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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