Aphaenogaster is an extremely ecologically important genus that spreads across many continents. In eastern North America, many species of Aphaenogaster dominate undisturbed/slightly disturbed habitats and are essential for the spreading of myrmecochorous plants. Many species will contribute in the decomposition of rotting wood by creating nests in them. Additionally, the sheer amount of insects that they scavenge from their surrounding habitat helps to keep the ecosystem in check. In captivity, their feeding responses are mind-blowing, the queens pump out eggs, brood grows at a moderate speed, the colonies don't get too big or too small, many species are very good solitary hunters, and they do well with as much or as little food that the keeper provides. In the wild, the many species fulfill so many different niches in so many habitats and is one of the most widespread genera in eastern North America. I feel as if they are very unappreciated in the ant keeping hobby, especially in the United States.
In Virginia, Aphaenogaster rudis is by far the most widespread species. It nests under stones, in wood, and in soil. It may create small mounds but their nests are usually inconspicuous.
Supposedly common in some parts of the US, it is unknown how commonly this morphotaxon is found in Virginia. These exist in drier, more open habitats than A. rudis and may have different coloration.
Aphaenogaster picea is the most cold-tolerant species of Aphaenogaster in eastern North America. In Virginia, they are restricted to high-elevation points on the western ridges of the Appalachians. Workers and queens are solid black and can be relatively easily differentiated from A. rudis.
Aphaenogaster carolinensis may supposedly be found throughout Virginia and can be differentiated from other species by the very narrow head. They are best differentiated from Aphaenogaster rudis by the missing CAD intron. They are mostly a xeric species here.
This species is also a very dark colored Aphaenogaster. However, they are much rarer in Virginia and are also a xeric species, making it easy to differentiate from A. picea. The spines are also very prominent in this species.
Similar in appearance to other large Aphaenogaster such as A. treatae and A. ashmeadi, this species is easily differentiated from the other two by the lack of an antennal lobe and the inwards pointing notch at the scape of the antennae. This species is relatively locally abundant and is extremely common along parts of the four rivers of Virginia (the Potomac, Rappahanock, York, and James). They often have red-orange abdomens similar to that of A. fulva but are differentiated based on the previously mentioned antennal notch, as well as a larger leg-body ratio and thinner head.
Aphaenogaster fulva is a very widespread species and gets relatively large colonies. Although it is regarded as part of the fulva-rudis-texana complex, it is, in reality, quite different from the other species in the complex. The queens of A. fulva have striations on the mesopleuron whereas other species in the complex have a smooth mesopleuron. The workers have a distinct raised mesonotum that only A. umphreyi shares. There are populations of this species that are polygynous and supposedly inbreeding. I have not recorded such populations in Virginia, however. A. fulva gets slightly larger colonies than other members of the fulva-rudis-texana complex and are most commonly found in or near rotting wood, as opposed to under stones. The easiest way to differentiate this species is the raised mesonotum, which is only shared by A. umphreyi.
Not much is known about this species. They have not yet been recorded in Virginia but are possibly present in the state due to their cryptic nature and undercollecting in the Southside (southern Piedmont). They are most similar to A. fulva, yet are completely subterranean, xeric, and pale in coloration. They also share the raised mesonotum in A. fulva.
This species was first recorded in Virginia in 2018 by Ivanov K. The coloration of the species is dependent on the coloration of the sand that they nest in. This is the only species of Aphaenogaster in the East that lacks propodeal spines. It is likely the largest, or at least one of the largest, species of Aphaenogaster in the East.
Although not yet officially recorded in Virginia, there are very likely populations of this species in Virginia. It is similar in appearance to A. floridana, but has a shinier exoskeleton and distinctly long, upward pointing propodeal spines.
A. tennesseensis is one of the most populous species in the hardwood forests of Virginia. The queens of this socially parasitic species invade the nests of host species of the fulva-rudis-texana complex and overtake the colony through temporary parasitism. A. tennesseensis get the largest colonies of the genus in Virginia, often hollowing out huge trees. The long spines, bright red color, and hairless head separate this species from all others.
A. mariae is my favorite native species. These arboreal, canopy-dwelling ants are also social parasites, usually of A. fulva, and once the queens have invaded a colony in the same fashion of A. tennesseensis, they migrate up into the treetops where they establish a nest. A. mariae seems to be limited to old-growth hardwood forests where they usually nest in oak. In Virginia, I have found a queen of this species in Pohick Bay and they appear to be relatively common in eastern MD (Delmarva) and along the Potomac. In Virginia, they may be found in much of the southern and western forests of the state. This species is quite slow moving and may be difficult to see on the reticulated bark of the trees that they inhabit. However, the workers and queens are easy to identify, as they are extremely punctate, the part of the gaster where the postpetiole connects have fan-like striations radiating from the postpetiole, and the long spines are backwards facing.
I am not familiar with this species, but it is said to be similar to A. treatae and A. ashmeadi in appearance but without the lobes. The males of this species have thick propodeal spines, it nests dry areas, and has nest entrances similar to that of A. treatae. It is medium-brown and the Umphrey 1995 paper says that it is usually distinct from all other species in the fulva-rudis-texana complex. (CONTINUE)
Also included in the fulva-rudis-texana complex is A. texana (N21B), N19, and N17.
Aphaenogaster texana is variable in color but is often bright and large. It should not be present east of the Mississippi river. Aphaenogaster N19 is a species found in Missouri by James Trager but is likely present throughout the Mississippi Basin. N17 is similar to picea (N18) in color but has longer scapes on average and is found west of the Appalachian Mountains.
Personal observation, Personal comm. with Joe MacGown, Umphrey 1995, DeMarco 2015, Frye 2012
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