In the world of insects and spiders, imitating the looks or behaviors of a more aggressive creature is known as Batesian mimicry. Ants, for example, are often the last creatures a typical predator wants to mess with. Many species of ant sting, bite and otherwise mob anything they encounter. Any animal that evolves to look and act like an ant benefits, because most would-be predators avoid them.
So it is with the many species of ant-mimicking spiders, like the Orange Ant-Mimic Sac Spider that recently crossed my path. Its bright colors and erratic movements caught my eye and I knew immediately that this was an ant mimic. Although some spiders are colorful, most ground-dwelling spiders are not, preferring to blend into their surroundings. This spider stood out. Along with more than 300 species of ant-mimicking spiders in 13 families, this species benefits from looking and acting like ants.
How spiders transform their typical body shape and behavior to mimic ants is fascinating. Spiders have two body segments (a cephalothorax and abdomen), four pairs of legs, and no antennae. Behaviors vary from active running to lying in wait. In contrast, like all insects, ants have three distinct body segments (head, thorax, and abdomen), three pairs of legs, and two antennae that they actively wave about to sense their world. In the case of ants, they walk about in what appears to be erratic ways, and many species have contrasting colors across their bodies.
Some ant-mimicking spiders take the transformation to an extreme. Some species have evolved to create a false waste in their abdomens to resemble the third body segment of insects. In the jumping spider Sarinda hentzi, it is the head that is simulated, by holding its two enlarged pedipalps (mouthpart structures) out together in front of its cephalothorax. In many of these advanced mimics, the front pair of legs are often thinner than the rest and are held aloft and waved in the air when walking, resembling the action of the antennae of ants. Their contrasting colors resemble many common species of ants.
I encountered the ant-mimicking Sarinda hentzi in my studies of the spiders of tidal marshes, where they live among a number of species of ants, like the similar-looking and common species of Crematogaster that, from personal experience, bite and sting! If you look like the local aggressive ant, you can get by. A video of this species wandering in its surroundings is worth a view https://www.rkwalton.com/salticids/Sarinda_hentzi.php. The Orange Ant-Mimic Sac Spider has the color contrast and the jerky walking and front leg-waving behavior of ants, but not the shape. In any case, both species benefit from looking like ants.
As if this is not enough, some species of ant-mimicking spiders have taken to looking, smelling, and acting so much like ants that the ants do not recognize them as anything other than a fellow ant. Their bodies are as thin as ants and they can simulate the odors of their target ant species. These species are examples of myrmecomorphy – living directly associated with ants, that they hunt as prey. In these cases, the mimicry gets them close enough to grab a meal.
So next time you see what looks like an ant, but not quite, take a closer look. It may be one of the many species of ant mimicking spiders in our world. After all, “imitation is the sincerest form of flattery.”
Hope to see you in our great outdoors!