Theridiosoma gemmosum
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| Theridiosoma gemmosum | |
|---|---|
 | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Subphylum: | Chelicerata |
| Class: | Arachnida |
| Order: | Araneae |
| Infraorder: | Araneomorphae |
| Family: | Theridiosomatidae |
| Genus: | Theridiosoma |
| Species: | T. gemmosum |
| Binomial name | |
| Theridiosoma gemmosum (L. Koch, 1877)[1] | |
Theridiosoma gemmosum is a species of spider in the family Theridiosomatidae, known as ray spiders. It is widely distributed in the Holarctic region.[1] A small spider with a shiny globular abdomen, it constructs a conical orb web.
Theridiosoma gemmosum is a small spider. Females are 2–3 mm long, males smaller still at 1.5–2 mm. In both sexes, the carapace (upper surface of the cephalothorax) is dark brown; the upper surface of the abdomen (opisthosoma) is silvery with variable dark lines and marks. The abdomen is globular, more or less circular from above. The male palpal bulbs and the female epigyne are distinctive.[2]
Web
Theridiosoma gemmosum constructs a small orb web. The radii do not run directly to a central hub as with other orb webs, but are first joined into groups of two or three before combining to meet in the middle. A single thread runs from the centre to a nearby support, and is held by the spider. While the spider is holding this thread the tension pulls the web into a conical shape, described as "like an umbrella turned inside out".[2] When prey, such as a mosquito gets near the web, the spider releases the web, which snaps forward and catches it. Experiments indicate the spiders are listening for prey, as they will release their webs when approached by an appropriately pitched tuning fork.[3]