Nature Notes - Bloodwood Gall

Features

The Desert Bloodwood Tree (Corymbia opaca) is host to an unusual female coccid insect which forms a gall around itself. Galls are swellings on the stems or leaves of plants. The coccid's name is Cystococcus pomiformis and her gall is called a “bush coconut”. The adult female is a yellowy-green colour and has no legs, wings or antennae.

Adaptations

The female coccid never leaves her gall.  Hidden away, she spends her life sucking sap out of the tree's veins. A small airhole is her only link with the outside world. She keeps this plugged with the tip of her tail.

Habitat

Desert Bloodwood Trees grow on the plains and low rocky rises in the desert woodland, shrubland and grassland.

Reproduction

The female mates inside the gall, never seeing her lover who pokes the tip of his abdomen through the airhole. She first gives birth to male offspring only.  These start life as tiny, dark nymphs which grow into small, winged adults inside the gall.  As her sons reach maturity, the mother then produces female offspring. The immature females cling to the long pointed tails of their older brothers when they leave the gall to find a mate.  Having hitch-hiked to a branch outside, each female finds a spot of her own to settle.  She injects a chemical into the plant tissue which causes a new gall to grow around her.  Inside she undergoes a series of moults and grows to her adult shape. The males find an adult female with which to mate. They die soon afterwards - within 48 hours of leaving the gall.

Range

The Desert Bloodwood range is confined to the desert regions of the Northern Territory, Western Australia and South Australia.

Extra Fun Facts

Bush Coconuts have been a source of food and water for desert Aboriginal people.