Taxonomy
Theridiidae
EOL Text
These spiders live in many different kinds of habitats, on the ground, on plants, in burrows and caves, pretty much anywhere they can spin their webs. They often build in dark, sheltered places, in piles of branches or basement corners. Some species in this group are common house spiders.
Habitat Regions: temperate ; tropical ; terrestrial
Terrestrial Biomes: taiga ; desert or dune ; chaparral ; forest ; rainforest ; scrub forest ; mountains
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Rights holder/Author | ©1995-2012, The Regents of the University of Michigan and its licensors |
Source | http://www.biokids.umich.edu/critters/Theridiidae/ |
These spiders eat Insecta and other invertebrates. Some build nests that can trap flying insects, others stick lines down to the ground that snap up and pull prey into the web. A few species sneak into the webs of other spiders and steal their prey. When cobweb weavers catch a prey animal, they wrap it in sticky silk and bite it, injecting venom that paralyzes or kills the prey. They sometimes leave the prey wrapped up and hanging in the web and eat it later. No other family uses sticky silk to wrap their prey, they just use regular silk that doesn't have glue on it.
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Rights holder/Author | ©1995-2012, The Regents of the University of Michigan and its licensors |
Source | http://www.biokids.umich.edu/critters/Theridiidae/ |
These spiders rely on camouflage colors to avoid predators. They also sometimes build a special hiding place in their webs. Some species put bits of soil or plant parts in their web to hide it. The few species with strong venom have warning colors and will bite if threatened.
Known Predators:
- other Araneae
- Hymenoptera
- Formicidae
- praying mantids
- Aves
- small Squamata
- Amphibia
- small mammals especially Soricidae
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Rights holder/Author | ©1995-2012, The Regents of the University of Michigan and its licensors |
Source | http://www.biokids.umich.edu/critters/Theridiidae/ |
Like all spiders, cobweb weavers are sensitive to vibrations and touch. They probably also use chemical sense to communicate, and they can see, but not too well. Some species in this family have special body parts they can rub together to make noise or vibrations. No one knows exactly what they are for.
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Rights holder/Author | ©1995-2012, The Regents of the University of Michigan and its licensors |
Source | http://www.biokids.umich.edu/critters/Theridiidae/ |
Spiders hatch from eggs, and the hatchlings look more or less like grown-up spiders, though sometimes their colors change as they age. To grow they have to shed their exoskeleton, which they do many times during their lives.
License | http://creativecommons.org/licenses/by-nc-sa/3.0/ |
Rights holder/Author | ©1995-2012, The Regents of the University of Michigan and its licensors |
Source | http://www.biokids.umich.edu/critters/Theridiidae/ |
Male cobweb spiders rarely live more than a year, but in some species females can live for three years or more.
License | http://creativecommons.org/licenses/by-nc-sa/3.0/ |
Rights holder/Author | ©1995-2012, The Regents of the University of Michigan and its licensors |
Source | http://www.biokids.umich.edu/critters/Theridiidae/ |
Mating System: polyandrous
Male cobweb weavers leave their webs and go looking for females. If they find one, they approach very cautiously, because sometimes females eat the males.
Key Reproductive Features: iteroparous ; seasonal breeding ; year-round breeding ; sexual ; fertilization (Internal ); oviparous ; sperm-storing
Female cobweb weavers lay eggs. They produce clutches of upto to 250 eggs at a time, and place them in egg sacks made of brownish silk. They hang the egg sacks in their web and guard them. In some species the female also feeds her babies after they hatch. They get digested food from her until they have grown enough to shed their skin the first time. After they shed they go off on their own. This is unusual, no other family of spiders is known to feed their offspring.
Parental Investment: female parental care
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Rights holder/Author | ©1995-2012, The Regents of the University of Michigan and its licensors |
Source | http://www.biokids.umich.edu/critters/Theridiidae/ |
The spider family Theridiidae (cobweb weavers or combfooted spiders) has a worldwide distribution and includes 2387 described species, ranking it among the few most species-rich spider families (Platnick 2014). According to Levi (2005), 234 theridiid species are known from North America north of Mexico. One of these species, the Common House Spider (Parasteatoda tepidariorum) may be the most common spider in the world, living in abundance in association with humans on every continent except Antarctica, occurring both indoors and outdoors (Bradley 2013).
Theridiids are sedentary and typically construct an irregular web with sticky strands attached to the substrate. The strands break when prey touches the line, pulling the prey toward the center of the web. The web is usually built beneath some sort of cover, such as a rock face, a branch, or even a single leaf. Some theridiids build webs consisting of just a few lines of silk. Members of some theridiid genera (Rhomphaea, Argyrodes) are found in the webs of other spiders, especially orb weavers, and may feed on their hosts, their host's eggs, or their host's prey. Other "atypical" feeding habits are knowns as well. For example, Dipoena and Euryopis are ground-dwelling ant predators. Latrodectus (the "widow" spiders) are well known for being venomous to humans, although they will choose to retreat rather than bite if given the option. (Levi 2005; Bradley 2013)
Theridiids typically have a rounded abdomen tapering to a point at the spinnerets. This shape gives the abdomen a characteristic teardrop shape when the spider is hanging upsidedown in its web. Some theridiids hang a leaf or other debris in the web and rest beneath this cover. Many theridiids are conspicuous and colorful. Like most spiders, theridiids have eight eyes. The fourth tibiae of most theridiids sport curved serrated bristles which the spider uses to draw out and fling sticky silk during a wrapping attack. (Levi 2005; Bradley 2013)
Levi (2005) reviews key aspects of the taxonomic history of the Theridiidae and provides some key references.
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Rights holder/Author | Leo Shapiro, Leo Shapiro |
Source | No source database. |
Tree simplified from Agnarsson (2006).
Despite major advances in the past few years, theridiid phylogeny is still a work in progress. Recent studies have analyzed data from morphology (Agnarsson, 2004), molecules (Arnedo et al., 2004), and both in combination (Agnarsson, 2006). These studies largely agree on the composition of subfamilies. The phylogenetic hypothesis illustrated above is simplified from Agnarsson (2006), the only published study combining molecular and morphological data.
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Rights holder/Author | Jeremy Miller, Tree of Life web project |
Source | http://tolweb.org/Theridiidae/2797 |
Cobweb spiders (Theridiidae) are one of the most diverse spider families, not only in terms of species numbers (>2200 described and many undescribed species), but also for the range of behavior, ecology, and morphology represented within the group. Theridiids include the widow spiders (genus Latrodectus), known for their potent venom and sexual cannibalism (females of some species typically eat the males during or shortly after mating). Sexual cannibalism is actually much more common in Tidarren and Echinotheridion, two genera where juvenile males amputate one of their two pedipalps (sperm transfer organs). Like Latrodectus, Tidarren and Echinotheridion have females much larger than males, a phenomenon known as sexual size dimorphism. Theridiids also include the majority of social spider species, which live in large colonies composed mostly of juvenile and adult females that cooperate in hunting, web building, and brood care. They include the largest group of kleptoparasitic spiders, which steel prey from other species.
License | http://creativecommons.org/licenses/by/3.0/ |
Rights holder/Author | Jeremy Miller, Tree of Life web project |
Source | http://tolweb.org/Theridiidae/2797 |