Thomisidae
The Thomisidae are a family of spiders, including about 170 genera and over 2,100 species. The common name crab spider is often linked to species in this family, but may also be used for spiders from other families. Many members of this family are also known as flower spiders or flower crab spiders.
Etymology
Spiders in this family are called "crab spiders" due to their body shape, behavior of holding their two front pairs of legs apart from the two rear pairs, and their ability to scuttle sideways or backwards, resembling true crabs. The Thomisidae are the family generally referred to as "crab spiders", though some members of the Sparassidae are called "giant crab spiders", the Selenopidae are called "wall crab spiders", and various members of the Sicariidae are sometimes called "six-eyed crab spiders". Some distantly related orb-weaver spider species such as Gasteracantha cancriformis also are sometimes called "crab spiders".
Description
Members of this family of spiders do not spin webs, though are ambush predators. The two front legs are usually longer and more robust than the rest of the legs. The back two legs are smaller, and are usually covered in a series of strong spines. Their coloration tend to either be dull colors such as brown, grey, or very bright green, pink, white or yellow to match their flower. These spiders are quite easy to identify though can occasionally be confused with the huntsman spiders, though the crab spiders are usually smaller.
The spiders of Thomisidae are not known to be harmful to humans. However, spiders of a distantly related genus, Sicarius, which are sometimes referred to as "crab spiders", or "six-eyed crab spiders", are close cousins to the recluse spiders, and are highly venomous, though human bites are rare.
Sexual dimorphism
Several different types of sexual dimorphism have been recorded in crab spiders. Some species exhibit color dimorphisms; however, the most apparent dimorphism is the difference in size between males and females. In some species, this is relatively small; females of Misumena vatia are roughly twice the size of their male counterparts. In other cases, the difference is extreme; on average, female Thomisus onustus are more than 60 times as massive as the males.
Several hypothesized explanations are given for the evolution of sexual size dimorphisms in the Thomisidae and other sister taxa. The most widely acknowledged hypothesis for female growth is the fecundity hypothesis: selection favors larger females so they can produce more eggs and healthier offspring. Because males do not carry and lay eggs, a growth in size does not confer a fitness advantage.
However, sexual size dimorphism may be a result of male dwarfism. The gravity hypothesis states that the smaller size allows the male to travel with greater ease, providing him with an increased opportunity to find mates. Females are comparatively stationary, and their larger size allows them to capture larger prey, such as butterflies and bees, granting females the additional nutrients necessary for egg production.
Other hypotheses propose that sexual size dimorphism evolved by chance, and no selective advantage exists to larger females or smaller males.
Behavior
Thomisidae do not build webs to trap prey, though all of them produce silk for drop lines and sundry reproductive purposes; some are wandering hunters and the most widely known are ambush predators. Some species sit on or beside flowers or fruit, where they grab and kill visiting insects. Individuals of some species, such as Misumena vatia and Thomisus spectabilis, are able to change color over a period of some days, to match the flower on which they are sitting. Some species await prey among leaves or bark, and some species are excellent mimics of bird droppings and sit out in the open; these species convergently evolved their mimicry with the so-called bird-dropping spiders of Araneidae.
Other species of crab spiders with flattened bodies either hunt in the crevices of tree trunks or under loose bark, or shelter under such crevices by day, and come out at night to hunt. Members of the genus Xysticus hunt in the leaf litter on the ground. In each case, crab spiders use their powerful front legs to grab and hold on to prey while paralysing it with a venomous bite.
The spider family Aphantochilidae was incorporated into the Thomisidae in the late 1980s; Aphantochilus species mimic and prey uponCephalotes ants.
Genera
, this family includes 172 genera and 2,195 species:Acentroscelus Simon, 1886 – South AmericaAcrotmarus Tang & Li, 2012 – ChinaAlcimochthes Simon, 1886 – China, Japan, Taiwan, Malaysia, Singapore, VietnamAmyciaea Simon, 1886 – Ivory Coast, Sierra Leone, Indonesia, Singapore, Vietnam, India, Australia, New GuineaAngaeus Thorell, 1881 – AsiaAnsiea Lehtinen, 2004 – Africa, Saudi Arabia, Sao ToméAnsistaria Sherwood, 2022 – AfricaAphantochilus O. Pickard-Cambridge, 1871 – Argentina, BrazilApyretina Strand, 1929 – MadagascarAustralomisidia Szymkowiak, 2014 – AustraliaAvelis Simon, 1895 – South AfricaBassaniana Strand, 1928 – China, Japan, Korea, Europe, North AmericaBassaniodes Pocock, 1903 – Egypt, West Africa, Asia, EuropeBoliscus Thorell, 1891 – Asia, New CaledoniaBomis L. Koch, 1874 – India, AustraliaBonapruncinia Benoit, 1977 – St. HelenaBoomerangiana Szymkowiak & Sherwood, 2021 – AustraliaBorboropactus Simon, 1884 – Africa, Asia, Papua New GuineaBucranium O. Pickard-Cambridge, 1881 – Cuba, Guatemala, Mexico, South AmericaCamaricus Thorell, 1887 – Africa, China, Indonesia, Philippines, Vietnam, Bangladesh, India, New CaledoniaCebrenninus Simon, 1887 – Asia, West AfricaCeraarachne Keyserling, 1880 – Brazil, ColombiaCetratus Kulczyński, 1911 – Australia, New GuineaCoenypha Simon, 1895 – Argentina, ChileCoriarachne Thorell, 1870 – China, Japan, Korea, Caucasus, Turkey, Russia, North AmericaCorynethrix L. Koch, 1876 – AustraliaCozyptila Lehtinen & Marusik, 2005 – Vietnam, Caucasus, Turkey, EuropeCrockeria Benjamin, 2016 – Indonesia, MalaysiaCymbacha L. Koch, 1874 – Sri Lanka, Australia, New GuineaCymbachina Bryant, 1933 – New ZealandCynathea Simon, 1895 – AfricaCyriogonus Simon, 1886 – MadagascarDeltoclita Simon, 1887 – Brazil, PeruDemogenes Thorell, 1895 – Indonesia, India, New Guinea, VanuatuDiaea Thorell, 1869 – Africa, Asia, Russia, United States, Oceania, ColombiaDietopsa Strand, 1932 – IndiaDimizonops Pocock, 1903 – YemenDiplotychus Simon, 1903 – MadagascarDomatha Simon, 1895 – Philippines, New GuineaEbelingia Lehtinen, 2004 – China, Japan, Korea, RussiaEbrechtella Dahl, 1907 – Asia, Russia, PortugalEmplesiogonus Simon, 1903 – MadagascarEpicadinus Simon, 1895 – Trinidad and Tobago, Panama, Mexico, South AmericaEpicadus Simon, 1895 – Mexico to South AmericaEpidius Thorell, 1877 – Africa, AsiaErissoides Mello-Leitão, 1929 – BrazilErissus Simon, 1895 – Brazil, Peru, VenezuelaFelsina Simon, 1895 – Cameroon, Senegal, Sierra LeoneFirmicus Simon, 1895 – Africa, Vietnam, Iran, Israel, Spain, FranceGeraesta Simon, 1889 – AfricaGnoerichia Dahl, 1907 – CameroonHaedanula Caporiacco, 1941 – EthiopiaHaplotmarus Simon, 1909 – VietnamHedana L. Koch, 1874 – Indonesia, Malaysia, Myanmar, Sri Lanka, Oceania, VenezuelaHenriksenia Lehtinen, 2004 – Indonesia, Malaysia, Singapore, Papua New GuineaHerbessus Simon, 1903 – MadagascarHeriaesynaema Caporiacco, 1939 – EthiopiaHeriaeus Simon, 1875 – Africa, Asia, EuropeHeterogriffus Platnick, 1976 – Angola, Democratic Republic of the Congo, UgandaHewittia Lessert, 1928 – AfricaHexommulocymus Caporiacco, 1955 – VenezuelaHolopelus Simon, 1886 – Africa, Indonesia, India, Sri LankaIbana Benjamin, 2014 – China, Indonesia, MalaysiaIndosmodicinus Sen, Saha & Raychaudhuri, 2010 – China, IndiaIndoxysticus Benjamin & Jaleel, 2010 – China, India, Sri LankaIphoctesis Simon, 1903 – MadagascarIsala L. Koch, 1876 – AustraliaIsaloides F. O. Pickard-Cambridge, 1900 – Cuba, Hispaniola, Panama, MexicoKryptochroma Machado, 2021 – Brazil, Colombia, French GuianaLampertia Strand, 1907 – MadagascarLatifrons Kulczyński, 1911 – IndonesiaLedouxia Lehtinen, 2004 – Mauritius, RéunionLoxobates Thorell, 1877 – AsiaLoxoporetes Kulczyński, 1911 – Indonesia, AustraliaLycopus Thorell, 1895 – China, Japan, Indonesia, Myanmar, Singapore, India, New GuineaLysiteles Simon, 1895 – Asia, RussiaMassuria Thorell, 1887 – China, Japan, Myanmar, IndiaMastira Thorell, 1891 – Asia, Australia, SamoaMecaphesa Simon, 1900 – North America, Chile, GalapagosMegapyge Caporiacco, 1947 – GuyanaMetadiaea Mello-Leitão, 1929 – BrazilMicromisumenops Tang & Li, 2010 – ChinaMisumena Latreille, 1804 – Africa, Asia, Europe, United States, Mexico, South America, New Guinea, Papua New GuineaMisumenoides F. O. Pickard-Cambridge, 1900 – India, North to South AmericaMisumenops F. O. Pickard-Cambridge, 1900 – Africa, Asia, North AmericaMisumessus Banks, 1904 – Bermuda, Dominica, Puerto Rico, North America, Grenadines?Modysticus Gertsch, 1953 – Mexico, United StatesMonaeses Thorell, 1869 – Africa, Asia, Bulgaria, Ukraine, Greece, Australia, GuyanaMusaeus Thorell, 1890 – IndonesiaMystaria Simon, 1895 – AfricaNarcaeus Thorell, 1890 – IndonesiaNyctimus Thorell, 1877 – South Africa, Indonesia, Malaysia, Thailand, BorneoOcyllus Thorell, 1887 – MyanmarOnocolus Simon, 1895 – South AmericaOstanes Simon, 1895 – Ivory Coast, Sierra LeoneOxytate L. Koch, 1878 – Africa, Asia, Russia, AustraliaOzyptila Simon, 1864 – Africa, Asia, Europe, North AmericaPactactes Simon, 1895 – Eastern Africa, South Africa, Ivory CoastPagida Simon, 1895 – Indonesia, Thailand, India, Sri Lanka, BorneoParabomis Kulczyński, 1901 – AfricaParasmodix Jézéquel, 1966 – AfricaParastrophius Simon, 1903 – Cameroon, Equatorial Guinea, PakistanParasynema F. O. Pickard-Cambridge, 1900 – GuatemalaParatobias F. O. Pickard-Cambridge, 1900 – Honduras, Panama, MexicoPasias Simon, 1895 – Philippines, IndiaPasiasula Roewer, 1942 – Equatorial GuineaPhaenopoma Simon, 1895 – South Africa, Senegal, Sierra LeonePharta Thorell, 1891 – AsiaPherecydes O. Pickard-Cambridge, 1883 – AfricaPhilodamia Thorell, 1895 – China, Myanmar, Singapore, BhutanPhilogaeus Simon, 1895 – Brazil, ChilePhireza Simon, 1886 – BrazilPhrynarachne Thorell, 1869 – Africa, Asia, New Guinea, Vanuatu, MoluccasPhysoplatys Simon, 1895 – ParaguayPistius Simon, 1875 – Asia, RussiaPlastonomus Simon, 1903 – MadagascarPlatyarachne Keyserling, 1880 – Brazil, French Guiana, PeruPlatythomisus Doleschall, 1859 – Africa, AsiaPoecilothomisus Simon, 1895 – AustraliaPorropis L. Koch, 1876 – Angola, Australia, New GuineaPrepotelus Simon, 1898 – Mauritius, RéunionPsammitis Menge, 1876 – Asia, Europe, Cuba, North America, North AfricaPseudamyciaea Simon, 1905 – IndonesiaPseudoporrhopis Simon, 1886 – MadagascarPycnaxis Simon, 1895 – AsiaPyresthesis Butler, 1880 – MadagascarRangkayo Dhiya'ulhaq & Benjamin, 2025 – IndonesiaReinickella Dahl, 1907 – IndonesiaRejanellus Lise, 2005 – Cuba, Hispaniola, Puerto RicoRhaebobates Thorell, 1881 – New GuineaRuncinia Simon, 1875 – Africa, Asia, Russia, Spain, Australia, New GuineaRuncinioides Mello-Leitão, 1929 – Argentina, Brazil, French GuianaSaccodomus Rainbow, 1900 – AustraliaScopticus Simon, 1895 – IndonesiaSidymella Strand, 1942 – Australia, New Zealand, South AmericaSimorcus Simon, 1895 – Africa, China, YemenSinothomisus Tang, Yin, Griswold & Peng, 2006 – ChinaSmodicinodes Ono, 1993 – China, Malaysia, ThailandSmodicinus Simon, 1895 – AfricaSoelteria Dahl, 1907 – MadagascarSpilosynema Tang & Li, 2010 – ChinaSpinaarachne Machado, 2025 – AustraliaSpiracme Menge, 1876 – Asia, Eastern Europe, North AmericaStephanopis O. Pickard-Cambridge, 1869 – China, Indonesia, OceaniaStephanopoides Keyserling, 1880 – Panama, South AmericaStiphropella Lawrence, 1952 – South AfricaStiphropus Gerstaecker, 1873 – Africa, AsiaStrigoplus Simon, 1886 – China, Indonesia, Malaysia, Myanmar, IndiaStrophius Keyserling, 1880 – Mexico to ParaguaySylligma Simon, 1895 – AfricaSynaemops Mello-Leitão, 1929 – Argentina, BrazilSynalus Simon, 1895 – AustraliaSynema Simon, 1864 – Worldwide except AustraliaTagulinus Simon, 1903 – VietnamTagulis Simon, 1895 – Africa, Sri LankaTalaus Simon, 1886 – South Africa, AsiaTarrocanus Simon, 1895 – Sri LankaTaypaliito Barrion & Litsinger, 1995 – PhilippinesTharpyna L. Koch, 1874 – Indonesia, India, AustraliaTharrhalea L. Koch, 1875 – Madagascar, Indonesia, Philippines, OceaniaThomisops Karsch, 1879 – Africa, ChinaThomisus Walckenaer, 1805 – WorldwideTitidiops Mello-Leitão, 1929 – BrazilTitidius Simon, 1895 – South AmericaTmarus Simon, 1875 – WorldwideTrichopagis Simon, 1886 – Gabon, Madagascar, South Africa, GuineaUlocymus Simon, 1886 – Argentina, BrazilUraarachne Keyserling, 1880 – South AmericaWechselia Dahl, 1907 – ArgentinaXysticus C. L. Koch, 1835 – WorldwideZametopina Simon, 1909 – China, Thailand, VietnamZygometis Simon, 1901 – Thailand to Australia