Tetranychus urticae
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| iTetranychus urticae | ||||||||||||||
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 Tetranychus urticae growing on Capsicum annuum
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| Tetranychus urticae C.L. Koch, 1836 |
Tetranychus urticae (an animal with over 60 common names, including red spider mite and two-spotted spider mite) is one of many species of plant-feeding mites found in dry environments, generally considered a pest.
T. urticae belongs to the arachnid class (order Acari) and is related to ticks, and, more distantly, to spiders and scorpions. Spider mites are extremely small, barely visible with the naked eye as reddish or greenish spots on leaves and stems; the adults measure about 0.5 mm. The most notable spider mite is the red spider mite, which can be seen in greenhouses and tropical and temperate zones spinning a fine web on and under leaves. The red spider mite is extremely polyphagous; it can feed on hundreds of plants, including most vegetables and food crops (peppers, tomatoes, potatoes, beans, corn, strawberries) and ornamentals: roses, etc. It lays its eggs on the leaves, and it poses a threat to host plants by sucking cell contents from the leaves cell by cell, leaving very tiny, pale spots or scars where the green epidermal cells have been destroyed. Although the individual lesions are very small, commensurate with the small size of the mites, the frequently-observed attack of hundreds or thousands of spider mites can cause thousands of lesions and thus can significantly reduce the photosynthetic capability of plants, greatly reducing their production of nutrients, sometimes even killing the plants. Although this way of feeding could spread plant viruses, this is considered of secondary importance.
Spider mites are less than 1 mm in size and vary in colors. They lay small, spherical, initially transparent eggs and many species spin webbing (as shown in the picture) to help protect the colony from predators; they get the 'spider' part of their common name from this webbing. Hot, dry conditions are often associated with population buildup of spider mites. The red spider mite is the easiest to spot.
During the summer, T. urticae has a greenish brown appearance with two darker spots, but as winter approaches it gains a strong red color. Some populations are pemanently greenish or reddish, and these are considered different species of Tetranychus by some authorities.
Spider mites, like hymenopterans and some homopterous insects, are arrhenotochous: females are diploid and males are haploid. When mated, females somehow avoid the fecundation of some eggs to produce males. Fertilized eggs produce diploid females. Unmated, unfertilized females still lay eggs, that originate exclusively haploid males.
Its natural predator, (Phytoseiulus persimilis), commonly used as a biological control method, is one of many predaceous mites which prey exclusively or mainly on spider mites.
[edit] External links
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Wikimedia Commons has media related to: |
- MEMS Movie Gallery, Spider mite used for demonstrating MEMS technology
- How Red Mites affect the Poultry Industry - Article by the Poultry Youth Association
