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NATURE NOTE - Number 79 October 28, 2023
Again, we are going to look at some common little critters that we probably don’t think about very much and know even less about, but we see them from time to time. Since it’s Halloween, let’s call them…
Our current topic: Slimy things
No offense intended to this grouping, but I think it applies to: earthworms, snails and slugs. So let’s explore.
Earthworms, or Night Crawlers, are, of course, an animal, but it does not fit most of the common classifications we normally think about. Without a backbone, this segmented invertebrate is in the uncommon Phylum called Annelida. Worldwide, there are thousands of species and many of the ones we find in North America are not native but introduced from Europe. Only in the very cold north and in deserts are they not found. We know they live in the soil – moist soil and a sign of healthy soil – and do a great service in improving the soil by aeration and by breaking down the soil and transporting various minerals and nutrients from deeper in the soil to the top. Their excretion, called “casts” are rich in nutrients. Different species inhabit different levels of the soil. Most prefer silty soil instead of clay or sandy soil. Their segmented body is covered with tiny bristles that provide the locomotion of the earthworm. So what do they eat? They eat the dirt. Within in this dirt are small roots, decaying leaves, manure of many small (and large) animals, and other organic matter that becomes part of the soil. Earthworms are often used in people-generated composite piles to breakdown organic material into rich garden soil. On the flip side, what eats earthworms? Lots of things. Our immediate thought is a worm on a hook, or being pulled out of the ground by a Robin. But they are also a major food for many birds, small mammals, reptiles, and amphibians. And there are humans that eat earthworms, mostly, indigenous people of Asia, Africa and New Zealand. Supposedly they are very high in protein, iron and other minerals. (I’m not sure I’d discuss this with scouts. You can never be sure what they might do.) We’ve all seen an earthworm struggling on a sidewalk after a rain, or when they dry out, they are kind of a worm jerky. They have been flushed from the soil by all the rain. Without lungs, they breathe through their skin, which must remain moist but not saturated. Perhaps we’ve picked up one, or tried, and found that they are rather fragile, often coming apart. Have we killed it? Probably. They can regenerate to some degree, but not as much as legend implies.
Snails and slugs, called gastropods, are in a class of the Phylum Mollusca, and are identified by these characteristics:
- a soft, tubed-shaped body
- a muscular foot for locomotion
- at least one pair of tentacles on top of the head (with eyes)
Snails have a hard spiral shell. Slugs don’t have the shell. Both are terrestrial mollusks. There are a number of snail species that inhabit coastal areas where the water is salty or brackish, but the ones we find here are strictly freshwater or terrestrial snails. Many are quite small with a shell diameter of less than one inch. They can be found in urban and suburban areas, but are often overlooked because of their size, slow movement and ability to blend in. Their shell is generally a light color.
Slugs are attracted to moist areas with vegetation, especially gardens where they can feed on almost any plant. They can often be a problem in gardens, and they generally trigger a negative reaction just based on their appearance. They move very slowly and are the source of those shiny, slimy trails you see around homes on sidewalks or porches. On the plus side, they are decomposers that consume insects and dead worms. Predators are birds (especially ducks), reptiles, amphibians, large beetles and small mammals. Slugs are not dangerous, but they are known to carry some parasites that can be harmful to humans. It’s best to avoid handling them.
As with all parts of nature, these creatures all have a part to play in the big nature picture, even if they do appear to be somewhat undesirable in the environment where we encounter them. It’s best to leave them alone and let them do their thing in nature.
If you see these critters on an outing, point them out to the scouts. Many may never have seen a slug or snail. You can have them try and figure out which order of the animal kingdom they belong. See NATURE NOTE #73. The answer is: none of the ones we generally think of (insects, reptiles, etc.) They are unique and are assigned their own phylum and class. Young scouts can easily understand mammals, birds, reptiles, etc. but some of these less-seen critters can throw a curve ball as to their classification. Don’t get bogged down with details. Just know there are animals out there that are not birds, reptiles, fish, etc. And some are sort of slimy.