| Ips | |
|---|---|
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| Ips calligraphus | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Coleoptera |
| Suborder: | Polyphaga |
| Infraorder: | Cucujiformia |
| Family: | Curculionidae |
| Subfamily: | Scolytinae |
| Tribe: | Ipini |
| Genus: | Ips De Geer, 1775 |
| Species | |
See text | |
Ips is a genus ofbeetles in the familyCurculionidae, the trueweevils. They arebark beetles, members of the subfamily Scolytinae. Species are distributed throughout the Northern Hemisphere.[1] Some are known asintroduced species inAustralia andAfrica.[2] Many species arepests of foresttrees, especiallypines andspruces.[3] They are known commonly asengraver beetles,[4]ips engraver beetles,[5][6] andpine engravers.[7]
Beetles of this genus are cylindrical in shape, 3 to 6.5 millimeters long, and reddish to black in color. The back end of theelytra is concave, and there is a ridge of three to six large spines on either side of the depression. The number and shape of the spines help to distinguish the species from one another.[3] The genus is distinguished from other groups in the tribeIpini by the flat, oval shape of the clubs at the tips of theantennae and by details of the concavity in the elytra and of the malegenitalia.[8]
The oblong white eggs are up to a millimeter long. The grub-likelarvae are whitish with reddish heads and lack legs.[6]
These bark beetles live in and feed on thephloem in the inner layer ofbark on trees. They usually inhabit dead, dying, and stressed trees, including fallen trees, cut logs, andslash. They can be found in trees that are already damaged bydrought,lightning, human activity, or pest infestation.[6] They are specialists onconifers, attacking many species of pine (Pinus) and spruce (Picea).[3][4] Less often, they are found on hemlocks (Tsuga) and firs (Abies).[6]
MostIps, like most all beetles of the tribe Ipini, have apolygynous mating system withharems of females.[9] Typically, a male establishes a nuptial chamber in a log and produces anaggregation pheromone that attracts both males and females. The males dig additional chambers and each female joins one of the males, digging an extension onto his nuptial chamber where she deposits her eggs. A male may have a harem of up to eight females.[10] Exceptions areI. latidens andI. avulsus, which aremonogamous in nature.[9]
The aggregation pheromones usually contain two or more active attractant compounds, such asipsdienol,ipsenol, andcis-verbenol.[1][11]
The beetles are called engravers because of the long, grooved galleries they excavate in thesapwood.[7] As the female digs her branch off of the male's nuptial chamber, she deposits eggs in individual niches along the walls. When the larva emerges, it digs a tunnel off of its niche. The multibranchedengraved galleries that result are often Y-, H-, or I-shaped.[6]Ips galleries are clear and open, unlike those of some other bark beetles, which are filled with wood dust andfrass.[4][7]
The beetles grow and develop more quickly during the warmer seasons. In the summer,I. grandicollis andI. calligraphus can complete an entire life cycle in 25 days, and there can be up to eight generations per year.I. avulsus can complete a life cycle in just 18 days and have 10 generations per year.[6] Afterpupation, the new adult beetledisperses from its birthplace and can fly several miles to locate an appropriate host tree in which to breed.[6] Some speciesoverwinter in aggregations inside the galleries, while others seek shelter in the outer bark layers or theleaf litter.[3]
As native species, these beetles are a natural part of their environment, excavatingsnags and providing food for insectivores.[7]I. typographus is described as "an essential component of every spruce forestecosystem" as it digs through dead and dying wood tissue, helping to initiate the process ofdecomposition.[12] In an abundance of dead and dying trees, afterwindthrow events, for instance, the beetles take advantage of plentiful food and shelter resources and their populations increase drastically. If the resources then dwindle, the large populations move into stands of healthy trees and become a problematic infestation.[12] Their damage is usually not as severe as that of certain beetles in the genusDendroctonus, which sometimes share the habitat.[3][6]Ips outbreaks are less common and usually shorter in duration,[3] though severe outbreaks ofIps typographus in Europe in the 1990s inspired many new research studies of ips engravers.[12]
A living tree can be killed by the feeding activity of adults and larvae, which damages the phloem in such a way that the tree isgirdled. The beetles also introduce several species offungi which invade and infect the wood, blocking thexylem. The first sign of anIps infestation in a tree may be thediscoloration of the needles that occurs when fungi block the xylem and prevent water transport to the foliage.[6] Several species ofblue stain fungus can be vectored by the beetles, including those of the generaOphiostoma andCeratocystis.[12]
Other signs ofIps infestation include particles of wood dust accumulating on the bark, foliage, and nearby objects as a result of the beetles' tunneling activity. The wood dust can mix withresin that bleeds from the injury site, creating whitish or reddish pitch tubes,[6] but these are more common inDendroctonus infestations.[3]Woodpeckers spend time on infested trees, chipping off bark as they forage for the beetles.[4]
Insecticides are not effective for activeIps infestations. Instead they are used to prevent the beetles' spread to healthy trees, such as landscaping conifers, newly transplanted trees, and healthy stands adjacent to outbreaks. The beetles are attracted to freshly cut wood, so logs and slash are chipped, dried, or removed from vulnerable areas. Infested wood can be chipped, stripped of bark, orsolarized in plastic to kill the beetles.[4]
If the sounds of related but different species of beetles, such as western pine beetles and southern pine beetles (which both feed on pinyon but never live together), are played into a tree the beetles present will tear each other apart.[13]
There are 37 species in the genus.[14] In a 2001 revision it was divided into four subgenera.[8]
Species include:[8]
GenusPseudips contains three species transferred fromIps in 2000:P. concinnus,P. mexicanus, andP. orientalis.[17]
Media related toIps at Wikimedia CommonsAuthority control databases: National |
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