Characteristics
The north temperate genus Clusiodes, like its southern sister-genus Hendelia, is characterized by reduced anterior and posterior fronto-orbitals, interfrontal bristles, well developed median genal bristles, swollen spermathecal ducts, a large subapical disc on the ventral receptacle, a longitudinal desclerotization on the female seventh sternite, a crested fin-like phallapodeme, a distiphallus that is rod-like basally with a membranous distal section, and an elongate pregonite that is perpendicular to the long axis of the hypandrium (Lonsdale & Marshall, 2007b). Clusiodes species are also sometimes black in colour, but a number of species have a yellow, vittate scutum. Most Clusiodes, particularly the smaller ones, are generally matt, setulose and rounder in appearance than other Clusiidae. Species of Clusiodes also have shorter legs (usually thin and cylindrical) and heads that are generally rounded with a broadly curved frons, narrow face and blunt features.

Adults of Clusiodes are most often found on hardwood logs, but several species have been collected from softwood trees such as pine, hemlock and fir (Caloren & Marshall, 1998; Roháček, 1995; Withers, 1985). North American Clusiodes have also been found in association with rotting fungus (Caloren & Marshall, 1998), rotting pork (Sasakawa, 1998) and small dung baits, particularly those placed on fallen wood that is bare and exposed. Fallen trunks are usually the most reliable microhabitat at which to collect adult Clusiodes, since they are often used as lekking sites. Roháček (1995) noted that pale, conspicuous trunks (generally fallen trunks without bark) were selected by males of several Clusiodes species to attract females. Roháček (1995) also observed numerous teneral specimens of C. ruficollis emerging from a moist, rotten beech trunk. These newly emerged adults were seen to search for new logs to use as mating places; males patrolled these logs defending territory, but females visited the mating sites only briefly to copulate before seeking softer wood at a more advanced stage of decomposition in which to oviposit. North American Clusiodes seem to prefer treefalls (both new and old) in sunspots, where males perform wing-flicking displays (alone, with conspecifics, or even with other genera of Clusiidae) and 'ambush-style attacks', in addition to territorial patrolling and head-to-head confrontations (Caloren & Marshall, 1998).

Relationships
Clusiodes can be divided into two well-supported Holarctic clades, the C. albimanus and C. geomyzinus species groups, which largely overlap each other's distributions. The C. albimanus group is most obviously characterized by bicoloured fore tarsi, and the C. geomyzinus group is characterized by two well-developed dorsocentral bristles and a large bulging gena. Caloren & Marshall (1998) revised the New World Clusiodes and Lonsdale & Marshall (2007b) provided a World revision focusing on Old World species. Most Clusiodes clades include widely separated sister species that often occur on separate continents. These repeated disjunctions between closely related Nearctic and Palaearctic species support the theory that trans-oceanic speciation events have been frequent in the genus (Caloren & Marshall, 1998).

Distribution
Clusiodes and its sister genus Hendelia show a clear north/south division, with Clusiodes almost entirely north temperate and Hendelia almost entirely tropical and south temperate in distribution. Clusiodes species appear to prefer a colder climate, with many species restricted to the north, and more southern species or locality records occurring only at higher elevations. 

Biology
European species of Clusiodes have been reared from puparia collected in numerous species of rotting deciduous tree trunks including aspen, ash, birch, poplar and alder (Caloren & Marshall, 1998; Roháček, 1995); several puparia and larvae of Clusiodes ruficollis (Meigen) have also been collected from under the bark of felled hornbeam in Britain (Withers, 1985). North American Clusiodes have been reared from dead tulip trees and likely also develop in elm and maple (Caloren & Marshall, 1998). Clusiodes species overwinter as puparia or late-instar larvae in the larval habitat (Caloren & Marshall, 1998).

Adults of Clusiodes are found predominantly on hardwood, but several species have been collected off of softwood trees such as pine, hemlock and fir (Caloren & Marshall, 1998; Roháček, 1995; Withers, 1985). North American Clusiodes have also been found in association with rotting fungus (Caloren & Marshall, 1998), rotting pork (Sasakawa, 1998) and small dung baits, particularly those placed on fallen wood that is bare and exposed. Fallen trunks are usually the most reliable microhabitat at which to collect adult Clusiodes, since they are often used as lekking sites. Roháček (1995) noted that pale, conspicuous trunks (generally fallen trunks without bark) were selected by males of several Clusiodes species to attract females. Roháček(1995) also observed numerous teneral specimens of C. ruficollis emerging from a moist, rotten beech trunk. These newly emerged adults were seen to search for new logs to use them as mating places; males patrolled these logs defending territory, but females visited the mating sites only briefly to copulate, and then searched for similar, but more rotten logs to oviposit in. North American Clusiodes have been noted to prefer treefalls (both new and old) in sunspots, where males perform wing-flicking displays (alone, with conspecifics, or even with other genera of Clusiidae!) and 'ambush-style attacks', in addition to territorial patrolling and head-to-head confrontations (Caloren & Marshall, 1998).

North American species:

  • Clusiodes americanus
  • Clusiodes apiculatus
  • Clusiodes ater
  • Clusiodes caestus
  • Clusiodes johnsoni
  • Clusiodes melanostomus complex
  • Clusiodes niger
  • Clusiodes nitidus
  • Clusiodes orbitalis
  • Clusiodes terminalis