It’s been a wetter than average season. We were certainly due. The rainfall that we’ve had this season has resulted in many implications. Of course, the herbaceous growth is going bananas. Just ask a trail overseer. It has certainly increased the seasonal population of fungi, for better or worse. The good news is that the rain supported the E. parasitic fungus, which feasted on the gypsy moth larva, or caterpillar. The cooler, wetter season has also slowed the production of the hemlock woolly adelgid; not that the hemlocks can last much longer in this region anyway. Maybe the release of the Japanese lady bug beetle will slow the spread of the adelgid to our north and west. Wouldn’t it be nice to image the Japanese lady bird beetles actually controlling the adelgids? The bad news is the flowering dogwood is really taking a beating. In fact, the fungus that affects this tree is still flourishing. (At least it has minimal impact on the alternate leaf dogwood; our other native arboreal dogwood, and none on the six or so native dogwood shrubs.) You can also presume the chestnut, beech, and butternuts have suffered at the hands of their host-specific fungi.
Perhaps not so noticed is the proliferation of slugs and snails in our forests. You may have noticed the damage in your home gardens. Those holes in the middle of the leaves of hosta, violets and impatiens are likely the results of slugs. (most chewing insects start on the edges of leaves). And, wouldn’t you know it, most of our urban slugs are introduced.
Slugs and snails are related to clams, oysters, squid and octopi. In the animal kingdom, slugs and snails are members of the Phylum Mollusca. This Phylum is an extremely diverse group. With over 50,000 species, the mollusks rank second to only the Phylum Arthropoda in total species. While the majority of mollusks are marine, a large number of species are found in freshwater and terrestrial habitats. The mollusks include at least seven classes (you remember, Kings Play Chess On Fine Green Silk?) including the Bivalvia (clams, oysters and mollusks) and the Cephalopoda (squid and octopi). But our friends are in the Class Gastropoda (snails, slugs, conchs, and a few others). Gastropods are by far the largest Class, comprising over 40,000 species, or 80% of the mollusks. The word is derived from the classical Greek word gastros meaning stomach, and podos meaning foot.
The slug form has evolved a number of times among the land snails. Slugs are not snails that have crawled out of their shells, but are the end products of a long line of evolutionary changes in which the shell was progressively reduced. While slugs do not have the protective shell, they have a pliable worm-like shape that can easily crawl into small cracks and crevices.
Slugs and snails are nocturnal. During the day they seek shelter beneath pieces of wood, plants, rocks, decaying logs and soil duff, trying to find protective moist sites. They are extremely susceptible to drying out. Native slugs stay in the forests, where they feed on decaying wood and leaves, and fungal hyphae. The great majority of land snails are herbivorous, feeding on decaying leaves and wood and fungal hyphae. However, there are a few carnivorous species that feed on other land snails, including one common throughout the eastern United States. Depending on the species, slugs can live 1 to 6 years. Snails can live from 2 to 20 years.
One adaptation enabling land snails and slugs to survive on land is their ability to produce plenty of slimy mucous. Mucus prevents moisture in the animals' bodies from being soaked up by the dry terrain being traveled across. Also, it protects the animal's fleshy underparts from sharp objects. Snails and slugs can actually glide across the sharpest razor blade without cutting themselves. They can also produce a heavy viscous mucus from their body for self defense.
When dry weather comes, snails and slugs bury themselves in the soil or find some other well- protected spot. Snails plug up their shell holes with mucous that hardens, and slugs secrete a sort of mucusy cocoon for themselves. Then through the dry spell the animals remain in a state of suspended animation, or estivation. Like hibernation, their body processes slow to a point almost like death. However, there's enough life for them to become active again once enough rain comes to dissolve the mucous and soak into their bodies.
Most land snails and slugs are hermaphroditic, possessing both male and female parts. In some species, an individual may behave as male for a while, then as a female. When snails mate, two individuals pull up next to one another, arrange themselves so that the male part of one is opposite the female part of the other, and then each ejects male sperm into the female opening of the other. In the case of slugs, a slow speed chase in the bushes ends with the two suspended by a mucusy rope, hanging in mid-air, in their own little world of ecstasy. The literature suggests that self-pollination does occur, but it’s not common.
But there’s another thing that makes snail sex so interesting. About a third of the species shoot darts into each other’s female reproductive parts. Or at least, they try to. With good reason, copulating snails commonly are seen jostling, in an attempt to hit but not be hit by these love darts. These darts are the equivalent of being stabbed with a hypodermic needle. The benefit to the shooter is that the darts contain mucus that temporarily contracts a part of the female reproductive system in a way that allows a greater number of sperm to reach her storage area and survive. Researchers have found that about one-third of all love darts either fail to penetrate the skin or they miss the target completely.
There’s one more thing that I have to mention about a slug’s mucus. Apparently, the slime is a natural anesthetic. If you lick a slug, your tongue will go numb. In fact, some Native Americans used to put slugs in their mouths when they had a tooth ache and let it crawl around. I guess I’ll have to try that some day. Boy, that’ll be a special moment.
Often, the penis of one of them must be gnawed off in order to release the pair. This unique phenomenon is known as apophallation.
Banana Slugs eat living and decaying vegetation, roots, fruit, seeds, bulbs, lichen, algae, fungi, animal droppings and even carcasses. Mushrooms are their favourite food. Predators include snakes, foxes, porcupines, crows, ducks, shrews, moles, salamanders and even humans.
Banana Slugs are the largest of all North American slugs. Most adult Ariolimax slugs are about 15 - 20 cm (six to eight inches) in length. They can reach a length of 25.4 cm (10 inces). They are the second largest slug in the world, the largest being the Limax cinereoniger of Europe, which can reach 30 cm (12 inches) in length.
They may be confused with an introduced species, the Black Garden Slug, as it is large and also comes in a brownish color. If you look closely at the Garden Slug, you can usually see an orange-striped edging around the foot and textured furrows on all upper parts of the body except the mantle. The Banana Slug does not have any orange on its body and its body is smooth.
A slug can travel over a razor blade or sharp edge of glass without cutting itself because of the slime that covers the foot.
Slugs use their two pairs of tentacles to sense their environment. The larger pair at the top of their head have a small black spot at each tip that are used to detect light. Slugs cannot see images like we can, but instead rely on brightness or darkness to tell them which direction they should move. They also have a second pair of antennae located at the lower front of the their body. This pair acts like a nose, picking up chemical smells. Both of these tentacles can telecope in and out as they move along the forest floor to protect them from damage when they bump into leaves and twigs.
Watch them do their important role as forest floor recyclers.
The Banana Slug lives in moist forest floors along the Pacific Coast of North America from California to Alaska. It is a decomposer, which means it chews up leaves, and animal droppings and other dead plant material and recycles it into soil. One of their favorite foods seems to be mushrooms.
The snails are related to the oyster, the clam, the mussel, the squid and the octopus. All of these animals are called mollusks. More than 30,000 kinds of snails have been described, of which about two-thirds still exist -- about half of them in salt water and the other half in fresh water or on land.
Some freshwater snails have gills by which they obtain oxygen from the water. Others, such as most of our common pond snails, and the land snails and slugs, breathe with a lung and those living in water must come to the surface frequently.
Land snails, slugs and air-breathing water snails do not have separate
sexes. Instead, each animal has both male and female organs. The land
snails and slugs lay their eggs, about 50 at a time, in summer or early autumn, among grass roots or other damp places. The air-breathing water snails lay tiny eggs, imbedded in clear blobs of jelly, at frequent intervals throughout the year. Most of the gill-breathers have separate sexes and bear their young alive.