Lemon Migrant

Catopsilia pomona pomona (Fabricius)

pomona adult
Pale form

Interesting Aspects

Occurs as pale and dark forms, which differ mainly in that the dark forms are more yellow and in the females the width of the black colour along the wing margins is better developed, and there is sometimes a dark purple central blotch in the hindwing beneath in the pale female form. The chief distinguishing feature is that the dark forms have black antennae while the pale forms have pink antennae. Both forms fly together and are produced from the same batch of eggs. Breeding studies suggest that higher temperatures and longer day length may promote the dark form. Genetic dominance studies have not been undertaken.

Observations in the eastern states indicate that the early stages of the butterfly are unable to survive frosts or extended cold periods below 15 degrees C, and in tropical monsoon areas the butterfly is reproductively dormant during the dry season.

Life History

How a butterfly grows into an adult.

Larval Food Host

Cassia and Senna spp, the tropical and subtropical varieties with larger flowers, including **C. brewsteri (cigar cassia), *C. fistula (golden shower), S. pleurocarpa (striped-pod cassia) (Caesalpiniaceae); also Neptunia spp (Mimosaceae).

Eggs

Laid dispersed in small batches on the leaves of the hostplants.

Larvae

Mature larvae are 45-50 mm long.

Pupae

30-34 mm long.

Flight Period in South Australia

The butterfly is seen all year round in the tropical north of Australia. It migrates south during the southern warmer months, particularly during the monsoon wet period. Very few butterflies reach the southern settled areas of South Australia and Victoria, and these usually arrive in April in a very worn condition. Flight records from the Alice Springs area (just north of the SA border) include early February 1975, late April to early May 1977, early July 1982 and late December 1974.

Distribution

Normally a tropical butterfly. Within South Australia there is only one old (1935) documented record of the butterfly, from Berri in the Riverland. The butterfly is more likely to be observed in the far north of the state. Within the central arid areas of Australia during the butterfly's migrations, the butterfly has a fondness for water bearing, shady gorges and ravines of rocky ranges.

map_pomona.gif (9.22 KB)
Habitat

The butterfly normally requires tropical, humid woodland habitat. However, its strong migrant tendencies take it south into subtropical areas during the warmer months. A hostplant Senna pleurocarpa is reasonably common in northern pastoral areas of South Australia, and the introduced Cassia fistula is sometimes grown in the homesteads and town gardens in the same areas. It is possible that opportunistic breeding may occur in those areas during favourable years. The butterfly is not biologically suited to the temperate conditions of southern South Australia.

Conservation Status in South Australia

A migrant. Common in the north of Australia.

Threats

No major threats.

Conservation Strategy

None required.