Eurema(Terias) hecabe (Linnaeus) (Large Grass-yellow)
Interesting aspects: From a distance, this butterfly along with other small yellow butterflies are often confused with the very common Eurema smilax. E. hecabe differs from the latter butterfly in being slightly larger and having the broad black apical and terminal margin to the forewing above, continuous to the inner margin (dorsum) of the forewing. The extent of the upperside hindwing black edge, and the brown spotting on the wing undersides is variable, and is usually due to seasonal variation between the cool winter (dry) and hot summer (wet) seasons. The brown spotting is better developed and the black hindwing margin is less developed in the 'winter' flying butterflies.
When not in a migratory mood, the butterflies are usually seen flying near their hostplants.
A recent DNA molecular study (Braby etal 2006) infers the small yellow butterflies of the Eastern Hemisphere, and particularly the nominotypical hecabe may belong in their own genus Terias or at least may form a separate subgenus group within Eurema. However, the study is incomplete and based on other morphological data, some other small yellow butterflies in this hemisphere group may not belong in the subgenus Terias. The genus Eurema was originally applied to some small yellow butterflies occurring in the Western Hemisphere.
Larval food-host: Various tropical and subtropical legumes. Documented hostplants occurring interstate and which can also be found growing in South Australia include **Cassia spp, **Caesalpinia spp, **Senna spp (Caesalpiniaceae); some Acacia spp incl. **A. baileyana (Cootamundra wattle), *Paraserianthes(Albizia) sp (Mimosaceae); *Aeschynomene sp (Budda pea), Indigofera spp (indigo's), Sesbania cannabina (yellow pea-bush) (Fabaceae). There has been a recent (2009) unconfirmed report of females in north Queensland laying eggs on *Medicago laciniata (Cut-leaf Medic) (Fabaceae), that have coiled bindii-like seed pods. Females have also been seen to utilise *Trifolium repens (White Clover) (Fabaceae) in Queensland, but in nearly all cases the larvae did not develop through to the adult stage, but if they did then they were 'stunted'. In South Australia its hostplants have not been recorded in the wild, but Sesbania cannabina is likely to be the principal candidate as adults have been seen lingering about these plants in the Far Northeast.
Flight period in S.A.: The butterfly is seen all year round in the tropical north of Australia. It flies south during the southern warmer months. In South Australia, it has been documented during April, early September, mid November and mid December, but as there have been very few butterfly surveys in the Far North of the state, these flight periods will certainly be extended.
Distribution: Normally a butterfly of the humid tropics and subtropics. It is a strong vagrant, moving south into subtropical latitude areas during the warmer months after monsoonal rains. The South Australian records are from Port Lincoln, the south side of Lake Eyre and from the extreme Far Northeast area. In the latter area they are usually seen flying near a hostplant Sesbania cannabina that grows along the banks of the ephemeral creeks and lakes after floods, or within their flood plains. Small semi-resident populations of the butterfly are likely to occur in this area during favourable seasons. Breeding stocks are replenished from interstate northern tropical areas after good monsoon rains, with the butterflies following the major creek-lines down into South Australia. These breeding populations die out during the winter months, as their early stages cannot tolerate the frosty nights. The population adults then die out or reverse migrate to northern, frost-free areas. A poor monsoon season in the inland areas of Queensland and Northern Territory will not produce a migration into South Australia. The butterfly is not biologically suited to the subtropical and temperate conditions of South Australia.
Habitat: The likely principle hostplant Sesbania cannabina occurs sporadically in the extreme Far North of the state, particularly along the ephemeral creeks of the Lake Eyre Basin and more particularly the flood plain areas of the Cooper and Diamantina-Warburton Creeks.
Conservation Status in S.A.: A vagrant. Locally resident after periods of good inland rains. Common in the north of Australia.
Threats: No major threats.
Conservation Strategy: None required.
Author: R. GRUND, © copyright 14 December 1999, all rights
Last update 20 January 2002.