Misumena vatia

Goldenrod Crab Spider
Female goldenrod crab spider capturing a wasp
Male is much smaller than female
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Arachnida
Order:	Araneae
Family:	Thomisidae
Genus:	Misumena
Species:	M. vatia
Binomial name
Misumena vatia (Clerck, 1757)
Synonyms
Araneus vatius Aranea calycina Aranea 4-lineata Aranea kleinii Aranea osbekii Aranea hasselquistii Aranea uddmanni Aranea scorpiformis Aranea virginea Aranea citrea Aranea citrina Aranea sulphereoglobosa Aranea sulphurea Aranea quinquepuncata Aranea albonigricans Aranea calicina Aranea cretata Misumena citrea Thomisus citreus Thomisus calycinus Thomisus dauci Thomisus pratensis Thomisus spinipes Thomisus scorpiformis Thomisus quadrilineatus Thomisus viridis Thomisus phrygiatus Thomisus devius Thomisus fartus Thomisus vatius Pachyptile devia Thomisus cucurbitinus Misumena oblonga Misumena calycina Misumena occidentalis Misumenops vatia

Misumena vatia is a species of crab spider with holarctic distribution. In North America, where it is the largest and best-known flower spider, it is called the goldenrod crab spider or flower (crab) spider,^[1] because it is commonly found hunting in goldenrod sprays in the autumn.

Golden rod spider, imitating a flower

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. Especially younger females, which may hunt on a variety of flowers such as daisies and sunflowers, may change color "at will". 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, especially 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.

Reproduction

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 onto her underside, where he inserts his pedipalps to inseminate her.

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.

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. ^[2] Selection for larger female body size thus increases reproductive success. ^[3]

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, compared to a yellow flower based on the spectral reflectance functions. ^[4] 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^[5]

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  Female on Achillea millefolium flowers

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  Female

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  On a daylily

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  With small prey

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  Preying on Trigona fulviventris

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  Yellow Female on Blue Dick, Dichelostemma capitatum

See also

• Active camouflage
• Camouflage
• Crab spiders

References

1. Acorn, John and Sheldon, Ian. Bugs of Ontario, Edmonton: Lone Pine Publishing, 2003
2. Fritz, Robert S., and Douglass H. Morse. "Reproductive success and foraging of the crab spider Misumena vatia." Oecologia 65, no. 2 (1985): 194–200.
3. Head, Graham. "Selection on Fecundity and Variation in the Degree of Sexual Size Dimorphism Among Spider Species (Class Araneae)." Evolution 49, no. 4 (1995):776.
4. Chittka, Lars. "Camouflage of predatory crab spiders on flowers and the colour perception of bees (Aranida: Thomisidae/Hymenoptera: Apidae)." Entomologia Generalis 25, no. 3 (2001): 181-187.
5. Oxford, G.S. & Gillespie, R.G. (1998). Evolution and Ecology of Spider Coloration. Annual Review of Entomology 43:619-643. doi:10.1146/annurev.ento.43.1.619 PMID 15012400

External links

• Pictures of M. vatia, BugGuide
• Pictures of M. vatia (free for noncommercial use) (another one)
• Goldenrod crab spider (female with male) Nature Pictures