Shall we say that 'every dog has its day'? These particular caterpillars/moths (Family Erebidae) are 'on a roll right now.' It's temporary; their populations might crash this coming year or keep going for another year or two---but 4-5 years seems about average for various insect populations to surge in numbers for a while.

I have seen more caterpillars like this in the last couple of years. If you're writing from Bernalillo Co. (?), I've received specimens from the 'i-40 corridor'---both west and east of you---and also from Lincoln Co. in the mid-elevations. They have been collected from rangeland as well as pihyon-juniper forest and the edges of various communities. The host range of the caterpillars seems broad, from various broad-leaf weeds to some common garden vegetables. They're not exactly pests in these situations, but they are attention getting from sheer size. Also, the larger ones show narrow red rings between the bristly segments and red spiracles (breathing pores). Their black bodies are covered in longer, very stiff bristles; they don't sting---but the bristles and the red rings look threatening. The adults are larger than other common tiger moths. These are snow white with black spots on the forewings especially. The larger 'spots' are rings of black rather than black dots.

So---populations of these critters have been on the increase for at least a couple of years. Not unusual. Periodically, the environment 'favors' some species---at least briefly; maybe it gets ahead of its natural enemies for a while. Does that mean that we'll be inundated with moths in the summer? Since a lot of moths in this family---Erebidae---are more active at night, we may not. They might be found around certain security lights before dawn or resting near various plants. They likely take nectar meals to keep up their energy levels; some may also frequent seeps or even 'salt licks' (for minerals) in the higher elevations. 

However, like other erebid caterpillars, they likely are 'tasty morsels' for a variety of enterprising animals including a variety of birds and small mammals. Also, caterpillars are prey for predatory insects like yellowjackets, hornets, paperwasps and the like. And then we have other flies and wasps that use caterpillars as nurseries for their offspring---the parasitoids. As these various natural enemies take advantage of the caterpillar situation from one year to the next, eventually the caterpillar population drops considerably and both they and moths they might become decrease to lower, sustainable levels We don't see a lot of this carnage.

If you see a bunch of these moths next year in your travels, consider yourself lucky. You can tell customers what they are---both as caterpillars and moths. Moths are harmless---and pretty. Caterpillars can be annoying on valued plants---but on weeds, have at it. They likely pupate in the soil or in various debris on the soil.

That should do it, I think.

Cool, thanks for your in-depth answer!