Image: MonarchWatch/ORLEY "CHIP" TAYLOR

It's been a bad winter for the monarch butterfly. Although most insects in temperate climates stay put in some form or another throughout coldest months of the year, the tiny monarchs annually migrate to Mexico by the millions. Of all species of Lepidoptera (butterflies and moths), no other travels so far. Indeed, some of them fly up to 3,000 miles for their winter sojourn south of the border (see map).

But this past season something went very wrong, and a large number died, according to a recent report from the University of Kansas. One possible explanation is a winter storm that hit the mountains of Mexico early in March. "It could conceivably have removed up to one sixth of the monarchs in the overwintering colonies," says Orley Taylor, a professor in the department of systematics and ecology at the University of Kansas, who has been studying monarch butterflies since the early 1990s and directs the MonarchWatch organization.

But there are also unconfirmed reports from both environmental groups and local people that loggers sprayed the trees with pesticides, killing the monarchs so that they could harvest the lumber. "There are reasons for people to spread this rumor, and there are reasons why it could be true," Taylor says. "It is very difficult to sort that out at this time." Either way, he adds that "the very idea that there are rumors about spraying and logging is very disconcerting to a lot of us. We look at this as being a real fight, a real battle for preservation, so that the butterflies will have a wintering safe site."