First migrants. On August 31 Mary Greene observed a monarch butterfly, “flying strongly south over the fields behind my house,” near Beaver Brook in Sullivan County. It was the earliest reported migrant in 2004.

Then, Eve Skier, coach of the girl’s tennis team at Honesdale High School, watched a monarch drift south across the courts during a practice on September 1.

And as I write on Labor Day, I’ve been handed a message from Joyce Rioult of Berlin Township, who observed a monarch flying south through her yard about 10:45 a.m.

Tagging pioneer. Curious about the southerly flights of monarchs each year, Canadian biologist Fred Urquhart began gluing handwritten tabs of paper to their wings, most of which washed off in the rain. That was in 1938.

Eventually, he perfected a workable adhesive and was rewarded on a visit to Mexico in January 1976, when he discovered a tag of his manufacture on a monarch clinging to a downed tree limb. Calling his office in Canada, Urquhart learned that butterfly PS397 had been tagged the previous autumn at the University of Minnesota.

Today, we know that central Mexico is the goal of eastern migrants, but migration routes are poorly understood.