Lerp

Lerp is an overlooked, but vitally important food source for Australian birds, particularly honey eaters and pardalotes - the sticky substances that exude from our plants known as manna, lerp and honeydew.  Lerp is 60% sugar - quite a treat for humans and birds.
Tiny insects in the larval state protect themselves from the sun and their enemies by building over themselves little tents, or rather crystal palaces, composed of a gummy and sugary secretion, which is exuded in a semi liquid state from the tube at the hinder end of the body. Lerp is modified bug excrement produced by aphid like bugs called psyllids. It contains starch, something few animals synthesise.  The word is indigenous, from the mallee tribes in Victoria.
In 1845 a stockman, stranded in the Mallee, afterwards wrote, "Lerp, in size and appearance is like a flake of snow, it feels like matted wool, and tastes like the ice on a wedding-cake." 
I would never have noticed this substance on the gum leaf had I not been with our bird watching group.  I came home and searched the net for the above information.  Not a great pic, but each flake is less than 2mm across. I was just pleased to pick up the shiny crystal like surface.
I have to admit I did not eat this sample after photographing it!
The extra shows more clearly how it sits on the leaf.
Looks better in large.