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 are ambush predators and do not spin webs. The two front legs are usually longer and more robust than the other legs. The back two legs are smaller, and are usually covered in a series of strong spines. Their coloration may be dull with colors such as brown or 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 usually larger huntsman spiders.
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 suggests 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 upon Cephalotes ants.
Genera
, 172 genera and 2,195 species were included in this family:
Acentroscelus Simon, 1886 – South America Acrotmarus Tang & Li, 2012 – China Alcimochthes Simon, 1886 – China, Japan, Taiwan, Malaysia, Singapore, Vietnam Amyciaea Simon, 1886 – Ivory Coast, Sierra Leone, Indonesia, Singapore, Vietnam, India, Australia, New Guinea Angaeus Thorell, 1881 – Asia Ansiea Lehtinen, 2004 – Africa, Saudi Arabia, Sao Tomé Ansistaria Sherwood, 2022 – Africa Aphantochilus O. Pickard-Cambridge, 1871 – Argentina, Brazil Apyretina Strand, 1929 – Madagascar Australomisidia Szymkowiak, 2014 – Australia Avelis Simon, 1895 – South Africa Bassaniana Strand, 1928 – China, Japan, Korea, Europe, North America Bassaniodes Pocock, 1903 – Egypt, West Africa, Asia, Europe Boliscus Thorell, 1891 – Asia, New Caledonia Bomis L. Koch, 1874 – India, Australia Bonapruncinia Benoit, 1977 – St. Helena Boomerangiana Szymkowiak & Sherwood, 2021 – Australia Borboropactus Simon, 1884 – Africa, Asia, Papua New Guinea Bucranium O. Pickard-Cambridge, 1881 – Cuba, Guatemala, Mexico, South America Camaricus Thorell, 1887 – Africa, China, Indonesia, Philippines, Vietnam, Bangladesh, India, New Caledonia Cebrenninus Simon, 1887 – Asia, West Africa Ceraarachne Keyserling, 1880 – Brazil, Colombia Cetratus Kulczyński, 1911 – Australia, New Guinea Coenypha Simon, 1895 – Argentina, Chile Coriarachne Thorell, 1870 – China, Japan, Korea, Caucasus, Turkey, Russia, North America Corynethrix L. Koch, 1876 – Australia Cozyptila Lehtinen & Marusik, 2005 – Vietnam, Caucasus, Turkey, Europe Crockeria Benjamin, 2016 – Indonesia, Malaysia Cymbacha L. Koch, 1874 – Sri Lanka, Australia, New Guinea Cymbachina Bryant, 1933 – New Zealand Cynathea Simon, 1895 – Africa Cyriogonus Simon, 1886 – Madagascar Deltoclita Simon, 1887 – Brazil, Peru Demogenes Thorell, 1895 – Indonesia, India, New Guinea, Vanuatu Diaea Thorell, 1869 – Africa, Asia, Russia, United States, Oceania, Colombia Dietopsa Strand, 1932 – India Dimizonops Pocock, 1903 – Yemen Diplotychus Simon, 1903 – Madagascar Domatha Simon, 1895 – Philippines, New Guinea Ebelingia Lehtinen, 2004 – China, Japan, Korea, Russia Ebrechtella Dahl, 1907 – Asia, Russia, Portugal Emplesiogonus Simon, 1903 – Madagascar Epicadinus Simon, 1895 – Trinidad and Tobago, Panama, Mexico, South America Epicadus Simon, 1895 – Mexico to South America Epidius Thorell, 1877 – Africa, Asia Erissoides Mello-Leitão, 1929 – Brazil Erissus Simon, 1895 – Brazil, Peru, Venezuela Felsina Simon, 1895 – Cameroon, Senegal, Sierra Leone Firmicus Simon, 1895 – Africa, Vietnam, Iran, Israel, Spain, France Geraesta Simon, 1889 – Africa Gnoerichia Dahl, 1907 – Cameroon Haedanula Caporiacco, 1941 – Ethiopia Haplotmarus Simon, 1909 – Vietnam Hedana L. Koch, 1874 – Indonesia, Malaysia, Myanmar, Sri Lanka, Oceania, Venezuela Henriksenia Lehtinen, 2004 – Indonesia, Malaysia, Singapore, Papua New Guinea Herbessus Simon, 1903 – Madagascar Heriaesynaema Caporiacco, 1939 – Ethiopia Heriaeus Simon, 1875 – Africa, Asia, Europe Heterogriffus Platnick, 1976 – Angola, Democratic Republic of the Congo, Uganda Hewittia Lessert, 1928 – Africa Hexommulocymus Caporiacco, 1955 – Venezuela Holopelus Simon, 1886 – Africa, Indonesia, India, Sri Lanka Ibana Benjamin, 2014 – China, Indonesia, Malaysia Indosmodicinus Sen, Saha & Raychaudhuri, 2010 – China, India Indoxysticus Benjamin & Jaleel, 2010 – China, India, Sri Lanka Iphoctesis Simon, 1903 – Madagascar Isala L. Koch, 1876 – Australia Isaloides F. O. Pickard-Cambridge, 1900 – Cuba, Hispaniola, Panama, Mexico Kryptochroma Machado, 2021 – Brazil, Colombia, French Guiana Lampertia Strand, 1907 – Madagascar Latifrons Kulczyński, 1911 – Indonesia Ledouxia Lehtinen, 2004 – Mauritius, Réunion Loxobates Thorell, 1877 – Asia Loxoporetes Kulczyński, 1911 – Indonesia, Australia Lycopus Thorell, 1895 – China, Japan, Indonesia, Myanmar, Singapore, India, New Guinea Lysiteles Simon, 1895 – Asia, Russia Massuria Thorell, 1887 – China, Japan, Myanmar, India Mastira Thorell, 1891 – Asia, Australia, Samoa Mecaphesa Simon, 1900 – North America, Chile, Galapagos Megapyge Caporiacco, 1947 – Guyana Metadiaea Mello-Leitão, 1929 – Brazil Micromisumenops Tang & Li, 2010 – China Misumena Latreille, 1804 – Africa, Asia, Europe, United States, Mexico, South America, New Guinea, Papua New Guinea Misumenoides F. O. Pickard-Cambridge, 1900 – India, North to South America Misumenops F. O. Pickard-Cambridge, 1900 – Africa, Asia, North America Misumessus Banks, 1904 – Bermuda, Dominica, Puerto Rico, North America, Grenadines? Modysticus Gertsch, 1953 – Mexico, United States Monaeses Thorell, 1869 – Africa, Asia, Bulgaria, Ukraine, Greece, Australia, Guyana Musaeus Thorell, 1890 – Indonesia Mystaria Simon, 1895 – Africa Narcaeus Thorell, 1890 – Indonesia Nyctimus Thorell, 1877 – South Africa, Indonesia, Malaysia, Thailand, Borneo Ocyllus Thorell, 1887 – Myanmar Onocolus Simon, 1895 – South America Ostanes Simon, 1895 – Ivory Coast, Sierra Leone Oxytate L. Koch, 1878 – Africa, Asia, Russia, Australia Ozyptila Simon, 1864 – Africa, Asia, Europe, North America Pactactes Simon, 1895 – Eastern Africa, South Africa, Ivory Coast Pagida Simon, 1895 – Indonesia, Thailand, India, Sri Lanka, Borneo Parabomis Kulczyński, 1901 – Africa Parasmodix Jézéquel, 1966 – Africa Parastrophius Simon, 1903 – Cameroon, Equatorial Guinea, Pakistan Parasynema F. O. Pickard-Cambridge, 1900 – Guatemala Paratobias F. O. Pickard-Cambridge, 1900 – Honduras, Panama, Mexico Pasias Simon, 1895 – Philippines, India Pasiasula Roewer, 1942 – Equatorial Guinea Phaenopoma Simon, 1895 – South Africa, Senegal, Sierra Leone Pharta Thorell, 1891 – Asia Pherecydes O. Pickard-Cambridge, 1883 – Africa Philodamia Thorell, 1895 – China, Myanmar, Singapore, Bhutan Philogaeus Simon, 1895 – Brazil, Chile Phireza Simon, 1886 – Brazil Phrynarachne Thorell, 1869 – Africa, Asia, New Guinea, Vanuatu, Moluccas Physoplatys Simon, 1895 – Paraguay Pistius Simon, 1875 – Asia, Russia Plastonomus Simon, 1903 – Madagascar Platyarachne Keyserling, 1880 – Brazil, French Guiana, Peru Platythomisus Doleschall, 1859 – Africa, Asia Poecilothomisus Simon, 1895 – Australia Porropis L. Koch, 1876 – Angola, Australia, New Guinea Prepotelus Simon, 1898 – Mauritius, Réunion Psammitis Menge, 1876 – Asia, Europe, Cuba, North America, North Africa Pseudamyciaea Simon, 1905 – Indonesia Pseudoporrhopis Simon, 1886 – Madagascar Pycnaxis Simon, 1895 – Asia Pyresthesis Butler, 1880 – Madagascar Rangkayo Dhiya'ulhaq & Benjamin, 2025 – Indonesia Reinickella Dahl, 1907 – Indonesia Rejanellus Lise, 2005 – Cuba, Hispaniola, Puerto Rico Rhaebobates Thorell, 1881 – New Guinea Runcinia Simon, 1875 – Africa, Asia, Russia, Spain, Australia, New Guinea Runcinioides Mello-Leitão, 1929 – Argentina, Brazil, French Guiana Saccodomus Rainbow, 1900 – Australia Scopticus Simon, 1895 – Indonesia Sidymella Strand, 1942 – Australia, New Zealand, South America Simorcus Simon, 1895 – Africa, China, Yemen Sinothomisus Tang, Yin, Griswold & Peng, 2006 – China Smodicinodes Ono, 1993 – China, Malaysia, Thailand Smodicinus Simon, 1895 – Africa Soelteria Dahl, 1907 – Madagascar Spilosynema Tang & Li, 2010 – China Spinaarachne Machado, 2025 – Australia Spiracme Menge, 1876 – Asia, Eastern Europe, North America Stephanopis O. Pickard-Cambridge, 1869 – China, Indonesia, Oceania Stephanopoides Keyserling, 1880 – Panama, South America