I found this to be interesting:
[url="http://abcnews.go.com/US/wireStory?id=155746"]Monarch Butterflies Go Missing in Vt.[/url]
"Probably the worst year in a decade," said Kent McFarland, a conservation biologist at the Vermont Institute of Natural Science. "I went to some of my favorite spots, and I've seen maybe two in Vermont this entire season."
Gordon Nielsen of Hinesburg, who has studied insects, backed up the observation: "I haven't seen that many this year."
Hundreds of miles south, in Cape May, N.J., volunteers are putting numbers to the Vermonters' hunch. They watch the skies for hours to count the migratory butterflies and in the waning days of the annual movement, they have noted just a fraction of the numbers from past years.
What became this year of the fluttering, seemingly fragile insects is up for speculation.
Monarch butterflies annually migrate from the maritime provinces, northern Canada and the northern United States to the mountains of western Mexico, where they spend the winter. They return north in the spring, though the generations breed, deposit eggs and die en route. The younger generation completes the northbound journey.
In 1999 and this year, monarch butterflies tagged with tiny tracking devices in Vermont were found in Mexico.
The southbound butterflies rely on an autumn abundance of milkweed to eat during their trip, McFarland said. The weed has been in excellent supply in Vermont this season, but with the first killing frost already coating many pockets of the state, that essential source of food is drying up.
McFarland, the director of the Vermont Butterfly Survey, suspects that a wet summer and cool temperatures in the Northeast exacted a heavy toll on caterpillars that would have eventually become butterflies.
Nielsen, a retired University of Vermont entomologist, wonders whether this year's paucity of monarchs didn't have its roots even earlier. In January 2002, large numbers of the butterflies perished in a freak Mexico snowstorm, which might have diminished the numbers that returned this far north and east.[/quote]:D