Onthophagus binodis

Beneficial

Common name(s)

humpbacked dung beetle

Taxonomy

Family: Scarabaeidae Subfamily: Scarabaeinae Genus: Onthophagus Species: Onthophagus binodis Thunberg, 1818

Adult diagnosis

Total body length 10.0–15.0 mm (0.39–0.59 in). Body shape oval; may be caked in dung. Color dull black. Small to medium-sized Onthophagus, over 6 mm. Clypeal apex of major male weakly produced and reflexed; minor male and female apex rounded, not reflexed. Head lacking horns in both sexes; female and male with curved ridge at base of head. Ocular canthus not completely dividing eye. Pronotum of major male with a quadrate, hump-like process; process reduced in minor male and female. Pronotum with anterior angles rounded in both sexes. Front tibia not gracile and elongate; male and female not noticeably dimorphic. Scutellum absent.

Larval diagnosis

Undescribed. For Onthophagus spp. (Ritcher, 1966): Grub C-shaped, hump-backed, cylindrical, and cream-colored. Maxilla with galea and lacinia distinctly separate. Epipharynx with tormae united mesally, anterior phoba present. Antennae 4-segmented, distal segment much reduced. Legs 2-segmented. Prothoracic shield without anteriorly projecting processes. Third abdominal segment bearing a prominent conical, dorsal gibbosity covered with numerous short, stout setae.

Native range

Africa. This species is known from regions of South Africa where annual rainfall exceeds 500 mm (19.7 in). It was introduced to Australia to control cattle dung and dung flies (Tyndale-Biscoe, 1990).

Plant host(s)

None. This species feeds on dung as both an adult and larva. There are no records of this beetle feeding on live plant tissues.

Life history

This diurnal species is a dung tunneler (Houston et al., 1982). After locating suitable (often very wet) dung, adults construct a tunnel 3.0–17.5 cm (1.1–6.9 in) (Barkhouse and Ridsill-Smith, 1986) beneath the fecal source in sandy soils (Tyndale-Biscoe, 1990). Larvae are particularly sensitive to desiccation, and adults will dig deeper tunnels to avoid dry soil (Barkhouse and Ridsill-Smith, 1986). Tunnels are provisioned with dung in the form of brood balls. Each brood ball is impregnated with an egg, and larval development occurs within. Development from egg to larvae takes 4–6 weeks, though poor conditions will increase development time (Tyndale-Biscoe, 1990). This species is quite sensitive to low moisture environments and is rarely found in areas with prolonged dry seasons (Barkhouse and Ridsill-Smith, 1986).

Pest potential

None. This species recycles dung and is beneficial for ranching and farming in Hawaii. Primarily being a dung feeder, this species has never been recorded damaging crop or ornamental plants. Additionally, this species is not a threat to native dung beetles because none occur in Hawaii or Guam.

Status in Hawaii

Established. This species was introduced to Big Island in 1973 to help control populations of the horn fly (Haematobia irritans), a biting pest of livestock (Markin and Yoshioka, 1998). It is now established on Big Island where it occurs at higher elevations (Markin and Yoshioka, 1998).

Status in Guam

Not established or recorded. This species has not been recorded from Guam.

Potential distribution and dispersal pathway

In Hawaii, this species was intentionally imported.

Similar species

This species could be confused with similarly colored small to medium-sized dung beetles (6+ mm) including Onthophagus species such as Onthophagus laminatus, Onthophagus cuniculus, Onthophagus incensus, Onthophagus armatus, and Onthophagus comperei.

Major males can be separated by examining the head armature (O. binodis lacking horns or tubercles versus O. laminatus, O. incensus, O. armatus, and O. comperei with horns versus O. cuniculus with two tubercles).

Females are separated by examining the base of the head (O. binodis with a slightly curved ridge versus O. cuniculus, O. laminatus, and O. incensus with a transverse ridge versus O. armatus with feebly bisinuate ridge versus O. comperei with 2 tubercles), pronotum (O. binodis with a lobe-like process versus O. cuniculus with a bi-lobed process versus O. incensus, O. armatus, and O. comperei without a process), and anterior pronotal angle (O. binodis with anterior angle rounded versus O. laminatus and O. cuniculus with angle curving outward).

Other names (synonyms)

Onthophagus columella Fahreus in Boheman

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Onthophagus binodis male; photo by E.L. Engasser

Onthophagus binodis male; photo by E.L. Engasser

Onthophagus binodis male; photo by E.L. Engasser

Onthophagus binodis male; photo by E.L. Engasser

Onthophagus binodis male; photo by E.L. Engasser

Onthophagus binodis male; photo by E.L. Engasser

Onthophagus binodis male; photo by E.L. Engasser

Onthophagus binodis male; photo by E.L. Engasser

Onthophagus binodis female; photo by E.L. Engasser

Onthophagus binodis female; photo by E.L. Engasser

Onthophagus binodis female; photo by E.L. Engasser

Onthophagus binodis female; photo by E.L. Engasser

distribution map for Onthophagus binodis

distribution map for Onthophagus binodis