like many plant and animal species, they (your typical fireflies) can't cross the rockies. but we do have glow worms out here.
and this time of year may be a good time to go out on a moonless night in the redwood forest to see them. but i'm not an expert on finding 'em. anyone know where and when is opportune to find them?

Vermont is beautiful, I have visited White Mountain before they put the guard on it, what an adrenaline rush looking down that rock and realizing that one false move could mean death. What are the fireflies doing when they migrate through your yard? Are they newborns?

So is it only your yard they migrate through? perhaps you have a food source that can not be found in your neighbors yards, are you aware of any unique plants you have in your yard that may be attracting them? I have not had the time to research their migration habits, or even if they do migrate, but right now it is breeding season for many insects. I am finding large male mosquitoes inside homes seemingly everywhere I go.

I looked at several sources for food. The sources I checked indicate that they are mostly predatory insects, the larva feed on other larva, snails, and slugs. The larva can overwinter for a long time (which I'm sure is happening in your weather). There is a species in New Zeland (Arachnocampa
luminosa) that the larva use their light to attract insects to them. The insects get tangled in a silen thread they weave and the larva feed on the insect.

A European variety (Lampyris noctiluca ) is reported to possess a nuerotoxin that acts much in the same manner that a spider uses the toxin, It imobilizes the prey and liqifies it. (www.conknet.com/~planter/g...flies.html)

I found nothing specific to the US variety, and could not find any references that detail the migration of fireflies, but several sources confirm that they do migrate. There is more documentation on migration of the Malaysian species than the species common in the United States. But I really did not look for more than 20 minutes. I am convinced that your beesties eat worms, slugs and snails. I am really interested in their syncronised lighting, if you can get some footage of this event please send it to me.