“Are these worms in this tree and this black stuff on a rock wall?” asks this reader about the mass of organisms pictured below. “It is from Mansfield, Ohio. Thank you for your time!” Based on the photo, this is nothing we think we have encountered before. The black organisms on the rock do not necessarily look like worms to us, and we cannot make out what organisms we are supposed to be looking at on the tree. Upon zooming in on the photo of the rock, it looks like the organisms could possess wings. That said, the photo makes it difficult to see the details of the organisms’ bodies, so this is merely an educated guess. In any case, we think these could be black bean aphids (otherwise known as blackflies). Usually, they are found swarming plants that they suck the sap from.
We want to note that there are plenty of species of black-colored aphids, so these could be something other than the black bean aphid specifically. Nonetheless, these creatures are not harmful to humans or pets, though, like other species of flies, it is best to avoid consuming them, as they can possibly carry disease and pathogens. The different species of aphids will have different diets, so perhaps this is a species of aphid that likes to eat the lichen or moss that grows on rocks. And if it is the same organisms on the trees, then perhaps they are a species that munches on bark, or sucks the sap from the trees.
Aphids can prove to be pests: since they come in such large numbers, they can do severe damage to the plants they swarm and stunt their growth as a result. For example, when a group of black bean aphids attack a black bean plant, they can negatively impact the formation of bean pods. With that said, in moderation aphids can prove to be a helpful part of an ecosystem, as they form the base of the food chain for many organisms such as beetles and ladybugs.
To conclude, we think it is possible that the black bugs our reader found swarming trees and rocks are aphids of some kind. Of course, this is an educated guess based on the physical characteristics we can make out and the sheer number of the bugs concentrated in one spot (which is behavior that is characteristic of the aphid). We hope our reader found this information useful, if not interesting, and we wish her the very best!
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