It’s summer. At the summer solstice on 6:46 a.m., the sun reached the tropic of the Cancer at 21.5 degrees north latitude, the highest point it attains on our globe before turning south.

Warming the earth, it also prompts responses that synchronize the life cycles of northern insects and host plants. If, for example, a black swallowtail female should hatch and mate before dill, carrots and parsley appear, she will lack a host for her eggs. Adapted to feed on members of the carrot family—including wild Queen Anne’s lace—black swallowtail larvae starve when placed on other plant species. (Note that the larva in the picture, right, is climbing a stem of dill.)

A similar tie binds monarch caterpillars to milkweed. It’s the single plant family on which adult females will place their eggs.

Several weeks before the solstice, grandchildren of monarchs that wintered in Mexico had reached Maine and southern Canada and begun to visit this region. Jane Harvey, a friend in Honesdale, PA, observed a monarch on her street on June 4, “progressing up through tree branches. Wow, what a lovely sight.”

Danielle Rutledge and her daughter, Kelsey, “saw our first monarch on Saturday, June 18 around 1:00 p.m. when we were mowing a lawn in Galilee.”

Because I try to record the monarch migration into this area, I’d appreciate hearing from readers who observe monarchs this month. Please contact me at 570/29-7053 or at info@butterflybarn.org.