Hard to see colors from the picture, but they look a lot like Tabacco/Tomato worms to me. If these are they, not a composting worm, but a pest to be eradicated.

Looks like beetle larva or grubs.

Shepard,

Where did you find them ? In decaying matter (compost pile) or in plain earth (while digging a hole, or in cracks of clay)

When alive, do they crawl on their backs to move away, or do they walk normally, on their belly ?

If they crawl on their back, they're composting larvae from the rose beetle (aurata cetonia) and they can't be the ones damaging your palm trees. When adult, the beetle does very little damage to flowers.

I agree with not-boring Charlie that they are grubs : not worms.
As far as I know, the tomato hornworm grub is green and needs to be differentiated from its relatives which are relatively harmless.

If you put aurata cetonia grub in a google image search, you can compare your grub to the images of the rose beetle grub.

Comparing hornworm grubs to others is good practice for noticing differences. IME grubs look too alike.

Here is a link that might be useful: green grubs

more

Here is a link that might be useful: grubs

If you have chickens, they'll be happy to get rid of them for you. Lots of protein, yummm, I think :)
Which part of the palm trees do they damage? The leaves or the roots?

Looks like a June bug grub or other scarab beetle grub.

Al

Thank you'll for ur insightful thoughts n opinions.

FrancoisefromAix, I found them when I was tilling the earth. And I think they walk on their belly.
Barbararose21101, I collected about 40 ones and none was green. They ranged from as small as 5 ml to 3 cm long. And thanks for the links.
Otis, Indeed, my chickens enjoy eating them when they find them :)
And I think they damage the root when they are young but I have seen great damage on the leaves and "heart" of the palm tree as well. The heart and leave damage is caused by beetles according to an agricultural specialist. After reading all the comments, those beetles might be the adult form of these larvae or whatever they called.

As I mentioned, I collected 40 larvae in a container and will see if they will make any compost or rather mature and be full insects!

I shall keep you posted with the outcome.

This post was edited by shepard.KSA on Fri, Nov 21, 14 at 18:08

Update
All 40 larvae have died! No compost made:(

Hey Shepard,
I'm sorry for your loss, I hope you weren't too much infatuated ;-) However don't cry too much, because if the larvae were in the earth, I guess that's because they feed on living roots.
Beetles whose kiddos live on decaying matter lay their eggs in decaying matter.
Beetles whose kiddos live on living roots lay their eggs in earth where there are roots.
So if those larvae wanted to eat your roots, and then when adults perhaps your plants or trees or palms, well good riddance then :-)
For compost better to rely on bacteria that you can't see and won't be disguted by !
Or you could get some worms and start vermicomposting ! It's great fun and at the end you get a fantastic compost !

Died or turning into cocoons? That is what these guys do isnt it? Isnt there a state between the picture above and a cocoon where they dont move much if at all?

And if they are in fact expired they will still contribute to the compost :)

I wanted to post this here before because it seemed somewhat along the same line of 'alternative' composting creatures, what about tomato hornworms? Anyone aware of what richness their castings might provide? I know they are sure effective at turning tomato leaves into black chunks.

If they hadn't died, what they put out will not be worm castings but more like worm food for the red wigglers. What I have observed from grubs, their digestive system don't seem that efficient.
At least that's what I remember reading re. BSF in worm bins.

I believe that is a larvae from those big green flying beetles. I know them as Japanese beetles. However I do believe that is not their true name.

Thanks a lot FrancoiseFromAix,
I think you are right those larvae lay their eggs in the earth and they later feed on the roots and when adult start to damage the palm tree leaves!
I got so interested in worm composting and contacted some suppliers from the states but they said that the worms will not make to where I am because of time and logistics constrains mainly. I have not been able to locate local suppliers so far.
Nexev, The guy that works for me told me that these larvae died, I didn't get to see them in that state, he told me that he threw them to the chickens.

Otis11,
That's an interesting piece of info

Time45z10,
I have to say that I have never seen green flying beetles. But who knows, it might be really the case. All I know is that there are many beetles and I dunno which type and I have seen the all-time-most-devastating insect which is the red Palm weevil

Those are VERY DESTRUCTIVE "June Bug" Cotinis nitida (Linnaeus, 1758)or "Japanese Beetle" Popillia japonica or a related species, larvae (grubs).

They do not 'compost' in the classic (this site) sense. Your infestation is SERIOUS! Get SERIOUS help or you will lose all of your plants!

They make great fishing bait.

Paul

Here is a photo of the adult.

As kids we would tie a thread onto a leg and fly them around... guess a kid does what a kid needs to do when they cant afford a kite.

"Those are VERY DESTRUCTIVE 'June Bug' ... or 'Japanese Beetle' ... or a related species, larvae (grubs). ... Your infestation is SERIOUS! Get SERIOUS help or you will lose all of your plants! "

Wow. That's quite a warning. The OP will not lose everything. They're not grubs of very serious Japanese beetles or harmless June Bugs. They will not destroy everything and applying enough of any sort of remedy to try to get rid of their resident population will arguably cause more damage than these things will. You might be very surprised to have an estimate of just how huge their soil population is, poisoned or not.

They don't eat leaves; they live in the soil. They're no big deal. Throw them to the birds, smash them, or ignore them and then get on with things. They're just a part of the system and a non-issue.