Onitis alexis

Beneficial

Common name(s)

Alexis dung beetle

Taxonomy

Family: Scarabaeidae Subfamily: Scarabaeinae Genus: Onitis Species: Onitis alexis Klug, 1835

Adult diagnosis

Total body length 15.0–22.0 cm (0.59–0.86 in). Body shape subquadrate posteriorly; may be caked in dried dung. Color of head and pronotum dark green to blackish-green. Clypeus weakly sinuate or rounded. Frons with weakly developed central tubercle; female tubercle comparatively larger than in male. Front tibia of male elongate, curving ventrally and inward at apex; female tibia less elongate and curved than male; tarsi lacking in both sexes. Tibia of middle leg gradually expanded to a triangulate apex. Hind trochanter lacking spine on posterior margin in both sexes. Hind femur of male with well-developed, curved spine on posterior margin; female lacking spine.

Larval diagnosis

Undescribed. For Scarabaeinae (Ritcher, 1966): Grub C-shaped, hump-backed, cylindrical, cream-colored. Maxilla with galea and lacinia distinctly separate. Epipharnyx with tormae united mesally, anterior phoba present. Antennae with 4 or 5 apparent segments. Distal segment of antenna reduced in size. Legs 2-segmented. Anal opening surrounded by fleshy lobes.

Native range

Africa and the Mediterranean. Onitis alexis is broadly distributed from Spain and Syria, southward to South Africa. It is, however, largely absent from the heavily forested areas of western Africa (Krikken, 1977).

Plant host(s)

None. Onitis spp. feed on dung as both adults and larvae (Edwards and Aschenborn, 1987).

Life history

This species inhabits savannahs, grasslands, and pastures where they are most active at dusk and dawn. Adults show a preference for the dung of large herbivorous mammals. The species is recorded feeding on elephant, cattle, and buffalo droppings (Krikken, 1977). Male-female pairs dig a dung-lined tunnel under a dung source to an average depth of 17 cm (6.7 in). The burrow is then stocked with 150–200 grams of dung, which is made into multiple sausage-like shapes. One to four eggs are deposited into each dung-sausage (Edwards and Aschenborn, 1987). The egg to adult lifecycle can be completed in as little as two months in the summer, but it may require over a year if conditions are poor. In good habitat, there can be several generations per year (Tyndale-Biscoe, 1990). Larvae cannot survive cool, wet winters (Tyndale-Biscoe, 2006).

Pest potential

None. This species recycles dung and is beneficial for ranching and farming in Hawaii. Being a dung feeder, this species poses no threat to crop or ornamental plants. Additionally, this species is not a threat to native dung beetles because none are known from Hawaii or Guam.

Status in Hawaii

Established. This scarab was released in 1976 at Parker Ranch on Big Island where it is now established (Nakao and Funasaki, 1979). Like most of Hawaii's dung beetles this species was introduced to help control populations of the horn fly (Haematobia irritans), a biting pest of livestock.

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 introduced.

Similar species

Three species of Onitis are recorded from Hawaii (none are known from Guam). Onitis alexis is separated from the other Onitis species by examination of the middle tibia (O. alexis with middle tibia gradually expanded to triangulate apex versus abruptly expanded to a trapezoidal apex in O. phartopus), the hind trochanter (O. alexis lacking a spine on the posterior margin versus O. phartopus with well-developed spine in male), hind femur of the male (O. alexis with a curved femoral spine versus O. vanderkelleni with straight spine, O. phartopus lacking a spine) and color (O. alexis dark green to blackish-green with brown elytra versus color entirely dull black in O. vanderkelleni and O. phartopus).

Other names (synonyms)

Onitis africanus Gillet, Onitis aygulus Latreille, Onitis inuus Klug, "Onitis sphinx" of authors, Onitis tuberculatus Balthasar

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Onitis alexis female; photo by E.L. Engasser

Onitis alexis female; photo by E.L. Engasser

Onitis alexis female; photo by E.L. Engasser

Onitis alexis female; photo by E.L. Engasser

Onitis alexis male hind legs, ventral view; photo by E.L. Engasser

Onitis alexis male hind legs, ventral view; photo by E.L. Engasser

Onitis alexis female hind legs, ventral view; photo by E.L. Engasser

Onitis alexis female hind legs, ventral view; photo by E.L. Engasser

Onitis alexis male genitalia, dorsal view; photo by E.L. Engasser

Onitis alexis male genitalia, dorsal view; photo by E.L. Engasser

Onitis alexis male genitalia, lateral view; photo by E.L. Engasser

Onitis alexis male genitalia, lateral view; photo by E.L. Engasser

distribution map for Onitis alexis

distribution map for Onitis alexis