Burrowing spiders, including the Idiopidae family (a broad term for burrowing spiders).

Detailed introduction

Trapdoor spiders are a large group of small to medium-sized spiders that are adept at digging burrows and creating "trapdoors" in the soil. It is not a single species, but rather a group of proto-arachid spiders encompassing multiple families and genera, such as Idiopidae and Ctenizidae . They are widely distributed in temperate and tropical regions worldwide and are characterized by their robust bodies and burrowing habits.

Classification Status and Naming

• Common Chinese names: Burrowing spider, Trapdoor spider (broad terminology)

• English name: Trapdoor spiders

• Representative groups: Idiopidae, Ctenizidae, and several other closely related families of burrowing spiders.

• Classification: Arthropoda → Arachnida → Araneae → Several families of protoarachnoids (such as Idiopidae, etc.)

Appearance and distinguishing features

Burrowing spiders are robust in appearance, with short but powerful legs adapted for digging and moving soil. They share the following characteristics:

• Size: Mostly small to medium-sized spiders, with adults measuring about 1 to 4 cm in length, and some larger species slightly exceeding 4 cm;

• Body color: mostly brown, dark brown or blackish brown, rarely bright colors, in order to disguise itself with soil and fallen leaves;

• Physical characteristics: The head and chest are broad and thick, the fangs are thick and strong, the abdomen is round, and the legs are short, thick and powerful, giving an overall impression of being solid and sturdy;

• Surface texture: The cephalothorax is mostly slightly glossy, and the feet and abdomen are often covered with short hairs, which help to sense vibrations;

• Sexual differences: Female spiders are more robust and live in the burrow for a long time, while male spiders often leave the burrow to find mates after they mature.

Distribution range and habitat

Burrowing spiders, in a broad sense , are widely distributed in many parts of the world , including Australia, South Africa, parts of Europe, North and South America, East Asia and Southeast Asia.

Typical habitats include:

• Woodland edges, shrub belts, and grassland slopes;

• Rocky slopes, earthen embankments, and loose soil areas at the foot of mountains;

• The edges of farmland, pastures, roadside slopes, and the area around garden flower beds;

• Slopes and soil layers that are well-drained and less prone to water accumulation.

They prefer digable, relatively stable soil , which facilitates the construction of deep burrows and the long-term use of the same nest.

underground tunnels and "trapdoor" structures

The most distinctive feature of burrowing spiders is their intricate burrows and trapdoors:

• Vertical or slanted holes are dug in the soil, with depths ranging from a few centimeters to tens of centimeters.

• The cave walls were reinforced with silk to form a stable silk-lined earth cave, which helps prevent collapse and retain moisture;

• The entrance to the cave is covered by a thick sheet made of soil, plant debris, and spider silk, resembling a small door.

• One side of the trapdoor is hinged with silk, which can be tightly closed to blend into the ground, or quickly pushed open to ambush prey.

Some burrowing spiders also lay out radiating silk threads around the entrance of their burrows to help them sense the vibrations of their prey's footsteps.

Lifestyle and Diet

Burrowing spiders are typical nocturnal ambush predators , spending most of their time in or near their burrows.

• During the day, they usually hide inside caves, keeping the trapdoors tightly closed to prevent dryness and predators from disturbing them;

• They wait behind the cave entrance at dusk and night, placing their forelegs on the trapdoor or surrounding threads to sense vibrations;

• Their main prey consists of beetles, cockroaches, ants, centipedes, other spiders, and occasionally small lizards and mollusks;

• When prey approaches the burrow entrance, the burrow spider will suddenly push open the trapdoor and rush out, biting the prey and then quickly dragging it back into the burrow to eat.

Female spiders use the same burrow year after year, which can last for many years; male spiders leave the burrow after they mature and are more easily seen by people because they walk on the surface.

Reproduction and life history

The life history of different groups of burrowing spiders varies slightly, but they generally share the following commonalities:

• During the maturing season, male spiders leave their burrows to find female spiders and will knock or pull silk near the entrance to send courtship signals.

• Mating usually takes place inside the burrow, after which the male spider typically leaves and dies shortly afterward.

• The female spider prepares an egg sac inside the burrow and guards it until the spiderlings hatch;

• Young spiders initially live together in the mother's nest, but gradually leave the nest and dig their own small burrows in the nearby soil.

Because the burrows are stable and safe, many female burrow spiders can live for many years, and some larger species can live for several years or even longer.

Toxicity and its impact on humans

Burrowing spiders generally possess well-developed fangs and venom glands, but most species are not highly dangerous to humans .

When bitten, the following may occur:

• Pain and local redness and swelling at the bite site;

• A small number of people may experience more noticeable swelling or allergic reactions;

• A small number of individual genera and species are highly toxic, and the risks need to be assessed in conjunction with local experts and medical advice.

Overall, burrowing spiders tend to bite defensively, and they only attack when forced, gripped, or when their burrows are being dug.

Relationship with humans and ecological role

Burrowing spiders are important terrestrial predators in the ecosystem, helping to regulate pest populations by preying on various terrestrial insects and other arthropods.

If burrows and trapdoors are found near residential areas, they generally do not pose a significant threat to people, as long as they are not located in areas frequently trampled. Many nature conservation organizations recommend preserving these spiders as much as possible, allowing them to continue to perform their ecological functions in their original locations.

References

York Main, B. 1976. Spiders. The Australian Naturalist Library, Collins, Sydney.

Brunet, B. 1996. Spiderwatch: a guide to Australian spiders. Reed/New Holland.

Simon-Brunet, B. 1994. The Silken Web: a natural history of Australian spiders. Reed Books.