I recently came across a male specimen of the "legionary ant" Neivamyrmex nigriscens while walking our dog in our Colorado Springs neighborhood. It was instantly recognizable to me, but it got me thinking about how most people would be hard-pressed to know what it was. Unfortunately, there are very few references for the identification of winged ants. This is a shame because it is often the "alates," males and winged queens, that are most obvious to the public.
Indeed, worker legionary ants are mostly subterranean and nocturnal in their habits (nomadic, raid the nests of other ants to prey on the larvae and pupae), so hardly ever observed by the average person. Meanwhile, a homeowner may not notice he or she has an ant "problem" until the colony swarms, liberating a cloud of alates.
Alates are typically larger than the worker caste of wingless, sterile females, so are more noticeable for that reason as well. In many cases, the winged reproductives resemble the workers in general appearance, but this is not always the case. The thorax of winged ants is frequently greatly expanded to accommodate the muscles that operate the wings, giving males in particular a distinctive "hump-backed" appearance.
Swarms are usually seasonal, and triggered by changes in day length, relative humidity, and air pressure, especially in the arid southwest U.S. where the onset of the monsoon rainy season sparks many ant species to swarm. These emergences can be spectacular events. Worker ants open new exits from nests in the soil, and scour the immediate vicinity to rout any potential predators and parasites.
Many swarm events take place in late afternoon, at dusk, after dark, or at dawn. Winged ants may be attracted to outdoor lights, which can lead to the assumption that the ants came from the house or building when that is not necessarily the case.
Colonies of a given species in a localized area swarm simultaneously such that members of different colonies can find each other and increase genetic diversity while decreasing the potential for inbreeding. Winds, and the insect's own muscle power, can take the ants far from their colony of origin.
How do you know whether it is a winged ant or a winged termite? Please read my post on termite swarms for a concise explanation, and images of winged termites. Below is an image of a winged termite to compare to the ants illustrated here.
What about wasp versus ant? That is a more problematic distinction, but most ants have distinctly "elbowed" antennae, whereas wasps often do not; or at least the first segment of the antenna is not as long as it is in ants. There are exceptions, of course, like the male Neivamyrmex ant shown at the top of this post that has no obvious elbow in the antennae.
Fortunately, I am not the only one who recognizes the need to pay more attention to alate ants in terms of research and public awareness. Laurel Hansen and Art Antonelli include a key to alates in their publication, listed below. Brendon Boudinot, in a guest post for Alex Wild's Myrmecos blog, extols the virtues of studying male ants for a clearer understanding of the phylogeny of the family Formicidae.
Sources: Boudinot, Brendon. 2013. "Male Ants Demystified," Myrmecos.Hansen, Laurel, and Art Antonelli. 2011. Identification and Habits of Key Ant Pests in the Pacific Northwest. A Pacific Northwest Extension Publication 624. Pullman, WA: Washington State University. 14 pp.
Houseman, Richard M. 2008. "Ants." University of Missouri Extension.