Monochamus is a genus of longhorn beetles found throughout the world. They are commonly known as sawyer beetles or sawyers, as their larvae bore into dead or dying trees, especially conifersThe Free Dictionary (TFD) (2008): Genus Monochamus. Retrieved 23 March 2009. such as pines. They are the type genus of the Monochamini, a tribe in the huge long-horned beetle subfamily Lamiinae, but typically included in the Lamiini today.
If sawyer beetles infest freshly cut pine logs, they can cause a 30–40% loss in value due to the tunnels their larvae bore. It is important to process logs within a few weeks of cutting or store them in water to minimize damage. Douglas Allen, "Sawyer Beetles", New York Forest Owner, May 1994 Some species are known to transport phoretic Bursaphelenchus nematodes, including B. xylophilus which causes pine wilt disease.Kansas State University Extension Horticulture (KSU-EH) (2005): Pine Wilt . Version of 28 February 2005. Retrieved 23 March 2009.
Description Beetles in this genus are black or mottled gray in colour. Like other Lamiinae, the head is oriented vertically with ventral mouthparts. The scape (first antennal segment) has a circatrix, a carinate ring or scar-like area near the tip. Antennae of females are roughly as long as the body, while antennae of males are twice as long. The tarsal claws are divergent.Benzel, J. S. 2015. Screening aid: Pine sawyer beetles, Monochamus sutor (Linnaeus) and M. alternatus Hope. Identification Technology Program (ITP), USDA-APHIS-PPQ-S&T, Fort Collins, CO. 7 pp.
Life cycle Adults feed within the crowns of healthy trees. Adult females oviposit (lay eggs) in slits in the bark of dying or dead trees. Larvae hatch from eggs and develop in wood, passing through several instars. Next is a pupal stage. In spring, new adults emerge, starting the life cycle again.
Association with nematodes The pine wood nematode Bursaphalenchus xylophilous is transmitted by several Monochamus species, and its life cycle is tied with that of its vector.
When nematode-infested adult Monochamus feed on healthy trees, they create wounds that allow nematodes to enter. In a susceptible host tree, nematodes breed in the xylem and eventually kill the tree. In a resistant host, the nematodes die instead.
When nematode-infested adult Monochamus oviposit in dying or dead trees, the slits they make in the bark for their eggs also allow nematodes to enter. Nematodes reproduce and feed on wood cells or fungi. Eventually, new Monochamus adults emerge from pupae, and while these are still callow, nematodes enter them via the thoracic spiracles.
Associations with other organisms Bark beetles oviposit on trees at around the same time as Monochamus, and they transmit blue stain fungi. Bursaphalenchus nematodes feed on this fungi, and the combination of fungi and nematodes may help in overcoming host tree defences, creating a more suitable habitat for bark beetles and Monochamus. Additionally, Monochamus compete with bark beetles for resources, prey on them (intraguild predation) and use their semiochemicals as kairomones.
Some species of braconid wasps in the genus Atanycolus are parasitoids of Monochamus, along with other wood-boring beetles.
The black-backed woodpecker is a predator on larvae of wood-boring beetles, including Monochamus.
Taxonomy The genus is very large, and its boundaries have varied considerably over time, with many species placed in this genus that have long since been removed, and species placed in other genera that have been added, and there are at least 20 subgenera presently recognized by most authorities.Monochamus
Species
Monochamus abruptus Holzschuh, 2015 Monochamus accri (Dillon & Dillon, 1959) Monochamus adamitus Thomson, 1857 Monochamus affinis Breuning, 1938 Monochamus alboapicalis (Pic, 1934) Monochamus alboscutellaris Breuning, 1977 Monochamus alternatus Hope, 1842 – Japanese pine sawyer beetle Monochamus aparus (Jordan, 1903) Monochamus asiaticus (Hayashi, 1962) Monochamus asper Breuning, 1935 Monochamus atrocoeruleogriseus Gilmour, 1956 Monochamus balteatus Aurivillius, 1903 Monochamus basifossulatus Breuning, 1938 Monochamus basigranulatus Breuning, 1952 Monochamus basilewskyi Breuning, 1952 Monochamus benito (Dillon & Dillon, 1959) Monochamus bialbomaculatus Breuning, 1948 Monochamus bimaculatus Gahan, 1888 Monochamus binigricollis Breuning, 1965 Monochamus binigromaculatus Breuning, 1959 Monochamus blairi (Breuning, 1936) Monochamus bootangensis Breuning, 1947 Monochamus borchmanni Breuning, 1959 Monochamus buquetii (Thomson, 1858) [= tuberosus] Monochamus burgeoni Breuning, 1935 Monochamus camerunensis Aurivillius, 1903 Monochamus carolinensis (Olivier, 1792) – Carolina sawyer Monochamus clamator (LeConte, 1852) – spotted pine sawyer Monochamus conradti Breuning, 1961 Monochamus convexicollis Gressitt, 1942 Monochamus dayremi Breuning, 1935 Monochamus densepunctatus Breuning, 1980 Monochamus dentator (Fabricius, 1793) Monochamus desperatus Thomson, 1857 Monochamus diores (Dillon & Dillon, 1959) Monochamus dubius (Gahan, 1894) Monochamus fisheri Breuning, 1944 Monochamus flavosignatus Breuning, 1947 Monochamus flavovittatus Breuning, 1935 Monochamus foraminosus Holzschuh, 2015 Monochamus foveatus Breuning, 1961 Monochamus foveolatus Hintz, 1911 [= unicolor] Monochamus franzae (Dillon & Dillon, 1959) Monochamus galloprovincialis (Olivier, 1795) – black pine sawyer or timberman beetle Monochamus gardneri Breuning, 1938 Monochamus grandis Waterhouse, 1881 Monochamus granulipennis Breuning, 1949 Monochamus gravidus (Pascoe, 1858) Monochamus griseoplagiatus Thomson, 1858 [= ochraceomaculatus] Monochamus guerryi Pic, 1903 Monochamus guttulatus Gressitt, 1951 Monochamus impluviatus Motschulsky, 1859 Monochamus inexpectatus Breuning, 1935 Monochamus irrorator (Chevrolat, 1855) [= plumbeus, ruficornis] Monochamus itzingeri Breuning, 1935 Monochamus jordani Nonfried, 1894 Monochamus karlitzingeri Tavakilian & Jiroux, 2015 Monochamus kashitu (Dillon & Dillon, 1959) Monochamus kaszabi Heyrovský, 1955 Monochamus kinabaluensis Hüdepohl, 1996 Monochamus kivuensis Breuning, 1938 Monochamus laevis Jordan, 1903 Monochamus lamottei Lepesme & Breuning, 1952 Monochamus latefasciatus Breuning, 1944 Monochamus lepesmei Breuning, 1956 Monochamus lineolatus (Dillon & Dillon, 1959) Monochamus lunifer (Aurivillius, 1891) Monochamus luteodispersus Pic, 1927 Monochamus maculosus Haldeman, 1847 [= mutator] – spotted pine sawyer Monochamus marmorator Kirby in Richardson, 1837 – balsam fir sawyer Monochamus maruokai Hayashi, 1962 Monochamus masaoi Kusama & Takakuwa, 1984 Monochamus mausoni Breuning, 1950 Monochamus mbai Lepesme & Breuning, 1953 Monochamus mediomaculatus Breuning, 1935 Monochamus melaleucus Jordan, 1903 Monochamus mexicanus (Breuning, 1950) Monochamus millegranus Bates, 1891 Monochamus murinus (Gahan, 1888) Monochamus nigrobasimaculatus Breuning, 1981 Monochamus nigromaculatus Gressitt, 1942 Monochamus nigromaculicollis Breuning, 1974 Monochamus nigroplagiatus Breuning, 1935 Monochamus nigrovittatus Breuning, 1938 Monochamus nitens Bates, 1884 Monochamus notatus (Drury, 1773) – northeastern sawyer or notable sawyerJohn Acorn and Ian Sheldon. Bugs of Ontario. Edmonton, AB:Lone Pine Publ., 2003. Monochamus obtusus Casey, 1891 – obtuse sawyer Monochamus ochreomarmoratus Breuning, 1960 Monochamus ochreopunctatus Breuning, 1980 Monochamus ochreosparsus Breuning, 1959 Monochamus ochreosticticus Breuning, 1938 Monochamus olivaceus Breuning, 1935 Monochamus omias Jordan, 1903 [= africanus] Monochamus pentagonus Báguena, 1952 Monochamus pheretes (Dillon & Dillon, 1961) Monochamus philomenus (Dillon & Dillon, 1959) Monochamus pictor (Bates, 1884) Monochamus principis Breuning, 1956 Monochamus pseudotuberosus Breuning, 1936 Monochamus quadriplagiatus Breuning, 1935 Monochamus rectus Holzschuh, 2015 Monochamus regularis (Aurivillius, 1924) Monochamus reticulatus (Dillon & Dillon, 1959) Monochamus rhodesianus Gilmour, 1956 Monochamus roveroi Teocchi, Sudre & Jiroux, 2015 Monochamus rubiginosus Teocchi, Sudre & Jiroux, 2014 Monochamus ruspator (Fabricius, 1781) Monochamus saltuarius Gebler, 1830 – Sakhalin pine beetle Monochamus sargi (Bates, 1885) Monochamus sartor (Fabricius, 1787) [incl. subspecies urussovii] – black fir sawyer Monochamus scabiosus (Quedenfeldt, 1882) [= centralis] Monochamus scutellatus (Say, 1824) – white-spotted sawyer or spruce sawyerSpruce Sawyer, Insects of Alberta Monochamus semicirculus Báguena, 1952 Monochamus semigranulatus (Pic, 1925) Monochamus serratus (Gahan, 1906) Monochamus shembaganurensis Breuning, 1979 Monochamus similis Breuning, 1938 Monochamus sparsutus Fairmaire, 1889 Monochamus spectabilis (Perroud, 1855) Monochamus strandi Breuning, 1939 Monochamus stuhlmanni Kolbe, 1894 Monochamus subconvexicollis Breuning, 1967 Monochamus subcribrosus Breuning, 1950 Monochamus subfasciatus (Bates, 1873) [= fascioguttatus] Monochamus subgranulipennis Breuning, 1974 Monochamus subtriangularis Breuning, 1971 Monochamus sutor (Linnaeus, 1758) – pine sawyer Monochamus taiheizanensis Mitono, 1943 Monochamus talianus Pic, 1912 Monochamus thoas (Dillon & Dillon, 1961) Monochamus thomsoni (Chevrolat, 1855) Monochamus titillator (Fabricius, 1775) – southern pine sawyer Monochamus tonkinensis Breuning, 1935 Monochamus transvaaliensis Gilmour, 1956 Monochamus triangularis Breuning, 1935 Monochamus tridentatus Chevrolat, 1833 Monochamus tropicalis (Dillon & Dillon, 1961) Monochamus vagus (Gahan, 1888) Monochamus variegatus (Aurivillius, 1925) Monochamus verticalis (Fairmaire, 1901) Monochamus villiersi Breuning, 1960 Monochamus x-fulvum Bates, 1884
Gallery
Three pictures of two separate sawyers found in a planting of Scots pines in Kansas.
References
External links
"Insect vectors of the pinewood nematode: a review of the biology and ecology of Monochamus species"