By Drs. Robert & Sonia Vogl
Swallows have returned, perhaps the most graceful creatures we’ve ever seen. Gliding through the sky, they dip and swoop to catch insect meals on the wing. They’re building nests in the barn, the corn crib, the garage. As they swooped, we wondered: What will they eat? Will they have enough to sustain them and their young? We can feed seeds to winter birds, but not enough insects to sustain summer residents.
Nearly everyone is aware of the decline of monarchs – big, beautiful, charismatic butterflies. Their numbers have dropped to less than 1/10th of what they were in 1996. Recent upswings in their population have been temporary and minuscule in comparison to their dramatic overall decline. Habitat loss (abandoning habitat lands and planting them with crops) and crop herbicides which drift to milkweed plants and kill them are understood to be the major causes. Milkweed are the host plant for Monarch caterpillars; without it, they will perish. Many people are now planting milkweed in their yards, hoping to help in some small way.
Populations of honeybees, the major crop pollinators, have plummeted. Although many possible causes have been posed, the drop is likely due in large part to the use of neonicotinoid insecticides.
Those who were entranced by fireflies are aware that their numbers have also dropped. Where they once lit up fields and valleys, only a few blink intermittently.
But what about other non-charismatic insects? According to an article by Gretchen Vogel in Science, those anonymous species that once gummed up many car windshields are no longer making a mess. Their numbers have fallen.
Although insects have been collected from around the world, a leading study has been done by members of the Krefeld society in Krefeld, Germany, housed in an old school building. Most of the insects have been collected from semi-natural areas – meadows and agricultural fields which still maintain populations of wildflowers, birds and small mammals.
Amateurs have been active in Europe since the early 20th century, quietly collecting their data. During the 1940s and 1950s a priest encouraged priests from around the world to send their insect specimens to him.
In the 1970s and 1980s local authorities asked the Krefeld society for information on insect populations to help manage their natural areas. Identical traps were used in all of the sites to standardize collection. Each trap catches about the daily diet of a shrew, so depletion is not a question.
In 2013, the Krefeld society made an alarming discovery: insect catches had declined nearly 80 percent since 1989. Insect species in decline included those overlooked by the general population, including hover flies, important pollinators, whose numbers dropped by nearly 85 percent.
Possible reasons for the decline include the elimination of semi-natural habitats and the use of neonicotinoid pesticides which have been implicated in the death of honeybee colonies. The chemicals, applied to seeds, are water soluble and can move to pollinator plants. While insects affected may not have been killed directly, they are less able to navigate, communicate, and find mates, showing drops in reproductive rates of over 50 percent.
Plans for future research include automated data collection stations.
Swallows are also in decline. We hope they can find enough food. When we return to the garage and they fly out, we’re reminded to check the windshield for insects.
For a humorous (but factual) perspective on the subject, see That Gunk on Your Car, by Mark Hoestetler, Ph.D.
Drs. Robert and Sonia Vogl are the President and Vice President of the Illinois Renewable Energy Association.