THE MONARCHS ARE MISSING

Scientists and citizen scientists investigate monarch butterflies.

The first question was where the butterflies went in the fall. After the discovery of their wintering colonies in the oyamel forests of Mexico, the question changed to why their numbers have dwindled. Scientists point to a number of possible causes: weather variations and climate change; habitat reduction; herbicide use that has reduced the population of milkweed, where monarchs lay eggs and their caterpillars feed, and other wildflowers, where adult butterflies feed during migration; widespread use of neonicotinoid pesticides; and the rise of a disease due to garden planting of a winter-blooming milkweed species that encourages the butterflies to overwinter in Southern states. Hirsch, a former biologist and graceful science writer, explains the monarch life cycle and its complex migration clearly, setting the stage for her exploration of the many mysteries that still surround the population’s ups and downs. She stresses the hopeful fact that monarchs can bounce back relatively quickly, because they lay so many eggs, and she offers realistic options for readers to participate in research and to encourage butterflies. Her clear explanation is attractively presented, illustrated with stock photographs of butterflies and some human researchers (of varying ages and ethnicities) as well as with occasional appropriate charts, all supported by extensive backmatter. Sadly, the index is skimpy, a disservice.

An excellent introduction to a familiar scientific puzzle.