Brief SummaryRead full entry
The spider family Uloboridae (hackled orbweb weavers) includes 268 described species (Platnick 2014). Most species are tropical, with relatively few species occurring in the temperate zone (Bradley 2013). Just over a dozen species in seven genera are found in North America north of Mexico (Opell 2005; Platnick 2014): Uloborus and Hyptiotes are represented by several species throughout the United States and Canada; Miagrammopes (M. mexicanus) is found only in southern Texas; Siratoba (S. referens) and Philoponella species are restricted to the southwestern United States and Texas; and Zosis (Z. geniculata) is found only in the Gulf Coast states. Octonoba sinensis is an introduced Asian species with a wide but patchy distribution east of the Rocky Mountains, where it appears to be confined to greenhouses and barns (Muma and Gertsch 1964; Opell 1979,1983 cited in Opell 2005). Uloborids resemble small araneids, but have a cribellum and calamistrum.
Uloborids are unusual in that they lack venom glands and do not use venom to subdue their prey. Instead, they apply thousands of wrapping movements with their hind legs and use up to hundreds of meters of silk to construct a thick shroud that applies substantial compressive force to their prey. These shrouds sometimes not only restrain prey, but also break the prey’s legs, buckle its compound eyes inward, or kill it outright. The spider then covers the entire surface of its prey with digestive fluid, liquefying it; the spider’s mouthparts usually never touch the prey itself. The silk is eventually consumed along with the prey. (Eberhard et al. 2006; Weng et al. 2006; Bradley 2013)
North Amerixan uloborids make three types of webs: orb webs (Octonoba, Philoponella, Siratoba, Uloboris, and Zosis), triangle webs (Hyptiotes), and simple webs formed of just a few capture lines and lacking a stereotypic architecture (Miagrammopes) (Opell 2005 and references therein). Triangle webs are oriented vertically. In contrast to the orbwebs made by most spiders that spin them (except for most tetragnathids), uloborid orbwebs are typically oriented horizontally. In addition to differences in their webs, North American uloborids vary in where they place their egg sacs. Hyptiotes females deposit their eggs on small twigs, Octonoba females place their egg sacs at the edge of the web, and Zosis females incorporate their egg sacs in the orb (Opell 1984 cited in Opell 2005). Uloborus females attach a growing chain of egg sacs along a radius at the edge of the orb. Philoponella and Miagrammopes females hold their egg sacs with one first leg until spiderlings emerge. (Opell 2005 and references therein).
Philoponella form communal aggregations, with many individuals sharing the support frame strands around their individual orb webs. Individuals in these aggregations often defend their own orbs from other spiders in the group, but in some species they engage in cooperative prey capture (Masumoto 1998 and references therein). Many uloborids add decorations, such as stabilimenta, to their webs (in some cases, young and adult spiders may add different decorations).
Opell (2005) reviewed the taxonomic history of the family Uloboridae.