By Dirk J. Stevenson
Trapdoor and purseweb spiders are a fascinating part of Georgia’s spider fauna.
These spiders are ground-dwellers related to tarantulas. They’re called mygalomorphs (of the infraorder Mygalomorphae). This ancient lineage has distinctive characteristics, including include two pairs of book lungs and large chelicerae and fangs that move vertically. Also, trapdoor and purseweb spiders can produce silk but they cannot fashion webs.
Georgia’s other spiders are araneomorphs. They have fangs that cross in a pinching motion and glands that produce sticky silk. This silk is a dramatic advance evolutionarily that allows them to anchor draglines and from there create aerial webs.Most spiders worldwide are araneomorphs. Only about 10 percent of species are mygalomorphs.
Trapdoor and purseweb spiders are found throughout the state. Habitats include deciduous forests, mesic coves, sandy hammocks and mossy banks and bluffs along streams. In the Coastal Plain, north-facing slope forests with oak-beech-magnolia communities along major rivers – the Altamaha, Ogeechee, Savannah and Satilla – are prime real estate for the species. Populations are widespread but tend to be locally distributed. Since the spiders are secretive and hard to find, some species may be far more common than records show.
Patience, Perseverance Required
Just how do you find their burrows? With patience and perseverance. I gently rake leaf litter along stream edges and roll logs – several thousand or so – to find them. Using a light at night to spot the open doors of hunting spiders also works.
Digging a burrow is a Zen exercise. I carefully thread the spider’s tunnel with a tiny, straight piece of vegetation and slowly excavate by hand. (Some burrows are more than a foot deep.) Sometimes I mistake as spider burrows tunnel-openings made by other animals.
A few weeks ago, in a live oak hammock at Altamaha WMA in McIntosh County, I unearthed a brassy-eyed spadefoot toad that squeaked when I first touched him. Then I dug up a beautiful, metallic green cuckoo wasp.
Trapdoor and purseweb reach sexual maturity at 3 to 6 years and are long-lived, with lifespans reaching to 10-25 years. Although they live alone in their silk-lined burrows, they tend to occur in colonies. In great habitat, the densities can be impressive, with burrows of cousins and siblings and parents and grandparents all close together.
Males are longer-legged than females and have modified pedipalps. They don’t live long after they become sexually mature. They are prone to wander in search of mates – they often look gaunt and starved – and often pop up in strange places, such as your garage or pool.
Adding to Our Understanding
Mygalomorphs have long been a poorly studied group. However, recent studies have revealed many cryptic species. Auburn University professor Jason Bond is an accomplished mygalomorph taxonomist who leads a group of skilled graduate students who help him with these studies.
The work of Bond and his colleagues have resulted in the discovery of dozens of new mygalomorph spiders. Of course, those who describe new species get to name them, even indulging in creative license. Bond has named species for Angelina Jolie and Neil Young, honoring their philanthropic contributions not their celebrity. But when The Late Show’s Stephen Colbert complained that Bond had never named a spider for him, Bond did so. Yes, the final “t” is silent in Aptostichus stephencolberti.
Along with colleagues, Bond revised the genus Myrmekiaphila and determined that these spiders, although similar in appearance, are quite diverse. Restricted to the southeastern U.S., the genus now has 12 species. Three are known to occur in Georgia.
I recently mailed to his lab specimens of a Myrmekiaphila species I found at two wildlife management areas – Atlamaha and Big Hammock – in the Coastal Plain of southeast Georgia. The genus had not been documented in the region. I was excited: Could these spiders be new to science?
Bond and his charges will let me know soon if they are or if they’re a significant range extension for an already-described species.
Dirk J. Stevenson is a naturalist and owner of Altamaha Environmental Consulting in Hinesville.