Diasemia grammalis, also known as the Arrowhead, is a moth of the family Crambidae.[1] It is likely endemic to New Zealand and has been observed in both the North and South Islands. The species inhabits open dry herb field areas. Adults are day flying and are on the wing most commonly from October until March. Larvae feed on the ground the roots of native grasses and shrubs including Muehlenbeckia axillaris.
The expansion of the wings is from 1⁄2 to 5⁄8 inch. The forewings, which have the termen very oblique, are dull brown; the dorsal and central area is cream-colour to about 2⁄3 there, are three short thick black bars on the dorsum and a straight oblique white: line from the costa at about 3⁄4 not quite reaching the dorsum. The hind-wings are dull-brown with two black-edged whitish bars.[4]
Adults can be variable in the depth of ground colour on their wings as well as the extent of the white markings, which in some specimens can become dominant.[4]
Distribution
This species is likely endemic to New Zealand and is found both in the North and South Islands.[5][4]
Behaviour
Adults are fast flying and diurnal.[6][7] They are commonly seen on the wing from October until March.[8] Adults are also attracted to light and have been captured with light traps.[9]
Habitat and hosts
Muehlenbeckia axillaris and roots
This species inhabits open dry herb field areas from the coast up to altitudes of around 1000m.[8][10][7] The larvae feed on the ground amongst leaflitter on the roots of native grasses and herbaceous plants including Muehlenbeckia axillaris.[5][11]
