- The unrelated sawyer beetles (Monochamus) and some other wood-boring beetle taxa (especially Cucujoidea
Cucujoidea is a superfamily of beetles. They include many fungus beetles, as well as ladybugs. Also included are a diversity of lineages of "bark beetles" unrelated to the "true" bark beetles , which are weevils...
) are sometimes called "bark beetles" too.
A
bark beetle is one of approximately 220
generaGenera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI and Texas Instruments...
with 6,000
speciesIn biology, a species is:* a taxonomic rank or* a unit at that rank ....
of beetles in the subfamily
Scolytinae. Traditionally this was considered a distinct
familyIn biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus...
Scolytidae, but nowadays it is understood that bark beetles are in fact very specialized members of the "true
weevilA weevil is any beetle from the Curculionoidea superfamily. They are usually small, less than 6 mm , and herbivorous. There are over 60,000 species in several families, mostly in the family Curculionidae...
" family (
CurculionidaeCurculionidae, also called snout beetles or curculios , is the family of the "true" weevils...
).
- The unrelated sawyer beetles (Monochamus) and some other wood-boring beetle taxa (especially Cucujoidea
Cucujoidea is a superfamily of beetles. They include many fungus beetles, as well as ladybugs. Also included are a diversity of lineages of "bark beetles" unrelated to the "true" bark beetles , which are weevils...
) are sometimes called "bark beetles" too.
A
bark beetle is one of approximately 220
generaGenera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI and Texas Instruments...
with 6,000
speciesIn biology, a species is:* a taxonomic rank or* a unit at that rank ....
of beetles in the subfamily
Scolytinae. Traditionally this was considered a distinct
familyIn biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus...
Scolytidae, but nowadays it is understood that bark beetles are in fact very specialized members of the "true
weevilA weevil is any beetle from the Curculionoidea superfamily. They are usually small, less than 6 mm , and herbivorous. There are over 60,000 species in several families, mostly in the family Curculionidae...
" family (
CurculionidaeCurculionidae, also called snout beetles or curculios , is the family of the "true" weevils...
). Well-known species are members of the
type genusIn biology, the phrase type genus is used differently depending on the nomenclatural Code that applies:* In zoological nomenclature, a type genus is "The nominal genus that is the name-bearing type of a nominal family-group taxon."...
Scolytus - namely the European elm bark beetle
S. multistriatus and the large elm bark beetle
S. scolytus, which like the American elm bark beetle
Hylurgopinus rufipes transmit
Dutch elm diseaseDutch elm disease is a fungal disease of elm trees which is spread by the elm bark beetle. Although believed to be originally native to Asia, the disease has been accidentally introduced into America and Europe, where it has devastated native populations of elms which had not had the opportunity...
fungi (
Ophiostoma). Another well-known species of Europe is the
Ips typographus.
Ecology
Bark beetles are so-named because the best known species reproduce in the inner bark (living and dead phloem tissues) of
treeA tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...
s. Some species, such as the
mountain pine beetleThe mountain pine beetle , Dendroctonus ponderosae, is a species of bark beetle native to the forests of western North America from Mexico to central British Columbia...
(
Dendroctonus ponderosae), attack and kill live trees. Most, however, live in dead, weakened, 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. However, several outbreak-prone species are known as notorious pests.
Bark beetles often attack trees that are already weakened by
diseaseA disease or medical condition isan abnormal condition of an organism that impairs bodily functions, associated with specific symptoms and signs...
,
droughtA drought is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average precipitation. It can have a substantial impact on the ecosystem and agriculture of the affected region...
,
smogSmog is a kind of air pollution; the word "smog" is a portmanteau of smoke and fog. Classic smog results from large amounts of coal burning in an area caused by a mixture of smoke and sulfur dioxide...
, conspecific beetles or physical damage. Healthy trees may put up defenses by producing
resinResin is a hydrocarbon secretion of many plants, particularly coniferous trees. It is valued for its chemical constituents and uses, such as varnishes and adhesives, as an important source of raw materials for organic synthesis, or for incense and perfume. Fossilized resins are the source of amber...
or
latexLatex refers generically to a stable dispersion of polymer microparticles in an aqueous medium. Latexes may be natural or synthetic. Latex as found in nature is a milky sap-like fluid within many plants that coagulates on exposure to air. It is a complex emulsion in which proteins, alkaloids,...
, which may contain a number of insecticidal and fungicidal compounds that can kill or injure attacking insects, or simply immobilize and suffocate them with the sticky fluid. Under outbreak conditions, the sheer number of beetles can however overwhelm the tree's defences, and the results can be disastrous for the lumber industry.
In some places, like Šumava National Park in the
Czech RepublicThe Czech Republic is a country in Central Europe that is sometimes considered to be Eastern European. The country borders Poland to the northeast, Germany to the west and northwest, Austria to the south and Slovakia to the east. The capital and largest city is Prague...
's
Bohemian forestThe Bohemian Forest is a low mountain range in Central Europe. Geographically, the mountains extend from South Bohemia in the Czech Republic to Austria and Bavaria in Germany. They create a natural border between the Czech Republic on one side and Germany and Austria on the other...
, problems with bark beetles have become a heated issue with a political dimension. On one side, some experts (usually with a background in
environmental scienceEnvironmental science is an interdisciplinary field that involves both the physical sciences and the social sciences . It encompasses the surrounding conditions that affect man and other organisms...
s) demanded that nature be left alone and that natural processes be allowed to take their course, even if it meant that the bark beetle would destroy most of the forest. On the other side, other experts (usually with a background in
forest managementForest management is the branch of forestry concerned with the overall administrative, economic, legal, and social aspects and with the essentially scientific and technical aspects, especially silviculture, protection, and forest regulation...
) demanded intervention. During the 1990s and 1980s, the Šumava park management mostly favoured intervention. Many outside groups became involved in the dispute, such as the lumber industry (which supported intervention because of possible profit to be made), or some local politicians, afraid that tourists would turn back from a forest decayed after a beetle invasion. The anti-intervention side got support from entomologists from the
Czech Academy of SciencesThe Academy of Sciences of the Czech Republic was established in 1992 by the Czech National Council as a Czech successor of the former Czechoslovak Academy of Sciences. The Academy is the leading non-university public research institution in the Czech Republic...
and from several
environmental organizationAn environmental organization is an organization that seeks to protect, analyze or monitor the environment against misuse or degradation or lobby for these goals....
s, such as
Friends of the EarthFriends of the Earth International is an international network of environmental organizations in 77 countries.Friends of the Earth International are the world's largest grassroots environmental network and they campaign on today's most urgent environmental and social issues...
. At the height of the dispute, there were cases where activists literally defended the trees with their bodies, tying themselves to the trunks, and the dispute was widely covered in the main Czech daily newspapers and on TV news.
Some bark beetles form a symbiotic relationship with certain
OphiostomatalesThe Ophiostomatales are an order of fungi within the class Sordariomycetes....
fungi, and are named "
ambrosia beetleAmbrosia beetles are beetles of the weevil subfamilies Scolytinae and Platypodinae , which live in nutritional symbiosis with ambrosia fungi and probably with bacteria...
s" after these "ambrosia fungi". The ambrosia beetles (such as
Trypodendron) feed on fungal "gardens" and are one of only three insect groups known to farm fungi. The other two groups are ants and
termiteThe termites are a group of eusocial insects usually classified at the taxonomic rank of order Isoptera . Along with ants and some bees and wasps which are all placed in the separate order Hymenoptera, termites divide labour among gender lines, produce overlapping generations and take care of...
s, neither of which is particularly closely related to beetles. Courtesy of the fungus, ambrosia bark beetles are 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 work of overcoming the plant's chemical defenses. The beetles carry the fungal spores in special structures called
mycangiaThe term mycangium is used in biology for special structures on the body of an animal that are adapted for the transport of symbiotic fungi . This is seen in many xylophagous insects , which apparently derive much of their nutrition from the digestion of various fungi that are growing amidst the...
, and inoculate the trees as they attack them.
Like many other insects, Scolytinae will emit pheromones to attract conspecifics which are thus drawn to trees already beset with bark beetles. This can result in heavy infestation and eventually death of the tree. Many are also attracted to ethanol, one of the by-products of decaying trees.
External links
on the
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/
IFASThe University of Florida’s Institute of Food and Agricultural Sciences is a federal-state-county partnership dedicated to developing knowledge in agriculture, human and natural resources, and the life sciences, and enhancing and sustaining the quality of human life by making that information...
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