|scientific name Rhizophagus |
Under bark of dead or rotting trees (Sengupta, 1988) and/or in decaying material (Bousquet, 1990).
In Alberta, adult Rhizophagus spp. are collected from early May through September
Adult has antennal grooves on either side and slightly under the head (Bousquet, 2004). Antennae are characteristic in the Monotomidae, helping distinguish this family from the family Nitidulidae. Rhizophagus antennae consist of 10 segments with an additional 1-2 segments forming a terminal club (Sengupta, 1988). Rhizophagus is also distinguished from many other genera in the Monotomidae by the suture forming a separation of the clypeus (lower facial segment) and the labium (lower lip). Body is fairly flattened, elongate and small, under 4.5 mm in total length (Bousquet, 2004) with few Rhizophagus species exceeding this (Sengupta, 1988). The pronotum, dorsal section of the exoskeleton directly behind the head, may be either squared or slightly elongated. The final abdominal tergite (the last segment of the abdomen from dorsal view) is not covered by elytra (Sengupta, 1988). On the ventral side of the thorax, the coxal cavities (from which the legs protrude) lie perpendicular to the body itself, and trochantins are visible as small protrusions from the body wall, placed slightly in front of the legs (Sengupta, 1988). Larvae of Rhizophagus are 2-6 mm in length and vary in their degree of flatness. They may be cylindrical or tapered at both ends (Lawrence, 1991). The upper body surface may be yellowish in colour and is smooth in comparison with other genera which are usually more textured in appearance (Lawrence, 1991).
Members of Rhizophagus are often found in bark beetle galleries in jack pine and lodgepole pine. An introduced species, R. parallelocollis Gyllenhal from Europe has been discovered in coffins (Bousquet, 1990). Although originally documented as root-feeders, the predatory or fungivorous (fungus-feeding) nature of rhizophagids is now known (Bousquet, 1990). Some study has been done to utilize predaceous members of Rhizophagus (especially R. grandis for its ability to detect chemical signals given off by bark beetles) as biological control for bark beetle pests (family Curculionidae; Scolytinae) (Miller et al., 1987). Although most common on pine and spruce trees in North America, Rhizophagus is found on pine, cedar, fir, maple and oak in other temperate climates and is able to survive from sea level to very high altitudes (~10,500 feet) (Sengupta, 1988). The genus has great economic importance due to an association with damaging bark beetles (Pakaluk and Slipinski, 1993).
A few species in this genus are considered rare in parts of Great Britain (Boxtowe Borough Council, 2005).
Some species feed on wood-eating insects (Sengupta, 1988) but may tolerate a diet of fungal hyphae, dead scolytid beetles, living bark beetle eggs or larvae (Perris, 1877 in Bousquet, 1990). Larvae may feed on fecal matter (Perris, 1877 in Bousquet, 1990). Most Rhizophagus are not restricted to specific prey, with the exception of R. grandis Gyllenhal which is restricted to great spruce beetle prey (Dendroctonus micans Kugel) (Potoskaya, 1977 in Bousquet, 1990).
Common in cooler climates, absent from South America, Australia, Southern Africa, Madagascar and Southern India (Sengupta, 1988). Distribution extends across non-tropical Europe and Asia, Northern Africa and North America (Bousquet, 1990).
Recently the family Rhizophagidae was joined with the Monotomidae. The genus Rhizophagus, therefore, previously of the Rhizophagidae, is now within the Monotomidae (Bousquet, 2004). The subfamilies Rhizophaginae and Monotominae remain the same within Monotomidae.
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