Insects display a huge variety of forms based on their basic structure, and they have more different species than all other animals combined. However, the similarities between related species allow us to sort them into recognizable groups.

The key characteristics of some of the main groups of insects found in Britain are described in the introductory paragraph of the information on each of the insects in our ‘Insect Index’. Butterflies and moths have two pairs of wings whose surfaces are covered with tiny coloured scales. Beetles have hard wing-cases in place of their fore-wings and they fly with the hind-wings that are folded under the wing-cases when they are at rest. Ants, wasps and bees all have a very narrow ‘waist’ in the middle of their bodies. True flies have only one pair of wings, the fore-wings – the hind-wings have become modified into organs of balance. Dragonflies and damselflies have shiny membranous wings and very large eyes, and their nymphs are aquatic and predatory. True bugs have mouthparts that are specialized for piercing and sucking fluid.

Within these recognizably similar large groups there are many sub-groups (e.g. ants, ladybirds, chafers), which themselves have many species differing to a greater or lesser extent. After looking at the differences between the Odonata, Hemiptera, Coleoptera and Hymenoptera in our ‘Insect Index’, look at the similarities and differences between the two species listed for each of these insect orders: Banded Demoiselle & Four-Spotted Chaser; Common Froghopper & Green Shieldbug; Seven-Spot Ladybird & Cockchafer; and Ruby-Tailed Wasps & Black Garden Ant. Related species are sometimes easily distinguished, especially when they are boldly coloured and patterned, e.g. the Red Admiral butterfly (Vanessa atalanta) featured in our ‘Insect Index’, with scarlet stripes and white spots on its black wings, and the Painted Lady butterfly (Vanessa cardui), with black and white markings on its brownish-orange wings. More usually, related species are so similar that they are difficult to separate without specialist experience, e.g. the various species of Ruby-Tailed Wasps and Drone-Flies noted in our ‘Insect Index’.

In the QCA Scheme, this topic is Unit 2C for Year 2. However, the concepts introduced at this stage are re-inforced and expanded by Units in later years that add to the pupil’s understanding of the variety of living organisms and the importance of biodiversity.