You mean wrap with insulation? If they are in the conditioned area, it's probably not necessary unless you have distant parts of the house that would not get enough heat because of the heat loss of the ducts, but if the ducts go through a normally unheated area of the house, of course they should be wrapped.

To wrap makes sense if the ducts are in an area where the heat loss from the ducts is not real beneficial. The more important information is to verify the duct does not leak at the joints. I heard a reference the other day that the majority of the duct systems in residential application leak more than 30% of the air moving.

These ducts will be running through a crawl space....THANKS

Is the crawl space cold in the winter and hot in the summer?

I'd think that, even if it's a nonvented, conditioned crawlspace, it'd probably be smart to insulate your ductwork. If it's a standard, vented crawl, doubly or triply so.

Just don't do that without first making sure that every possible seam is sealed with foil tape (only if really clean), mastic, or butyl-backed foil tape. That's joints, seams along straight sections, and even the adjustable/miter joints of fittings. And make sure that the boots at the outlets are sealed to the drywall/whatever with caulk, foam, or tape, as appropriate (I like foam b/c it's wicked sticky).