What is it about slugs that so repels us? After all, they are closely related to snails, with their pretty shells and to some their associations with gastronomy. Their other relatives, shell-forming marine invertebrates from around the world, are highly desirable to collectors who want to own their exquisitely beautiful protective armour. But a slug? The reason why slugs suffer from such a poor image is, unfortunately, abundantly clear: they have the temerity to wear their slime on the outside, rather than on the inside like the rest of us.
Very large, up to 20cm. Various shades of grey, with pale tentacles. The radula is a tongue-like organ that has teeth-like protrusions that help it saw through food before ingestion. Most slugs are light brown or gray in color, although the famed banana slug of the Pacific Northwest is often a bright yellow. The skin of a slug is exceptionally moist, and often covered in a thin layer of slimy mucus that helps it retain moisture and protects it from most predators, which dislike the taste.
Two key things attract slugs: food and moisture. Unfortunately for gardeners, just about every plant — vegetables and flowers in particular — can serve as food for slugs.
They are definitely not picky eaters! Any area that stays moist during the day or during lengthy hot spells will be attractive to slugs. In particular, they are drawn to the moisture-retaining qualities of mulch, sod, leaves and straw. Another interesting attractant to slugs are spaces where they can lay their eggs. Gardeners have found that slugs will often lay eggs in areas that have been raked or hoed, while they will avoid soil that has been left smooth by a garden tool.
The creases and bumps left by such tools create an ideal incubation area for slugs. Yes, slugs can be very destructive garden, farm and landscaping pests. The sheer numbers of slugs in many areas — particularly in irrigated and overly wet locations — can result in massive plant destruction. A slug, which eats many times its body weight each night, simply destroys too much of the plant for it to recover. First off, the mucus produced by slugs can cause excess drool or induce vomiting.
People tend to call something a slug if it looks like a snail but has no shell. However, many distantly related critters among the gastropods—the group that contains snails and slugs—have independently evolved a sluggy, shell-free shape.
And then there are the in-betweeners. So-called semi-slugs have tiny shells on the outside of their bodies that are way too small for them to retract into.
Honestly, they look pretty ridiculous. First, check out the tentacles. Two are for seeing and smelling, and they can be operated independently: a slug can gaze at you or smell you and a friend simultaneously. The other two are for touching and tasting. Slugs also have thousands and thousands of teeth. And in case that doesn't seem weird enough, slugs essentially breathe through a blowhole that opens up on one side of their bodies. This round pore is called a pneumostome.
Sea slugs have their own incredible features. For example, some breathe using delicate feather-like gills that surround their butt holes, and they smell with neon-colored, bizarrely shaped protrusions called rhinophores. Melibe leonina from Santa Cruz. Some slugs do this. The aptly named taildropper slugs, such as the reticulated taildropper , can quickly amputate their own tails.
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