests surrounding an open field maintained by seasonal mowing. Over the years I’ve recorded around 35 species of ants, including some gems: Stigmatomma dracula ants, Polyergus amazon ants, Formica thatch-mound ants, Temnothorax acorn ants, and others. I have yet to find a single non-native ant. It’s a pretty special place, and one I was happy to revisit.

Mid-October is the end of the season. With the autumn flights of Myrmica Lasius the year’s last ants have mated and above-ground activity dwindles. Below ground, though, some species remain busy. I spent a couple hours looking under stones and logs, curious about the late-season ants, finding a surprising amount of activity from one species in particular: Lasius nearcticus, a common but poorly-studied subterranean ant. Below are photos of these attractive yellow ants, along with photos a few others.

Lasius nearcticus with eggs and young larvae. Given the prolific rate of fall egg-laying, colonies must overwinter with eggs.

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The first live photographs of Aenictogiton

As far as I know, I’ve just uploaded the first living photographs ever taken of the rare African ant Aenictogiton. Go see.

Aenictogiton (Kibale Forest, Uganda)

Based on genetics and morphology, this creature is probably an army ant. Someone will have to spend time finding and watching the ever-elusive workers to confirm, though.

This individual was one of the treasures collected at Ant Course/Uganda in August.

Swollen-thorn acacias without ants are a sad sight

As the more clever among you surmised, Wednesday’s mystery photo depicted an ant-acacia without a large colony of protective ants strung up with vines. Another giveaway that the poor plant hadn’t developed friendly ants, though not visible in the previous posting, was the abundance of Beltian bodies:

Swollen-thorn acacias produce yellow Beltian bodies to feed their guardian ants. The bodies sit unharvested on this ant-less plant. (Armenia, Belize)

A healthy plant with ants sees the yellow food bodies harvested as soon as they are ripe, like so:

Pseudomyrmex peperi pulls a ripe Beltian body from an acacia leaf.

The ants repay the plant’s generosity by protecting it from intruding vines and other competing plants:

Pseudomyrmex peperi pull a unwelcome tendril off their Acacia host. Note that the Beltian bodies have already been harvested from this inhabited plant, leaving the leaflet tips barren.
More Pseudomyrmex workers team up to attack an intruding vine.

To photograph this scene during our whirlwind 4 days in Belize, I couldn’t just wait for a vine to happen by the Acacia. I’d still be there. Instead, I staged the lower photos by clipping some tendrils from the first, unprotected plant and applying them to the protected plant to watch the action. As expected, the ants didn’t hesitate to perform their guard duties.

By the way, Belize was unexpectedly charming. Hardly anyone lives in the country. The human population is only 300,000, so Belize retains the undeveloped rural ambiance I imagine was commonplace a century ago across much of Central & South America and is now sadly rare between the sprawl of cities and conversion to mechanized agriculture. Belizean forests are largely intact, the air is clean, the roads are empty of traffic, and the people are friendly. We’ll be going back.