Reframing the Status of Harvester Ants

By Derek Uhey

Derek Uhey

The the explanation why some species are perceived as pests are sometimes flawed. That is very true for native species that play vital roles of their ecosystems. Each entomologist is aware of the battle of convincing somebody of the significance of a maligned species or of convincing somebody that social perceptions of a supposed pest are literally garbage. No insect higher exemplifies this than the harvester ant.

Harvester ants are frequent to most arid areas of the world. The title refers collectively to ants that harvest and eat seeds, primarily these within the genera Pogonomyrmex, Messor, and Veromessor. These ants accumulate a variety of plant seeds and sometimes assemble massive nests cleared of vegetation. Some species possess highly effective stings, and most are opportunistic predators and scavengers. By sheer abundance, harvester ants dominate many habitats, having huge results on related ecosystems and human actions.

In November 2021 within the Annals of the Entomological Society of America, Richard Hofstetter, Ph.D., professor of forest entomology at Northern Arizona College, and I revealed an intensive evaluation of analysis and data about harvester ants, laying out the case for understanding them as keystone species somewhat than pests.

Harvester ants play many vital roles in ecosystems. The Californian harvester ant (Pogonomyrmex californicus), pictured right here, harvests seeds from quite a lot of vegetation, builds massive nests which improve soil vitamins, preys upon numerous arthropods, and is a meals supply for a lot of insectivores. (Photograph by Derek Uhey)

Harvester Ant Nests: ‘Islands of Fertility’

The true impact of harvester ants on landscapes is greatest seen from above. In some circumstances, the nest-clearings from ants account for over 15 p.c of land space. Traditionally, this seemingly apparent discount in vegetation didn’t sit properly with some ranchers. Within the western United States, ants have been seen as enemies of vary productiveness. Nevertheless, whereas ants clear vegetation on nest disks (the world instantly above and round a nest), vegetation thrives alongside nest rims.

Alongside a harvester ant colony’s nest rim, vegetation profit from entry to elevated vitamins deposited within the soil by the ants and from decreased competitors due to the ant’s diligent clearing on the disk aspect. As soon as ecologists started measuring the expansion of vegetation alongside ant nest rims, it grew to become clear that the nest-rim vegetation greater than made up for the cleared vegetation. Extra importantly, ecologists discovered that, following disturbances akin to fireplace, grazing, and drought, nest rims develop into factors of restoration for vegetation. Nest rims typically host the primary vegetation to develop again, and people go on to recolonize the remainder of the panorama. Harvester ants are actually identified to be useful for creating these “islands of fertility.”

Vegetation typically thrives on the edges of harvester ant nests. These microhabitats develop into refugia for vegetation throughout disturbances like droughts. Following the disturbance, nest rims improve vegetation restoration. (Photograph by Derek Uhey)

Biodiversity Hotspots

Not solely are nests islands of fertility for vegetation, however in addition they present a house for a variety of organisms. “Home company” akin to mites, silverfish, beetles, and springtails stay alongside ants inside their nests, and soil biota akin to micro organism, mycorrhizae, and protists are ample in ant nest soils. An assortment of beetles and different arthropods scavenge from harvester ant “trash dumps,” the place ants pile their refuse; these typically comprise discarded seeds and are nutrient wealthy environments. Nests subsequently develop into biodiversity hotspots, internet hosting dozens and even lots of of species that every one play an element in recycling vitamins and power throughout the ecosystem.

Harvester ants themselves play vital roles in meals chains as each predators and prey. Opportunistic and armed with highly effective mandibles, something the ants can overpower is a possible supply of meals (along with seeds, after all!). In the meantime, for a lot of different arthropods, birds, lizards, and small mammals, harvester ant employees are an ample meals supply. Some species of horned lizards are solely depending on harvester ants as a supply of meals. Harvester ants are additionally an vital meals supply for the endangered sage grouse—which, by the way, additionally likes to climb on high of ant mounds when it dances for mates!

Harvester ant nests will be stuffed with “home company.” Many different species stay aspect by aspect with ants, such because the silverfish (left) and scarab beetle Trinodia opaculus (proper) pictured right here. Different organisms akin to micro organism and fungi are enhanced in nest soils, that are excessive in nutrient contents. (Photograph by Derek Uhey)

Manageable Threats

Harvester ants are superior, however would possibly they probably pose a risk to seed crops from which they might harvest seeds for themselves? Nicely, as soon as once more ecologists have flipped that perceived pest narrative by cautious analysis. Many research present that harvester ants truly choose seeds of weedy species, somewhat than crop species we people are focused on. Ants take few if any of the specified crop species, however they do assist suppress weeds.

Ants, nevertheless, might take seeds utilized in ecological restoration, hampering some broadcast seeding efforts counting on dropping of seed on floor surfaces. But easy efforts akin to selecting seed species the ants don’t like to reap or making use of seeds when ants aren’t lively will help deal with the issue and keep away from pointless seed loss from ants throughout restoration efforts.

Harvester ants, such because the Pogonomyrmex californicus  employee proven right here, take and eat all kinds of seeds. Relying on their plant preferences, this can be useful or detrimental to human actions. (Photograph by Derek Uhey)

Some species of harvester ants have highly effective stings. Whereas fairly painful, stings trigger little bodily injury. Seen right here is the stinger on the stomach of a western harvester ant (Pogonomyrmex occidentalis). (Photograph by Derek Uhey)

Some species of harvester ants do possess highly effective stings, which definitely have contributed to their perceived unfavourable picture. The truth is, probably the most venomous insect identified is the Maricopa harvester ant (Pogonomyrmex maricopa). Getting stung shouldn’t be one thing you’ll quickly overlook. Just like many wasps and bees, the sting is painful however often causes little bodily injury, and the venom injected by a sting is a particularly small quantity. In uncommon circumstances, ant stings will be harmful for people with an allergic response inflicting anaphylaxis or if people can’t take away themselves from nest areas and develop into swarmed. However, happily, harvester ant stings are comparatively simple to keep away from as they don’t fly and infrequently enter houses.

Keystone Species

Harvester ants’ big selection of ecological results are fascinating and present how small bugs will help form whole ecosystems. The standing of harvester ants as useful and keystone species, vital for his or her ecosystems, is properly supported, whereas most pest perceptions, akin to injury to vary or croplands, aren’t totally supported and largely stem from prejudice or assumption. There are uncommon circumstances the place it could be cheap to take away harvester ants, for instance when a stinging species is nesting in a playground or yard. However, on the entire, harvester ants must be admired for his or her arduous work in sustaining our native ecosystem stability and never solid as pests.

Derek Uhey, M.S., is a Ph.D. candidate within the Faculty of Forestry at Northern Arizona College in Flagstaff, Arizona. E-mail: dauhey44@gmail.com.

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