Need ID on caterpillar having a bad hair day.

[Tim Benzedrine]

I found these critters devastating small walnut sapling. I'm not sure if they look this way normally or if they may be hosting some sort of fungus or parasite. If they are infested with something, it sure hasn't affected their appetites. I'm starting to lean towards them being infected with something, they just don't look natural to me.
I checked all my field guides and searched the 'net but came up with nothing, so I thought I'd give folks here a shot at it. Maybe my Google-fu was weak.

The first is a single caterpillar, the second is a group of three feeding on a walnut leaf. Any ideas?

 

[OldHag]

Butter Nut Woolly worm!!!


http://bugguide.net/node/view/32179

 

[Tim Benzedrine]

Ding-ding-ding! You nailed it!

I even looked at BugGuide and struck out! How did you find it? Or did you already know what it was and just referred to BugGuide as photographic confirmation?
Either way, good job! I'm a little relieved, I hate to see things suffering from nasty infestations of some sort.

 

[OldHag]

I cheated!!!
I googled Caterpillar white stuff. Then looked at the images... Found a pic of it then went to the link found the name then looked it up on Bug Guide...

 

[ZergFront]

Looks like a couple of the insects I've seen with waxy substances on them; aphids, mealybugs, scale insects etc. Most predators hate eating insects with that substance. Tried feeding my jumping spiders some kind of collard aphid and they steered clear of them.

 

[dtknow]

It'd be interesting to confirm if that is indeed extruded wax. Can it be brushed off? It appears in most of the photos to follow a pattern yet can also be haphazard.

 

[spiderfield]

Beautiful find! I was going to point out that they had too many prolegs to be Lepidopteran. :}

 

[Tim Benzedrine]

I cheated!!!
I googled Caterpillar white stuff. Then looked at the images... Found a pic of it then went to the link found the name then looked it up on Bug Guide...

Hey, whatever works! I'm just pleased to have it identified!

Beautiful find! I was going to point out that they had too many prolegs to be Lepidopteran.[/i]

On following up on OldHags's ID I learned that they are the larvae of a type of sawfly rather than something Lepidopteran. Of course then I had to look up what a sawfly might be.