Hybosorus roei

Potential Invader

Common name(s)

none known

Taxonomy

Family: Hybosoridae Subfamily: Hybosorinae Genus: Hybosorus Species: Hybosorus roei Westwood, 1845

Adult diagnosis

Total body length 5.0–7.0 mm (0.19–0.28 in). Color above shiny black. Body vaguely egg-shaped in dorsal view; dorsal surface convex. Elytra with numerous distinct, punctate striae. Antennae with 3-segmented club; first segment of club enlarged, hollowed to hold second segment. Mandibles prominent, visible in dorsal view. Clypeus narrow, not widely broadened.

Larval diagnosis

Undescribed. For Hybosorus spp. (Grebennikov et al., 2004): Grub C-shaped, cylindrical, not hump-backed, whitish. Maxilla with galea and lacinia distinctly separated. Frontoclypeal suture distinct. Labrum at apex with 3 truncate lobes. Antennomeres 2 and 3 separate. Combined apical antennomere with markedly narrowed base and widened apex; two combined apical antennomeres with 10 long setae; tormae united. Short and flattened setae of palidia pointed towards apex.

Native range

Old World. The native range of this species includes vast regions of the Old World, ranging from temperate areas in Europe and China to tropical and subtropical regions of the Middle East, India, Vietnam, and all of Africa except the Sahara (Ocampo, 2002).

Plant host(s)

Possibly turf grasses. Larvae of this species are reportedly pests of turf in the mainland U.S. (Barden, 2011). Adults are not known to feed on plants (Ocampo, 2002).

Life history

(Ocampo, 2002): Adults of this species appear to be carnivorous, feeding on both carrion and other invertebrates. Adults are attracted to dung where they feed on small dung beetles and other coprophagous insects. In the U.S., adults have been collected from February to October and are most active in the months of May and June. Eggs are laid in the soil. Larvae may feed upon plant roots and/or detritus, similar to other hybosorid species.

Pest potential

Moderate. Although it is not clear that larvae feed on grass roots, this species is reported as a destructive turf pest (Barden, 2011). Because adults feed on dung beetles, this species could be problematic for ranching. Hybosorus roei also has a well-recorded history of rapid invasion into new areas (Ocampo, 2002) where it can reach high population densities (Buss, 2006). This species arrived to the mainland U.S. (probably South Carolina) sometime in the 1840's, possibly on an incoming slave ship from Africa (Woodruff, 1973). Though its range expanded slowly at first, the second half of the 20th century saw a rapid expansion of the species' range in the Americas. Hybosorus roei is now known from much of the southern half of the U.S., Mexico, Caribbean Islands, Central America, and Colombia (Ocampo, 2002).

Status in Hawaii

Not established or recorded. There are no records of this species from Hawaii, although it should be regarded as likely to arrive in the future.

Status in Guam

Not established or recorded. There are no records of this species from Guam.

Potential distribution and dispersal pathway

This species is strongly attracted to lights at night and is a capable flier (Ocampo, 2002). Thus, it is likely that this beetle would be attracted to well-lit ports and airports. This would allow for hitchhiking on marine or air cargo. Further, it is possible that larvae or eggs could be transported in shipments of commercial turf. It should be regarded as having a significant chance of arriving to Hawaii or Guam in the future.

Similar species

While the egg-shaped body of this species is distinctive, it might be confused with similar-sized dung beetles. It is separated from the dung beetles based upon the clypeal shape (Hybosorus roei with narrowed clypeus versus comparably broad clypeus in most dung beetles) and mandibles (Hybosorus roei with mandibles visible when viewed dorsally versus mandibles never visible dorsally in dung beetles).

Other names (synonyms)

Hybosorus carolinus LeConte, Hybosorus illigeri Reiche, Hybosorus nitidus Lansbergel, Hybosorus oblongus Dahlbom, Hybosorus pinguis Westwood, Hybosorus thoracicus Westwood

Special note

This species was long known as Hybosorus illigeri, and it remains widely known and reported under that name.

Report your observation

In Hawaii, this species represents a new invasive species. Prevent the spread of this species by reporting your observation at our iNaturalist project.

Hybosorus roei female; photo by E.L. Engasser

Hybosorus roei female; photo by E.L. Engasser

Hybosorus roei female; photo by E.L. Engasser

Hybosorus roei female; photo by E.L. Engasser

Hybosorus roei male genitalia, lateral view of right side; photo by E.L. Engasser

Hybosorus roei male genitalia, lateral view of right side; photo by E.L. Engasser

Hybosorus roei male genitalia, lateral view of left side; photo by E.L. Engasser

Hybosorus roei male genitalia, lateral view of left side; photo by E.L. Engasser