User:Eanisman/sandbox

... that Misumena vatia, the goldenrod crab spider, can change between white and yellow depending on the color of the flowers on which it lives?

... that Misumena vatia, the goldenrod crab spider, can change between white and yellow depending on the color of the flowers on which it lives?

Misumena vatia is a species of crab spider with holarctic distribution. In North America it is called the goldenrod crab spider or flower (crab) spider, because it is commonly found hunting in goldenrod sprays in the autumn. Young males in the early summer may be quite small and easily overlooked, but females can grow up to 10 mm (excluding legs); males reach 5 mm at most.

Description
These spiders may be yellow or white, depending on the flower in which they are hunting (active camouflage). Younger females especially, which may hunt on a variety of flowers such as daisies and sunflowers, may change color at will. However, the color-changing process is not instant and can require up to 25 days to complete. Older females require large amounts of relatively large prey to produce the best possible clutch of eggs. They are therefore, in North America, most commonly found in goldenrod (Solidago sp.), a bright yellow flower which attracts large numbers of insects, particularly in autumn. It is often very hard even for a searching human to recognize one of these spiders on a yellow flower. These spiders are sometimes called 'banana spiders' because of their striking yellow color. They are known to prey on insects such as bumblebees (bombus ternarius) and, in Central America, Trigona fulviventris (a stingless bee).

Physical Characteristics
This species has a wide, flat body that is short and crab-like. It can walk sideways in addition to being able to move forwards and backwards. Of its eight legs, the first two pairs are the largest. These sets of legs are usually held open, as the spider uses them to capture its prey. 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. Females are larger than males, and tend to fall between six and nine millimeters in length. Males, on the other hand, are only three to four millimeters long. Females have light complexions as they are either white or yellow with somewhat darker sides. They may have some markings on the abdomen that can be brown or red. Males are darker than females, with red or brown outer shells. They have a characteristic white spot in the middle that continues to the area around the eyes. Males specifically have two sets of red and white bands both dorsally and laterally.

Mesuma vatia also have two rows of eyes. The anterior row are equally spaced and curved backward while the second row 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 metatarsal bones 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. 

Population Structure, Speciation, and Phylogeny
Misumena vatia are found only in North America and Europe. Other species of crab spider, however, can be found all over the world.

The species prefers a temperate climate and generally inhabits forest biomes.

Habitat and Distribution
Misumena vatia are terrestrial spiders and can be found on many plants and flowers such as milkweed, trillium, white fleabane, white flower, and goldenrod.

Diet
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.

Misumena vatia are primarily dependent on vision to hunt, so they find and capture food during the day. Adult females will hunt, “in the upper stratum of the field vegetation, primarily on the flowers of ox-eye daisy (Chrysanthemum leucanthemum), red clover (Trifolium pratense) and buttercups (Ranunculus acris).” Adult males, in pursuit of potential mates, will search these areas for females. The spider can hunt bugs and insects larger than itself because it has the ability to use venom to immobilize its prey. Misumena vatia will wait, camouflaging itself on a flowering plant or on the ground, for prey to pass by, and then grab the prey with its forelegs. It is able to immobilize prey by injecting venom with its fangs. Unlike many spiders which wrap their prey in silk, Misumena vatia use their fangs to suck the liquid out of prey until satiated.

Though Misumena vatia are most often found hunting during the daytime, there is evidence that the spider will be driven to hunt nocturnally by an increase in nocturnal prey activity. This behavior occurs most commonly in response to increased night-time activity by moths in early September.

Non-Reproductive Cannibalism
Cannibalism is uncommon among Misumena vatia, however it has been observed in individuals in roughly 1% of broods. In these broods, cannibalism tended to occur among spiderlings. Cannibalistic individuals can be up to three times larger than those who are non-cannibalistic.

Excretion
Misumena vatia have the ability to retain their excretions for at least 50 days and will not excrete when confined to small spaces or near their hunting sites. Excretion may alert predators to the spider's whereabouts

Reproduction and Life Cycle
Sex ratios among Mesumena vatia vary from a primary sex ratio of 1.5 females to 1 male to a ratio of 2.5-5.1 females to 1 male by the time they reach adulthood. It is thought that since males must spend considerable time searching for females, they face danger from the environment. Males cannot mate multiple times in quick succession, but require a two day interval between matings.

Female Mesumena vatia prefer common milkweed (Asclepias syriaca) over spreading dogbane (Apocynum androsaemifolium), pasture rose (Rosa carolina), and chokecherry (Prunus virginiana) for nest construction. Females who lay eggs on milkweed have higher nesting success, which correlates with early survival of clutches.

In nature, Misumena vatia will produce a single brood. However, females are capable of producing another brood if artificially induced.

Mate Guarding
A minority of males will guard pre-reproductive females. About 10% of males will guard penultimate females as they molt into the adult stage. Almost all males who guard pre-reproductive females will mate with them after they have molted. Low levels of guarding are related to the female leaning sex ratio expressed by Misumena vatia. Males of this species tend to guard less frequently and exhibit less aggression than other closely related species, such as Misumenoides Formosipes, that do not have a female-biased sex ratio.

Life Cycle
In May and early June, males molt into adulthood, with the number of adult males peaking between June 5th to July 15th. Females do not molt into adults until mid to late june, with numbers of adult females peaking around June 25th. After males molt, their body mass does not increase, remaining at about 4mg however they do undergo body changes as they enter the adult stage. The front legs of males lengthen while the abdomen shrinks.

Mating
The much smaller males scamper from flower to flower in search of females, and are often seen missing one or more of their legs. This may be due either to near misses by predators such as birds or to fighting with other males.

When a male finds a female, he climbs over her head, over her opisthosoma and onto her underside, where he inserts his pedipalps to inseminate her.

The female then lays her eggs on plants from the Asclepias genus (milkweeds).

The young reach a size of about 5 mm by autumn and spend the winter on the ground. They molt for the last time in May of the next year.

When preparing to lay eggs, the pregnant female Misumena vatia will roll up the end of a leaf of her desired plant, usually a milkweed leaf. She will secure the leaf by spreading silk, and lay her eggs inside the nest she has created. The Misumena vatia tends to lay its eggs at night.

Because Misumena vatia employs camouflaging, it is able to focus more energy on growth and reproduction rather than finding food and escaping from predators. As in many Thomisidae species, there is a positive correlation between female weight and egg clutch size, or fecundity. Selection for larger female body size thus increases reproductive success.

Sexual Cannibalism
Like many other arachnids and insects, Misumena vatia may express sexual cannibalism, however it is not routinely practiced and is only considered moderately common. In cases of precopulatory sexual cannibalism, older males are more likely than younger males to be targets of attack and are more likely to suffer death or injury as a result of an attack from a female, especially during the latter half of the mating season. This could be a result of a decreased ability among older males to evade attack from females. Older males do not tend to display riskier mating behavior than younger males. The size of the male does not influence its likelihood of being cannibalized during copulation. Females increase cannibalistic attacks as the mating season progresses. More males tend to be cannibalized after mid July, which could be a result of male aging but is more likely a result of increased female aggression during this time.

Color change
These spiders change color by secreting a liquid yellow pigment into the outer cell layer of the body. On a white base, this pigment is transported into lower layers, so that inner glands, filled with white guanine, become visible. The color similarity between the spider and the flower is well matched with a white flower, in particular the Chaerophyllum temulum (the rough chervil), compared to a yellow flower based on the spectral reflectance functions. If the spider dwells longer on a white plant, the yellow pigment is often excreted. It will then take the spider much longer to change to yellow, because it will have to produce the yellow pigment first. The color change is induced by visual feedback; spiders with painted eyes were found to have lost this ability.

The color change from white to yellow takes between 10 and 25 days; the reverse about six days. The yellow pigments have been identified as kynurenine and 3-hydroxykynurenine.

Diet-Induced Color Change
Misumena vatia can also change color as a result of prey consumption. Once consumed, colorful prey can show through the thin, transparent epidermis of the abdomen, affecting opisthosomal coloration. Ingestion of red-eyed fruit flies will cause the abdomen to turn pink. Coloration changes caused by prey consumption will revert to normal white or yellow 4-6 days after ingestion. Color change intensity is positively correlated with the amount of colorful prey consumed. Color change intensity also decreases with the spider's age. These spiders have been observed to have pink, orange, yellow, brown, green, or white opisthosomas depending on the prey consumed.

Egg Guarding
Like many species, Misumena vatia will guard nests to protect vulnerable eggs from attack. Guarding the nest has been shown to increase the overall reproductive success of the spiders by protecting against predation from ichneumonid and dipteran egg predators. These spiders are usually observed guarding the nest by standing on its underside, the most vulnerable face of the nest. Most guarding spiders will remain by the nest until the young have begun to emerge from their eggs, with some variance in guarding times. A minority of spiders may abandon their nests before spiderlings have hatched, while some may remain until all young have hatched or longer. Misumena vatia usually die within a few days of young hatching.

Enemies
Parasitization by the ichneumonid wasp, Trychosis cyperia, an egg predator, is common. The wasp attacks the nest and feeds the eggs. One attack can destroy the nest completely. Misumena vatia experience strong selection to minimize attack from wasps, which is why egg guarding by the female is important for reproductive success. Wasps tend to feed on small egg masses guarded by small spiders, as small spiders cannot defend their nests as effectively. When defending the nest from an approaching predator, females will typically raise their front legs in a display otherwise observed when the spider is attacking prey.