As fall approaches, our landscapes begin to transition.
Summer bloomers like purple coneflower, prairie blazing star and milkweeds begin to fade, while fall bloomers like asters and goldenrod begin their colorful displays.
These plants are commonly covered in pollinators, one of which is the goldenrod soldier beetle.
While seeing large numbers of beetles on flowers may be alarming to some, these beetles are beneficial and don’t pose a threat to our fall floral displays.
Adult goldenrod soldier beetles (Chauliognathus pensylvanicus), also known as the Pennsylvania leatherwing, are around a ½-inch long.
Their elytra (front wings) are yellow-orange to orange with a large black spot at the tip, and the thorax also has a black spot in the center.
Unlike most other beetles, which have hard, shell-like elytra, soldier beetles’ elytra are soft and leathery, similar to fireflies.
Additionally, their elytra don’t fully cover the abdomen, leaving it partially exposed.
Goldenrod and margined soldier beetles are often confused with one another.
Margined soldier beetles (C. marginatus) are found earlier in the year (May-July), are smaller, and have different markings.
They have a black band on the thorax, and the black markings on the elytra are much larger.
Goldenrod soldier beetles are one of the most commonly encountered soldier beetles in Illinois.
Adult beetles are active from July to early October, but are most prevalent in August.
The adults primarily feed on pollen and nectar and are a common sight on goldenrods, thus their common name.
In addition to goldenrod, they have been recorded visiting over 180 different species of flowers, including asters, milkweeds, Queen Anne’s lace and sunflowers and can be important pollinators of them.
In addition to pollen and nectar, the adults may also feed on small insects like aphids and insect eggs.
After mating (which usually happens on flowers), the females will lay eggs in the soil.
The larvae are dark and covered in short, dense hairs, which gives them a velvety appearance.
Goldenrod soldier beetles will overwinter as larvae in the soil.
When the temperatures warm in the spring, they will begin feeding.
The larvae are predatory and will feed on insect eggs, small caterpillars, slugs, snails and beetles, such as the larvae of plum curculio.
They have also been reported to feed on ticks in a laboratory setting.
Occasionally, goldenrod soldier beetles will become infected with a fungus, Entomophthora lampyridarum, which takes control of them (think zombies).
Infected beetles will climb toward the tops of plants and clamp down on plant material with their mandibles and die.
After the beetles die, the fungus will force the beetle to spread its wings, and it will begin to produce spores (the abdomens of the beetles will look fuzzy).
Why does the fungus make the beetle spread its wings?
There are two theories: First, it helps the spores spread (they aren’t trapped under the wings), and second, it may entice other beetles to try and mate with the infected beetle, allowing the fungus to infect them.
Unfortunately, nothing can be done to prevent this disease from infecting the beetles; it’s simply part of the circle of life.
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