American Bolas Spider

Back on September 14, I visited an interesting property in rural Pike County, Ohio (well, I guess nearly ALL of Pike County is rural) to assist with a one-year bioblitz project spearheaded by John Howard. I'd been trying to get there all summer, but this is the year of talks for me, thanks to the new Gardening for Moths book, and the speaking gigs have thrown wrenches in many plans (but I'm not complaining).

John and the scores of experts he's had to the property have found a mountain of species, and I'll hope to report on that after the project has concluded. John, Stefanie Paeg and I roamed the property most of the day and managed to extricate some new species for the list - mostly insects and plants. Later, spider expert Rich Bradley joined us, as did Laura Hughes and Vince Howard. Towards day's end, photographer Sam James finally caught up with us way out on the trail, and shared news of a great find that he made soon after heading out on foot.

This is Sam's find, as it appears from 15 feet away. As you've probably guessed, it's the little white blob amongst all of the Black Willow (Salix nigra) foliage.

We move in closer, and voila! The apparent bird dropping reveals itself to be an American Bolas Spider (Mastophora hutchinsoni). Bolas spiders are always notable finds, and generally everyone, at least in my circle of friends, wants to see them. During the day, the females, which are much larger and more conspicuous than males, hide in plain sight atop leaves. From almost any distance they resemble fresh bird droppings and thus presumably escape the attention of would-be predators. The bulbous waxy-white body, intermixed with brownish tones, looks remarkably similar to bird scat.

Staring straight into the grill of the spider, we see her legs neatly tucked around her head. This one appears to have spun a pad of silk which she's sitting atop. I do not know what that's about, but perhaps to help hold her in place if the wind starts buffeting her perch. She'll remain like this all day, so we made sure to re-visit her after nightfall.

When we returned, she had already caught a moth, even though it was barely past dusk. Her Lepidopteran victim, enshrouded in silk, hangs behind her. Bolas spiders, at least from my limited experience, do not make much of a web. Basically, they weave a flimsy trellis of silk lines from which they hang and hunt from. Given their highly specialized moth-hunting skills, a fancy web is not necessary.

We stopped back a while later, and the bolas spider had just captured another moth. She's fangs deep in the freshly captured victim in this shot.

Bolas spiders in the genus Mastophora - there are about 50 species - occur only in the Americas. They specialize on moths and use some amazing tactics to capture them. The female spider emits pseudo-pheromones from its body that mirror those emitted by certain female moth species. The males of those species detect those airborne false flags, and thinking a female of their species is nearby, flutter ever closer. When the moth comes into range, the bolas spider flicks a strong silken strand tipped with a sticky globule at it. If her aim is true, the moth is snared, reeled in, killed, and eaten. In times of plenty, as apparently was the case this night, she will cache victims as in the previous photo.

I never saw her line, or bolas, on this night, but presumably she used one to capture these moths. For a good image of a bolas spider's bolas, CLICK HERE for the story of an encounter with a Toadlike Bolas Spider, (M. phrynosoma).