Hacklemesh Weaver (Metaltella simoni)

Physical description and identification

The hacklemesh weaver is a compact, stocky spider with a low, glossy carapace and a slightly larger, velvety abdomen. Seen up close it looks purposeful rather than delicate: thick legs, a broad head region and a body that sits close to the ground. Most people meet it when a male runs across a garage floor or bathroom tile at night.

Adults

• Size: females measure about 7–9 mm in body length, males slightly smaller at 6–8 mm. With legs spread the spider covers roughly the diameter of a US quarter.
• Color: the carapace and legs are dark reddish brown to purplish black with a faint sheen. The abdomen is dark grey-brown, often with a paler heart-shaped mark near the front and a row of faint, pale chevrons running toward the spinnerets. Some individuals look almost uniformly black in poor light.
• Eyes: eight small eyes arranged in two short, gently curved rows. There are no enlarged forward-facing eyes, which separates the hacklemesh weaver from jumping spiders and wolf spiders of a similar size.
• Distinctive features: like all cribellate spiders it carries a cribellum, a flat spinning plate in front of the spinnerets, and a calamistrum, a comb of curved bristles on the fourth leg. Under magnification the silk it produces looks woolly or “hackled” rather than smooth. Males have swollen, boxing-glove pedipalps and longer legs than females.

Eggs and egg sac

The female lays her eggs inside the silk retreat and wraps them in a flattened, papery sac of white silk that she guards and rarely leaves. Egg sacs are tucked into the same crevices the adults use, so they are almost never found in the open.

Spiderlings

Hatchlings are pale and translucent and darken with each molt. They stay in and around the mother’s retreat for a short period, then disperse to build their own small mesh webs nearby. Because the species produces several small broods in warm climates, all stages can be found together under one board or stone.

The web

The web is an irregular, three-dimensional mesh of cribellate silk that radiates from a short silk tube where the spider hides. The dry, hackled threads are not sticky in the usual sense; they snag the tiny bristles and claws of crawling insects on contact, so the web works like flypaper without glue. Webs are almost always low to the ground, spun under bark, in the gaps of stone walls, under flower pots, in wood piles and along the base of exterior walls. Fresh webs look bluish-white; old ones collect dust and turn grey, which is why a garage corner can look untidy long after the spider has moved on. For how cribellate silk differs from the sticky silk of orb weavers, see our guide to spider webs.

Where the hacklemesh weaver lives

Metaltella simoni is native to the temperate grasslands and river country of southern South America, in Argentina, Uruguay and southern Brazil. It travels easily in shipped goods, nursery plants and building materials, and it has been established in the United States for decades. Records cluster along the Gulf Coast and in California, with confirmed populations in Texas, Louisiana, Mississippi, Alabama and Florida, and scattered sightings farther north where winters are mild.

Within its range it is a ground-level spider of edges: leaf litter, the underside of logs and boards, stone and brick walls, mulch beds, sheds, crawl spaces and the dark corners of garages. It tolerates people well and is one of the species most often listed among common house spiders in the southern states, although it prefers the outside of a building to the living room.

Are hacklemesh weaver spiders venomous?

Yes, in the same sense that almost every spider is venomous: it uses venom to subdue small insects. There is no evidence that Metaltella simoni venom is medically significant to people or pets. It is not related to the recluse spiders or the widow spiders, and it lacks the potent neurotoxins or tissue-damaging enzymes that make those groups dangerous.

Can hacklemesh weaver spiders bite?

A hacklemesh weaver can bite if it is pinned against skin, for example when a wandering male is trapped in clothing or bedding, but bites are rare and the spider’s first response to disturbance is to bolt for cover. Reported bites cause brief, localized pain similar to a bee sting, sometimes followed by mild redness or itching that clears within a day or two. Wash the area with soap and water, apply a cool compress and watch for any unusual swelling, which would suggest an allergic reaction rather than the venom itself. Because this species is often mistaken for more dangerous spiders, save the specimen or a photo for identification rather than assuming the worst.

Ecological importance and behavior of the hacklemesh weaver

The hacklemesh weaver is a sit-and-wait predator that spends daylight hours inside its silk tube and comes to the mouth of the retreat after dark. Vibrations in the mesh tell it when an ant, beetle, earwig, springtail or small cockroach has stumbled into the hackled threads. It rushes out, bites, and drags the prey back to the retreat to feed.

Natural predators: ground-foraging birds, lizards and toads take adults that wander at night, while centipedes, larger spiders and parasitoid wasps hunt them in their retreats. In houses the long-bodied cellar spider is a regular predator of small ground spiders like this one.

Prey-predator dynamics: because its webs sit at soil level, the hacklemesh weaver intercepts a different set of insects from the aerial webs of orb weavers above it. A dense population along a foundation wall removes a surprising number of ants and small pest insects each season.

Seasonal behavior: mature males abandon their webs in autumn and early winter to search for females, which is when most indoor sightings happen. Females can live and reproduce through more than one season in mild climates, producing several egg sacs. Like all spiders, juveniles grow by molting, and the discarded skins are often found near the retreat.

Relationship with humans: the species is harmless and beneficial. If a web is unwelcome, brushing it away and sealing gaps at ground level is enough; no treatment is needed.

Similar spiders and how to tell them apart

Quick facts

Did you know?

• The species was described in 1878 by the German arachnologist Eugen von Keyserling and named for the French arachnologist Eugène Simon.
• “Hackled” refers to the woolly, combed texture of cribellate silk, which the spider teases out with the calamistrum on its hind legs; the same word gives the family Amaurobiidae its North American common name.
• Metaltella was moved from Amaurobiidae to Amphinectidae and then, after a 2017 molecular revision of the spider tree of life, into Desidae, the same family as Australia’s black house spider.
• Because it hitchhikes so readily in potted plants and lumber, it is often the first non-native spider to appear in new housing developments in the Gulf states.

In summary, the hacklemesh weaver is a harmless, useful neighbor: a small dark spider whose fuzzy ground-level web quietly removes ants and other pests. Learn its eye pattern and glossy carapace and you will never again confuse it with a recluse.