Onthophagus sagittarius

Beneficial

Common name(s)

Sri Lankan dung beetle, Sagittarius dung beetle

Taxonomy

Family: Scarabaeidae Subfamily: Scarabaeinae Genus: Onthophagus Species: Onthophagus sagittarius (Fabricius, 1775)

DNA barcode

DNA barcode available: specimen information 

Adult diagnosis

Total body length 10.0–13.0 mm (0.39–0.52 in). Body shape oval; may be caked in dung. Color dark brown; elytra pale brown. Medium-sized Onthophagus, more than 10 mm. Clypeal apex rounded to sinuate; not strongly produced or reflexed in either sex. Head of male with paired tusk-like horns on the clypeus; female with single horn on the frons. Ocular canthus not completely dividing eye. Pronotum with anterior angle rounded. Pronotum of male with broad, hump-like process; female with spine-like process. Front tibia of male and female similar. 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

Southeastern Asia. This species is native to southeastern Asia, where it has been recorded from Malaysia, Indochina (Hawaiian Entomological Society, 1964), India (Chandra, 2000), and Sri Lanka (Edwards, 2007). This species was introduced to Australia (Edwards, 2007).

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

Like related Onthophagus species, this nocturnal scarab is a dung tunneler, with the female creating a burrow under or near a fresh dung source (Simmons and Emlen, 2008). 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. This species is confined to tropical areas that experience warm, wet summers, and annual rainfall over 800 mm (31.5 in) (Edwards, 2007).

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.

Status in Hawaii

Established. There is conflicting information regarding the arrival of this species to Hawaii. Markin and Yoshioka (1998) reported that Onthophagus sagittarius was purposely released on Oahu in 1957 and 1958. However, Harris et al. (1982) stated that the species was accidentally introduced. Regardless, this scarab is now established on both Molokai and Oahu, where it is one of the most commonly encountered dung beetles (Nishida, 2002; Harris et al., 1982).

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 probably intentionally imported.

Similar species

This scarab could be confused with Onthophagus of similar color and medium size (more than 10 mm): Onthophagus nigriventris and Digitonthophagus gazella.

Major males of these species can quickly be distinguished by examination of the head armature (O. sagittarius with two tusk-like horns on the clypeus versus O. nigriventris without horns or ridges, D. gazella with two short, upward curving horns at the base of the head).

Females and can be separated by examining the base of the head (O. sagittarius with a single horn O. nigriventris with a sinuate ridge, D. gazella with a straight, transverse ridge).

Other names (synonyms)

Onthophagus erectus Wiedemann, Onthophagus javanus Fabricius, Onthophagus obtusus Wiedemann, Onthophagus oryx Fabricius, Scarabaeus sagittarius Fabricius

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Onthophagus sagittarius male; photo by E.L. Engasser

Onthophagus sagittarius male; photo by E.L. Engasser

Onthophagus sagittarius male; photo by E.L. Engasser

Onthophagus sagittarius male; photo by E.L. Engasser

Onthophagus sagittarius male; photo by E.L. Engasser

Onthophagus sagittarius male; photo by E.L. Engasser

Onthophagus sagittarius male; photo by E.L. Engasser

Onthophagus sagittarius male; photo by E.L. Engasser

Onthophagus sagittarius female; photo by E.L. Engasser

Onthophagus sagittarius female; photo by E.L. Engasser

Onthophagus sagittarius female; photo by E.L. Engasser

Onthophagus sagittarius female; photo by E.L. Engasser

distribution map for Onthophagus sagittarius

distribution map for Onthophagus sagittarius