Friday, July 1, 2011

Identification and Distribution of Dorymyrmex

This is one of the more confusing genera I've done despite it's manageable size. As previously stated by Myrmecos species out west have been somewhat ignored by science. I strained to find a study dated after the 1800's in regard to describing them. I'm not done looking but for now I feel the need to post something. Roy R. Snelling was in the process of clearing up this mess but sadly I don't believe his full study was ever completed or written up before his death in 2008. I did find a preliminary paper by him though published in 1995. It's helpful but I wish it were a little more descriptive. As a result western species are still slightly confusing and is all the more apparent when reading a study done by James C. Trager

Just to give you an idea of how confusing this is, back in the 1800's Dorymyrmex wasn't a genus yet and most members were originally described as Formica... which is a different subfamily entirely. Later on the genus would be call Conomyrma which was a step in the right direction. When they started being classified as Dorymyrmex though I haven't stumbled upon yet.

So here is what I have written up so far.

The traits to pay attention to with this genus seem to be: the eye placement in regard to the side head margins, the shape and orientation of the cone, and the pro-mesonotum area. Color is helpful too but some species clearly have multiple color patterns which can look similar to other species. Things like hair and pubescence are also important but these ants are so small it's often straining to see these, even on antweb images. I do mention hairs where I feel it's important though.

The common name "Cone Ants" refers to the structure on the propodium. Basically it's a spine but not as sharply pointed, and it's typically webbed between the two highest points almost all the way up. 

Dorymyrmex bossutus SE
Found in sand dunes, nesting underground in open spots. Nests do not hold up to tilling. Often associated with Turkey Oak, Quercus laevis. Pro-mesonotum are fairly even, the mesosotum drops off somewhat sharply but not very far. There is almost no valley where the mesonotum and propodium meet. Cone is typically not much higher than mesonotum. This ant has three color patterns. The most common of which is a yellowish to reddish body, with a dark spot on the dorsum of the head, and the gaster is dark brown to black. Over it's northern range this pattern shifts to having a light brownish body, the entire head is a darker reddish brown, and the gaster is dark brown. The least common color pattern is uniformly yellowish brown and is restricted to an isolated population. 

Dorymyrmex bureni SC, SE, NC, NE
Found abundantly in sandy areas and disturbed locations. It's one of the first species to recolonize tilled land and is not noxious to humans. It's also an avid predator in citrus and soybean fields. Occasionally multiple nests are utilized but they are otherwise monocalic living. Eyes are pretty much level with the widest head margin. Their cone is lower and generally not as pointed. Color ranges from orange yellow with dark patches on the head and rear of gaster, to a "mousy" brown with thorax lighter and yellower. The lighter coloration is more common and the darker is only found in coastal Georgia and North East Florida.

Dorymyrmex flavopectus SE (only Florida?)
This ant is restricted to what's called the sugar sand area of Florida. They are also associated with the roasmary plants that grow there, Ceratiola ericoides. The pro-mesonotum is less arched than D. bureni. Cone is slightly higher and sharper looking. Colonies are polycalic. Color is very similar to the darker form of D. bureni where the head and gaster are brown and the mesosoma is yellow or orange, and with the mandibles are orange yellow. Colonies are connected by foraging trails.

Dorymyrmex elegans SE (Florida)
Found in xeric woodlands and post fire succession areas, but has a low tolerance for other kinds of disturbed environments. Nests are often near Scrub hickory, Carya floridana. The mesosoma is pretty much flat. Cone is barely more than a nub too. Color is a clear yellow. Despite having very long legs they only run in quick dashes when disturbed. They otherwise have a slow pace, or jerky gait to get around. Similar to D. bureni but has longer scape.

Dorymyrmex grandulus SC, SE, NC, NE
Found typically in sandy areas in both forests and fields, dry and mesic habitat. Eyes are are lower than the widest head margin. Mesosoma is pretty much flat with the cone only moderately high. Color ranges from yellowish brown to dark brown, occasionally the head and thorax are yellowish brown and the gaster is darker. 

Dorymyrmex smithi SW, SC, SE, NC
This is both a social parasite and incipient dulosis of D. bureni. Incipient dulosis is fascinating because they invade surrounding host colonies and force a mixed nest upon them until they are 100% D. smithi. Colonies are aggressive and form polycalic super colonies. Similar to D. grandulus but scape are shorter. Color is a dark brown to black. Sometimes with the head and mesosoma lighter than the gaster.
*One study that I have yet to locate says that only 3% of Solenopsis invicta queens were able to establish in their territory. Nickerson et al (1975b)

Dorymyrmex reginiculus SE (Florida)
Very similar to D. smithi but slightly longer scape? Head is redder but still a warm brown color. They are shinier, have a reddish mesosoma. Queens have a very narrow head while D. smithi queens have a much wider head.

Dorymyrmex insanus SW, SC, SE, NW, NC, NE
~1-2.5mm long. The common name is Crazy Ant (though I think a few species have that as a common name), becuase they are highly aggressive. Nest underground in a series of small holes with numerous entrances, sometimes comprising an area of 50' in diameter. Color ranges from black to soft brown. They are very shiny and have a rather large mandible tooth, (that the smallest workers are lacking?)

Dorymyrmex bicolor SW, SC
Nests underground and forms small craters. Body color is red to orange brown with the gaster black.

Dorymyrmex flavus SW, SC, SE
Honey yellow color. Antennae are tipped with black.

Dorymyrmex wheeleri SW (Arizona)
Pubescence is sparse but they are otherwise identical to D. insanus.

Dorymyrmex lipan SC (Texas)
Worker's head is nearly devoid of any pubescences. Very smooth and shiny looking species. Color is reddish brown with gaster darker.

Dorymyrmex paiute SW, NW
Lacks erect hair on the pronotum, and when hairs do rarely occur there they are shorter and notably thinner looking. Color is light reddish brown with gaster slightly darker brown. Antennae and legs are sometimes slightly paler too.

Dorymyrmex medeis SE, NE (synonym with D. smithi?)


Now what to do with all these?
Dorymyrmex ca01
Dorymyrmex az02
Dorymyrmex az03
Dorymyrmex az05
Dorymyrmex bca01
Dorymyrmex bca02
Dorymyrmex lrd-ant
Dorymyrmex cr01

Sources
Buckley, S. B. 1866. Descriptions of new species of North American Formicidae. Proceedings of the Entomological Society of Philadelphia 6: 152-172.
McCook, H. C. 1880. Formicariae. Pages 182-189, in J. H. Comstock, ed., Report upon cotton insects. 511 pp.

Snelling, R. R. 1995. Systematic of Nearctic Ants of the Genus Dorymyrmex (Hymenoptera: Formicidae) Contributions in Science, Number 454: 1-14

Trager. J. C. 1988. A Revision of Conomyrma (Hymenoptera: Formicidae) From the Southeast United States, Especially Florida, With Keys to the Species. The Florida Entomologist, Volume 71, number (1): 12-29.
Wheeler, W. M. 1906. The ants of the Grand Canon. Bulletin of the American Museum of Natural History 22: 329-345.

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