Theridiosoma gemmosum · spiders.fyi

Turning a surface into a cone

Theridiosoma gemmosum holds a tension line and draws the centre of its orb out of the original plane. The resulting capture surface forms a cone, with the small spider at its tip. A front-facing photograph can conceal this three-dimensional shape. A side view reveals that the trap is preloaded before an attack begins.

Launch can precede contact

An experimental study recorded web strikes at passing prey before it touched capture threads. This differs from a trap triggered only by direct disturbance of its surface. After release, the preloaded capture area moves towards the insect. Silk serves both as trapping material and as a component of an actively moving mechanical system.

Vibrations arriving through air

Experiments using flying prey and artificial vibration sources investigated what triggers these strikes. Results support a role for airborne cues and show that direction matters. Attributing the performance simply to good eyesight would miss the question under study. Different sensory channels provide different kinds of information about events in the surrounding space.

A damp stage on a small scale

The species is known from North America and much of the temperate Old World. Damp vegetation supplies attachment sites for its small webs. Its place in this selection comes from mechanism rather than a giant body or striking colour. An inconspicuous site can hold a remarkably mobile hunting architecture that is easily missed while walking past.

What do we know, and where are the limits?

Experiments on T. gemmosum support a response to airborne vibrations. They imply neither human-like hearing nor conscious planning.

Sources & image credits

Sources and classification checked on 3 November 2026. Scientific names and interpretations may change with new evidence.