Waterhouse (Ina or No-brand Grass-dart)
Interesting aspects: This small skipper is very similar to its close relative Taractrocera anisomorpha and both are often found together. It belongs to a group of skippers (Hesperiinae) that are more at home in the hot tropics and subtropics, and this skipper is no exception being found in the northern half of Australia. The skipper, along with most others in the group, has a characteristic wing pose when settled in full sun, with the forewings being held vertical (or nearly so) while the hindwings are held horizontal.
The two skippers are very difficult to distinguish in the field. If you can get close enough while they are sunning themselves with wings opened, then T. ina males can be differentiated from T. anisomorpha males in that the latter possess a dark silvery grey sex mark situated transversely across the middle of the forewing upperside, which is absent in the former. The females are almost impossible to differentiate, but often the yellow forewing postmedian band on the upperside does not touch the yellow subapical-costal patch in T. ina, but the band and patch either touch or are joined by a yellow streak in T. anisomorpha. T. ina could also be confused with the more common Ocybadistes walkeri which may fly together in the Murray-Darling Basin. These two skippers are quickly differentiated from each other by the shape of the thickened antennae tips, which are spoon shaped in T. anisomorha, whereas in O. walkeri the thickened antennae tips are strongly bent or hooked.
It is one of the few endemic skippers that have adapted to the inland arid areas of Australia. It has yet to be found in South Australia, but does occur in the adjacent area of Alice Springs to the north of S.A. and also in NSW on the Hay Plain.
The early stages and habits are similar to its inland relative T. anisomorpha.
Larval food-host: Native and introduced grasses, and those which also occur in South Australia include Urochloa(Brachiaria) species (arm-grasses), Cymbopogon spp (lemon-scented grasses) both native and introduced, *Panicum spp, *Paspalum spp incl. *P. dilatatum and *Sorghum spp (Poaceae). They seem to have a preference for introduced grasses. The larvae eat the leaves of the foodplant.
Eggs: Large, domal or hemispherical shaped, base flat circular, pale yellow when newly laid. Eggs turn white near hatching. The small micropylar area on top of the egg is depressed, the upper part of the egg surface has a very fine indistinct raised polygonal pattern, while the lower part has indistinct, very fine vertical ridges. The base is rimmed. Laid singly on the leaves of the foodplant. The eggs hatch after three days, and the egg shell is eaten by the larva after its emergence.
Larvae: The larval period in captivity is 4-6 weeks in the October-March period in southeast Queensland.
Pupae: The pupal period in captivity is 8-11 days in the October-March period in southeast Queensland.
Flight period: The skipper can be found flying for most of the year in northern Australia but seems to be more common during the wetter months. In the Alice Springs area of the Northern Territory it has been recorded flying during late October. In southeast Queensland the skipper can complete a brood in about 7 weeks in late spring-summer.
Distribution: This skipper is known to occur sporadically throughout the tropical and subtropical northern half of Australia, and has been recorded in the Alice Springs area immediately to the north of S.A. There is also a singular report from the Hay Plain in NSW, which is unusual and may indicate the skipper has a more extensive range that includes the warmer parts of the Murray-Darling Basin. It has yet to be found in S.A. but there seems to be no reason why it should not fly with Taractrocera anisomorpha in the Far Northwest Region of S.A. along the ephemeral creeks and rivers that have their origins in the Musgrave and Macdonnell Ranges, provided its early stages have the ability like T. anisomorpha to aestivate during the drought periods when the grasses die back. It should also be looked for in the Riverland where it could be confused with Ocybadistes walkeri.
Habitat: The skipper seems to favour open woodland habitat having a grassy understorey. In South Australia it may occur along the ephemeral creek and river systems in the arid northwest of the state where perennial grasses commonly occur and remain in a living condition throughout the year. It may also occur in the warmer parts of the Riverland where ample irrigated grasses occur.
Conservation Status: Although the hostplants are widely distributed the skipper tends to be rare, but can be locally common when the habitat and conditions are favourable, particularly in areas of urban and agricultural developments.
Threats: The main threats in its native habitat would be drought, periodic floods, and the effects of pastoral disturbances through over-grazing and trampling by cattle. In agricultural areas it would have to put up with the usual spraying activities.
Conservation Strategy: None required. If it occurs on aboriginal lands in the Far Northwest where cattle grazing no longer occurs, it should be reasonably protected.
Author: R. GRUND, ©
copyright 9 August 2004, all rights reserved.