Beetle (Black lawn beetle) Heteronychus arator
Species: H. arator
Binomial name: Heteronychus arator
Synonyms: Scarabaeus arator, Heteronychus sanctaehelenae
Common name: Black lawn beetle, African black beetle, Black maize beetle, Black beetle.
Heteronychus arator is a species of beetle in the subfamily Dynastinae, the rhinoceros beetles. It is native to Africa and it is an introduced to the North Island of New Zealand via Australia early last century and is causing increasing damage to northern North Island pastures. It is present in Northland, coastal Auckland, Bay of Plenty, Gisborne, northern Waikato and northern Taranaki.
It is a shiny black oval-shaped beetle 12 to 15 millimeters long. Males have a thickened tarsus on each foreleg. Heteronychus arator eggs are a greyish white, oval, about 2 mm long.
All life stages are subterranean, although adults can fly. There is one generation per year. Adults generally overwinter in free-draining soil. Adults begin to feed in spring, mate, then lay eggs singly in soil at a depth of about 10 mm. Egg lying continues until early summer. Depending upon soil temperature, eggs hatch within 6 weeks.
Young larvae are white or bluish-white with a brown head capsule and orange spiracles along the sides of the thorax and abdomen. Fully developed larvae are 25 mm long and 6 mm in diameter. Young larvae feed on soil organic matter, while more mature larvae attack plant roots. There are three larval instars. The final instar burrows to a depth of 100 mm to pupate. The pupas are a pale yellow to light brown turning reddish-brown before the adult emerges.
It is a pest beetle as it causes tremendous damage to lawns and other turf, especially during the summer. It also attacks many crop plants and garden flowers, as well as trees and shrubs. The adults and larvae prefer to feed on the roots of pasture or amenity grasses. However is polyphagous, and potato is the most important economic host. Other hosts include maize, grapevine, vegetables such as turnip, cabbage, cauliflower, carrot, lettuce, pea, strawberry, tomato and rhubarb. In New Zealand damaging outbreaks of H. arator in New Zealand are closely associated with above-average spring temperatures.
A photo showing size compare with common slater,