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Spiders and Insects First read through the list of characteristics describing spiders, or insects, or both. Then, as you listen, put each of the descriptions into the correct category below. arachnids often have wings studied by entomologists 30,000 known species very seldom dangerous lay eggs undergo metamorphosis compound eyes arthropods a hard outer shell antennae generally spin webs many eyes often vegetarian found all over the world Answers Spiders Insects both arachnids often have studied by 30,000 known species very seldom dangerous generally spin webs many eyes wings undergo entomologis ts metamorph lay eggs osis arthropods often vegetarian compound eyes antennae a hard outer shell found all over the world Script Ants and wasps are insects, but spiders are not. The group of animals that they belong to is called arachnids and this group also includes smaller animals like mites and ticks. Arachnids differ from insects for a number of reasons. First of all, and most obviously, spiders have 8 legs whereas insects have 6. Many insects have wings, but spiders never do. Nevertheless, for many people spiders and insects are close relatives. Strictly speaking, entomology is the study of insects, but if you study entomology at university you will study spiders and other arachnids too. Over 30,000 kinds of spiders have been found all over the world. Like insects, they can live in almost any environment. Of course, there are many more insects and about one million species have been identified to date. Spiders can provoke strong feelings in people. Many people are terrified of harmless spiders, such as the long-legged house spider, though still may feel that they are in luck if a money spider lands on them. In fact, very few spiders are dangerous and there are only one or two deaths worldwide each year caused by poisonous spider bites. By contrast, millions of deaths per year can be attributed to insects. Many more people die from bee or wasp stings, and malaria and other diseases which are passed on by the mosquito cause about two million deaths a year. Both spiders and insects start life as eggs. The mother spider protects her eggs with a silk sac and then baby spiders (called spiderlings) emerge. Unlike spiders, insects undergo what is called metamorphosis. This means that their bodies change during their lives. Out of the eggs crawl larvae and the larva looks nothing like the adult insect. They are often white and move around rather like a worm. Eventually these larvae wrap themselves up in a cocoon and some time later the adult insect emerges. The feeding habits of insects and spiders are often very different too. All spiders spin silk and their main reason for doing so is to make webs to catch their prey. Some insects spin silk too, but not for the same purpose. Spiders feed off other animals – normally insects and other spiders, but sometimes larger animals too. Unlike insects, spiders have two poisonous fangs, which are rather like large teeth, with which they can kill the prey that is caught inside the web. Insects, on the other hand, have jaws which are more suited to chewing and many insects are entirely vegetarian. Insects have 3 distinct body parts whilst spiders have just 2. Other interesting differences include the eyes. Spiders have a number of simple eyes (generally eight) whilst insects have two compound eyes. Insects also have antennae, but spiders don’t have these. Although antennae are sometimes called feelers, their primary function is to detect smell. The adult insect is similar to a spider in that it is protected by a hard outer shell, called an exoskeleton. Animals such as insects and spiders which possess this outer skeleton are called arthropods. During its lifetime a spider will shed its outer shell a number of times, as it grows. Some insects shed their shells too, but not all. Spiders and insects are found all over the world and have adapted to many different habitats. Most spiders live solitary lives, but, as with insects, there are some social spiders too. To the untrained eye there may be very little difference between spiders and insects but if you look hard then they’re actually worlds apart. Now listen again and complete the following table with numbers and letters A=all/always Examples number of legs types number of human deaths per year lay eggs emerge from a cocoon as adults spin silk have poisonous fangs have strong jaws developed for chewing number of main body parts number of eyes possess antennae periodically shed their shells are social S=some/sometimes Spiders money spider, house spider 8 30,000 Spider bites account for 1 or 2 deaths per year N=none/never Insects Ants, wasps A N 6 1,000,000 Mosquito borne diseases account for 2 million deaths per year A A A A N S N A 2 3 8 N A 2 A S S S