Linyphiidae, spiders commonly known as sheet weavers (from the shape of their webs), or money spiders (in the United Kingdom, Ireland, Australia, New Zealand, and in Portugal, from the superstition that if such a spider is seen running on one, it has come to spin the person new clothes, meaning financial good fortune) is a family of very small spiders comprising 4706 described species in 620 genera worldwide. This makes Linyphiidae the second largest family of spiders after the Salticidae. The family is poorly understood due to their small body size and wide distribution; new genera and species are still being discovered throughout the world. The newest such genus is Himalafurca from Nepal, formally described in April 2021 by Tanasevitch. Since it is so difficult to identify such tiny spiders, there are regular changes in taxonomy as species are combined or divided.
Money spiders are known for drifting through the air via a technique termed “ballooning”.
Within the agriculture industry, money spiders are regarded as biological control agents against pest species like aphids and springtails.
Description
In Linyphiidae, the clypeus is normally over twice as high as the diameter of the anterior median eyes. The chelicerae have lateral stridulating ridges and lack lateral condyles.
The legs are long and thin, and bear macrosetae. The abdomen is usually oval or elongated.
Distribution
Spiders of this family occur nearly worldwide. In Norway many species have been found walking on snow at temperatures of down to −7 °C.
While these spiders are light enough to utilize ballooning for travel, they are limited by the physics of an often turbulent atmosphere and microclimate. For this reason ballooning spiders have little control over where they land, leading to a high mortality rate for the practice and its predominant usage by spiderlings and juveniles. The travel of money spiders by ballooning likely contributes to their vast distribution and speciation.
Predators and prey
Among birds, goldcrests are known to prey on money spiders. Money spiders are known to prey on aphids, springtails, flies, and other spiders.
Taxonomy
The Pimoidae are the sister group to the Linyphiidae.
There are six subfamilies, of which Linyphiinae (the sheetweb spiders), Erigoninae (the dwarf spiders), and Micronetinae, contain the majority of described species.
Many species have been described in monotypic genera, especially in the Erigoninae, which probably reflects the scientific techniques traditionally used in this family. Common genera include Neriene, Lepthyphantes, Erigone, Eperigone, Bathyphantes, Troglohyphantes, Tennesseellum and many others. These are among the most abundant spiders in the temperate regions, although many are also found in the tropics. The generally larger bodied members of the subfamily Linyphiinae are commonly found in classic "bowl and doily" webs or filmy domes. The usually tiny members of the Erigoninae are builders of tiny sheet webs. These tiny spiders (usually 3 mm or less) commonly balloon even as adults and may be very numerous in a given area on one day, only to disappear the next. Some males of the erigonines are exceptional, with their eyes set up on mounds or turrets. This reaches an extreme in some members of the large genus Walckenaeria, where several of the male's eyes are placed on a stalk taller than the carapace.
A few spiders in this family include: Bowl and doily spider, Frontinella pyramitela Filmy dome spider, Neriene radiata Blacktailed red sheetweaver, Florinda coccinea Orsonwelles, a genus of giant Hawaiian Linyphids containing the largest Linyphiid, O. malus. Erigone atra, a dwarf spider
Genera
, the World Spider Catalog accepts the following genera: