''Scolytus jacobsoni'' is an elm bark beetle occurring in forests of mixed broad-leaves with elm trees in Asia. In southeastern Russia, during years of outbreaks ''S. jacobsoni'' often attacks healthy trees along forest edges or standing alone along roads and in fields and gardens, making it an important pest for elm trees there. Reported hosts include '' Ulmus davidiana'', ''

Ulmus japonica ''Ulmus davidiana'' var. ''japonica'', the Japanese elm, is one of the larger and more graceful Asiatic elms, endemic to much of continental northeast Asia and Japan, where it grows in swamp forest on young alluvial soils, although much of this ...

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Ulmus laciniata ''Ulmus laciniata'' (Trautv.) Mayr, known variously as the Manchurian, cut-leaf, or lobed elm, is a deciduous tree native to the humid ravine forests of Japan, Korea, northern China, eastern Siberia and Sakhalin, growing alongside ''Cercidiphyllu ...

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Ulmus propinqua ''Ulmus davidiana'' var. ''japonica'', the Japanese elm, is one of the larger and more graceful Asiatic elms, endemic to much of continental northeast Asia and Japan, where it grows in swamp forest on young alluvial soils, although much of this ...

'', ''

Carpinus betulus Hornbeams are hardwood trees in the plant genus ''Carpinus'' in the family Betulaceae. Its species occur across much of the temperateness, temperate regions of the Northern Hemisphere. Common names The common English name ''hornbeam'' derives ...

'', and ''

Pyrus ussuriensis ''Pyrus ussuriensis'', also known as the Ussurian pear, Harbin pear, and Manchurian pear, is a species of flowering plant in the family Rosaceae. It is native to Korea, Japan, China, and the Ussuri River area of far eastern Russia. It has flo ...

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Description

Body length is 3–5 mm long. The general color is dark-brown and shining, with lighter legs, elytra and antennae. The forehead of males is depressed and red hair covers its edges, which are curled toward the middle of the forehead. Female forehead is convex, bearing a medium longitudinal groove. Longitudinal wrinkle near the mouth and vertex punctured in both sexes. The

pronotum The prothorax is the foremost of the three segments in the thorax of an insect, and bears the first pair of legs. Its principal sclerites (exoskeletal plates) are the pronotum (dorsal), the prosternum (ventral), and the propleuron (lateral) on e ...

is somewhat longer than wide (7:6 ratio). It is covered with coarse punctures that are larger at the edges, particularly at its anterior. The length of the elytra is almost equal to their combined width. The elytra have longitudinal grooves made of large round punctures. The spaces between these grooves contain rows of smaller punctures, which are irregular on the first two inter-groove spaces, but form regular single lines on the others. The

abdomen The abdomen (colloquially called the gut, belly, tummy, midriff, tucky, or stomach) is the front part of the torso between the thorax (chest) and pelvis in humans and in other vertebrates. The area occupied by the abdomen is called the abdominal ...

is covered with short reddish hairs, which are denser on the first two and the last segments. The abdomen of males is concave toward the rear, with a steep depression on the second abdominal

sternite The sternum (: sterna) is the ventral portion of a segment of an arthropod thorax or abdomen. In insects, the sterna are usually single, large sclerites, and external. However, they can sometimes be divided in two or more, in which case the su ...

, and bearing a horizontally extended finger-shaped tubercle on the middle of the posterior edge of the second abdominal sternite. This structure distinguishes it from other Russian ''

Scolytus ''Scolytus'' is a genus of bark beetles (subfamily Scolytinae). It includes several species notorious for destroying trees in the forests. The Dutch elm disease is spread in North America by two species : the native elm bark beetle, ''Hylurgopin ...

'' species. Males also have bumps on the 3rd and 4th abdominal sternites, which females lack.

Life cycle

The usual flight period is June–July in southeastern Russia. The female bores a vertical egg gallery (5–7 cm in length and up to 2.5 mm of diameter) below the bark of the trunk or thick branches of declining elms, either standing or fallen, including elms burned by grass fires, and also on healthy elms when beetle population is high or if the elms stand a short while away from the forest. Eggs are laid on the sides of this gallery on the inner surface of the bark. Long galleries contain about a hundred eggs. Upon hatching, larvae bore their own galleries perpendicularly from the egg galleries, close to one another, often touching adjacent larval galleries, but rarely intersecting. Larvae pupate in mid–July. Adults emerge in late July and early August. Soon after emerging, adults feed on thin young branches of elms, chew the thin bark and part of the sapwood, thus making grooves that run along or around these branches. There is usually a single generation per year. Sometimes there is a second generation, which flies in July–August, and lay eggs in mid–August. Their larvae develop in September, and reach near full larval maturity prior to the winter. Larvae overwinter. Several species of

Chalcidoidea Chalcid wasps (, , for their metallic colour) are insects within the superfamily Chalcidoidea, part of the order Hymenoptera. The superfamily contains some 22,500 known species, and an estimated total diversity of more than 500,000 species, m ...

parasitoid In evolutionary ecology, a parasitoid is an organism that lives in close association with its host (biology), host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionarily stable str ...

s use ''S. jacobsoni'' larvae as their host.

Distribution

This species has been reported from southeastern Russia ( Primorsky Krai province and

Sakhalin island Sakhalin ( rus, Сахали́н, p=səxɐˈlʲin) is an island in Northeast Asia. Its north coast lies off the southeastern coast of Khabarovsk Krai in Russia, while its southern tip lies north of the Japanese island of Hokkaido. An islan ...

), northeastern China (

Heilongjiang Heilongjiang is a province in northeast China. It is the northernmost and easternmost province of the country and contains China's northernmost point (in Mohe City along the Amur) and easternmost point (at the confluence of the Amur and Us ...

and

Liaoning ) , image_skyline = , image_alt = , image_caption = Clockwise: Mukden Palace in Shenyang, Xinghai Square in Dalian, Dalian coast, Yalu River at Dandong , image_map = Liaoning in China (+all claims hatched).svg , ...

provinces), and Japan. The only North American report is with a single ''S. jacobsoni'' specimen caught in the wild in 2009 in the Vernon landfill in southern British Columbia, Canada, with a Lindgren funnel trap (multiple black funnels aligned vertically to mimic a tree trunk, with a collection vial at the base, to collect insects associated with trees) baited with a ''

Scolytus multistriatus ''Scolytus multistriatus'', the European elm bark beetle or smaller European elm bark beetle, is a bark beetle species in the genus '' Scolytus''. In Europe, while ''S. multistriatus'' acts as vector of the Dutch elm disease, caused by the Ascom ...

'' pheromones lure and an ultra high release ethanol lure. More traps were deployed in and around this area the following years but this species was never caught again.

References

{{Taxonbar, from=Q29032368 Scolytinae Insect pests of temperate forests Beetles described in 1802