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Serving Northern St. Louis County, Minnesota

Wild and woolly aphids

These unusual insects are on the move this time of year

Marshall Helmberger
Posted 10/14/20

One of the stranger insects in the North Country can be commonly seen right now in an alder thicket near you. They’re woolly alder aphids, and if you spend time in the late summer or autumn …

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Wild and woolly aphids

These unusual insects are on the move this time of year

Posted

One of the stranger insects in the North Country can be commonly seen right now in an alder thicket near you. They’re woolly alder aphids, and if you spend time in the late summer or autumn woods, you’ve probably noticed them before without even knowing it.
These insects, which gather in clumps on the branches of alders this time of year, look more like collections of white mold than insects. That’s because these aphids are covered by white and waxy fuzz that is produced as a form of protection against predators. To most insects, aphids are considered a tasty treat, but in the case of woolly aphids, that tasty morsel is covered in a coat of unappetizing wax fibers.
These aphids are easiest to spot once the leaves fall and often continue to feed on alders through much of the fall. Most of these aphids are wingless, but the final generation of the season is winged, which allows them to disperse. You may have spotted these dispersing aphids on mild autumn afternoons— they appear like tiny tufts of flying white cotton, but up close they have a bluish tint.
This final generation each year also includes some males, which allows the aphids to mate, at which point the females will lay their eggs on silver maples. That’s where the woolly alder aphids start their next generation each spring. The generations come fast with these aphids, as they reproduce without mating, producing clones of themselves every couple weeks or so. Aphids often have as many as a dozen generations in a single season. That’s a succession of generations that would take about 360 years for us humans.
At some point by late spring or early summer, the most recent generation will grow wings, at which point they disperse in search of alder, where they’ll spend the rest of the summer until the final generation of the season disperses, mates, and lays eggs on silver maple to start the process all over again.

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