Cressida cressida

Cressida cressida
male
female
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Lepidoptera
Family:	Papilionidae
Genus:	Cressida
Species:	C. cressida
Binomial name
Cressida cressida (Fabricius, 1775)
Synonyms
Papilio cressida Fabricius, 1775

The Clearwing Swallowtail or Big Greasy, Cressida cressida, is a medium-sized swallowtail butterfly (family Papilionidae) found in Australia, Papua New Guinea and Indonesia. It is not a threatened species.

Description

The adults are dissimilar in appearance. Males have translucent forewings with two black spots and a fine black border thickest at the apex of the wing. The hindwing has a thick black border surrounding a central white area with black veining. The black border encloses a series of red spots, whose size and number can vary. Females have wings that are a semi-translucent tawny colour, similar to aged greaseproof paper. This colouration is most intense immediately after the butterfly emerges, but soon fades and renders the wing almost totally transparent. Patterning of the female wing is similar to that of the male, but greatly reduced and diffused, with white areas on the hindwing extremely reduced and all red markings replaced by pale pink. Both sexes have a black body heavily marked with red scales.

Ecology

The larvae feed on Aristolochia species, including A. tagala in the tropics. More usually, it utilises smaller growing species such as A. thozetii and Eucalyptus forest where its hosts grow as small scrambling vines in open areas. It is most common in forests bordering the Great Dividing Range.^[2]

Mating

Cressida cressida is unique in having modified the spermatophore into an external mating plug known as a sphragis (plural sphragides). The sphragis acts to increase the chance of individual males successfully producing offspring by preventing other males from inseminating already mated females. There is evidence that females have attempted to counter this strategy by evolving remarkably broad genitalia that makes it more difficult for sphragides to remain in place. The evolutionary incentive to counter the sphragis is likely the nutritional benefit females obtain from the spermataphore, hence multiple matings provide female butterflies with additional resources. Orr provides an excellent summary of the evolutonary dynamic between males and females of C. cressida.^[3]

References

1. ^ Australian Plant Census (2010). "Aristolochiaceae" (PDF). http://www.chah.gov.au/chah/apc/interim/Aristolochiaceae.pdf. Retrieved 6 March 2010. 
2. ^ Michael F. Braby (2000). Butterflies of Australia: their Identification, Biology and Distribution. Melbourne: CSIRO Publishing. ISBN 9780643065918. 
3. ^ A. G. Orr (1999). "The Big Greasy, Cressida cressida (Papilionidae)". In R. L. Kitching, E. Scheermeyer, R. E. Jones & N. E. Pierce. Biology of Australian Butterflies. Monographs on Australian Lepidoptera. 6. Melbourne: CSIRO Publishing. pp. 115–134. ISBN 9780643050273. http://books.google.com/books?id=cTFychx78QIC&pg=PA115.