Jack Longino unveils the new 2009 line of Pheidole species

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New Species: Pheidole bigote

Doesn’t “bigote” mean “moustache” in Spanish?

Why, yes.  It does.

Pheidole bigote Longino 2009
Chiapas, Mexico

The inimitable Jack Longino published a taxonomic paper today on the Central American Pheidole, including descriptions of some 23 new species.  Among these is the marvelously moustached P. bigote.  The function of the fantastic facial hair remains unknown.

source: Longino, J. T. 2009. Additions to the taxonomy of New World Pheidole (Hymenoptera: Formicidae).  Zootaxa 2181: 1-90. 

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Predator vs Harvester

A recent study by Gabriela Pirk in Insectes Sociaux provides me with an excuse to share this photo:

Minor workers of the seed harvester Pheidole spininodis (left) and the predatory Pheidole bergi lock jaws in combat. Jujuy, Argentina.

Pirk et al examined the diet of both Pheidole species in the Monte desert of Northern Argentina.  Why would someone spend time doing this?   Ants are important dispersers of seeds, and these Pheidole are two of the most abundant seed-eating ants of the region.  What they do with the seeds, which ones they choose to take, and how far they take them has implications for the ecology of the desert.

The interesting bit in my opinion is that the two ant species are rather different, both ecologically and biomechanically.  Pheidole spininodis is a dedicated seed harvester.  Their majors have enormous blocky heads with blunt mandibles for milling seeds:

Pheidole spininodis, major worker

In contrast, Pheidole bergi is primarily predatory, taking seeds only opportunistically.  Their majors are slender, fast, and with relatively small heads and sharper mandibles better for slicing up the insects that they most commonly feed on:

Pheidole bergi, major & minor workers

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Pheidole Friday: P. rosae

Pheidole rosae, major worker, Entre Rios, Argentina

At the nest entrance

photo details: Canon MP-E 65mm 1-5x macro lens on a Canon EOS 20D
ISO 100, 1/250 sec, f/13, flash diffused through tracing paper

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New Study: Older Ants are Better Workers

Pheidole dentata, older worker with larva.

A study out in pre-print by Muscedere, Willey, and Traniello in the journal Animal Behaviour finds little support for a long-held idea that worker ants change specializations to perform different types of work as they age.  By creating colonies out of different age classes in the ant Pheidole dentata, the researchers showed that older workers were good at pretty much everything, while younger ants performed only a few tasks, but did those less efficiently.  Here is the abstract:

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A mysterious tramp: Pheidole moerens

Pheidole moerens, major worker, Louisiana

Pheidole moerens is a small, barely noticeable insect that travels about with human commerce, arriving without announcement and slipping quietly into the leaf litter and potted plants about town.   As introduced ants go, P. moerens is timid and innocuous- it’s certainly no fire ant.  The species is now present in the southeastern United States, a few places along the west coast, and Hawaii.  Conventional wisdom suggests that P. moerens originated in the Greater Antilles, but even though the ant was first described from Puerto Rico a century ago its exact origin remains uncertain.

The Greater Antilles were a major hub in the global trade of the colonial era, receiving slaves from Africa and shipping sugar north to the distilleries.  A great number of pests had already been carried to the islands by the time European scientists started to fully describe the fauna, so it’s not unlikely that many animals considered native there may have merely used the archipelago as a way-station between their actual origin and their ultimate global distribution.

Now that scientists are equiped with the tools of molecular genetics, we have the ability to determine more precisely the historical routes of spread. It would not take too much work to pin down the origin of P. moerens.  But this ant is just one species of many that are both globally trampy and not particularly troublesome.  Elucidating its origin is thus more an academic than an applied matter, so Pheidole moerens will likely remain mysterious for some time yet.

Pheidole moerens, minor worker, Louisiana

photo details: Canon MP-E 65mm 1-5x macro lens on a Canon EOS 20D
ISO 100, 1/250 sec, f/13, flash diffused through tracing paper

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New Species: Pheidole rugithorax

Pheidole rugithorax Eguchi 2008 – Vietnam

In today’s Zootaxa, Katsuyuki Eguchi has a taxonomic revision of the northern Vietnamese Pheidole, recognizing six new ant species for a genus that is already the world’s most diverse.  The revision also contains several nomeclatural changes and a key to the thirty or so species occurring in the region.

As in most tropical taxonomy this research has a comedic/tragic effect of adding several more species, about which nothing is known, to a catalog already overflowing with equally mysterious species.  We don’t know what they eat, how long they live, how large their colonies are, or when or how they mate.  Many will meet extinction without ever receiving more than a cursory taxonomic registration.  Perhaps Pheidole rugithorax has something to teach us; the odds that anyone will get around to learning it are slim indeed.

source: Eguchi, K. 2008. A revision of northern Vietnamese species of the ant genus Pheidole (Insecta: Hymenoptera: Formicidae: Myrmicinae). Zootaxa 1902: 1-118.

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New Pheidole photos up at myrmecos.net

Pheidole megacephala

Go see!

Incidentally, you might want to surf back here to Myrmecos Blog on Monday afternoon.  There’s been a very, very exciting discovery…

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Pheidole tepicana

A century ago, William Morton Wheeler inked this iconic illustration of the striking polymorphism displayed among members of an ant colony. You may have seen it; Andrew Bourke and Nigel Franks used it as the cover for their 1995 text Social Evolution in Ants.

I always assumed Wheeler’s figure depicted some exotic tropical marauder ant, a voracious jungle species with massive soldiers for slicing up hapless prey. I don’t read captions carefully enough, I guess, because I learned recently that this charismatic creature is actually a local harvester ant, Pheidole tepicana. Not only that, but the lab downstairs from mine keeps several captive colonies for research on caste development. Obligingly, last week they let me stop in with my camera to take some photos.

The largest workers have absolutely massive heads:

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New Species: Pheidole pegasus

Pheidole pegasus Sarnat 2008
Fiji

Eli Sarnat, the reigning expert on the Ants of Fiji, has just published a lovely taxonomic revision of a group of Pheidole that occur on the islands. Pheidole are found in warmer regions worldwide, but Fiji has seen a remarkable radiation of species that share a bizarre set of spines on the mesosoma. Eli sorted through hundreds of these things to determine that the group contains seven species, five of which had not previously been described. Pheidole pegasus is largest and among the most distinct of the group.  It was collected only once, from the summit of Mt. Delaikoro.

Source: Sarnat, E.M. 2008. A taxonomic revision of the Pheidole roosevelti-group (Hymenoptera: Formicidae) in Fiji. Zootaxa 1767: 1-36.

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