Thomisus

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Thomisus
Temporal range: Palaeogene–present
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Spider and bee June 2008-1.jpg
Thomisus onustus capturing a bee
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Chelicerata
Class: Arachnida
Order: Araneae
Infraorder: Araneomorphae
Family: Thomisidae
Genus:Thomisus
Walckenaer, 1805
Type species
Thomisus onustus
Walckenaer, 1805
Species

See text

Diversity
145 species
male Thomisus kitamurai from Japan Thomisus kitamurai.male.-.tanikawa.jpg
male Thomisus kitamurai from Japan
female Thomisus kitamurai Thomisus kitamurai.female.1.-.tanikawa.jpg
female Thomisus kitamurai

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 predator Predator that waits for prey to come to it

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.

Contents

Description and habits

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. [1] 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. [2] 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. [3] The colour changes that such species can achieve are typically in ranges of white, pink, and yellow.

Thomisidae family of arachnids

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 guide

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. [4] 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.

Distribution

female Thomisus okinawensis Thomisus.okinawensis.female.1.-.tanikawa.jpg
female Thomisus okinawensis
South African species of Thomisus in ambush on Lavandula, by a flower too small for her to occupy Crab Spider (Thomisus) on Lavandula 5623.jpg
South African species of Thomisus in ambush on Lavandula, by a flower too small for her to occupy
South African species of Thomisus disturbed on Lavandula inflorescence Crab Spider (Thomisus) on Lavandula 5637.jpg
South African species of Thomisus disturbed on Lavandula inflorescence
female T. labefactus Thomisus labefactus.jpg
female T. labefactus

The distribution of Thomisus species is almost worldwide, with the notable exception of most of South America. [5] 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 A continent in the Western Hemisphere, and mostly in the Southern Hemisphere

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.

Old World Collectively Africa, Europe, and Asia

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 Island in the Pacific Ocean

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.

Species

As of February 2017, the World Spider Catalog accepted the following species: [5]

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.

<i>Thomisus onustus</i> species of arachnid

Thomisus onustus is a crab spider species in the genus Thomisus belonging to the family Thomisidae.

Related Research Articles

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<i>Diaea</i> Genus of spiders

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<i>Neoscona</i> Genus of spiders

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References

  1. Murphy, Frances & Murphy, John (2000). An Introduction to the Spiders of South-East Asia. City: Malaysian Nature Society. ISBN   983-9681-17-6.
  2. Filmer, Martin (1997). Southern African Spiders. City: BHB International / Struik. ISBN   1-86825-188-8.
  3. Reuven Dukas and Douglass H. Morse ; Crab spiders affect flower visitation by bees ; OIKOS 101: 157–163, 2003
  4. Gawryszewski, F. M., A. L. Llandres, and M. E. Herberstein. "Relationship between colouration and body condition in a crab spider that lures pollinators." Journal of Experimental Biology 215, no. 7 (2012): 1128-1136.
  5. 1 2 "Gen. Thomisus Walckenaer, 1805", World Spider Catalog, Natural History Museum Bern, retrieved 2017-02-25