Discovery of insects on a walk

Many people think that nature exists primarily in parks and wild lands, but our gardens can also be filled with life and wonderful discoveries if we have wildlife-friendly plants.

Even if you don’t have a garden, a stroll down a city street, college campus, or green space provides opportunities to observe plant and insect interactions that we typically think are only found in wild lands. Every walk or hour spent working or sitting in the garden is truly time in nature. Different insects and birds are active in every part of the season and also throughout the day. Depending on the date and time of your release, different creatures will be active.

I thought about it recently while taking a walk on a hot day with my dog ​​in the lovely tree-shaded landscape of the Whitman College campus in Walla Walla, Washington. The simple walk became a journey into the previously hidden (to me) gory and fantastical world of insect predation.

I heard the buzz of flies coming from a tree – not a typical noise on a college campus. The tree was the prickly castor bean (Kalopanax septemlobus), a hardy, late-flowering, exotic-looking species with compound, ivy-like leaves. It is in the ivy family (Araliaceae) native to Korea, Japan and parts of China. A multitude of very large flower clusters in pale yellow umbels resembling ivy blossoms foamed above the leaves and teemed with large black flies drawn to the lemony scent of the flowers.

There were also bees, but the main visitors to the flowers were the flies. I watched, repelled but fascinated, and suspected these were not the type of flies that land on our food, but parasitoid flies that are insect predators in larval form and feed on nectar flowers in adulthood.

A week later, in a few gardens I visited, the mint was in full bloom. Mint is both a boon and a bane in gardens. In the right place, it is a deeply fragrant and useful ground cover with abundant showy white flowers. In the wrong place, it’s a monster that devours everything in its path.

Mint produces delicious leaves for tea, of course, but its long-lasting flowers are also extremely attractive to solitary and beneficial parasitoid wasps, native bees and honeybees – insects that need nectar for food inside. adulthood. It too was crawling with the same black spiky flies and also hoverflies.

I took photos and a video and sent them to a friend, Rachael Long, a crop advisor and entomologist at the University of California Cooperative Extension for Yolo, Solano, and Sacramento counties. She suspected it was a tachinid fly, but to identify which one, she sent the photos to a former University of California Davis colleague, Corin Pease, now a northeastern pollinator conservation specialist. western Pacific at the Xerces Society for Pollinator Conservation.

The Xerces Society is a national organization that promotes pollinator conservation and education for gardens, farms and wild lands. The website,, has many excellent regionally relevant and often free publications on pollinators and pollinator conservation. It’s worth the detour.

Pease identified the most abundant species present on the tree probably as “Archytas apicifer, a parasitoid of caterpillars, including corn earworm, tomato earworm and cutworms (all insect pests of the garden and the farm)”.

This widespread tachinid fly lays its eggs on caterpillars. In a case where reality is bloodier than fiction, after hatching, the larvae (maggots) enter the caterpillar’s body and live inside the host, eventually consuming vital tissues and causing death. of the caterpillar. The larvae emerge from the host’s body to pupate.

Some tachinid flies parasitize specific hosts like the elm leaf beetle, while others feed on a wider range of butterfly and moth caterpillars. The tachinid species Erynnia torttricis attacks fruit tree pests such as codling moth, peach tree moth and oriental fruit moth. All species of spotted flies lay eggs on, in, or near the host. Some are ingested; others burrow into the host. In any case, the maggots enter the body of the host to feed on it.

Tachinid flies are considered very important for the biological control of farm and garden pests like caterpillars, beetles, earwigs, sawflies, earwigs, true insects and grasshoppers. There are 1,500 species in North America.

Late summer is a good time to see tachinid flies. They are commonly found and easily seen in gardens feeding on flowers. Tachinids resemble houseflies and are large and black or gray and have distinctive bristly hairs on their abdomen.

Who knows where each step will take us?