Yes, we are looking for baby monarchs. Caterpillars, that is. We have two types of milkweed currently in bloom in Riverside Park, common milkweed (Acelpias syriaca) and butterfly weed (Asclepias tuberosa), but we have no caterpillars.
Adult monarchs (Danaus plexippus) regularly feed on these flowers, but in nearly 20 years of watching, I have witnessed only one crop of monarch caterpillars, and those were on a cultivar of (Asclepies incarnata), swamp milkweed. We have a mating population, we have food sources for both adults and larvae, so what gives?
If you don't know, monarchs that overwinter in Mexico, breed, then return northward where they lay eggs on a member of the Asclepias genus. Four generations are then born during the summer months, the first three generations live only 2 to 6 weeks. Those that migrate — the fourth generation — live 6 to 8 months and don't breed until the following spring.
Common milkweed (left) and butterfly weed (right) blooming in RIverside Park near the 97th Street overlook parking lot.