Adult insects nearly always have males and females, which can differ substantially in appearance, with some females even being flightless. A few, but very important insects such as aphids are fully or partially parthenogenetic
, females reproducing for some or all of the year without males.
Why are insects so successful?
This is a classic undergraduate essay topic, and like so many isues in biology, there isn't a clear answer. Firstly, the arthropod body design is a major element, and other arthropods such as crustaceans and spiders are also very succesful. The apparent drawback of growth by ecdysis is probably a major advantage, allowing larvae and adults to exist without competing with one another for resources. Certainly, the most succesful insect orders have complete metamorphosis.
The insect exoskeleton is wonderfully adapted for life on land, and avoiding desiccation, being very watertight. Insects limit water loss from breathing by being able to close the spiracles
that connect their internal breathing tubes to the outside. They also lose little water from excretion by dumping their nitrogen waste as insoluble uric acid.
The last obvious major factor in insect success is flight. There are some primitively flightless insect groups, but these are not rich in species. Some insects have become secondarily flightless, through parasitism (like fleas) or with flightless females, but these are the exceptions. The flying insects vastly outnumber the flightless ones, in the same way that the most successful land vertebrates (birds and bats) are also flying. Flight enable distribution over very large distances, allowing migration through the year as the weather changes, and being able to locate and lay eggs on rare host food plants.
Major groups in UK gardens
This website attempts to provide a working introduction, with references to take you further, into all the insect groups you are likely to find in the garden. We will concentrate most on the less popular groups, while butterflies for example are extremely well covered in many websites.
Insects are most conveniently addressed within Orders, and then at the level of Family
The key orders are:
- but there are lots more which you can find through the menu system.
Paul D. Brock 2014 A Comprehensive Guide to Insects of Britain & Ireland. Publisher Nature Bureau
Richard Lewington 2008 Guide to Garden Wildlife. British Wildlife Publishing
Michael Chinery 1993 Insects of Britain & Northern Europe Collins Field Guide
Page drafted and edited by Steve Head, reviewed by Andrew Salisbury