Misumena vatia is a species of crab spider found in Europe and North America. In North America, it is called the goldenrod crab spider or flower (crab) spider,Acorn, John and Sheldon, Ian. (2003). Bugs of Ontario Edmonton: Lone Pine Publishing as it is commonly found hunting in goldenrod sprays and milkweed plants. They are called crab spiders because of their unusual ability to walk sideways as well as forwards and backwards. Both males and females of this species progress through several molts before reaching their adult sizes, though females must molt more to reach their larger size. Females can grow up to while males are quite small, reaching at most. Misumena vatia are usually yellow or white or a pattern of these two colors. They may also present with pale green or pink instead of yellow, again, in a pattern with white. They have the ability to change between these colors based on their surroundings through the molting process. They have a complex visual system, with eight eyes, that they rely on for prey capture and for their color-changing abilities. Sometimes, if Misumena vatia consumes colored prey, the spider itself will take on that color.
Misumena vatia feed on common insects, often consuming prey much larger than themselves. They use venom to immobilize their prey, though they are harmless to humans. They face threats due to parasites and larger insects. For Misumena vatia, survival depends on the choice of hunting site. The spiders closely monitor multiple sites to see if others nearby are frequented by greater numbers of potential prey. The primary sex ratio is biased toward females. Females are stationary and choose a flower to settle on, while males cover great distances searching for mates. Females do not emit pheromones; rather, they leave "draglines" of silk behind them as they move, which males follow. Females live longer than males, on average. After mating, females guard their nests until the young have hatched, after which they die.
Taxonomy and phylogeny The species Misumena vatia was first described by Swedish arachnologist and entomologist Carl Alexander Clerck in his book Aranei Svecici. Misumena vatia belongs to the family Thomisidae, or spiders known as crab spiders. The family includes more than 2,000 species, which are found all over the world. The genus Misumena includes many other species which are found worldwide. Misumena vatia falls into the Thomisus clade. Other clades in the family Thomisidae include the Borboropactus clade, the Epidius clade, and the Stephanopis clade.
Similar species Close relatives include Mecaphesa asperata, which is also found in North America, as well as Central America and the Caribbean. It is similar in size and shape but is light-gray to brown with pink stripes on the abdomen and cephalothorax. It is also coated with hairs that are short and stiff.
Similar species of the Misumenoides and Misumenops genera tend to be found south of Misumena vatia’s home range, but some species, such as Misumenoides formosipes, are found in North America as well. Philodromidae is a closely related family of wandering spiders. These spiders differ from those in the family Thomisidae in that their front legs are of a similar length as their back legs. Thus, their hunting style is quite different.
Description
This species has a wide, flat body that is short and crab-like. It can walk sideways in addition to being able to move forward and backward. Of its eight legs, the first two pairs are the longest. These sets of legs are usually held open, as the spider uses them to capture its prey. Misumena vatia is harmless to humans, as its fangs are not powerful enough to penetrate human skin and its venom is too weak to harm larger animals.
Color These spiders may be yellow or white. This ultimately depends on the flower on which they are hunting (active camouflage). Younger females especially, which may hunt on a variety of flowers such as daisies and sunflowers, have a strong tendency to adapt to the color of the surrounding flower. However, the color-changing process is not instant and can require up to 25 days to complete. Older females need large amounts of relatively large prey to produce the best possible clutch of eggs. In North America, they are most commonly found in goldenrods, bright yellow flowers which attract large numbers of insects, particularly in autumn. It is often very hard even for a searching human to spot this spider on a yellow flower. These spiders are sometimes called 'banana spiders' because of their striking yellow color.
Females have light complexions, either white or yellow with darker sides. They may have some markings on the abdomen that can be brown or red. These markings are genetically determined and not affected by a background color change. Males are darker than females, with red or brown outer shells. They have a characteristic white spot in the middle that continues through the area around the eyes. Males specifically have two sets of red and white bands both dorsally and laterally. Similar species of the crab spiders appear in a variety of colors such as those of the genus Diaea, which can be lime green, or some species of Xysticus and Coriarchne which are brown.
Color change
These spiders change color based on visual cues. The color-change is most obvious on females of this species. The ability of males and juveniles to change color has not been documented. Two other known spiders with this color change ability include Thomisus onustus and Thomisus spectabilis. Depending on the color of flower they see around them, they can secrete a liquid yellow pigment into the body's outer cell layer. The baseline color of the spider is white. In its white state, the yellow pigment is sequestered beneath the outer cell layer so that inner glands which are filled with white guanine are visible. They are able to match with greater accuracy to white flowers, such as Chaerophyllum temulum (the rough chervil) in particular, compared to yellow flowers based on the spectral reflectance functions. While the spider is residing on a white plant, it tends to excrete the yellow pigment instead of storing it in its glands. In order to change back to yellow, the spider must first produce enough of the yellow pigment. For this reason it takes these spiders much longer to turn from white to yellow than it does for them to go from yellow to white. The color change from white to yellow can take between 10 and 25 days while the opposite color change takes only about six days. The yellow pigments are kynurenine and 3-hydroxykynurenine. Color changes are induced by visual cues and spiders with impaired vision lose this ability.
Notably, spiders of this species sometimes choose to hunt on flowers that, to the human eye, they do not appear to match in color. For instance, they can be found hunting on the pink petals of the pasture rose (Rosa carolina). The spider appears white, or changes to white, causing it to stand out to human observers. Arthropods, on the other hand, serve as both predators and prey to Misumena vatia, and have photoreceptors that allow them to see ultraviolet, blue, and green light but oftentimes lack red receptors altogether. As a result, Misumena vatia is camouflaged, appearing dark on a dark background.
Sexual dimorphism Misumena vatia is highly sexually dimorphic. Females are larger than males and tend to fall between in length. Males, on the other hand, are only long. The female's legs are white or yellow, while the male's first and second legs are brown or red and the third and fourth are yellow. Additionally, in concurrence with the male’s smaller size, the male Misumena vatia molts two fewer times than the female.
Other physical characteristics Misumena vatia has two rows of eyes. Those in the anterior row are equally spaced and curved backward while those in the second row vary in appearance from animal to animal, and can be curved more or less than the first. The area around the eyes is narrower in the front than the back. The spider's hair is erect and can be either filiform or rod-shaped. The legs do not have spines, except under the tibia and metatarsus of the first two sets of legs. The appearance of the clypeus and the structure of the cephalothorax can be used to distinguish the genus Misumena within its subfamily.
Habitat and distribution
Misumena vatia is found only in North America and Europe. Other species of crab spiders, however, can be found all over the world. The species prefers a temperate climate and generally inhabits forest biomes. Misumena vatia is terrestrial and can be found on several plants and flowers such as milkweed and goldenrod in North America, as well as trillium, white fleabane (Erigeron strigosus), ox-eye daisy (Chrysanthemum leucanthemum), red clover (Trifolium pratense) and buttercups (Ranunculus acris)."
Home range Females of this species do not travel more than a few yards (meters) from their feeding location. They are attracted by the fragrance of flowers, though other visual and tactile clues also help them choose a territory. Their survival depends on their ability to choose a small area home to flowering plants which will attract prey. Males are highly motile and may disperse great distances as they search for mates. Additionally, spiderlings may travel great distances by ballooning, if they find the area around their nest to be lacking in resources. However, this is risky as there is no guarantee that the search for a new territory will be successful.
Patch choice Misumena vatia hunts large prey with a low rate of success. Hunting success rate is highly dependent upon the spider's choice of hunting site. Before they lay their eggs, females are heavy and slow, which necessitates that they choose a hunting site on which to stay. When hunting on their preferred plant of milkweed, they monitor nearby umbels to see if another site would be more profitable. Over the course of a few hours, Misumena vatia may recognize and move to another nearby hunting site. Most often, they move to flowers that produce more nectar and attract more prey, however occasionally some intentionally and consistently pick less profitable sites to hunt on. Thus, the population is dimorphic in terms of patch choice behavior. The reason a minority might choose poorer hunting sites on purpose remains unknown.
Diet Hunting patterns
Crab spiders are carnivorous, feeding on invertebrate insects such as flies, bees, butterflies, grasshoppers, dragonflies, and hoverflies. Bumblebees (Bombus appositus) provide the spider with the most biomass, but small syrphid flies (Toxomerus marginatus) are the prey captured most frequently. Other frequently captured prey include honeybees (Apis mellifera) and moths. Immature Misumena vatia commonly feed on smaller-sized prey such as thrips, aphids in the family Aphididae, and dance flies in the family Empididae. They may also use nectar and pollen as food sources when prey is scarce.
Misumena vatia primarily depends on its vision to hunt, so it typically finds and captures food during the day. They are commonly found on the upper strata of field vegetation, where females do their hunting, and males look for mates.
The spider can hunt prey larger than itself because of its paralyzing venom. Misumena vatia waits camouflaged, usually on flowering plants, and then grabs prey to inject its venom. Unlike many spiders which wrap their prey in silk, Misumena vatia relies entirely on its venom to immobilize its meals. It then uses its fangs to inject the prey with digestive enzymes before sucking out liquidated insides. This is a form of external digestion. As a result, prey size is not a limiting factor for consumption.