Flora and fauna of the Athens County area, and occasionally habitats outside Ohio. Subject matter will consist of both interpretive material and taxonomic issues in plant and animal identification.

Friday, January 20, 2012


Aphids are small insects that suck liquid nutrients from plants. Most are colonial. Many greenhouse and nursery growers label them as pest insects. I'm not an expert on aphid species, but this is likely the Brown Ambrosia Aphid.

This yellow and black critter is Aphis nerii, the Oleander Aphid. Originally restricted to the tropics and its preferred foodplant Oleander, it has since spread across the country feeding on Milkweed. The white guys are simply molted skins from an earlier instar (growth stage).

Near their backend you will notice two black tubes. These are known as cornicles. These emit defensive chemicals. When in danger that chemical stimulates the others to move, sometimes just dropping off the plant to avoid predators.

On their rear is a smaller black tube. This is where they excrete excess sugar water, sometimes called honeydew. Bees, Ants, and Wasps love the sweet taste and will seek out aphids and feed on this liquid. Ants will actually take the time to protect them from predators in order to keep getting that 'sugar high'.  In the animated movies Ants and A Bugs Life, the main characters are always shown drinking from aphid butts at the bar. This explains the joke so many didn't get watching those films.

Please visit Lisa Sells at her blog Zen Through A Lens to see a detailed post on this aphid species.

Aphids are Homoptera, or in a broader sense, part of the order Hemiptera. Like all True Bugs, they have piercing sucking mouthparts. Here's a closeup of one getting ready to drill a plant stem.

Aphids have many predators. Here a larva of a Syrphid Fly is busy munching down. With exotic invasive species, we often import their natural enemy to control them. This works in many areas of pest control, but in regards to aphids, one such import has now itself become a problem, the Asian Ladybug.

Wooly Aphids comprise an entirely different group of aphids. Many are host specific feeding on alder, members of the Rose family, etc. This is the Beech Wooly Aphid, Grylloprociphilis imbricator.

The sugar water produced by these aphids falls on Beech leaves. These black blotches are a fungus that grows on the honeydew. It rarely does any actual harm to the tree.

Even the twigs can be covered by large clumps of this fungus known as Black Sooty Mold. They are hard and crusty, but feel like a sponge when wet. This mold will also accumulate at the base of Beech trees. It will look like a pile of gray black dust, as if someone emptied their barbecue grill.

The brown spot is the head region. Most of these aphids feeding are immatures. The winged reproductives can be seen in the left corner. Many aphids practice parthenogenesis, essentially reproduction without sex (asexual). Throughout the summer each generation is all females, and you might say they are 'born pregnant'. A form of cloning. As the days get shorter in late summer, a hormonal change occurs, and both male and female are born. This last generation mates sexually, and produces eggs for next year.

The thin smooth bark of White Pine Pinus strobus, makes it susceptible to yet another pest people often just call 'pine wooly aphids'. To be accurate, it is the Pine Bark Adelgid, Pineus strobi. Adelgids superficially resemble aphids, and are related, but belong to a different family. Adult adelgids resemble miniature Cicadas. This is another non native introduced species. Bigger pines can withstand any serious damage, but saplings can have their growth stunted by a large infestation.


  1. Recently seeing a lot of Beech Trees covered with Black Sooty Mold here in Pennypack Park, a forested park in Philadelphia. In fact, today along the stream there seemed to be clumps just fallen on the ground among the leaves. We had some heavy rain yesterday, could that have caused the sponge like wet mold to fall off branches because of the weight caused by the water accumulated in the mold? It was like all this mold suddenly appeared along the path, even on fine branches of other species saplings.

  2. Pretty pictures and informative article!