That's a grub. They're the yongsters of scarab beetles.

A number of grubs eat roots. But determining just which particular grub you might have is easier said than done.

All those grubs means its time to go fishing

Yup, those are the bad old grubs that everyone loves to hate. They do eat some plant roots, however, more than likely they will have pupated and emerged from the soil as adult beetles by the time your tomatoes would be in danger from them. As you turn these up you could put them someplace where the birds can get to them, especially if you have blackbirds and strlings about.

Thanks everyone, one more question, should I put any Grub killer in the soil? I hate to use pesticides, but was wondering if I should? there are only a very few of them that Ican find...maybe one overy 6 to 10 inches as I was digging around.

You could apply Bacillus popilliea, Milky Spore Disease, and/or beneficial nematodes to aid in controlling these grubs if that is necessary. Any of the "grub poisons" will also harm the beneficial soil life you have, earthworms, etc., and will do little to actually control the grubs because if those things really did we would not have very many beetles around after all the poison that has been applied.
If you have fewer than 5 grubs per square foot you do not have enough to be concerned about. If you have 10 or more grubs per square foor you might have something to think about in terms of control.