Swift crab spiders (Misumenops on the west coast. They are also very common in Canada, particularly southern British Columbia, Alberta, and Saskatchewan. They have also been found in Mexico. (Bradley, 2012; Johnson, 1996; Knutson and Gilstrap, 1989; McIver and Belnavis, 1986)) are native to the Nearctic region. They are found across the entirety of the United States, as far south as Texas and Florida, and from coast to coast. They are the most common species of genus
Swift crab spiders can typically be found on shrubs, flowers, and small trees (both deciduous and coniferous), as well as on many crop species. They are generally found on plants that grow in meadows, forests, agricultural fields, and on vegetation-covered dunes. (Gregory Jr, et al., 1989; Johnson, 1996; Knutson and Gilstrap, 1989; McIver and Belnavis, 1986)
As a crab spider from family Thomisidae, their first two pairs of legs are significantly longer than their third and fourth pair, and are held out in a crab-like position, hence the common name of this family. Swift crab spiders exhibit sexual dimorphism, with females larger than males. The mean width of a female carapace is 1.65 mm; while the mean width of a male carapace is 1.28 mm. Adults are yellow or yellowish-white, with dark stripes on each side of their cephalothorax. Males are typically darker than females, and have red bands around their legs. Females have a double row of red dots at the end of their abdomen, while males have two dark lines that converge in a V-shape. Some individuals have other red or black patterns on their abdomen. Swift crab spiders also have a thick covering of setae on their body. Adult female swift crab spiders have a reported average mass of 28.1 mg and a basal metabolic rate of 0.011 cubic cm oxygen/hour. Their eggs are yellow and 0.75 mm in diameter. First instar spiderlings have a white or transparent prosoma, white legs, and a yellowish abdomen. They are smooth bodied, with no color markings or hairs. Second instars are yellowish, with many hairs covering their body. Mature females can be distinguished from immature females by two atrial openings on the epigynal plate not seen in immature females. (Anderson, 1996; Bradley, 2012; Branson, 1966; Marshall and Gittleman, 1994; Muniappan and Chada, 1970; Prenter, et al., 1999)
Eggs of swift crab spiders are laid in an egg sac, and remain there for 5 to 11 days. After hatching, spiderlings remain attached to the chorion of the egg by the end of their abdomen. Appendages are kept close to the body, and spiders are enclosed in a transparent membrane. This post-embryo stage lasts for 1 to 2 days, in which spiderlings remain motionless. Then first instar spiders emerge from the membrane. If they remain undisturbed, they will stay in the egg sac, where they do not feed. They are unable to walk or stand on smooth surfaces. About 23 days after oviposition, swift crab spiders develop into second instar spiderlings and emerge from the egg sac. This stage and the rest of their instars are active stages. Males typically have 4 or 5 instars, while females have 6 or 7 instars before reaching maturity. Their 2nd instar lasts for 27.1 days on average, their 3rd instar lasts 41.8 days, their 4th instar lasts 50.4 days, their 5th instar lasts 43.7 days, their 6th instar lasts 45.1 days, and their 7th instar lasts 17.0 days. Both juveniles and adults can usually be found at the same time throughout the summer. There are typically two population peaks during the year, one in July when overwintered spiderlings reach maturity, and another in late August. Males live for an additional 35 to 64 days once reaching adulthood, while females live for more than a year after oviposition. When cold weather begins, any spiders that are still alive overwinter. (Corey and Taylor, 1989; Dowdy, 1955; Johnson, 1996; Knutson and Gilstrap, 1989; Muniappan and Chada, 1970)
A day after their last molt, male swift crab spiders coat their palpi with seminal fluid to ready for mating. They also build a triangular web inside their mating chamber. Females also ready themselves to mate soon after their last molt, sometimes as soon as 1 hour after. A male acknowledges a receptive female by vibrating his abdomen, moving his first 2 pairs of legs and palpi, and slowly approaching her. He then touches her legs with his first and second pair of legs. If the female is receptive, she lifts her legs and allows herself to be suspended in the web. There is typically either very little or no pre-mating activity. The male may immediately begin mating, or he may rub the epigynal plate of the female with his chelicerae. Fertilization is internal; the male transfers his sperm using his pedipalps. After mating, the male usually stays with the female for an extended time, until she becomes active. In laboratory studies, females cannibalized males when they were forced to remain together post-copulation. Swift crab spiders are polygynous. Males typically mate with more than one female, but require about 12 hours between mating to recharge the seminal fluid on their palps. Females only mate once, and then a waxy coating covers the opening on the epigynal plate to prevent more mating. Mating usually occurs in mid-summer. (Muniappan and Chada, 1970)
Female swift crab spiders do not lay eggs until 11 to 43 days after mating, 23 days on average. By this point, her male mate is long gone, either cannibalized, mating with new females, or dead. Four to 10 days before laying her eggs, females construct a white sheet of web. This becomes enlarged into a concave sac; the eggs are then laid in the center of the sac. Oviposition occurs at night. The egg mass is then covered in silk, creating an egg sac. One sac contains an average of 145 eggs, though this can vary from 55 to 234 eggs. A single egg weighs 0.28 mg on average. One female typically constructs and lays two egg sacs in her life, though this varies from 1 to 3. Eggs incubate in the sac for 5 to 11 days before hatching. About 23 days after oviposition, spiderlings develop into second instars and leave the egg sac. Females remain near the egg sac until the offspring leave. Males typically reach maturity after 4 or 5 instars, while females reach maturity after 6 or 7 instars. (Marshall and Gittleman, 1994; Muniappan and Chada, 1970)
Adult swift crab spiders likely provide provisioning in their eggs for the offspring to grow and develop. Females construct an egg sac for each clutch to provide protection. Females also stay with the egg sac until the spiderlings are ready to leave, which is typically about 23 days after oviposition, when the offspring develop into second instars. This is also likely for protection. Males do not provide any parental care, as they may be cannibalized after copulation. Males move on to other mates and typically die much earlier than females. (Muniappan and Chada, 1970)
Development time from hatching to adulthood can take 100 to over 200 days. Upon reaching adulthood, males live an additional 35 to 64 days, while females can live for more than a year after oviposition. (Muniappan and Chada, 1970)
Swift crab spiders are largely nocturnal, with mating and most hunting taking place at night, though they are sometimes active during the day. They are a 'sit and wait' predator, and can usually be found on flowers and the upper parts of crop plants, where they catch insects. On flowers, they often use their silken drag line to tie several flower petals together to form 'bowers', where they sit and wait for prey. They prepare for attack by raising their first pair of legs, and then snatch the insect. They pierce the prey with their chelicerae and paralyze them with venom. Females are typically more efficient predators than males, likely due to their larger size. Females have also been documented cannibalizing their male mates. This spider species does not construct webs, except for egg sacs and those used in mating. Swift crab spiders are solitary. This species overwinters, and can often be found on herbs, shrubs, and in dead leaf litter. (Dowdy, 1955; Gregory Jr, et al., 1989; Knutson and Gilstrap, 1989; Muniappan and Chada, 1970; Ott, et al., 1998)
Swift crab spiders have eight eyes and view their environment, prey, and other spiders visually. Their sense of touch is also important when catching prey or communicating during mating behaviors. Male often signify their interest by stroking the female's front legs with their own legs. Other crab spiders have been documented using chemical cues to choose hunting sites, such as particular flowers, this is likely true for swift crab spiders as well. (Branson, 1966; Krell and Kramer, 1998; Muniappan and Chada, 1970)
Swift crab spiders are predatory insectivores, feeding on a vast variety of insects species, including many pest species. They are 'sit and wait' predators, sitting within flowers and crop plants, preying on any insect that visits the plant. These insects include flies (Diptera), butterflies (Lepidoptera), dragonflies (Odonata), hemipterans (Hemiptera), grasshoppers (Orthoptera), and wasps and bees (Hymenoptera). They feed on crop pests such as aphids (Aphididae), whiteflies including silverleaf whiteflies (Bemisia tabaci), velvet bean caterpillars (Anticarsia gemmatalis), a major soybean pest, and cotton fleahoppers (Pseudatomoscelis seriatus), a major cotton pest. After capturing their prey, swift crab spiders first insert their chelicerae into the insect and paralyze them with venom. They feed by inserting their chelicerae first into the head and eating the insides of their prey, and then they eat the abdomen, thorax, and legs. First instars do not feed. Younger instars tend to eat smaller prey, while later instars and adults eat larger prey. (Breene, et al., 1990; Gregory Jr, et al., 1989; Hagler, et al., 2004; Knutson and Gilstrap, 1989; Muniappan and Chada, 1970)
Mud-dauber wasps from family Sphecidae prey on swift crab spiders. Captured spiders are paralyzed and left in the wasp's nest, with their egg. Young wasps eat the spider upon hatching. Spider wasps from family Pompilidae also use swift crab spiders as larval food. Early instars (particularly the second instar) have a high rate of predation by other insects. As predators themselves, later instars and adults have few predators. (Evans, 1964; Muma and Jeffers, 1945; Muniappan and Chada, 1970)
Swift crab spiders are significant predators, feeding on many species of insects. They also feed on many important crop pests, giving them the potential to reduce and control the size of these populations. They are also prey to several wasp species that use them to provide food for their larval offspring. (Breene, et al., 1990; Evans, 1964; Knutson and Gilstrap, 1989; Muma and Jeffers, 1945; Muniappan and Chada, 1970)
Since swift crab spiders feed on many important insect crop pest species, they can function as biological control agents and reduce the size of pest populations. This helps decrease crop damage and economic losses. They are considered an important predator in grain, sorghum, and cotton fields. They have also been found in corn, soybean, alfalfa, peppermint, and peanut fields. (Agnew, et al., 1985; Hagler, et al., 2004; Knutson and Gilstrap, 1989; McIver and Belnavis, 1986)
There are no known adverse effects of swift crab spiders on humans.
Swift crab spiders have no special conservation status.
Swift crab spiders have also be identified as Mecaphesa celer. (Bradley, 2012)
Angela Miner (author), Animal Diversity Web Staff, Leila Siciliano Martina (editor), Animal Diversity Web Staff.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
living in landscapes dominated by human agriculture.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
uses smells or other chemicals to communicate
in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
parental care is carried out by females
union of egg and spermatozoan
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.
An animal that eats mainly insects or spiders.
fertilization takes place within the female's body
A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
having more than one female as a mate at one time
breeding is confined to a particular season
offspring are all produced in a single group (litter, clutch, etc.), after which the parent usually dies. Semelparous organisms often only live through a single season/year (or other periodic change in conditions) but may live for many seasons. In both cases reproduction occurs as a single investment of energy in offspring, with no future chance for investment in reproduction.
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
an animal which has an organ capable of injecting a poisonous substance into a wound (for example, scorpions, jellyfish, and rattlesnakes).
uses sight to communicate
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