Theridiosomatidae

Simon, 1881

ray orbweavers, ray spiders, slingshot spiders

Genus Guides

Theridiosoma(ray spiders)

Theridiosomatidae is a small of orb-weaving spiders known for constructing distinctive cone-shaped or slingshot webs. The family comprises approximately 137 extant in 20 , distributed primarily in tropical and subtropical regions worldwide. Members are commonly called "ray spiders" or "slingshot spiders" due to their unique web architecture where the web center is pulled back and anchored, then released to propel the spider toward prey. Most species are small, typically under 1 cm in body length. The family exhibits remarkable behavioral diversity in web construction, with some genera showing specialized adaptations including cave-dwelling and high-elevation preferences.

Theridiosoma by (c) Katja Schulz, some rights reserved (CC BY). Used under a CC-BY license.

Theridiosoma by (c) Katja Schulz, some rights reserved (CC BY), uploaded by Katja Schulz. Used under a CC-BY license.

Theridiosoma gemmosum by (c) Katja Schulz, some rights reserved (CC BY). Used under a CC-BY license.

Pronunciation

How to pronounce Theridiosomatidae: /ˌθɛrɪˌdiːoʊˌsoʊməˈtaɪdiː/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Theridiosomatidae spiders are distinguished from other orb-weaving by their characteristic cone-shaped or ray-formed webs, where the web center is pulled back into a cone rather than lying flat. The family includes small-bodied spiders, with most measuring under 10 mm; Simonia species range 1.50–1.65 mm (males) and 1.90–2.45 mm (females). Morphological identification to requires examination of genitalia: male palps often feature distinctive embolic structures (torch-shaped in Simonia), and female epigynes show characteristic surface patterns and copulatory bursae. The web architecture itself serves as a field diagnostic when observable.

Images

Habitat

Tropical and subtropical forests constitute the primary , with occupying diverse microhabitats from lowland swamps to high-elevation meadows. Several show habitat specialization: Sennin is troglophilic (cave-dwelling), with species known from limestone caves; Aculepeira species occur at high elevations and latitudes, including montane forests above 2,500 meters; Wendilgarda builds webs on running water surfaces. Some species occupy artificial structures near water bodies.

Distribution

Global distribution concentrated in tropical and subtropical regions. Neotropical: Amazon basin, Central and South America (including slingshot spiders in Peru). Oriental: Southeast Asia including Laos, Vietnam, southern China, Sumatra (Indonesia), and the Ryukyu Islands (Japan). Palearctic: Europe, Siberia, northern China, Russian Far East; recently recorded in Romania. Nearctic: Alaska, Yukon, northern Mexico, with disjunct in northeastern United States.

Diet

Flying insects constitute the primary prey. Observations document capture of mosquitoes and other small aerial insects. Some exploit abundant emerging aquatic insects (, mayflies) near water bodies. Species near artificial lights capture phototactic insects drawn to illumination.

Life Cycle

with internal ; detailed copulatory organ described for multiple . sacs produced, subject to attack (documented in Theridiosoma gemmosum). specimens observed occupying web hubs during daytime more frequently than mature individuals.

Behavior

The exhibits highly specialized web-building : spiders construct cone-shaped webs by pulling the center back and anchoring it to vegetation, then releasing tension to slingshot themselves toward prey. This "ray" or "slingshot" mechanism allows active prey capture rather than passive entanglement. Spiders typically occupy web hubs at night or during overcast conditions, retreating to web periphery during daylight. Wendilgarda build on water surfaces. Web reconstruction occurs nocturnally. Some species demonstrate rapid web-resetting behavior after missed strikes.

Ecological Role

of small flying insects in tropical and subtropical . Near water bodies, they function as significant consumers of emerging aquatic insects, potentially influencing aquatic-terrestrial subsidies. sac exploit the as , indicating their integration into dynamics.

Human Relevance

Slingshot spider has generated substantial public and scientific interest, with observation videos viewed hundreds of thousands of times. Some occupy urban environments near water bodies and artificial lighting, facilitating human encounters. No medically significant bites documented.

Similar Taxa

AraneidaeBoth construct orb webs; Araneidae webs are flat, circular, and passive, while Theridiosomatidae webs are conical with active slingshot mechanism. Araneidae are generally larger with different abdominal patterning.
TetragnathidaeBoth are orb-weaving with elongated body forms in some ; Tetragnathidae construct horizontal or inclined orb webs without the conical tension structure, and typically have more pronounced cheliceral elongation.