Bust Out Your Dance Moves
Have you ever been hiking during the summer and come across what appears to be a thin layer of snow on some trees (pic 1)? Maybe it made you wonder where the expression ‘Christmas in July’ comes from. If you look closely, you’ll find tiny insects covering branches of our American beech trees (Fagus grandifolia). These beech blight aphids (Grylloprociphilus imbricator) are also called woolly aphids because of the white waxy strings attached to their bodies (pic 2). In addition to appearing unappetizing to predators, groups of aphids wave their fuzzy posterior ends in the air at the same time to mimic herding behavior and confuse or intimidate predators (see video below). They did not trick me, however, but instead reminded me of a bunch of feather dusters from Beauty and the Beast singing and swaying to “Be Our Guest.” It seems that I’m not the only one to interpret their bobbing and fanning as dance moves because they are also nicknamed the boogie woogie aphids. If these two defense mechanisms don’t work, the nymphs (juvenile aphids) will sting predators with their piercing mouthpart, called a stylet. More often they use their stylet for removing sap out of the twigs and leaves of beech trees, causing them to excrete a sugar-rich byproduct called honeydew. A sooty mold fungus (Scorias spongiosa) grows exclusively on this beech honeydew. The thick, gooey, black fungus becomes golden and furry over time, growing on the branches and on the ground below the aphids. This leads to the misconception that woolly aphids hurt beech trees. Occasionally minor damage, such as a few branches dying, may result, but it does not harm the overall health of the tree. In fact, the sugary honeydew and sometimes the aphids themselves provide food for other insects such as wasps, flies, and ants. Some of the aphid offspring will develop wings and disperse to form new colonies. Upon finding a fresh beech tree, beech blight aphid females reproduce asexually, creating clones. In order to mix up their gene pool, some males are produced in the fall before overwintering. I encourage you to get outside, turn on your favorite jam, and bust out your best dance moves if you find these dancing insects during a summer or fall hike!
Check out our woolly aphid video (video credit to Kayla Martin)