Population Building
One sign that the new generation is emerging in the south is an increase in the number of butterflies. This Oklahoma report suggests the population is building.

"Finally my first sighting of 2015 today — and it was of four monarchs — in the vicinity of Green Antelope Horn milkweed."
       — Dennis of Stillwater, OK  May 10, 2015

Compare Years
The timing of arrival in the northern breeding grounds is important and it can vary from year to year, as the migration maps show. The size of future generations is largely determined by arrival time according to Dr. Chip Taylor. He believes the ideal window is the 10-day period from May 11 - 20. Let's see what happens in the week ahead!

Watch Out for Look-Alikes
Thousands of observers track the monarch's migration every spring. These people expand the eyes and ears of scientists, but proper identification is critical.

Look carefully for the monarch's tell-tale field marks — and try to snap a picture. We review all sightings reported to the migration map and will contact you if we need more information for verification.

These identification tips will help you distinguish monarchs from other butterfly species.

• Do You Know a Monarch?