Temporal range: Palaeogene–present
|Thomisus onustus capturing a bee|
| Thomisus onustus |
Thomisus is a genus of crab spiders (family Thomisidae) with almost 150 species described. The genus includes species that vary widely in their ecology, but the best known crab spiders are those species that people call the flower crab spiders, because they are ambush predators that feed on insects visiting flowers. The flower crab spiders are the species for which the popular name was coined, because of their crab-like motion and their way of holding their front legs in an attitude reminiscent of a crab spreading its claws as a threat.
A genus is a taxonomic rank used in the biological classification of living and fossil organisms, as well as viruses, in biology. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclature, the genus name forms the first part of the binomial species name for each species within the genus.
Ambush predators or sit-and-wait predators are carnivorous animals that capture or trap prey by stealth or by strategy, rather than by speed or by strength. Ambush predators sit and wait for prey, often from a concealed position, and then launch a rapid surprise attack.
As with most Thomisidae species, Thomisus exhibit sexual size dimorphism: females are four to ten mm in length, whereas males are only two to seven mm. Many are brightly colored, usually matching the color of the flower in which they are waiting in ambush.Not all species are flower-dwelling, but among those that are, at least some species can change their colour over a period of some days to match the flower colour. Studies suggest that bees are inclined to avoid a flower that contains a spider-sized object of a non-matching colour; whether this is specifically a mechanism for avoiding crab spiders, or simply that they are not attracted to flowers whose nectar guides are obscured however, is a more difficult question. The colour changes that such species can achieve are typically in ranges of white, pink, and yellow.
The Thomisidae are a family of spiders, including about 175 genera and over 2,100 species. The common name crab spider is often linked to species in this family, but is also applied loosely to many other species of spiders. Among the Thomisidae, "crab spider" refers most often to the familiar species of "flower crab spiders", though not all members of the family are limited to ambush hunting in flowers.
Nectar guides are markings or patterns seen in flowers of some angiosperm species, that guide pollinators to their rewards. Rewards commonly take the form of nectar, pollen, or both, but various plants produce oil, resins, scents, or waxes. Such patterns also are known as "pollen guides" and "honey guides", though some authorities argue for the abandonment of such terms in favour of floral guides.
For example, in the Thomisus spectabilis species, the method of camouflage is similar to the Misumena vatia except the Thomisus spectabilis blend in with their environment while being visible to their prey, but not their predators. This species of crab spiders are UV reflective while the flower is UV absorbing creating a contrast between the spider and flower through the eyes of the pollinator.The contrast created greatly attracts pollinators such as honeybees. This evolutionary method of camouflage increased the likelihood the crab spiders encountered prey, which in turn effects the fitness of the crab spiders. Due to the increased encounter rate of prey the spiders are able to focus energy on reproduction therefore leading to increased fitness in the spiders. The evolutionary method of camouflage greatly increases the survivability and fitness of crab spiders.
The distribution of Thomisus species is almost worldwide, with the notable exception of most of South America.Although Thomisus species can be found almost anywhere on earth, most species occur in the tropics and the warmer regions of the Old World, with fewer species in the region from New Guinea to Australia and the New World. Only T. guadahyrensis is known from South America, and only in Peru.
South America is a continent in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. It may also be considered a subcontinent of the Americas, which is how it is viewed in the Spanish and Portuguese-speaking regions of the Americas. The reference to South America instead of other regions has increased in the last decades due to changing geopolitical dynamics.
The term "Old World" is used commonly in the West to refer to Africa, Asia and Europe, regarded collectively as the part of the world known to its population before contact with the Americas and Oceania. It is used in the context of, and contrasts with, the New World.
New Guinea is a large island separated by a shallow sea from the rest of the Australian continent. It is the world's second-largest island, after Greenland, covering a land area of 785,753 km2 (303,381 sq mi), and the largest wholly or partly within the Southern Hemisphere and Oceania.
As of February 2017 [update] , the World Spider Catalog accepted the following species:
The World Spider Catalog (WSC) is an online searchable database concerned with spider taxonomy. It aims to list all accepted families, genera and species, as well as provide access to the related taxonomic literature. The WSC began as a series of individual web pages in 2000, created by Norman I. Platnick of the American Museum of Natural History. After Platnick's retirement in 2014, the Natural History Museum of Bern (Switzerland) took over the catalog, converting it to a relational database.
The yellow crab spider,, is a species of spider of the genus Thomisus. It is found in Sri Lanka, Singapore, Sumatra, Nias Island, and Java. They often hide in flowers and are able to change colors just to blend in to capture preys.
Thomisus granulifrons is a species of spiders of the genus Thomisus. It is native to India and Sri Lanka.
Thomisus onustus is a crab spider species in the genus Thomisus belonging to the family Thomisidae.
Myrmarachne is a genus of jumping spiders which imitate an ant by waving their front legs in the air to simulate antennae. Some species also look strikingly like ants. Spiders in this genus are commonly called antmimicking spiders, although there are many other spiders that mimic ants. Panachraesta used to be a synonym until it was removed and made into its own genus
Rhene is a spider genus of the Salticidae family.
Drassodes is a genus of ground spiders that was first described by Niklas Westring in 1851. They are brown, gray, and red spiders that live under rocks or bark in mostly dry habitats, and are generally 3.8 to 11.6 millimetres long, but can reach up to 20 millimetres (0.79 in) in length.
Diaea is a genus of crab spiders first described by Tamerlan Thorell in 1869. Most species are found in specific locations except for D. livens, which occurs both in the United States and D. dorsata, which has a palearctic distribution. Adults are 5 millimetres (0.20 in) to 7 millimetres (0.28 in) and tend to hide in and around vegetation, especially flowers, where their color allows them to blend in to their surroundings.
Cyclosa, also called trashline orbweavers, is a genus of orb-weaver spiders first described by Anton Menge in 1866. Widely distributed worldwide, spiders of the genus Cyclosa build relatively small orb webs with a web decoration. The web decoration in Cyclosa spiders is often linear and includes prey remains and other debris, which probably serve to camouflage the spider. The name "Cyclosa" comes from Greek 'to move in a circle', referring to how it spins its web.
Neoscona, also called spotted orb-weavers and barn spiders, is a genus of orb-weaver spiders first described by Eugène Simon in 1895 to separate these from other araneids in the now obsolete genus Epeira. They have a mostly pantropical distribution and one species, N. adianta, has a palearctic distribution. The name was derived from the Greek νέω, meaning "spin", and σχοῐνος, meaning "reed".
Theridion is a genus of tangle-web spiders with almost 600 described species around the world. Notable species are the Hawaiian happy face spider (T. grallator), named for the iconic symbol on its abdomen, and T. nigroannulatum, one of few spider species that lives in social groups, attacking prey en masse to overwhelm them as a team.
Runcinia is a genus of crab spiders with about 30 described species.
Pardosa is a large genus of wolf spiders, with more than 500 described species that are found in all regions of the world.
Cyrtarachne is a genus of orb-weaver spiders first described by Tamerlan Thorell in 1868.
Oxyopes is a genus of lynx spiders found worldwide. It includes arounds 300 species and is classified under the lynx spider family Oxyopidae. Like other lynx spiders, they are easily recognizable by the six larger eyes arranged hexagonally on top of the head (prosoma), with the remaining smaller two eyes in front. They are also characterized by long spine-like bristles (setae) on their legs. They are ambush predators, actively hunting prey by sight. Though they produce and use silk, they do not build webs to capture prey.
Monaeses is a genus of crab spiders in the family Thomisidae, containing twenty seven species.
Poecilochroa is a genus of ground spiders that was first described by Niklas Westring in 1874.
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