Corinnidae spp. [Ground Sac Spider]

2 years ago

Good day, Hive!

This week's spider is a real treat. You've probably heard of the sac spider, and likely also the lies about them being "dangerous". I have to do my part in saying that no sac spider is considered medically significant. There, said it.

Actually, sac spiders are quite shy and gentle. They're also adorable, in my opinion. They get a really bad rep and it's not their fault. So here's to sticking up for the little guys.

With that out of the way, let's hop in and explore one of these sac spiders, from the family Corinnidae.

• CORINNIDAE SPP. •

^{Female Corinnid spp.}

The Ground Sac spider!

Like what the common name suggests, these sac spiders are often found on the ground, in their silk retreats under rocks and foliage. And while the spider here doesn't look like the sac spider you're thinking of, you're correct in that they don't belong in the same family. They once did, however, before taxonomic revision ¹.

They're also called Dark Sac spiders! Because, well, most are dark in colour but not all. But wait, there's more. They're also called Ant-Mimicking Sac spiders, because most of this family mimic ants (with one or two genera mimicking wasps).

This particular one is not ant-like, though I have spotted an ant-mimic, but that's a post for another day. And I found this cutie under a rock when I was looking for spiders, tucked away in her little silk sac.

• GENUS •

^{A better view of the legs of a female Corinnid spp.}

Unlike all my spider posts so far, I haven't been able to determine which genus of Corinnidae this species belongs to. Not from a lack of trying. I scoured through all the literature of Corinnids known in South Africa and haven't found a description that fits.

It's possible this female is an undescribed species, considering my town and the surrounding region has not been surveyed yet. I suspect she might belong to the genus Messapus because of the size, the raised ocular region, the long chelicera, and the closely grouped eyes. But this is just a guess.

How I know she's a Corinnid is because of those attributes as well. And the general body shape and legs. I almost thought she might be a mesh-web weaver spider from the family Amaurobiidae, but she didn't fit with the descriptions. Plus, I found her in a silk sac retreat, iconic of sac spiders.

• DESCRIPTION •

^{Eyes and carapace of this Corinnidae spp.}

Taxon:

Class: Arachnida
Order: Araneae
Infra-Order: Araneamorph (true spiders)
Family: Corinnidae
Genus: Unknown
Species: Unknown

Female

About 8mm in body length. Leg span of approximately 20mm diagonally.

Cephalothorax:
Carapace yellow-brown with thin dark stripe down centre, thin black border around raised cephalic region, and 3 black spots on either side near edges. Thin faint white line above chelicera. Chelicera reddish brown and long. Sternum brown with faint dark border.

Abdomen:
Abdomen oval and brown, mottled faintly, with 2 short dark lines anterior centre of dorsum followed by two faint dark patches in column down centre, then two columns of irregular patchy lines down to spinnerets. Ventral abdomen yellowish with faint broad band down centre. Epigyne dark.

Legs:
Legs yellowish reddish brown and banded. Metatarsus and tarsus greyish. Coxae yellowish brown.

Male

Unknown.

• ABOUT THE GENUS •

^{A look at the "face" of a female Corinnid spp.}

Corinnids are fast, agile ground-hunting spiders. They often prey on ants, but also sometimes on termites, wasps, and other small invertebrates. Like other sac spiders, they build silken retreats that look like cocoons where they stay to rest and/or recover or when they're about to molt.

The females lay their eggs in such retreats as well. I can't find literature on the maternal nesting habits of Corinnidae, however, and haven't been able to observe any such behaviour so I have no idea whether the female remains to guard her eggs and spiderlings or not.

• NOTES •

When I found this female Corinnid, tucked away safely in her sac, she pretended to be dead. Her legs were tucked close to her body and she made no effort to run. Until I fully opened her sac to collect her, which is when she bolted.

They're very fast spiders, and I nearly lost her. When I managed to cup her, she continued to race around the circumference of the cup, making it difficult to observe and describe how she looked. Strangely, too, was her skittish behaviour whenever I shone a light at her. Perhaps they're sensitive to light. Which, considering that Corinnids are mainly mimic spiders and are diurnal (active during the day, unlike most spiders who are nocturnal), this makes sense.

Thanks for stopping by and reading and supporting!

And remember, spiders are friends.