A Little Bit More
Although almost every housekeeper has “met” a Silverfish at some time, this animal is unusual enough in appearance that many people are not sure whether or not it’s an insect. Silverfish are small, primitive, secretive insects that avoid light and aren’t obvious until we move or turn over an object under which they’ve been living. Silverfish probably got their name from the shiny scales that cover their abdomen as well as their wiggly way they scramble about.
The metamorphosis (change) of a Silverfish, from newly hatched to adult, is a gradual one. Gradual metamorphosis is considered to be a primitive characteristic, with newly hatched individuals looking virtually like the adults. No dramatic caterpillar-to-buttery transformation here! One unusual feature about this insect is its ability to become fully mature before it is fully grown. After maturation, it continues to grow, molting from time to time, throughout a life that may last up to 8 years – a long time for an insect!
The Silverfish’s scientific name, Lepisma saccharina, translates to “sugar guest”. But these pests are better known for their affinity for paste and may even attack starched linens or curtains as well as woolen material. Silverfish need moisture so they’re usually not found in dry rooms unless there is a water source. A good cleaning is probably the best way to rid this animal from your home – pesticides do work but you’ll be inhaling them right along with the Silverfish if you use them.
Activities
Science – Transformer
Objectives: Become a little more familiar with metamorphosis in insects
Materials: Library and/or internet
Metamorphosis – (meta means change, and morphosis means structure) a change in structure over time
In any study of insects, the term metamorphosis comes up again and again. Although we may know that metamorphosis is a change in form, we need to be aware that this change takes place in different ways – it’s not all the same! Some insects undergo very little change in form from young to adult while in others, the young and adult are very different and may even live very different “lives”.
Two Basic Kinds of Metamorphosis:
Incomplete metamorphosis – wings, if any, develop on the outside in the immature stage and there is no “resting” period before adulthood. Usually the young of these insects are called nymphs. Not all insects change in the same way during this development but in general, they look much like their parents on hatching and gradually become larger as they approach adulthood.
Complete metamorphosis – wings, if any, develop on the inside in the immature stage and there is a “resting” period or pupal stage before adulthood. These insects pass through an egg, a larval, a pupal, and then adult stage in their lives. In these insects, it’s quite common to totally unrecognize the young from the adults; they’re that different.
Activity: Either assign an insect or have your students select an insect they know about (grasshopper, cricket, butterfly, housefly, stink bug, ant, wasp, cockroach, whatever) and see if they can find out what kind of metamorphosis their insect goes through – incomplete or complete. If your students can include some pictures of their animal’s changes, all the better.
Questions
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Posted by Mary Bergerson on January 19, 2006 at 11:55 AM
Q: How can you explain the way birds space themselves on a power line?
A: It's obvious that you're a good observer! There is a very good reason why birds space themselves this way. Many animals, and this includes humans, have what is called an "individual distance" - an intolerance for members of their own species to be within a certain distance or "comfort zone". These distances vary from species to species but for many birds, the comfort zone is merely the distance beyond which one bird can reach over and peck its neighbor.
In the fall large flocks of Starlings congregate and are often seen sitting on telephone wires spaced out just as you've noticed. Each bird wants to be close to its neighbor but not any closer than its "individual distance" makes it comfortable - hence the spacing. If you've ever been to a social gathering and found yourself uncomfortable with someone who's individual distance is "closer" than yours, you may have have experienced this phenomenon yourself! In fact, since some cultures have a much closer individual distance tolerance than others, when some cultures mix, it can make for some uncomfortable gatherings. Thanks for your great question.