Ornithoptera Alexandrae - Biology

Biology

The female Queen Alexandra’s Birdwing lays about 27 eggs during its entire lifespan; this estimate was made by Ray Straatman by dissecting adult females. Newly emerged larvae eat their own eggshells before feeding on fresh foliage. The larva is black with red tubercles and has a cream-colored band or saddle in the middle of its body. The larvae always ringbark the host vine before moving onto adjacent leaves or vines to become a pupa, which is golden yellow or tan in colour with black markings. Male pupae may be distinguished by a faint charcoal patch on the wing cases; this becomes a band of special scales in the adult butterfly called a sex brand. The time taken for this species to develop from egg to pupa is approximately six weeks, with the pupal stage taking a month or more. Adults emerge from the pupae early in the morning while humidity is still high, as the enormous wings may dry out before they have fully expanded if the humidity drops. The adults may live for three months or more and have few predators, excluding large Orb Weaving spiders (Nephila spp.) and some small birds.

The adults are powerful fliers most active in the early morning and again at dusk when they actively feed at flowers. Males also patrol areas of the host plants for newly emerged females early in the morning. Females may be seen searching for host plants for most of the day. Courtship is brief but spectacular; males hover above a potential mate, dousing her with a pheromone to induce mating. Receptive females will allow the male to land and pair, while unreceptive females will fly off or otherwise discourage mating. Males are strongly territorial and will see off potential rivals, sometimes chasing small birds as well as other birdwing species. Flight is usually high in the rainforest canopy, but both sexes descend to within a few meters of the ground while feeding or laying blue eggs.