Thanks.
Well, I know many females use that waxy secretion to protect the eggs they lay. And I know many other insects, such as aphids and many kinds of nymphs have it, as well. Not sure of the function off-hand. No need for guessing. I'll go have a look.
Here ya go:
"Nymphs of many Fulgoroids produce wax from special glands on the abdominal terga and other parts of the body. These are hydrophobic and help conceal the insects. Adult females of many families also produce wax which may be used to protect eggs."
There seems to a bit of debate and not enough research into the specifics of this. Some adults produce the filaments, as well, in both male and female. Some cover certain parts and not others, etc. Some believed to do it for different reasons.
I know certain aphids release these waxy filaments that are made up of excess sugars produced from feeding from their host plant. Some ants are attracted to this, as well, and will care and protect for the aphids in return for feeding off of these sugars, (in filament or liquid form.) I think the filaments are the same in these planthoppers, however, I've never heard of them working in sort of symbiotic nature with another creature for them.
Anyway, that's my quick synopsis on it. It is subject to change.