SOUTH AUSTRALIAN BUTTERFLIES
Data Sheet

Ocybadistes walkeri hypochlorus Lower   (Southern Grass-dart)
Ocybadistes walkeri sothis Waterhouse   (Greenish Grass-dart)


Male

Interesting aspects:  This skipper belongs to a group of skippers (Hesperiinae) that are more at home in the hot tropics and subtropics.  Along with Taractrocera papyria, it has adapted to cold temperate areas of Australia and Tasmania.  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 (somewhat reminiscent of the FA-18 fighter jet).

The skipper occurs as two subspecies in South Australia.  The subspecies hypochlorus is presently recognised as a separate relict population having its centre of distribution in the South Mt Lofty Ranges.  Another subspecies sothis that occurs in similar moist habitat areas of Victoria, Tasmania, NSW and Qld, has been gradually extending its range westwards from southeast NSW and eastern Victoria, either by natural incursion or by accidental introduction on instant-lawn products or other fresh-cut grass/hay products.  Prior to 1970 the latter subspecies was unknown in central and western Victoria, although interestingly it has been known in Tasmania from historical times.  Subspecies hypochlorus differs from subspecies sothis on the wing uppersides by having slightly more extensive orange-yellow markings, and the brown areas in new specimens are dusted with yellow scaling.  On the hindwing undersides, the ground colour is yellow with only a faint green suffusion (distinctly greenish in sothis) and the postmedian band is indistinct.

The skipper flies in grassy areas just above the tops of the grass, and has a very rapid flight.  Both sexes are fond of feeding from small herby flowers.  Males will set up small territories in grassy habitat where they will wait with the characteristic open wing pose, but periodically will fly off to either check out nearby grassy areas looking for new females with which to mate, or to chase off other males.  Females also fly in grassy areas, and have a slower flight when in an egg laying mode, and will periodically land on the grass to lay eggs or sun themselves, and will cover large areas looking for suitable grassy habitat to lay eggs.  The skipper is easily approached with care when settled, but once in full flight they are quickly lost to sight due to their small size.

Life History

Larval food-host:  Native and introduced grasses including *Brachypodium distachyon (false brome), *Bromus spp (brome), *Cynodon dactylon (couch), *Ehrharta erecta (panic veldt grass), *E. longiflora (annual veldt grass), Enteropogon acicularis (branching umbrella grass or curly windmill grass), E. ramosus (tussock umbrella grass or windmill grass), Imperata cylindrica (blady or kunai grass), *Lolium spp (ryegrass), *Panicum sp, *Paspalum vaginatum (salt-water couch), *Pennisetum clandestinum (kikuyu), *Piptatherum miliaceum (rice millet), Themeda triandra (kangaroo grass) (Poaceae); also rarely Dianella sp (flax lilies) (Liliaceae) and the soft leaved Cyperus vaginatus (Stiff Flat-sedge) (Cyperaceae).  The larvae eat the leaves of the grasses and lillies, or in the case of the flat-sedge, the leaf-like bracts.

Eggs:  Large, domal or hemispherical shaped, base flat circular, pale yellow when newly laid, but after 2 days if fertile the eggs acquire a ragged red lateral ring and a similarly coloured micropylar area.  Eggs turn white near hatching.  The small micropylar area on top of the egg is depressed.  The base is rimmed.  Laid singly on the leaves of the foodplant.  Eggs start to hatch after 7 days in early summer.  The egg shell is eaten by the larva after its emergence.

Larvae:  About 23 mm long.

Pupae:  11-13 mm long.

Flight period in S.A.:  It flies during the warmer months, from late September to early May.  There are continuous broods over the warmer months, which can be completed within 11 weeks in summer.  It overwinters as larvae.

flight_walkeri.gif (3297 bytes)

Distribution:  In South Australia subspecies hypochlorus is mainly found in the South Mt Lofty Ranges, but there are other odd records in the eastern temperate parts of the agricultural belt.  It has yet to be found on Eyre Peninsula, southern Yorke Peninsula, Kangaroo Island or the extreme southern parts of the Lower Southeast Region.  It may have a wider distribution than presently known as the skipper is small (bee size) and is easily overlooked.   Subspecies sothis is reported to occur at Barmera and Berri in the Riverland of SA, and also at nearby Broken Hill in NSW.   Another subspecies of the skipper occurs in northwest Australia.  Other subspecies occur in the northern tropical island areas of the Australian Faunal Region.

map_walkeri.gif (11485 bytes)

Habitat:  The skipper is found in areas where its grass foodplants remain in a soft green condition throughout the year.  It is particularly fond of urban areas where lawn grass occurs in a rank condition, along open damp grassy creek courses, and also in irrigation areas.

Conservation Status in S.A.:  It is often locally common in urban Adelaide and in surrounding areas where its habitat has not been interfered with, but outside of the South Mt Lofty Ranges area it is very rare.

Threats:  In the natural environment the main threat is drought and the effects of agricultural disturbances.  In the urban environment, well manicured lawns and gardens will keep skipper numbers down, as will the use of toxic sprays and herbicides, especially in irrigated areas.  The gradual incursion of subspecies sothis into South Australia may pose a threat to the integrity of subspecies hypochlorus.

Conservation Strategy:  None required at present, although the incursion by subspecies sothis presents an interesting dilemma as to whether subspecies hypochlorus should be protected by introducing it to Kangaroo Island and southern Eyre Peninsula.

 

Author:  R. GRUND, copyright 4 July 2002, all rights reserved.
Last update 4 July 2002.