Identifying Beneficial & Harmful Insects

There are about 2,000 different species of ground beetles in North America and 450 species in Michigan alone! The ground beetles we encounter in the garden are nocturnal, and they dig down into the mulch and other organic matter during the day. They help the garden by eating common garden pests like Caterpillars (and other insect larvae), Ants, Aphids, Maggots, Wireworms, and Slugs. A few species of ground beetles will also eat the seeds of invasive weeds such as lambs quarter, foxtail, ragweed, and thistle.

(Image: A Scarites beetle on the sidewalk. Photo by David Lowenstein, MSU Extension.)

The Praying Mantis is an interesting and enjoyable beneficial insect to have around the garden.  Praying Mantis has an enormous appetite and will eat a variety of aphids, leafhoppers, mosquitoes, caterpillars, and other soft-bodied insects when they are young. Later, they will eat larger insects, such as beetles, grasshoppers, crickets, and other pest insects. Praying mantises are large, solitary, slow-moving, and predaceous insects that catch their prey with their front legs. They are not selective in feeding habits, so they eat other beneficial insects. However, they tend to eat more harmful insects than beneficial ones. There are no native mantis species in Michigan, but you will find Chinese Praying Mantis and European Praying Mantis in your yard.

(Image: European Praying Mantis photo by The Michigan Nature Guy)

This non-aggressive species commonly visits flowers for nectar, making them great pollinators. They prefer fields and other grassy, open areas. They dig their nests in sandy soils. This species catches grasshoppers, which commonly eat food and ornamental plants; they aerate the soil and improve water’s ability to soak into the ground with their digging, which benefits our trees!

(Image: Kal McLane)

Brown marmorated stink bug is a pest accidentally introduced into the United States from its native Asian range. Stink bugs are members of a large group of insects called the true bugs, characterized by piercing-sucking mouthparts. Like other true bugs, the brown marmorated stink bug feeds by sucking on plant juices with its proboscis—which is a straw-like mouthpart. Its beak is longer than most stink bug species and is strong enough to penetrate the bark of trees. The damage it causes to plants can range from mild to severe, depending on how long it feeds on the plant. This stink bug is highly mobile and can switch host plants throughout the seasons.

An invasive adelgid insect from Asia, the Hemlock Wooly Adelgid (HWA), attacks our native Eastern Hemlock trees. Once hatched, juvenile HWA, known as crawlers, search for suitable sites on their host tree, usually at the base of the needles. They insert their long mouthparts and feed on the tree’s stored starches. HWA remains in the same spot for the rest of their lives, continually feeding, developing into adults, and severely damaging the host tree’s canopy. HWA disrupts the flow of nutrients to its twigs and needles, preventing its photosynthesizing abilities. The tree’s health declines, and mortality usually occurs within 4 to 10 years. This pest is currently only found in counties along Michigan’s Lakeshore but is slowly making its way inland due to a shifting climate.

An invasive insect species native to the continent of Asia, currently with populations in 18 States that first appeared in the US in 2014. It was confirmed in southeast Michigan in 2022. The Spotted Lanternfly is a planthopper that feeds through sap-sucking. Sap-sucking means it feeds on the sugary sap produced in foliage and transported in the soft phloem tissue beneath the bark. Numerous insects on an individual plant weaken it since our native trees do not have natural defenses for spotted lanternflies. When these insects feed, they secrete a sticky and sugary substance called honeydew. This honeydew attracts black sooty mold, which is detrimental to plant health. This invasive insect’s host tree is Tree-of-Heaven, which is also highly invasive in Michigan.