Heteronympha merope merope (Fabricius)
The Common Brown is probably the main butterfly associated with the exclamation of many people, "Where have all the butterflies gone? They used to be everywhere when I was a child!" This butterfly used to be particularly common in woodland settings in the Adelaide Hills and along the hills face, flying through the understorey or congregating in large numbers on flowering bushes to feed. With the increased pressures of urbanisation and agriculture, and also due to the fear of bushfires and snakes, many native grassland settings for this butterfly have disappeared near Adelaide, and consequently this butterfly has also decreased in numbers. If some grass areas were left uncleared during the annual bushfire preparation, (rather than a total clearance), then this butterfly would recover rapidly.
It is a very interesting butterfly which, like its sister species the Wonder Brown (Heteronympha mirifica) confined to the eastern states, has adapted well to the browning (loss of forests) of Australia since the Miocene geological time period (20 million years BP), having evolved from the more primitive members within the Heteronympha group. The sexes are strongly dimorphic (different appearance), and along with H. mirifica are the only satyrs in Australia to exhibit this morphology difference. The male has silvery-grey sex brand patches on the uppersides of all wings. Both male and female butterflies sometimes also occur in melanic dark forms, particularly in cold mountainous areas of the eastern states of Australia, and this is possibly thermoregulatory related. In South Australia the females occur in two colour forms in which the hindwing underside is either yellowish or purplish. In the Adelaide area the purple form is more common, while in the Lower Southeast Region the yellow form is more common.
Both sexes start emerging in mid-spring (the males slightly earlier), the females mate and then go into hiding (aestivate), and they continue to do so until the following early autumn, some four months away. During this aestivation, the females may occasionally fly during the early mornings or late evenings, or on cool overcast days, particularly to suck on moisture, but do not actively feed from flowers during the day. Their abdomens are full of fat tissue which they live off through the summer months. Although fertile, they remain in a non-gravid state (eggs not developed) until the early autumn. Egg development and laying then commences, with the result that young larvae (especially in the drier temperate areas of Australia) are assured of a good supply of young grass shoots stimulated by mid-autumn rains. Females will also start to feed from flowers in early autumn, and in some cool areas such as in the Lower Southeast of the state, hundreds of them can be seen feeding during the day from scabiosa flowers growing along the edges of roads and pine plantations. A clap of the hands will cause these females to explode off the flowers into a cloud of flying butterflies, but they quickly drop back onto the flowers.
When active, the butterflies have a particular liking for moisture and on hot days are readily attracted to garden sprinklers. The rare mid-summer rain shower will even bring females out from hiding. Both sexes are attracted to seeping gum from tree wounds and fermenting fruit, and during the wine making season the females are attracted to the alcoholic dregs and pressings in large numbers. Both sexes are also attracted to sugary secretions of large aggregations of scale insects on trees, where they can be so intoxicated with the feeding that they can be lifted off the scale by hand. When not feeding, the males actively try to seek out the aestivating or newly emerged females, by flitting close to the ground or searching every nook and cranny. Disturbed, fertile females will reject males by lying on the ground with closed wings. The males sometimes congregate in large numbers when feeding on a favourite flowering plant, and the 3 m flowering stalk of some yacca grass trees (Xanthorrhoea) can literally drip with butterflies. They are also partial to flowering tea-trees growing along creek lines, (such as occur at Morialta Conservation Park), on Christmas bush (Bursaria), and on the purple flowers of Scabiosa. On very hot days the butterflies will congregate in cool, shady areas.
The butterflies have an irregular flight, and prefer to settle on or near the ground. Like most satyrs, the wing undersides are cryptically camouflaged, and it is very difficult to detect these butterflies when they are settled with wings closed and erect, owing to their close resemblance to the ground, or to dead leaf and plant debris. The butterfly is one of the first to fly in the morning, and one of the last to finish flying in the afternoon. It will also fly on heavy overcast days, and sometimes even in drizzle. Males will hilltop, particularly late in their flight season.
Both sexes are normally very timid when not feeding at flowers, and can only be approached with extreme care. Females can be less timid during their aestivation period. Recently, a crew on a fishing vessel going about their business near the edge of the continental shelf some 26 km south of Cape Gantheume on the south side of Kangaroo Island, reported a male fly pass heading south towards Antarctica!
Native and introduced grasses including Austrostipa species (spear grasses), *Agrostis capillaris (brown-top bent), *Brachypodium distachyon (false brome), *Bromus catharticus (prairie grass), *Cynodon dactylon (couch), *Ehrharta species including *E. erecta (panic veldt grass), *E. longiflora (annual veldt grass), Imperata cylindrica (blady or kunai grass), Microlaena stipoides var. stipoides (meadow rice-grass), *Pennisetum clandestinum (kikuyu), Poa spp (tussock grasses) incl. P. crassicaudex, P. meionectes, P. poiformis (coast tussock grass), *P. pratensis (Kentucky blue-grass), P. tenera (slender tussock grass), Themeda triandra (kangaroo grass) (Poaceae); also rarely on Gahnia sieberiana (red-fruit saw-sedge) (Cyperaceae). Early instar larvae feed on the hostplant leaves. The larger, later instar larvae will devour all the softer parts of the hostplant including young seed heads. Kikuyu is toxic to early instar larvae, but older larvae can survive eating this grass. Females have not been observed to lay eggs on Gahnia sieberiana but larvae have been found on young plants of this sedge and managed to complete their development.
Small, pale yellow, subspherical (domal), expanding basally, base and apex flattened, with very indistinct vertical ridges. If green hostplant is present then the eggs are laid near ground level in small batches on the undersides of the hostplant leaf. If the hostplant is not in a green condition, then eggs are laid on the dead leaves or on other debris or plants in the vicinity of the hostplant. Some females will lay on plants (such as soursob Oxalis pes-caprae) adjacent to the hostplant grass. The females flutter close to the ground, then settle and walk about until they find a place to their liking in which to lay their eggs. Females become gravid during March, when they start laying eggs, and continue laying through April to mid May until they die out. The eggs hatch in about 12 days.
The first instar is pale greyish yellow, later becoming green after eating the green leaves of the hostplant, and with sparse long black hairs that are knobbed at their tips. Head brownish black, smooth, shining, with short hairs. The posterior end is not forked in the first instar. Newly hatched larvae eat their egg shells first, then do one of two things. One group will move away to other parts of the hostplant and eventually begin to eat the green leaves if present, or if green hostplant is not present then they will attempt to actively seek it out. The other group, comprising the bulk of the larvae, remain stationary in the position where the egg was first laid. This group will remain in a torpid stationary position until they become wet from rain, but immediately upon receiving the moisture will begin to feed or actively seek out young growing grass tips. If they do not receive the rain they will eventually starve to death (after 2-4 weeks) in this torpid position! This non-active (no loss of energy) diapause stage presumably helps the larvae survive until young grass tips are produced.
The immature larvae nibble the leaf edges, but later instars devour the entire leaf. The long knobbed hairs on the first instar are lost in later instars, and the rear end becomes forked, typical for the Satyrinae. The first three larval instars are green coloured with a narrow yellow lateral line. The final two instars are usually brown in South Australia, with the fourth instar being a much paler brown than the fifth, final instar. Young larvae while still with a green colour remain exposed on the hostplant leaves, but later instars hide around the base of the hostplant coming out at night to feed. The latter larvae emerge soon after sunset to climb the hostplant, and move very slowly. If disturbed while feeding the larva will often release its hold on the grass and drop to the ground, remaining motionless for some time with its head tucked under its body in the shape of a figure 9.
Mature fifth instar larvae are cylindrical shaped, about 35 mm long, being fatter in the middle, the lateral edge is slightly flanged. They are sometimes coloured in shades of green, but in South Australia they are more usually pinkish grey-brown, speckled with darker markings, and with indistinct pale coloured wavy or broken lateral and sublateral longitudinal lines, and a broken black dorsal longitudinal line. (Both brown and green coloured larva forms can develop from a single batch of eggs laid by the same female). The body is without long hairs, but bears numerous short pointed secondary setae imparting a rough scabrous appearance. The head is large, rugose, dark brown with irregular black front and side markings, and numerous short hairs. The top of the head is flat, with a pair of inconspicuous, vestigial horns. The rear end is forked.
Initially the wing areas are pale, subtranslucent greyish green coloured with dark cryptic ventral markings, and the abdomen and dorsal areas are pinkish brown. The greenish colour gradually turns grey after one week and the pupa also gradually becomes opaque, and near the latter stages of the pupa period the pupa turns pale brown. About 12-17 mm long, short and fat, with a roughened surface, generally rounded anteriorly and posteriorly, although the head is wedge shaped anteriorly without horns, there is an indistinct thoracic keel, and the pupa is slightly ridged laterally at the thorax-wing junction, the wing joints are protuberant, and the cremaster is short and spinose.
Most of the pupations take place during spring, either at the base of the hostplant in a silk lined cavity formed by the larva, or more often on the ground where the pupation occurs beneath vegetation debris in a shallow larva formed cavity in the soil with the roof of the structure loosely lined with silk. Although the silken roof has a flimsy appearance, the silk strands are thick and quite strong and prevent the debris above from falling down on the larvae during pupation. The larvae seem to prefer to pupate on their backs and the pupae lie loose inside the cavity. The pupa shell usually breaks into four small pieces when the butterfly emerges. The pupa duration decreases as the season becomes hotter. Near Adelaide it is initially about 45 days in early spring, decreasing to about 28 days in early summer.
Early October to usually mid May, but very dependent on area and elevation, and tend to emerge later in elevated and cooler areas. Females are occasionally seen into early June dependant on the start of the winter season. Only one brood a year. The bulk of the brood emerge together during late spring in warm areas, or early summer in cool areas, but both sexes continue to emerge sporadically into February. Females aestivate until early autumn before commencing egg laying. In contrast, the males (which do not aestivate) gradually die off, and apart from the rare late emergence the males have mostly disappeared by late summer. In the cooler areas such as the Mt Lofty Range and the Lower Southeast the females often congregate in large numbers during the late summer and autumn. The females are one of the longest-lived butterflies to fly in Australia and commonly live for six months, comparable to the Wanderer (Danaus plexippus) and Blue Tiger (Tirumala hamata), and there are records to 7 months.
Occurs in woodland areas in the southern temperate parts of the state receiving more than about 250 mm of annual rainfall. In the Flinders Ranges it is mainly confined to the protected and shady moist valleys. The butterfly also occurs on Kangaroo Island and some other smaller islands. The local subspecies of the butterfly is also found in similar temperate areas of Victoria, New South Wales and southern Queensland, and in elevated areas of the Great Dividing Range in central Queensland. A similar subspecies is found in Tasmania, while a very different subspecies is found in south-west Western Australia.
The butterfly occurs in open temperate woodland and forest, having some grass in the understorey. It prefers a moist habitat where its hostplant remains in a green condition.
No major threats. In urban areas, the nematodes used to combat the introduced Portuguese millipede will also kill larvae of this butterfly.