Here is a follow up picture. You can see the small flies sitting on the leaf underside

I'd start spraying those leaves with water...yesterday.

tj

Not small flies. Instead, winged aphids.

That "grub" is a predator. But too many aphids for one lone fellow.

should I turf a rockmelon this bad?

==>>.what does that mean.. pull it out and throw it in the lawn???

that grub looks.. sorta like a ladybug type nymph ... but the color is wrong ... but i think you are on the right track suspecting a predator ...

melons grow so aggressively ... that it would not surprise me.. that they outgrow this ... i wouldnt give up.. unless you have a different shorter season crop you can insert in the spot ...

google jeans suggestion.. and try junkies remedy.. if you have the patience to lift every leaf and spray with water ... and quart bottle with water.. and a hand cramp or two.. should knock the population back to more manageable terms. .. dont forget.. our goal is reduction.. not necessarily eradication .... at this point.. all you have is some leaf disfiguration... rather than a plant killing plague ...

how it all works out.. is unknown at this time ...

ken

Here is a link that might be useful: link

I'd guess a syrphid fly larva, a beneficial. My choice of tools for spraying the underside of the leaves would be a hose, not a spray bottle! Your goal is to physically spray the pests away.

This is something you'll need to tend to a couple of times a week, at the least. It's a lot easier if you catch the problem much earlier. Better take a close look at your other plants!

Thanks fellas. Yes turfing means throwing the plant out. I have taken a hose shower attachment at mist setting and blasted the little pricks off at point blank while being careful to avoid blasting the predatory grubs off as well. They are much reduced now so hopefully the melon will recover over the next week.

I also took the liberty of laying out piles of 1:1 icing sugar/bicarb soda out to distract the ants from guarding the aphids and kill them off at the same time. Just meaning to confirm that bees will ignore the piles and go for the flowers instead as I don't want to kill them too?

Thanks for the help people. I can save these guys as I have checked the other plants and aphids aren't really bad on them.

Understanding Aphids can be of great help in keeping them under control, and this link from UCDavis provides a lot of good information about them.
I find lugging a hose through the garden to spray off any Aphids to be more work than just a spray bottle, and often the pressure from the nozzle often does more damage to the leaf then the Aphids would.

Here is a link that might be useful: About Aphids