The bush coconut, or bloodwood apple, is an Australian bush tucker food. It is an insect gall with both plant and animal components: an adult female scale insect and her offspring (of genus Cystococcus) live in a gall induced on a bloodwood eucalypt tree (Corymbia). Bush coconuts can vary from golf ball to tennis ball size. They have a hard and lumpy outer layer. The inner layer is a white flesh that contains the female insect and her offspring. There are three known species of Cystococcus responsible for forming the bush coconut: Cystococcus pomiformis, Cystococcus echiniformis and Cystococcus campanidorsalis. C. pomiformis is the most common species. The bush coconut is found in Western Australia, the Northern Territory, Queensland and New South Wales.
The bush coconut is picked from the host tree and cracked open to allow the flesh and scale insects to be eaten. Both have a high protein content and are used as a food source by humans and other animals. The name ‘bush coconut’ is derived from the white flesh of the inner layer, which is similar in appearance to that of a coconut, and the taste of the flesh has been said to have a coconut flavour. The bush coconut has been depicted in Indigenous Australian dreaming and used as inspiration in their artwork.
Discovery
The bush coconut was not mentioned in early documents about Aboriginal insect foods and is considered one of the lesser known bush tucker foods eaten by Aboriginals. The bush coconut was first described by Walter Wilson Froggatt in 1893 as Brachyscelis pomiformis. Froggatt collected material from north-western Australia and listed two locations in his original description of the species: Torrens Creek, North Queensland and Barrier Ranges, North Western Australia. Froggatt noted Aborigines ate both the insect and soft flesh of the young gall. The species identified by Froggatt has been revised several times from Brachyscelis pomiformis to Apiomorpha pomiformis, Ascelis pomiformis and finally to Cystococcus pomiformis. Australian entomologist Claude Fuller briefly described another species of insect inducing the bush coconut, Cystococcus echiniformis, in 1897. Fuller provided a more detailed description along with line drawings of the adult female and its gall in 1899. Some scientists considered C. pomiformis and C. echiniformis to be of the genus Ascelis. This was, however, rejected in 1986 by P. J. Gullan and A. F. Cockburn who found that Ascelis and Cystococcus are closely related but distinct genera. They identified what they suspected as a third species in a paper published in 1986. This species was then named and formally described as C. campanidorsalis in 2015 by Semple et al. Bush coconuts are found on many different species of bloodwood eucalypts (Corymbia) across Australia.
Description
The bush coconut is an insect gall. It is a combination of plant and animal: an adult female scale insect lives in a gall induced on a Corymbia, the bloodwood eucalypt.
Scale insect
The insect inducing the gall is a coccid in the genus Cystococcus. Three species have been identified: C. pomiformis and C. campanidorsalis and C. echiniformis. The most common species is C. pomiformis. The live coccid is a yellow-green colour.
Female
The female Cystococcus has no legs, wings or antennae and has been described as ‘grub-like’. Females grow up to 4 cm long. The body is elliptical to sub-spherical in shape and yellow-green in colour. The female scale insect lives within the fleshy interior of the gall. The female's anus is non-functional. Females are generally soft-bodied although sclerotisation produces a hard dorsal 'button' and ventral pore plates.
The button is used to plug the gall entrance and it is also the site where mating occurs. The shape of the button distinguishes the species of Cystococcus. This allows the female to be identified without opening the gall. C. pomiformis has a convex-shaped button that varies from broad and dome-shaped to pointy and conical, C. campanidorsalis has a bell-shaped button and C. echiniformis has a concave-shaped button.