Frank Drzal, age 14, of Bridgeport, Connecticut,for his question:
Are slugs related to insects?
Whether we like it or not, there are bound to be slugs and insects in our gardens. Both do a lot of damage to our favorite vegetables. However, though slugs and insects often share the same territory and even dine on the same foods, they are not related to each other. In some cases, an insect chrysalis is shaped somewhat like a slug. But the slug is a slimy slowpoke and the chrysalis will hatch into a lively, very, very different sort of animal.
When the sun shines, frisky grasshoppers leap from leaf to leaf, devouring the greenery. They are, of course, insects. After dark, the slimy, slowpoke, garden slugs come forth to feed on plants and on small helpings of meat. Slugs belong to a large group of animals called mollusks and their closest cousins are the snails.
Some people say that slugs are snails that have lost their shells. This may be so, because a few slugs have the tiny remains of shells hidden on their backs. The mollusk clan also includes clams and oysters, squids and octopuses. All of the mollusks have soft, boneless bodies with rather slippery skins.
The slugs hatch from jellified eggs and the infants are miniature copies of their parents. On the other hand, the insects also hatch from eggs and some of them develop through stages that somewhat resemble those of the slugs. Butterflies start out as sluggish caterpillars that crawl around, devouring their favorite leaves. Later the caterpillars go through a pupa stage, forming chrysalises that look somewhat like sleep¬ing slugs.
However, at all stages the basic differences are very great. Scientists have classified more than a million different members of the animal kingdom into a few major groups called phyla, or phylums. The members of each phylum share a number of outstanding features. Many are either related or descended from common ancestors. The slugs are classified in the phylum Mollusks—the soft bodied ones.
As a rule, scientists base their classifications on the adult, mature form of an animal. Caterpillars and chrysalises are immature forms of adult butterflies. True, these infants and teenagers resemble the slowpoke slugs—somewhat. But their adults do not. A butterfly, as we know, is a frisky, wide winged insect with six legs. A slimy, slowpoke slug never gets off the ground and never sprouts any legs.
The insects belong is the huge phylum called Arthropods, a name which refers to their special joints. Together they outnumber all other creatures by far and they occupy a special arthropod class called Insects.
Grasshoppers have tough skins that protect them in the dry summery air. The slimy skin of a garden slug must be kept moist and an hour or so in the hot sun is fatal. So, while the grasshoppers leap through the day, the slugs are hiding in the soil and in various shady crevices. The grasshoppers go to bed with the sun, which is when the slugs come forth to dine in the garden.