Woolly Alder Aphids, Honeydew & Black Sooty Mold
Once leaves start to fall, one often observes white, fuzzy patches along the branches of Speckled Alder (Alnus incana). These fuzzy patches consist of colonies of aphids feeding on the sap of the shrub. In order to get enough nitrogen, they must drink volumes of sap, much of which is exuded from their abdomens as a sweet liquid called honeydew. The honeydew accumulates and hardens onto the branches as well as the ground beneath the shrub. Yesterday’s Mystery Photo was the honeydew of Woolly Alder Aphids (Paraprociphilus tessellates) which has been colonized by a fungus known as black sooty mold, a fairly common phenomenon.
Woolly Alder Aphids produce white wax, or “wool,” filaments from their abdominal glands. Clustered together, these aphids look like a white mold. If disturbed, the individual aphids pulse their abdomens in unison – apparently an effective defense mechanism.
Woolly Alder Aphids, also known as Maple Blight Aphids, have two host plants at two different stages of their lives. In the fall they lay their eggs on Silver Maple trees. The eggs hatch in the spring and the aphids feed on the maple leaves. During the summer a winged generation flies from maple leaves to alder shrubs and establishes colonies. In the fall, some of these aphids fly to Silver Maples and lay eggs, while some overwinter in the leaf litter beneath alders.
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Spring Azures Mating
Every spring tiny, delicate blue butterflies known as Spring Azures (Celastrina ladon) are one of the first butterflies one sees. Your impression of this butterfly depends on the angle from which you view it. From above, the wings are a bright, pale blue (females’ have a dark border). From beneath, the wings are very pale and lightly marked with brown speckling. Thus, at rest or mating (as pictured) with wings folded vertically, they are not as startling to the eye as when they are seen flying.
After spending the winter as pupa, encased within a chrysalis, the adult emerges, mates and the females lay eggs. The larva, or caterpillar, is slug-shaped, and is tended by ants which stimulate it to excrete a clear greenish “honeydew” which they consume. (It is thought that the ants discourage parasitism by wasps and flies.)
At one time all North American azures were considered to be one species but now they have been identified as several different, but very similar, species collectively referred to as the “Spring Azure complex.”
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Ants “Milking” Treehoppers
Certain species of treehoppers (a type of true bug) release a sugary liquid called honeydew, made mostly from excess plant sap that they consume. Ants farm these treehoppers, much as they farm aphids, for their honeydew. An ant grasps a treehopper and strokes it with its antennae, causing a droplet of honeydew to appear at the tip of the treehopper’s abdomen, which the ant then consumes. Both insects benefit from this mutualistic arrangement. The ants get honeydew, and in return, provide protection for the treehoppers from predators. The plant indirectly benefits from the ants, as well, for if the ants were not there, the treehoppers’ honeydew would fall onto the plant, causing mold growth on fruits and leaves. Eggs, nymphs and adult treehoppers can usually all be found in one location. (Photo insert: a treehopper nymph on left, adult treehopper on right) To see a video of ants farming a type of treehopper called a thornbug, go to https://www.youtube.com/watch?v=HoeJn3Imss4.
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