The big grub looks similar to the big Narcissus fly larva. They are active when the leaves are still growing - then the little grubs go down the neck of the bulb, using the hole left by the now-dead leaves. The grubs then have all winter to feast...:(

There is a spray you can use several times over the season but you have to be qualified to apply it.

Another possible is to cover the leaves with horticultural fleece weighed down very well to stop ambitious female flies from finding a way in.

The other grubs are probably just gate-crashers, come for the feast on the remains of the bulbs.

For really precious bulbs, if you can squeeze out the grub - or hook it out - leave the frass behind because it stops the bulb rotting before it can be eaten (cunning, eh!), and replant the bulb in a pot with a gritty mix to grow on/recover. It takes a couple of years but I know from experience it can be done.

panchiro,

I believe the previous post corretcly identified the large grub. I would tend to believe the smaller critters are fairly common bulb maggots or bulb borers that also attack onions, garlic, lilies and other below ground crops. The rot normally ocurs from the bulb being damaged by either of these critters. It may be that the small ones are immature forms of the large one you pictured but either way I have found the best way to control any critter that spends at least a part of their life in the ground is through an application of beneficial nematodes that consume the critter from the inside out and like I say is effective against any critter that spends its larval stage on or in the ground. However, there are different strains of nematodes and I don't recall the one that is most effective in your area. At the link below you can contact them and they will direct you to the one for your area and best of all it can be sprayed on and watered in rather than digging. Being completely honest with you though, it is not inexpensive to do but it is highly cost effective and best of all, it is totally environmentally safe. For the bulbs you do save, I think I would do well to dust them with a little sulfer before I replanted them to give some protection against bacteria and further rot. Any that are already showing signs of rot you might give them a rinse of a 10% bleach solution, rinse and let dry. Then dust them and replant. It often works and you have nothing to loose.

Here is a link that might be useful: Gardening Resource

Thank you both for the info and tips. I'm going to look into the nematodes. It may not be in the budget for this year though. I did dig up what remaining bulbs I have and will try the bleach solution. I will also have to find a source for the sulfur.

Thanks,
Simone