Onthophagus granulatus

Beneficial

Common name(s)

granulose dung beetle

Taxonomy

Family: Scarabaeidae Subfamily: Scarabaeinae Genus: Onthophagus Species: Onthophagus granulatus Boheman, 1858

Adult diagnosis

Total body length 6.0–8.0 mm (0.23–0.31 in). Body shape oval; may be caked in dung. Color dull brownish. Small-sized Onthophagus, 6-10 mm. Clypeal apex of major male produced, strongly recurved; not produced and recurved in minor male or female. Head of male lacking horns; minor male and female with transverse ridge near base. Ocular canthus not completely dividing eye. Pronotum with anterior angle rounded or weakly acute. Pronotum of major male with single lobe-like process; minor male and female with 4 weak, tubercle-like processes. Front tibia of male slender, female tibia comparatively more robust. 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

Australia. This species is native to eastern Australia. It has been recorded occurring from the province of Victoria northward to Mackay in Queensland (Matthews, 1972). It is also known from New Zealand, where it established in the 1870's (Forgie, 2009).

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 scarab is known from pastures and other open areas, particularly where soils are sandy (Matthews, 1972). Adults live up to 46 weeks (Forgie, 2009) and have been recorded from carrion as well as dung (human, cattle, sheep, and wallaby) (Matthews, 1972). After locating suitable feces, females create a burrow under or near the dung source (Forgie, 2009). The burrow is then provisioned with dung in the form of brood balls. Each ball is impregnated with an egg; larval development occurs within the brood ball. There is a single generation per year (Forgie, 2009). Duration from egg to adult is 6–10 weeks, with adult numbers peaking in early summer (Forgie, 2009).

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 scarab is not a threat to native dung beetles because none occur in Hawaii or Guam. An odd record of this species killing a horse through perforation of the horse's stomach (Matthews, 1972) should be regarded with skepticism.

Status in Hawaii

Recorded, not established. This species was intentionally brought to Hawaii in 1921, though it is unclear if any individuals were released (Hawaii Division of Forestry, 1923). Similar dung beetle introductions were undertaken to help control populations of the horn fly (Haematobia irritans), a biting pest of livestock (Markin and Yoshioka, 1998). If this species was released, it failed to establish populations in the state (Nishida, 2002).

Status in Guam

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

Potential distribution and dispersal pathway

In Hawaii, this species was intentionally imported.

Similar species

This scarab could be confused with Onthophagus of similar color and small-size (6–10 mm): Onthophagus foliaceus and Onthophagus nuchicornis.

Major males of these species can quickly be distinguished by examination of the head (O. granulatus lacking horns, instead with strongly recurved, produced clypeal apex versus O. nuchicornis with single spine-like horn, O. foliaceus with a single, long forward curving horn).

Minor males and females are somewhat more difficult to distinguish but can be separated by examination of the pronotum (O. granulatus with four tubercle-like processes versus O. nuchicornis with a rounded peg-like process, O. foliaceus without a process).

Other names (synonyms)

None known

Report your observation

Report your observation of this beneficial species at our iNaturalist project.

Onthophagus granulatus male; photo by E.L. Engasser

Onthophagus granulatus male; photo by E.L. Engasser

Onthophagus granulatus male; photo by E.L. Engasser

Onthophagus granulatus male; photo by E.L. Engasser

Onthophagus granulatus male; photo by E.L. Engasser

Onthophagus granulatus male; photo by E.L. Engasser

Onthophagus granulatus male; photo by E.L. Engasser

Onthophagus granulatus male; photo by E.L. Engasser

Onthophagus granulatus female; photo by E.L. Engasser

Onthophagus granulatus female; photo by E.L. Engasser

Onthophagus granulatus female; photo by E.L. Engasser

Onthophagus granulatus female; photo by E.L. Engasser

Onthophagus granulatus male genitalia, caudal view; photo by E.L. Engasser

Onthophagus granulatus male genitalia, caudal view; photo by E.L. Engasser

Onthophagus granulatus male genitalia, lateral view; photo by E.L. Engasser

Onthophagus granulatus male genitalia, lateral view; photo by E.L. Engasser