[Video] Amazing outbreak of Orange Hairstreak

Nice. I would like to have an 'outbreak' here in So Cal...of anything!

Thanks for the video mokky.

This not all that uncommon for some species in the US and in other countries, some years. Here in the western US the most noticeable are the spring Vanessa cadui migrations that can contain a few V. carye and virginiensis as well. Some years they are normal or relatively small migrations, but some they actully blanket everything, the ground, all plants, buildings, etc and can be a serious driving hazard. Their spring migrations can run from a week or two to a month or more depending on where you are south to north as they repopulate all the places they usually don't survive the winter at. One year in the late 80's or early 90's was a massive migration year. I lived in Salt Lake City on the west side of the Rocky Mountains, and decided to see just how big the migration was. The Rockies were an eastern edge, but I got in the truck and drove west across the Great Basin looking for the western edge of it. Two states and about 450 miles later I gave up, still hadn't found the edge. Had to be billions of them. Vanessa cardui also migrate south in the fall to overwinter, but in much smaller numbers.

Not counting Danaus plexippus near their overwintering spots along the Pacific Coast, and in Hawai'i, other species spike some years here in the west. But not on a regular schedule like the Vanessa. I remember on one of my trips to SE Arizona to collect for a couple of weeks, there were localized large swarms for miles like in your video of 3 unrelated species, with most blanketing plants in their own habitats. One swing of a net could catch hundreds. They were Brephidium exilis, Libytheana carinenta and Phoebis senna, all resident species there.

I remember another year in extreme SW Utah in the early 90's when Eurema nicippe were the same, and they were considered an influx species that were not resident in Utah. I lived there for 6 years retired , so did leps more days than not. In a normal year there if you saw any E. nicippe at all it was singles, or maybe a couple that had flown in from the south.

There have been many others that I've seen since 1964 when I started doing lepidoptera, but these make the point.

Dear ladobe

Thank you for your interesting story. Yes, Vanessa cardui is sometimes numerous in Japan, but not often as in US.

The outbreak of Gypsy moth is also sometimes observed in Japan.

In those cases, the outbreak seems to continue only for a year. But now we are observing the unusual outbreak of Orange Hairstreak for these several years. Moreover the total amount seems to increase year after year. Thus we assume that this trend is not natural...

At present parasite bees or flies are scarce, so it is hard to imagine when this outbreak ceases.

Cheers,
mokky