Temporal range: Palaeogene–present
|Thomisus onustus capturing a bee|
|Genus:|| Thomisus |
| Thomisus onustus |
Thomisus is a genus of crab spiders (family Thomisidae) with around 150 species described. The genus includes species that vary widely in their ecology, with some that ambush predators that feed on insects visiting flowers. Like several other genera in the family Thomisidae, they are sometimes referred to as flower crab spiders, from their crab-like motion and their way of holding their front legs, reminiscent of a crab spreading its claws as a threat.
As with most Thomisidae species, Thomisus exhibit sexual size dimorphism: females are 4 to 10 mm (0.16 to 0.39 in) in length, whereas males are only 2 to 7 mm (0.079 to 0.276 in). Many species 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.
For example, in Thomisus spectabilis , the method of camouflage is similar to the Misumena vatia , though T. spectabilis are visible to their prey, but not their predators. This species of crab spiders is 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 Thomisus guadahyrensis is known from South America (in Peru).
As of February 2017 [update] , the World Spider Catalog accepted the following species:
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 families of spiders. Many members of this family are also known as flower spiders or flower crab spiders.
Misumena is a genus of crab spiders sometimes referred to as flower crab spiders. They are similar in appearance to several other genera in the family Thomisidae, such as Misumenoides and Mecaphesa.
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.
Neoscona, known as spotted orb-weavers and barn spiders, is a genus of orb-weaver spiders (Araneidae) 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, Neoscona adianta, has a palearctic distribution. As of April 2019 there are eight species that can be found in the United States and Canada:
Runcinia is a genus of crab spiders that was first described by Eugène Louis Simon in 1875. The former R. elongata is a synonym of Thomisus elongatus.
Tetragnatha is a genus of long-jawed orb-weavers found all over the world. It was first described by Pierre André Latreille in 1804, and it contains hundreds of species. Most occur in the tropics and subtropics, and many can run over water. They are commonly called stretch spiders in reference to their elongated body form and their ability to hide on blades of grass or similar elongated substrates by stretching their front legs forward and the others behind them. The name Tetragnatha is derived from Greek, tetra- a numerical prefix referring to four and gnatha meaning "jaw". On the Hawaiian islands, a shift of cursorial behavior occurred long ago, when their ancestors first arrived on the island chain.
Pardosa is a large genus of wolf spiders, with more than 500 described species that are found in all regions of the world.
Tibellus is a genus of slender crab spiders described by Simon in 1875, belonging to the order Araneae, family Philodromidae. Species of this genus are present in Eurasia, Africa, Americas and Australia.
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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