Birdwing

• Troides prattorum × Troides oblongomaculatus bouruensis — Troides mixtum
• Ornithoptera rothschildi × Ornithoptera priamus poseidon — Ornithoptera akakeae
• Ornithoptera victoriae × Ornithoptera priamus urvillianus — Ornithoptera allotei

After mating, females immediately begin to seek appropriate host plants; climbing vines of the genera Aristolochia and Pararistolochia (both in the family Aristolochiaceae) are sought exclusively. The female lays her spherical eggs under the tips of the vine's leaves, one egg per leaf.

Early instar larva of Troides minos

The caterpillars are voracious eaters but move very little; a small group will defoliate an entire vine. If starved due to overcrowding, the caterpillars may resort to cannibalism. Fleshy spine-like tubercles line the caterpillars' backs, and their bodies are dark red to brown and velvety black. Some species have tubercles of contrasting colours, often red, or pale "saddle" markings. Like other members of their family, birdwing caterpillars possess a retractable organ behind their heads called an osmeterium. Shaped like the forked tongue of a snake, the osmeterium excretes a fetid terpene-based compound and is deployed when the caterpillar is provoked. The caterpillars are also unappealing to most predators due to their toxicity: the vines which the caterpillars feed upon contain aristolochic acid, a poisonous compound known to be carcinogenic in rats. The feeding caterpillars incorporate and concentrate the aristolochic acid into their tissues, where the poison will persist through metamorphosis and into adulthood.

Pupa of Ornithoptera victoriae

Birdwing chrysalids are camouflaged to look like a dead leaf or twig. Before pupating, the caterpillars may wander considerable distances from their host plants. In O. alexandrae, it takes about four months to get from egg to adult. Barring predation, this species can also survive up to three months as an adult.

Birdwings inhabit rainforests and adults are usually glimpsed along the forest periphery. They feed upon—and are important long-range pollinators of—nectar-bearing flowers of the forest canopy, as well as terrestrial flowers, such as lantana. They are strong flyers and seek sunlit spots in which to bask.

Breeding behaviour varies little between species; the female's role is relatively passive, slowly fluttering from perch to perch while the male performs an elaborate, quivering yet stationary dance 20–50 cm above her.

Copulating pair of Ornithoptera euphorion (female above, male below). The sexes are quite dissimilar in appearance, as is typical of species in the genus Ornithoptera.

Birdwings are typified by large size (up to a maximum body length of 7.6 cm or 3 inches and a wingspan of 28 cm or 11 inches in O. alexandrae), showy colouration (in contrasting shades of green, yellow, black, white, and sometimes blue or orange), and slender, lanceolate forewings. With few exceptions (i.e., the New Guinean O. meridionalis and O. paradisea), the hindwings lack tails. Sexual dimorphism is strong in Ornithoptera species only, where males are black combined with bright iridescent green, blue, orange, or yellow while the larger and less colourful females are overall black or dark brownish with white, pale brown, or yellow markings.

Males and females of most Troides birdwings are similar and have jet black to brown dorsal forewings, often with the veins bordered in grey to creamy white. At least one of these darkly-coloured species (T. rhadamantus) possesses thermoreceptors on the anal veins (A2 and A3) of the wings and on the antennal clubs. The antennal receptors of the clubs—which also possess hygroreceptors that measure atmospheric humidity—are known as sensilla basiconica. The thermoreceptors are sensitive to sudden increases in temperature; they are thought to help the butterfly thermoregulate and avoid overheating while basking.

The colours of most species are pigmentary (via papiliochrome); but two species, Troides magellanus and the much rarer T. prattorum, are noted for their use of limited-view iridescence: the yellow of the dorsal hindwings is modified by bright blue-green iridescence which is only seen when the butterfly is viewed at a narrow, oblique angle. This "grazing iridescence" is brought about through diffraction of light (after back-reflection) by the wings' extremely steeply-set, multilayered rib-like scales (rather than the ridge-lamellae of most other iridescent butterflies, such as Morpho species). Such limited-view iridescence was previously only known from one other species, the riodinid Ancyluris meliboeus. In A. meliboeus, however, the iridescence is produced by ridge-lamellar scales and features a wider range of colours.

The close evolutionary relationship between Troides and Ornithoptera butterflies is well demonstrated by the fact that commercial breeders have produced numerous hybrids between the two.

The final and smallest genus is Trogonoptera with just two species. They resemble each other, being overall black with iridescent green markings and a red head. Females are duller than males.

Female choice can have a serious impact on mate selection and successful reproduction. Several species of Ornithoptera have been known to create hybrids if they have no access to their own species.[9] Troides oblongamaculatus females have been known to choose to mate with other species such as Ornithoptera priamus poseidon, which will attempt mating if their own species is not to be found near by. The females will typically resist mating attempts by covering their abdomen with their forewings or dropping to the ground, making mating near impossible. Although the females usually resist these mating attempts, they have been noted to be more susceptible if they have not had previous encounters with males of their own species.

Some male Ornithoptera species demonstrate courtship behaviour. Ornithoptera priamus posedion males will approach a female carefully, and examine the female for several minutes. After consideration, the male may choose to hover twenty to thirty centimeters above the female, displaying the bright yellow marking on its hindwings. Meanwhile, the forewings will move forward, exposing the abdomen and androconial hair tufts. Mating is only attempted when the female has ceased to flap her wings.[12] After about thirty seconds of the display, the male will attempt copulation.

In many animals, females often mate with more than one male.[13] Males who are able will adapt strategies such as postcopulatory guarding to ensure the paternity of the offspring. Following insemination, it is common for the male Ornithoptera to produce a mating plug, which will seal the ostium bursae and prevent remating by the female, as new sperm is unable to enter the opening. The plug does not impede oviposition and may stay in place for the duration of the female's life.

Sexual dimorphism is very prominent in Ornithoptera species, the males being black with brightly colored markings of blue, green, orange or yellow and the females are overall black or dark brown.[14] The sexual dichromatism functions in mate recognition by the use of photoreceptors. Due to the protected nature of Ornithoptera it has been difficult to study the spectral sensitivities of the sexes although this difference in coloration alludes to the idea of sensory exploitation of the female's photoreceptors. The sensory bias of females to select for males with brighter wings has yet to be studied in Ornithoptera.

Gyanandromorphism is a very rare condition in which an organism simultaneously expresses both male and female phenotypes. It is only observed in species that express strong sexual dimorphism. Gynandromorphs are suspected to be due to genetic errors associated with cell division such as nondisjunction, as well as fertilization of binucleate ova and fertilisation of multiple sperm that may fuse and act as a second nucleus. Ornithoptera is known to commonly exhibit this phenomenon, but little to no research has been successful in determining why. Those who experience this phenomenon, usually females, show male-pigmented tissues on their wings.

• Wikimedia Commons has media related to Ornithoptera and Troides
• Wikispecies has information related to Ornithoptera, Trogonoptera, and Troides