Gap in the Map
The egg map reveals the shortage of monarchs in the northeastern end of the range, where not a single egg has been reported yet.

It's not uncommon for monarchs to arrive much later in this region. In fact, they are often not detectable until July when the 2nd generation is on the wing. The late arrival means monarchs can complete fewer generations during the summer breeding season. This is one reason the northeast is typically a less productive region.

Concentrated in Corn Belt
The egg map shows breeding is concentrated in the Corn Belt now. In the fall, 50% of the monarchs that make it to Mexico typically come from that region. This is why agricultural practices in the Corn Belt raise such concern. Habitat loss on the principal monarch breeding grounds is now considered the main threat to the population.

• Habambee Environmental Science School