Can anyone tell me what this is?

[Dudzy]

I have seen this on a few trees before but never found out what the go is.
We have a big bottlebrush in our front yard (taller then the power poles) and near the top are these growths.



You can see the difference in leaves

[Paul B]

its a bit hard with these pics...my guess is sawfly larvae
see if you can squirt some down with the hose

[Paul B]

It might also be galls, abherrant growth/swellings caused by insect attack

[Ash]

It is a mistletoe in the family Loranthaceae, probably a Dendropthoe species and the native food host for Jezabel butterflies Delias. It is a parasitic plant whose seed is dropped onto the tree in bird poo and then germinates and taps into the water supply of the tree and parasitises it. It is a type of hitch-hiker. If you get a close up of the leaves or if it gets flowers I might be able to tell which one it is.
cheers
Ash

[Luke308]

spitfires? Although I haven't seen them since I was a kid. But we used to get them in a tree (euc I think) every year. They are ugly black things with white hairs that look like caterpillars of sorts. They a found in bunches on branches and spit some sort of liquid which burns from memory.

Oops I just googled them and they are known as sawfly larvae as banksiaman already mentioned.