High Sierra Topix

Earlier this month we were at Pingree Lake in the Emigrant Wilderness. About 7:30 p.m. there was a high-pitched whine that sounded like a sick turbine or some sort of machinery. It lasted for about 45 minutes. It repeated each night about the same time.

On night two we figured it out. Looking up, about 20 feet above us, there were clouds of insects. I don't think they were mosquitos, since few of them troubled us.

I've not had a similar experience in years of hiking. What are the insects?

I can't answer you for sure but I have had similar experiences many times--including earlier this year at Many Islands Lake in northern Yosemite--so not too far from Emigrant at all. It also was at about 7:30 on the dot and lasted only 30-45 minutes. I would guess it was the same phenomenon we both saw. My best guess is that it was a mayfly hatching. It is easy to initially mistake them for mosquitoes--especially since their abdomens are striped like a mosquito, but they don't bite, don't have a proboscis, and have two distinctive threads on their tails. Mayflies always hatch all at once and live for only one or two days. Almost their whole lifecycle is in earlier stages, they are adults only briefly to reproduce.

Of course, it could be some other kind of hatching, too.