Cressida cressida
Encyclopedia
The Clearwing Swallowtail or Big Greasy, Cressida cressida, is a medium-sized swallowtail butterfly (family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Papilionidae) found in Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, Papua New Guinea
Papua New Guinea
Papua New Guinea , officially the Independent State of Papua New Guinea, is a country in Oceania, occupying the eastern half of the island of New Guinea and numerous offshore islands...

 and Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...

. It is not a threatened species.

Description

The adults are dissimilar in appearance
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...

. 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
Greaseproof paper
Greaseproof paper is paper that is impermeable to oil or grease and is normally used in cooking or food packaging. Normally greaseproof paper is produced by refining the paper stock and thus create a sheet with very low porosity. This sheet is supercalendered to further improve the density...

. 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
Aristolochia
Aristolochia is a large plant genus with over 500 species. Collectively known as birthworts, pipevines or Dutchman's pipes, they are the namesake of the family . They are widespread and occur in the most diverse climates. Some species, like A. utriformis and A...

species, including A. tagala
Aristolochia tagala
Aristolochia tagala is commonly known as Indian birthwort and locally as Dutchman's pipe.-Distribution:It is widely distributed: the distribution is from the Himalaya to Sri Lanka through South East Asia and China, to Oceania...

in the tropics. More usually, it utilises smaller growing species such as A. thozetii and A. meridionalis ssp. centralis (formerly listed as A. pubera, A. sp. D'Aguilar Range and A. sp. Mt. Coot-tha) in southern Queensland. Cressida cressida occurs predominantly in drier forest throughout its range; in Australia, it is often encountered in dry Eucalyptus
Eucalyptus
Eucalyptus is a diverse genus of flowering trees in the myrtle family, Myrtaceae. Members of the genus dominate the tree flora of Australia...

forest where its hosts grow as small scrambling vine
Vine
A vine in the narrowest sense is the grapevine , but more generally it can refer to any plant with a growth habit of trailing or scandent, that is to say climbing, stems or runners...

s in open areas. It is most common in forests bordering the Great Dividing Range
Great Dividing Range
The Great Dividing Range, or the Eastern Highlands, is Australia's most substantial mountain range and the third longest in the world. The range stretches more than 3,500 km from Dauan Island off the northeastern tip of Queensland, running the entire length of the eastern coastline through...

.

Mating

Cressida cressida is unique in having modified the spermatophore
Spermatophore
A spermatophore or sperm ampulla is a capsule or mass created by males of various animal species, containing spermatozoa and transferred in entirety to the female's ovipore during copulation...

 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.
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