a bright male sipping dew from the grass
a female feeding on a dandelion blossom
a faded butterfly laying eggs on poke milkweed
four eggs on six plants in a suburban garden

Stalled in Northeast
The migration is lagging behind in the northeast, where it's stalled at latitude 41°N. The distance to this region from Mexico always means a later arrival; this is the outermost extent of the breeding range.

Cold temperatures appears to be holding the butterflies back this year even more than normal as the comparative maps show. A delayed arrival will delay generations and allow less time for numbers to build. Monarchs may be more scarce than normal this summer. In the short life-span of a butterfly, single days or weeks can impact the population significantly.

Late-May Surge
Of the 12 week migration so far, 33% of the seasons sightings were reported during the last 2 weeks. This graph documents the late-May surge that represents the emergence and northward migration of the 1st spring generation. Thanks to the observations contributed by citizen scientists we know when this year's northern breeding season began and can estimate generation timing.

Counting Generations
Monarch generations are continuing to cycle. It takes about one month for each to develop. Over the summer, three generations will be produced in the north.

June: grandchildren

July: great-grandchildren

August: great-great-grandchildren—the generation that migrates to Mexico.

Recent observations along California's Trinity River reveal a migration pathway. The river concentrates the monarchs to detectable levels and makes tagging and studying possible.

• Monarchs of the Pacific Northwest