Posts Tagged ‘trapdoor spiders’

Fossorial Spiders in Georgia

July 2, 2021

2 different groups of spiders live underground in Georgia soils: trapdoor spiders and wolf spiders. Trapdoor spiders belong to the Myglamorph order which also includes tarantulas, funnel web spiders, and purse web spiders. (The latter make tube shaped webs on tree trunks.) In Georgia there are 3 families of trapdoor spiders including the Ctenizidae (ravine trapdoor spiders), the Antrodiactidae (folding door spiders), and the Eucterizidae (wafer lid spiders). Spiders in the Ummidia genus belong to the Ctenizidae family, and as their name would suggest, their preferred habitat is moist ravines located next to rivers. However, most species of trapdoor spiders seem to prefer this type of environment. 1 recent study searched for trapdoor spiders in moist ravines along the Altamaha, Savannah, and Satilla Rivers in Georgia, and the spider hunters found 51 specimens including 3 species. Along with 1 species of ravine trapdoor spider, they also found wafer lid and folding door spiders.

All trapdoor spiders construct underground burrows where they wait for prey to cross across the door. When the spider senses an insect on its door, it will seize the unfortunate prey with fangs and pull it inside the burrow where the spider feeds upon it. The families differ in how their doors are constructed. Ummidia spiders use their abdomen covered in webbing as a door. Folding door spiders pull the rims of their burrows closed, unfolding it in time to catch an insect. Wafer lid spiders have a thinly-webbed door. Incredibly, the wafer lid spider, Myrmekiaphilia, constructs its burrows inside or alongside ant nests. Some species of wasps hunt trapdoor spiders. The arachnids have a defense–they desperately attempt to hold the door shut while the wasp tries to pull it open. Somehow, they are able to tell the difference between prey and a wasp.

There are at least 8-10 known species of trapdoor spiders in Georgia. Auburn University professor, Jason Bond, has discovered 37 species of trapdoor spiders in North America, and there likely are more than 10 species living in Georgia with many undiscovered. He’s named newly discovered spiders after celebrities including Barack Obama, Tobey Maguire, Angelina Jolie, and Stephen Colbert.

The moist mesophytic slopes where trapdoor spiders occur are particularly rich habitats for all wildlife. William Bartram described walking through a “magnificent” slope forest in his Travels. (See: https://markgelbart.wordpress.com/2011/04/11/william-bartrams-magnificent-forest/ ). A forest such as Bartram described no longer exists in Georgia, but even logged over 2nd growth forests are richer on these sites because they are wetter and cooler than the surrounding habitats. During Ice Ages when much of the surrounding environment was dry scrub, these sites likely provided refuge for hardwood forests and hence relic habitat for trapdoor spiders.

This photo angle is not good enough to identify what species of spider this is in my rain gauge, but I can tell it is not a trapdoor spider as I wrongly assumed at first. I made this false assumption because I thought a trapdoor spider was using an existing structure that imitated its burrow, but that is not the case.
Photo of a ravine trap door spider in the Ummidia genus. Photo from spiderid.com.
Wolf spider from the Tigerosa genus. This is the kind of spiders I see when I dig in my garden. Photo from spiderid.com.

I often come across spiders when I dig in my garden. Until I started researching information for this blog article, I wrongly assumed they were trapdoor spiders. Instead, I learned these are wolf spiders, probably belonging to the Tigrosa genus (named for the striped appearance). Wolf spiders are in the Lycosidae family, and they also construct burrows underground. Unlike trapdoor spiders, they are not sedentary predators. They hide from predatory birds in their burrows during the day, but they leave their burrows at night and actively hunt insects. They probably attack crickets, homing in on their noisy chirping. A wolf spider’s burrow can be as deep as 3 feet, keeping them safe from inclement weather and birds, but moles can find them. Female wolf spiders carry their eggs and young on their backs when they hunt at night. They are far more common than trapdoor spiders, and worldwide there might be as many as 2000 species.

Reference:

Stevenson, D.; and R. Godwin

“Notable Myglamorph Spiders (Aranae: Myglamorphae) Records for the Coastal Plain of Georgia”

Southeastern Naturalist 19 2020