Bark beetle
From Freepedia
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| Image:Dendroctonus ponderosae.jpg Adult mountain pine beetle Dendroctonus ponderosae | ||||||||||||||
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A bark beetle is one of approximately 220 genera with 6,000 species of beetles in the subfamily Scolytinae in the weevil family Curculionidae (traditionally the bark beetles were placed in their own family Scolytidae).
They are known for their ability to bore into the cambium layer of trees to lay eggs and reproduce. Some species, such as the mountain pine beetle (Dendroctonus ponderosae), attack and kill live trees. Most however, live in dead or dying hosts. Bark beetles are ecologically and economically significant. Even outbreak species can help to renew the forest by killing old trees. Other species aid in the decomposition of dead wood.
Bark beetles often attack trees that are already weakened by disease, drought, smog, and physical damage. Healthy trees may put up defenses by producing resin or latex, which may contain a number of insecticidal and fungicidal compounds that can kill or injure attacking insects, or simply immobilise and suffocate them with the sticky fluid. Under outbreak conditions, the sheer number of beetles can however overwhelm the tree's defences.
Some bark beetles form a simbiotic relationship with fungi, and thus are named "Ambrosia beetles" after the fungus. The ambrosia beetles (such as Trypodendron spp.) feed on fungal "gardens" and are one of only three insect groups known to farm fungi. The other two groups are ants (Hymenoptera: Formiciade) and termintes (Isoptera). Ambrosia bark beetles are thus able to indirectly feed from many more species of trees than their evolutionary relatives that do not feed on fungi, by having the fungi do the dirty work of surpassing the plant's defenses.
Beetles will emit pheromones to attract other beetles, which are drawn to target trees and may result in heavy infestation and eventually death of the tree. Many are also atracted to ethanol, one of the by-products of decaying trees.
