What are Insects?
Float like a butterfly, sting like a bee, sing like a grasshopper, work like an ant. Each different, yet all these creatures are insects. Insects from Latin insectus, meaning "cut into sections". The total number of current species, including those not yet known to science, is estimated to range from two million to fifty million. To date, there are approximately 5,000 dragonfly species, 2,000 praying mantis, 20,000 grasshopper, 170,000 butterfly and moth, 120,000 fly, 82,000 true bug, 360,000 beetle, and 110,000 bee, wasp and ant species.
What do they have in commmon? Members of this huge group share many traits:
- their bodies consists of 3 parts – head, thorax and abdomen
(Fact: Did you know that ‘insect’ means ‘in segments’ ?)
- six jointed legs attached to the thorax; insects are part of a larger group called arthropods which means ‘jointed foot’
- they have no internal skeleton or bones; instead a hard covering outside the body which is called exoskeleton
- insects have holes in their thorax and abdomen for them to breathe air, called spiracles
- insects have 2 antennas to sense smell, touch and sometimes sound
- they usually have 2 pairs of wings but sometimes one or none
- they have piercing, sucking, sponging, or chewing mouthparts
Do insects have brain? Yes they do, an insect’s brain is indeed tiny and it connects to a nerve cord that runs down the body.
Insects have two kinds of eyes. Simple eyes react to light but can’t see images and compound eyes to recognise colours, shapes, patterns and movement. Compound eyes consists of thousands of facets and each of those sees a single image. So the whole picture is formed by many many dots.
Just behind the head, the thorax or midsection is where the legs and wings are attached.
Then comes the abdomen which is softer and more flexible than its other parts because breathing takes place here. Insects take in air and let it out through holes called spiracles. The spiracles lead to a maze of air tubes, which circlate oxygen through the body. This is actually a primitive system, so if insects grew bigger, it might not work!
And luckily, ther aren’t any giant ants and monster cockroaches. Why? Because having an external ‘suit of armour’ instead of a body skeleton limits the size of insects and other arthropods.
Did you know: Not all creepy crawly critters are insects!
Other arthropods we may think of as insects or ‘bugs’ also have segmented bodies, jointed legs, and hard external coverings, but scientists classify them differently.
Arachnids - Spiders, scorpions, ticks
- two body regions
- eight legs
- no antennas (But some spiders have feelers called pedipalps)
- mouthparts may have pincers or fangs, often poisonous
[ Have you hear of this word: Arachnophobia ?– Yes, it means the fear of spiders! ]
Crustaceans – Crabs, lobsters, shripms, sow bugs
- two body regions
- ten or more legs
- four antennas
- mouthparts may have pincers
Centipedes – means 100 feet
- a head and trunk of 15 to 181 segments
- two legs per segment
- two antennas
- may have claws and a venomous bite
Millipedes – name means 1000 feet although no speicies has that many
- a head and trunk of nine to 100 segments
- two legs per segment (two segments often fuse together)
- two antennas