Rajah Brooke’s birdwing (Trogonoptera brookiana)
Rajah Brooke’s birdwing is listed on Appendix II of CITES (1).
Creating beautiful flashes of colour when gathered in large groups, Rajah Brooke’s birdwings are dramatically patterned butterflies. The male’s elongated, jet black forewings are decorated with metallic green triangles along the edges and there is a small area of iridescent azure blue towards the butterfly’s body. The black hind wing of the male is smaller than the forewing and also has a large area of green colouration. The body and antennae of this species are black, and the head is red. Females have browner wings with white patches in place of the green found on males. The caterpillars are brown and green with paler brown spikes. There are many subspecies, and all differ slightly in their colouration (2).
Rajah Brooke’s birdwing is found in Malaysia, Borneo, and Sumatra, as well as many of Sumatra’s offshore islands. It has at least 11 subspecies: Trogonoptera brookiana albescens inhabits Burma, Thailand, and peninsular Malaysia; T. b. mollumar inhabits peninsula Malaysia; T. b. trogon inhabits Sumatra, Simeulue Island, and the Sipura Islands; T. b. jikoi inhabits the Tuangku Islands and the Banyak Islands; T. b. akikoae inhabits the Tanahmasa Islands; T. b. mariae inhabits the Batu Islands; T. b. toshikii (also known as T. b. apolloniae) inhabits Siberut Island; T. b. cardinaali inhabits the Singkep Islands and the Lingga Islands; T. b. natunensis inhabits the Natuna Islands; T. b. brookiana inhabits North Borneo; T. b. haugumei inhabits East Kalimantan (3).
Found on the sandy banks of rivers and hot springs within tropical rainforest (3).
Rajah Brooke’s birdwing was named after the White Rajah of Sarawak, Captain Brooke, who ruled an English Province in northern Borneo in the middle of the 19th century (3). It is a striking species which gathers in groups of up to 80 individuals to drink from puddles. Newly emerged males must absorb mineralised water containing the sodium and potassium ions necessary to activate adult behaviour. Holding the wings in a V-shape, the butterflies drink and squirt the excess water from the abdomen in small jets or droplets. Rajah Brooke’s butterfly also drinks nectar from Bauhinia plant species (2).
It was previously thought that the sex ratio of this species favoured males, as females are rarely encountered, but there are now known to be equal numbers of males and females, although females are secretive and elusive. Courtship takes place in flight and the male will chase the female as she dives to evade him. If she accepts his advances, they will mate in flight; however, she may reject him, displaying her intentions by lying with the wings flat on the ground and the abdomen pointing upwards. Some males do not court the females, instead ambushing them in order to mate. Once the female is ready to lay eggs, she flies slowly and erratically in search of a food-plant, identifying the correct plant species using taste-sensitive chemoreceptors on the forelegs. Up to 50 small, round, white eggs are laid on the plant, hatching to produce caterpillars that rapidly consume the leaves, before pupating. In the pupa, metamorphosis occurs before an adult butterfly emerges (2).
These butterflies are threatened by habitat loss, as rainforests are removed for urbanisation and conversion to agriculture. Loss of tree cover and vegetation around rivers can cause them to run dry, as water is not retained in the soil. This also causes soil erosion, and both these factors are potential threats to Rajah Brooke’s butterfly (3).
These butterflies occur in several protected areas across their range and are listed on Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) which limits and regulates trade in this species (1).
For further information on this species see:
Matsuka, H. (2001) Natural History of Birdwing Butterflies. Matsuka Shuppan, Japan.
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- Antennae: pair of sensory structures on the head of invertebrates.
- Metamorphosis: an abrupt physical change from the larval to the adult form.
- Pupa: an inactive stage in an insect’s development when reorganisation takes place to create the adult form from the larval form. In butterflies the pupa is also called a chrysalis.
- Pupation: the process of becoming a pupa, the stage of an insect’s development, when huge changes occur that reorganise the larval form into the adult form. In butterflies the pupa is also called a chrysalis.
- Subspecies: a population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.