Most trapdoor spiders have a body length of about 1 inch (2.5 centimeters), with some species reaching 1.5 inches (4 centimeters). These are stocky, compact spiders, built more like a cork than a sprawling web-spinner. Their leg span typically adds another inch or so beyond the body, giving them an overall footprint roughly the size of a large coin.
Typical Body Length by Sex
Female trapdoor spiders are consistently larger than males. In most species, females reach the full 1 to 1.5 inch body length, while males tend to stay on the smaller end. This size difference is common across spider families, but it’s especially pronounced in trapdoor spiders because females spend their entire lives in one burrow, growing slowly over many years. Males, by contrast, leave the burrow after reaching maturity to search for mates, and they stop growing at that point.
The body shape is distinctive. Trapdoor spiders are heavily built through the front half of the body, with thick, powerful legs designed for digging rather than running. Their abdomens are rounded and smooth. If you’re comparing them to other spiders you might encounter, they look more like small tarantulas than the leggy house spiders you’d find indoors.
The Largest Known Trapdoor Spider
The biggest trapdoor spider on record is a species discovered in Queensland, Australia, in 2023. Females of this species grow up to 5 centimeters (about 2 inches) long, which is large by trapdoor spider standards. Males are smaller, reaching around 3 centimeters. A spokesperson for the Queensland Museum compared the spider’s size to an Australian 50-cent coin, which is slightly larger than an American half-dollar.
This species is rare and lives only in a specific region of central Queensland. It’s an outlier. The vast majority of the roughly 300 known trapdoor spider species worldwide fall into the 1 to 1.5 inch range.
How They Grow to Full Size
Trapdoor spiders grow slowly compared to most spiders. Like all spiders, they increase in size by molting, shedding their rigid exoskeleton and expanding into a new, larger one before it hardens. Young trapdoor spiders molt frequently, but as they age, molts become less common.
Here’s where trapdoor spiders differ from the spiders you see in webs around your house. Most common spiders stop molting entirely once they reach sexual maturity. Trapdoor spiders belong to an older group called mygalomorphs (the same group that includes tarantulas), and females in this group continue molting throughout their lives. This means a female trapdoor spider can keep growing, even if slowly, for years or decades. Females commonly live over 20 years in the wild, and one mygalomorph tracked by researchers in Australia lived to 43. Each molt also gives them the ability to regenerate lost legs.
Males stop molting once they mature, which is one reason they stay smaller. After their final molt, they leave the burrow to find a mate and typically die within a year or two.
Burrow Size Relative to Body
The burrow itself gives you a good sense of scale. Trapdoor spiders dig burrows up to 6 inches (15 centimeters) deep, lined with silk and capped with a hinged lid made of soil and silk. The entrance is roughly the width of the spider’s body, usually somewhere between a dime and a quarter for average-sized species.
The trapdoor lid fits flush with the surrounding ground and is almost invisible when closed. If you find one, the diameter of the lid tells you roughly how big the spider inside is. A lid the size of a nickel likely houses a spider about an inch long. A lid closer to a half-dollar could belong to one of the larger species.
How They Compare to Similar Spiders
- Tarantulas: Much larger. Common tarantula species have body lengths of 2 to 4 inches with leg spans of 5 to 10 inches. Trapdoor spiders are close relatives but significantly smaller.
- Wolf spiders: Similar body size (0.5 to 1.5 inches) but with longer, more visible legs and a leaner build. Wolf spiders hunt on the surface rather than from burrows.
- Funnel-web spiders: Comparable body length to larger trapdoor species, around 1 to 2 inches. Often confused with trapdoor spiders in Australia, though funnel-webs build open, funnel-shaped webs rather than sealed lids.
If you’ve spotted a dark, stocky spider around an inch long near a small hole in the ground, there’s a reasonable chance you’re looking at a trapdoor spider. Their compact build and short, thick legs set them apart from the longer-legged spiders that tend to get more attention.