Introduction to the arthropods
Quite simply, the Phylum Arthropoda
is the biggest and most important animal group on earth. Losing the vertebrates wouldn't affect ecosystems very greatly, but losing arthropods would interfere with all ecological processes including nutrient recycling and pollination.
It is estimated that there are 5-10 million species of arthropod in the world, most still undescribed, and we have well in excess of 20,000 species in Britain and Ireland, nearly all insects.
What is an arthropod?
Arthropods are easily recognised, they have:
• A hard external skeleton in the form of cuticle
made of chitin
and protein, that supports their body
• The body is made up from front to back of repeated segments, although these can be heavily modified.
• The segments are grouped into functional blocks forming the head, thorax and abdomen
• Some segments carry pairs of jointed limbs - giving the name to the group.
• Some limbs are modified into mouthparts, antennae and reproductive structures
• Because of the external skeleton, they have to shed their cuticle to grow - a process called ecdysis
What are the arthropod groups in Britain and Ireland?
There are five groups relevant to gardens. These are:
The most familar and abundant group, generally with six legs and two pairs of wings. They are by far the most successful terrestrial invertebrates, but they do pretty well in freshwater too. Most have larval stages that differ a lot in their structure and way of life from the reproductive adults, probably one clue as to their great success - along with flight and a highly waterproof cuticle that resists desiccation. We introduce the insects at our page here