Sunday, March 23, 2014


 Amyema cambagei
With a careful look, you’ll find the tangled-looking foliage of a needle-leaf mistletoe Amyema cambagei among the vertical branchlets of its host bull oak, Allocasuarina luehmannii. I photographed it  this morning, out near Kulpi.
These mistletoes are flowering their little hearts out at present. they can be found on bull oaks, and on belahs (Casuarina cristata).

Here is a closer look at the flowers.There is a bit of shortage of nectar in the wild, at the moment, so these blossoms were very popular with a wide variety of insects.

The Family Loranthaceae. (The Edible Mistletoe family)

Bull Oak and its Galls
Allocasuarina luehmannii

Though not usually thought of as a tree of the eastern Darling Downs, this plant can be found here.
It doesn’t like our dominant soil types, the red and black soils, high in clay, that are derived from basalt bedrock. Geologically speaking, however, basalt is a relative late-comer to the area. It arrived here only some 35 million years ago, as lava welling up through cracks and vents, and spreading to cover an older, sandstone-based landscape, and the rich soils which have formed from it - red where they have weathered in situ, and black where they were washed further afield into what was once an upland swamp - are the soils that make our area famous.
The sandstone still shows through at the surface in some spots, though, and that is where we can find bull oaks. Some examples are: between Goombungee and Meringandan, in the Silverleigh Road area, North of Kulpi and around Peranga, and around Leyburn.
Bull oaks are distinguished from the other local members of the casuarina family by their rather open, light green, upright branchlets. Small trees look as though they have all been carefully gelled and combed upwards. Older trees may have drooping branches, but all the branchlets end with an upward lift.
A curious characteristic of these trees are these rather beautiful galls. They look like some kind of woody fruit, but are actually formed as a result of an insect, laying an egg on a branch. The tree responds by growing this surprisingly complex gall.

Cutting it open reveals a little grub. Note its cozy little cave in the gall, with a hole for excreta at the tip.

I know almost nothing about gall insects, though I am fascinated by the beauty of the galls they are able to create on their host plants. When I originally published this post, I was able to track down that the insect (see above and below) was a species of Cylindrococcus, but mistakenly thought that the tiny red insects were some kind of parasitic mite.
So I am delighted to have been set right by someone who was kind enough to write a comment saying "The insect is indeed a Cylindrococcus sp. The red guys are crawlers or the offspring of female who spends her life entombed. The crawlers exit the hole and a dispersed by wind."
 Not "mites", but babies! Isn't nature wonderful?

What’s the difference?
Most Casuarinas and Allocasuarinas (until recently all called Casuarinas) are known as “she oaks”. This was an early colonial name, and was insulting both to the trees and to women.
The timber was thought to resemble the familiar oaks of England Quercus robur, whose hard, heavy wood was used for shipbuilding.  The timber of these colonial “oaks” however, was not good enough for that purpose, which was frustrating in a colony whose first expansion was along the coast, and which therefore badly needed boats and ships. So the local “oak” was given the derogatory appellation “she”.
The name “bull oak” defies explanation.
It usually used for just one species, now called Allocasuarina luehmannii, though in a few localities it is applied to the plant more often known as black oak, or black she oak -  Allocasuarina littoralis.
A modern myth, to be found on the internet, is that Allocasuarina species (plants whose seeds are shiny red-brown or black) are “bull oaks” and that Casuarina species (with dull grey or yellow-brown seeds) are “she oaks”. This doesn’t stand up to inspection, however. There are about 58 Allocasuarina species, and most are called “she oaks”.
So why are they “bull” oaks?
Do you know? (Tell me, if you do!)


Unknown said...


The insect is indeed a Cylindrocooccus sp. The red guys are crawlers or the offspring of female who spends her life entombed. The crawlers exit the hole and a dispersed by wind.

Patricia Gardner said...

Well, well,well!
Not mites, but babies.
Thank you so much for the response.

adam g said...

Thanks I couldn't find the casuarina galls in a google image search anywhere else on the net! We have something similar in Melbourne, Australia.

Patricia Gardner said...

Hi Adam.
There is a great sense of wonder, isn't there, on discovering that these lovely galls are the result of some sort of combination between the DNA of the plant, and the interaction with the insect. What a world of marvels we live in!