Xylosandrus morigerus
(brown twig beetle)

Pictures

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Identity

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Preferred Scientific Name

• Xylosandrus morigerus (Blandford)

Preferred Common Name

• brown twig beetle

Other Scientific Names

• Xyleborus coffeae Wurth
• Xyleborus luzonicus Eggers
• Xyleborus morigerus Blandford
• Xylosandrus coffeae (Wurth)

International Common Names

• English: brown coffee borer; brown coffee twig borer; coffee beetle
• Spanish: barrenador del tallo del cafeto; pasador de las ramas del cafeto
• French: scolyte brun des rameaux; scolyte brun du caféier

Local Common Names

• Germany: Bohrer, Brauner Kaffeezweig-; Borkenkaefer, Dendrobium-
• Netherlands: bruine takkenboeboek; koffietakkenboeboek; takkenboeboek

EPPO code

• XYLSMO (Xyleborus morigerus)

Summary of Invasiveness

Top of page X. morigerus should be considered a high-risk quarantine pest; most of the species in Xylosandrus and related genera should be considered potential quarantine pests. This is because members of the tribe Xyleborini (Xylosandrus plus related genera) are all inbreeding, with the males generally mating with their sisters within the parental gallery system before dispersal. Thus the introduction of only a few mated females may lead to the establishment of an active population if suitable host plants can be found and environmental conditions are satisfactory. A very wide range of host plants have been recorded for many of the species of Xylosandrus. The direct risk of establishment of species of Xylosandrus in tropical and subtropical areas should be considered extremely serious.

Taxonomic Tree

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• Domain: Eukaryota
•     Kingdom: Metazoa
•         Phylum: Arthropoda
•             Subphylum: Uniramia
•                 Class: Insecta
•                     Order: Coleoptera
•                         Family: Scolytidae
•                             Genus: Xylosandrus
•                                 Species: Xylosandrus morigerus

Notes on Taxonomy and Nomenclature

Top of page Many species previously classified in the genus Xyleborus have now been transferred into other genera such as Ambrosiodmus, Euwallacea, Xyleborinus and Xylosandrus, including X. morigerus. A number of species within the Xyleborini, the tribe in which Xyleborus and related genera are placed, can be considered potential pests to agriculture and forestry; X. morigerus is one of the more important species. Xylosandrus difficilis was listed as a synonym by Bright and Skidmore (1997), but is usually considered to be a distinct species, and is listed as such by Bright and Skidmore (2002).

Description

Top of page Adult Female

Length 1.4-1.7 mm. Frons broadly convex, surface shining, reticulate, with sparse, small and large punctures. Antennal club solid on posterior face, no sutures visible. Pronotum slightly wider than long, sides strongly arcuate, anterior margin broadly rounded, with 8 coarse serrations. Elytra slightly longer than pronotum, about as long as wide, apex broadly rounded. Elytral declivity commencing about middle of elytra, steep, broadly convex; strial and interstrial punctures larger than those in striae, with distinct granules and rows of fine, short, strial setae and rows of much longer interstrial setae.

Egg

White, elliptical, with a smooth surface, averaging 0.5 mm long and 0.28 mm wide (Verbeek, 1930).

Larva

The following description of the mature larva is translated from Muskus Arrieta (1984). Head capsule is free, as long as it is wide (0.34 mm), sides curved and posterior margin emarginate; frons triangular , wider than long and slightly shorter than half the length of the head capsule; frontal suture undifferentiated; frontal section of the median dorsal cranial furrow is slightly longer than half the length of the frons. Posterior epicranial seta 1 is long and the other three are extremely short; a feature used to identify this species.

Clypeus with anterior margin almost straight, the posterior is a little concave and the basal part has a very narrow pigmented area. Seta 2 is slightly shorter than 1. Anteromesal sensillum is closer to seta 2.

Labrum wider than long; its sides are semi-parallel, the anterior margin has a median protuberance and uniform pigmentation. The tormae are robust and long, and extend almost to the base of the clypeus, the tips are free, separated and divergent.

Maxilla shows a narrow area of dark pigmentation on the inner side of the ventral face of the stipes. The stipital seta is in the middle of the base of the stipes. Palpiferal setae are situated in the membranous area at the base of the palps.

Labium with posterior prolongation of the median premental arm short and triangular; one sensillum is in the base of the lateral premental arms; the basal segment of the palpus is undifferentiated. Postlabial setae are arranged in a straight line that runs anterolaterally.

Mandible slightly curved; tridentate; a small protuberance on the cutting margin near the third tooth; two setae arranged transversely; two sensillae near the basal margin.

Thorax and abdomen: dorsal plate present on the prothorax; body covered in microtrichia; setae small; spiracles biforous.

Pupa

No detailed description of the pupa has been made.

Distribution

Top of page There are unpublished records from Christmas Island (Indian Ocean) and Gabon (RA Beaver, Chiangmai, Thailand, personal communication, 2004).

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

History of Introduction and Spread

Top of page As with some other species of Xyleborini that now have a nearly pantropical distribution as the result of commerce, it is not always possible to be sure of the native distribution, and in which countries the species is exotic. It has been assumed that the native distribution ranged from India and Sri Lanka to Papua New Guinea, but not to Australia and the Pacific Islands, although it may have been introduced to these areas early in the history of human settlement. Similarly, it has been assumed that, except in Europe, the species is invasive where introduced, although there is often no evidence for or against such an assumption. In Europe, the species is occasionally found in glasshouses, usually in orchid pseudobulbs or stems. There are no records of its spread outside the glasshouse environment in Europe North of the Mediterranean area. There seems no reason to doubt that Eggers (1939) did identify one or more specimens of X. morigerus from Taiwan. However, the species has not been found there again since that time. It seems likely that the species was introduced but did not become established. Similarly in Hawaii, the species was recorded from imported orchids in the 1930s, but did not become established (Samuelson, 1981).

Risk of Introduction

Top of page Two other species of Xylosandrus, Xylosandrus compactus and Xylosandrus crassiusculus, with similar habits to X. morigerus, have become important pests of tree crops, ornamental and native trees in tropical and subtropical areas where they have been introduced. The risk of introduction for X. morigerus must be considered high, most probably in the twigs and small branches of imported plants. Once established, such species are difficult to eradicate, and are likely to spread with the movement of infested plants, as well as by normal dispersal of the adults. X. morigerus is listed as a quarantine pest in New Zealand, but apparently not elsewhere. This should be remedied.

Hosts/Species Affected

Top of page Members of Xyleborus and the related genera Ambrosiodmus, Euwallacea, Xyleborinus and Xylosandrus are all ambrosia beetles that feed and breed in a variety of forest trees and shrubs. Depending on the species, they may be found in small branches and seedlings to large logs. All are potentially damaging to agriculture and/or forestry under suitable conditions. Many species, previously considered of only minor importance, may become important pests in agriculture and forestry as a result of the continuing destruction of natural forests and the expansion of forest and tree crop plantations, agroforestry and agriculture.

X. morigerus occurs in a very wide variety of host plants (e.g. Kalshoven, 1958, 1961; Browne, 1961; Schedl, 1963; Beaver, 1976). Schedl (1963) lists 75 species in 33 families, and many more species have since been added to this list (Wood and Bright, 1992). Almost any broad-leaved tree or sapling can potentially be attacked, although the species has not yet been recorded from conifers. It is important as a pest of crop and ornamental trees, and is well-known as a pest of coffee, and as a borer in orchid stems. It frequently infests shade trees in coffee plantations. Its attacks are sometimes primary on apparently healthy hosts. Given the range of host trees attacked, and the differences between geographical areas, it is scarcely possible to distinguish 'main host' trees from 'other host' trees. It may be expected that most crop, plantation or ornamental trees in a particular area can be attacked. The Host list in this datasheet contains a selection of recorded hosts.

Host Plants and Other Plants Affected

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Growth Stages

Top of page Flowering stage, Fruiting stage, Seedling stage, Vegetative growing stage

Symptoms

Top of page Attacked plants may show signs of wilting, branch die-back, shoot breakage, chronic debilitation, sun-scorch or a general decline in vigour.

List of Symptoms/Signs

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Biology and Ecology

Top of page The important pest species in the genus Xylosandrus and the related genera Euwallacea, Xyleborinus and Xyleborus are all ambrosia beetles in the Xyleborini, a tribe with a social organization of extreme polygamy. The sexual dimorphism is strongly developed, and the ratio of females to males is high. All are closely associated with symbiotic ambrosia fungi, which are transported by the female, and form the sole food for both adult and larvae.

Studies of the biology of X. morigerus have been made by Browne (1961) in Malaysia, and Kalshoven (1958, 1961) in Indonesia. These and other studies have been reviewed by Schedl (1963) and Le Pelley (1968). Some additional information is given by Beaver (1976, 1988) for Samoa and the Seychelles respectively, and Jordal and Kirkendall (1998) for Costa Rica. Many further references are given by Wood and Bright (1992) and Bright and Skidmore (1997, 2002).

The species usually breeds in shoots, twigs and small branches, but also attacks seedlings, and sometimes larger stems up to a diameter of about 20 cm (Browne, 1961; Roberts, 1977). It is usually secondary, but primary attacks on healthy plants often occur. Seedlings are normally killed by such attacks, which often extend into the tap root deep below the soil surface (Verbeek, 1930; Le Pelley, 1968). The species can also breed in the large fallen leafstalks of trees such as Cecropia (Beaver, 1979; Jordal and Kirkendall, 1998). Only the females initiate attacks. In small stems an entrance tunnel cut into the pith or wood is extended into a longitudinal tunnel or irregular chamber. In larger stems, the gallery may branch once or twice in the transverse plane, with a brood chamber in the longitudinal plane, but not penetrating far into the wood. The female feeds on the ambrosia fungus which she has introduced into the gallery system before oviposition begins. The eggs are laid loosely in the gallery over some days, and the larvae feed on the ambrosia fungus on the walls of the gallery.

The size of the brood varies considerably. In Indonesia, Kalshoven (1961) found a mean of 30 offspring, with occasional galleries holding 70 offspring at various stages of development. In Malaysia and Samoa, brood sizes are much smaller (up to 25) (Browne, 1961; Beaver, 1976). In leafstalks, brood sizes are normally not more than 2 or 3, possibly because of poor conditions for the growth of the ambrosia fungus (Beaver, 1979; Jordal and Kirkendall, 1998). Pupation and mating of brood adults occurs within the gallery system, the (usually) single male in each gallery mating with his sisters. The new generation of females emerges through the entrance hole made by the parent. The males do not normally emerge. Development times are probably similar to the related species, Xylosandrus compactus (about 4 weeks from egg to adult, and 5-6 weeks from the time the female begins her gallery to the sexual maturity of the next generation (Ngoan et al., 1976). In most parts of the range, breeding is continuous, with overlapping generations, so that the species is active at all times, and in all stages of development. However, populations may increase during the rainy season (Browne, 1961). Attacks on healthy hosts are less successful in periods of vigorous host growth, and when humidity is low (Browne, 1961).

Natural enemies

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Notes on Natural Enemies

Top of page The immature stages have few natural enemies. The female parent normally remains in the gallery entrance whilst the immature stages are developing, preventing the entry of potential predators and parasitoids. Provided that the female remains alive and the growth of the ambrosia fungus on which the larvae feed is satisfactory, mortality of the immature stages is likely to be very low. Most mortality is probably during the dispersal of the adults, and during gallery establishment.

In Indonesia, the species is attacked by the parasitoid Tetrastichus xylebororum (Kalshoven, 1960). This oviposits through the twig onto the beetle larvae. An unidentified bethylid enters the gallery system and paralyses larvae and pupae before ovipositing on them (Kalshoven, 1960). Neither parasite provides effective control (Le Pelley, 1968).

Adults of ambrosia beetles are predated by lizards, clerid beetles and ants as they attempt to bore into the host tree. In Ecuador, the following ant genera have been reported to attack adults of X. morigerus: Crematogaster, Leptothorax, Pheidole, Pseudomyrmex and Solenopsis (Barrera, 2003). The adults may also be attacked by the pathogenic fungus Beauveria bassiana (Barrera, 2003).

Means of Movement and Dispersal

Top of page Natural Dispersal

The adult females fly readily, and flight is one of the main means of movement and dispersal to previously uninfected areas. Of more importance for long distance movement, however, is the transport of infested seedlings, saplings or cut branches.

Vector Transmission

The female has a mycangium, a pouch used to carry spores of the ambrosia fungus on which both adult and larvae feed, opening between the pronotum and mesonotum, and extending below the pronotum (Beaver, 1989). No detailed studies appear to have been made of the ambrosia fungus of X. morigerus. Most species of Xylosandrus are associated with Ambrosiella or Fusarium species (Norris, 1979; Kajimura and Hijii, 1994). Fusarium species are known to be plant pathogens, and their pathogenicity to host plants when transmitted by ambrosia beetles has been confirmed (Hara and Beardsley, 1976; Dixon and Woodruff, 1983). 'Contamination' of the mycangia by the spores of pathogenic fungi is possible. Spores of pathogenic fungi can also be transported on the cuticle of the beetle, although their chance of survival there is much less than in the mycangial pouch. Browne (1961) and Le Pelley (1968) noted that most of the damage following attacks by X. compactus is due to accompanying fungal attack. However, the fungi involved do not appear to have been investigated.

Plant Trade

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Plant parts not known to carry the pest in trade/transport
Flowers/Inflorescences/Cones/Calyx
Fruits (inc. pods)
Growing medium accompanying plants
Leaves
True seeds (inc. grain)

Wood Packaging

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Impact Summary

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Impact

Top of page X. morigerus can be a primary pest of coffee in Indonesia, attacking living trees and capable of causing important damage (Le Pelley, 1968). However, Kalshoven (1961), citing a number of other workers, suggests that it is principally a secondary borer, attacking plants which are in poor condition as the result of nematode attacks on the roots, or other causes. It is primarily a pest of robusta coffee, and less injurious to excelsa coffee (Kalshoven, 1961). The chief damage to the tissues of the host plant is caused by associated fungi (Browne, 1961; Le Pelley, 1968). In general, it is less important as a pest of coffee than the related species, Xylosandrus compactus (Kalshoven, 1958). It is a minor pest of cocoa (Entwistle, 1972), and of tea. Tea seedlings may be killed by its attacks in Indonesia (Verbeek, 1930; Kalshoven, 1961). Waterhouse (1997) lists the species as an 'important' pest of forest plantation trees (probably Swietenia) in Fiji, but attacks on mahogany seedlings, and other forest trees are not normally of major importance (Kalshoven, 1961). Attacks on orchid pseudobulbs and stems are of minor importance, although plants can be killed (Kalshoven, 1961).

Detection and Inspection

Top of page Some success has been obtained by using traps baited with ethanol placed in and around port facilities where infested material may be stored, and around nurseries or plantations with plants susceptible to attack. A simple type of trap is described by Bambara et al. (2002). Visual inspection of suspected infested material is required to detect the presence of ambrosia beetles. Infestations are most easily detected in living plants by the presence of wilting shoots or shoot dieback. Entry holes made by the attacking beetles, and the presence of frass produced during gallery construction, are additional indicators.

Prevention and Control

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When Xylosandrus species are detected in plant material, it is necessary to immediately destroy all of the infested material. When they are detected in traps, plant material in the vicinity of the trap should be actively inspected. If an active infestation is detected, chemical control using insecticides is possible but not generally effective since the adult beetles bore deep into the host material. The following insecticides were effective against a species of Euwallacea destructive to tea: fenvalerate, deltamethrin, quinalphos and cypermethrin (Muraleedharan, 1995); these insecticides may also be effective against other ambrosia beetles. For the related species, Xylosandrus crassiusculus, Bambara and Casey (2003) suggest the use of permethrin, but note that multiple treatments may be required during a season. They consider that dursban is ineffective. In plantations and orchards, they suggest the use of some attacked trees as trap trees, which need to be removed and burned before the life cycle of the beetle is completed.

The concealed habitats in which these species feed and reproduce, the difficulties and high costs of insecticide application, and environmental concerns all limit the effectiveness of chemical control. Practices that promote tree vigour and health will aid recovery from beetle damage. Biological control measures are not considered likely to be effective.
 

References

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Acu±a J; De Zayas F, 1940. Fruta bomba o papaya. Revista de Agricultura (Cuba), 23:49-80.

Atkinson TH; Equihua-Martinez A, 1988. Notes on the biology the scolytids and platypodids (Coleoptera) from Mexico and Central America. Folia Entomologica Mexicana, No. 76:83-105

Bambara S; Casey C, 2003. The Asian ambrosia beetle. North Carolina Cooperative Extension Service. http://www.ces.ncsu.edu/depts/ent/notes/O&T/trees/note111/note111.html.

Bambara S; Stephan D; Reeves E, 2002. Asian ambrosia beetle trapping. North Carolina Cooperative Extension Service. http://www.ces.ncsu.edu/depts/ent/notes/O&T/trees/note122/note122.html.

Barrera JF, 2003. Proyecto taladrador de las ramas del café robusta. http://www.tap-ecosur.edu.mx/proyectos/entomo/mip/mip.htm.

Beaver RA, 1976. The biology of Samoan bark and ambrosia beetles (Coleoptera, Scolytidae and Platypodidae). Bulletin of Entomological Research, 65(4):531-548

Beaver RA, 1979. Leafstalks as a habitat for bark beetles (Col.: Scolytidae). Zeitschrift fur Angewandte Entomologie, 88(3):296-306

Beaver RA, 1987. The bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) of Tonga. New Zealand Entomologist, 9:64-70

Beaver RA, 1988. Biological studies on ambrosia beetles of the Seychelles (Col., Scolytidae and Platypodidae). Journal of Applied Entomology, 105(1):62-73

Beaver RA, 1989. Insect-fungus relationships in the bark and ambrosia beetles. Insect-fungus interactions. 14th Symposium of the Royal Entomological Society of London in collaboration with the British Mycological Society [edited by Wilding, N.; Collins, N.M.; Hammond, P.M.; Webber, J.F.] London, UK; Academic Press, 121-143

Beeson CFC, 1929. Platypodidae and Scolytidae. Insects of Samoa, 4:217-248.

Bigger M, 1988. The insect pests of forest plantation trees in the Solomon Islands. Solomon Islands' Forest Record, No. 4:v + 190 pp.

Bright DE, 2000. Scolytidae (Coleoptera) of Gunung Mulu national Park, Sarawak, Malaysia, with ecological notes and descriptions of six new species. Serangga, 5:41-85.

Bright DE; Peck SB, 1998. Scolytidae from the Galápagos Islands, Ecuador, with descriptions of four new species, new distribution records, and a key to species (Coleoptera: Scolytidae). Koleopterologische Rundschau, 68:233-252; 28 ref.

Bright DE; Skidmore RE, 1997. A catalog of Scolytidae and Platypodidae (Coleoptera), Supplement 1 (1990-1994). Ottawa, Canada: NRC Research Press, 368 pp.

Bright DE; Skidmore RE, 2002. A catalogue of Scolytidae and Platypodidae (Coleoptera), Supplement 2 (1995-1999). Ottawa, Canada: NRC Research Press, 523 pp.

Browne FG, 1961. The biology of Malayan Scolytidae and Platypodidae. Malayan Forest Records, 22:1-255.

Browne FG, 1972. Some oriental Scolytidae and Platypodidae (Coleoptera). Oriental Insects, 6(1):19-32

Browne FG, 1980. Bark beetles and ambrosia beetles (Coleoptera, Scolytidae and Platypodidae) intercepted at Japanese ports, with descriptions of new species, I. Kontyu, 48(3):370-379

Browne FG, 1986. Bark beetles and ambrosia beetles (Coleoptera, Scolytidae and Platypodidae) intercepted at Japanese ports, with descriptions of new species, XIII. Kontyu, 54(1):89-99

Cognato AI; Rubinoff D, 2008. New exotic ambrosia beetles found in Hawaii (Curculionidae: Scolytinae: Xyleborina). Coleopterists Bulletin, 62(3):421-424. http://www.bioone.org/perlserv/?request=get-current-issue

Dixon WN; Woodruff RE, 1983. The black twig borer, Xylosandrus compactus (Eichhoff) (Coleoptera: Scolytidae). Entomology Circular, Division of Plant Industry, Florida Department of Agriculture and Consumer Services, No. 250:2 pp.

Eggers H, 1939. Japanische Borkenkäfer II. Arbeiten über Morphologische und Taxonomische Entomologie, Berlin-Dahlem, 6:114-123.

Entwistle PF, 1972. Pests of cocoa. London, UK: Longman, 779 pp.

EPPO, 2014. PQR database. Paris, France: European and Mediterranean Plant Protection Organization. http://www.eppo.int/DATABASES/pqr/pqr.htm

Haack RA, 2001. Intercepted Scolytidae (Coleoptera) at US ports of entry: 1985-200. Integrated Pest Management Reviews 6: 253-282.

Hara AH; Beardsley JW Jr, 1976. The biology of the black twig borer, Xylosandrus compactus (Eichhoff), in Hawaii. Proceedings of the Hawaiian Entomological Society, 23(1):55-70

IPPC, 2016. Xylosandrus morigerus (Blandford) detected in Timor-Leste. IPPC Official Pest Report, No. TLS-02/1. Rome, Italy: FAO. https://www.ippc.int/

Jordal BH; Kirkendall LR, 1998. Ecological relationships of a guild of tropical beetles breeding in Cecropia petioles in Costa Rica. Journal of Tropical Ecology, 14(2):153-176; 39 ref.

Kajimura H; Hijii N, 1994. Electrophoretic comparisons of soluble mycelial proteins from fungi associated with several species of ambrosia beetles. Journal of the Japanese Forestry Society, 76(1):59-65

Kalshoven LGE, 1958. The occurrence of the primary twig borer Xyleborus morstatti Hag. in Indonesia. Entomologische Berichte, 18:220-252.

Kalshoven LGE, 1960. Observations on the parasites of Xyleborus twig borers in Java. Entomologische Berichten, 20:259-262.

Kalshoven LGE, 1961. A study of the twig borer Xyleborus morigerus Blandford, mainly based on observations in Java. Tijdschrift voor Entomologie, 104:93-110.

Muraleedharan N, 1995. Strategies for the management of shot-hole borer. Planters` Chronicle, (January):23-24.

Ngoan ND; Wilkinson RC; Short DE; Moses CS; Mangold JR, 1976. Biology of an introduced ambrosia beetle, Xylosandrus compactus, in Florida. Annals of the Entomological Society of America, 69(5):872-876

Norris DL, 1979. The mutualistic fungi of xyleborine beetles. In: Batra LR, ed. Insect-fungus Symbiosis. Chichester, Sussex, UK: Halsted Press.

Nunberg M, 1958. Zur Kenntnis der neotropischen Scolytiden- und Platypodiden-Fauna (Coleoptera). Acta Zoologica Cracoviensia, 2:479-507.

Ohno S, 1990. The Scolytidae and Platypodidae (Coleoptera) from Borneo found in logs at Nagoya port. I. Research Bulletin of the Plant Protection Service, Japan., No. 26:83-94

Ohno S; Yoshioka K; Yoneyama K; Nakazawa H, 1988. The Scolytidae and Platypodidae (Coleoptera) from Solomon Islands, found in logs at Nagoya Port, I. Research Bulletin of the Plant Protection Service, Japan, No. 24:91-95

Pelley RH le, 1968. Pests of Coffee. London and Harlow, UK: Longmans, Green and Co Ltd.

Roberts H, 1977. Observations on the biology of some tropical rain forest Scolytidae (Coleoptera) from Fiji. II. Subfamily Ipinae - tribe Xyleborini. Journal of Natural History, 11(3):251-272

Samuelson GA, 1981. A synopsis of Hawaiian Xyleborini (Coleoptera: Scolytidae). Pacific Insects, 23:50-92.

Schedl KE, 1963. Scolytidae und Platypodidae Afrikas, Band II. Revista de Entomologia de Moçambique, 5 (1962):1-594.

Verbeek FATH, 1930. Xyleborus morigerus Bldfd. als kiemplant-boeboek. Archief voor de Theecultuur in Nederlandsch-Indie, 3:152-170.

Waterhouse DF, 1997. The Major Invertebrate Pests and Weeds of Agriculture and Plantation Forestry in the Southern and Western Pacific. ACIAR Monograph No. 44. Canberra, Australia: ACIAR.

Wood SL; Bright DE, 1992. A catalog of Scolytidae and Platypodidae (Coleoptera), Part 2: Taxonomic index. Great Basin Naturalist Memoirs, 13: 1-1553.

Links to Websites

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Distribution Maps

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