Invertebrates
It is estimated that there are about 1.3 million species of multi cellular animal (so far classified and named). Of these nearly 54000 are vertebrates – the rest or about 96% are invertebrates!
Invertebrate just means “with out a back bone” so it is not a very precise classification term! Scientists classify invertebrates into more than 30 major groups (Phyla – see Classification) which include such well known creatures as Mollusks – e.g. snails, and segmented worms – e.g. earthworms, but the vast majority of invertebrates belong to the major group called Arthropoda . With well over a million species discovered so far, with more added every day, it is by far the largest group of animals. As this is also the group that we tend to notice – for good and bad this is the group described here.
Arthropods
There are 4 major classes of arthropods (with 18 more obscure ones). They are all well represented in Lebanon, they are:
| Myriapods |
| Literally lots of legs! |
| Characteristic: Long bodies with many legs. |
| Centipedes and Millipedes. The centipedes are fast. active predators with poison fangs that paralyze their prey – there is one species in Lebanon that can give you a nasty bite. The millipedes with their cylindrical bodies and even more legs are gentle herbivores, by contrast. |
| Arachnids |
| Spiders, scorpions, mites, ticks and others. |
| Characteristic: Two part body with 8 legs. |
| This group includes some of the most feared (but fascinating) of all invertebrates. In Lebanon, like any where else, the vast majority are harmless and perform the useful function of eating flies and other insects. However some will bite or sting and the large hairy tarantulas, quite common on the hillsides, and the scorpions are best avoided! |
| Crustaceans |
| It encompasses crabs and shrimps, but also woodlouse. |
| Characteristic: they have a strong exosqueleton, biramous limbs (two-part ends of the legs), and a multi-stages larva form, each stage being separated by a moult. |
| The majority lives underwater, it has a lot of fossil records of water species, and insects – that are mainly terrestrial in their adult form – evolved from them. |
| Insects |
| Most animals are Insects! Examples include butterflies, beetles, ants, grasshoppers, cockroaches….. |
| Characteristic: 3 body parts with 6 legs often with wings. |
| They are everywhere and fundamental to the functioning of the environment. |
Arthropods and particularly the insects are found in all habitats and are easy to observe. We fear some, we enjoy watching others, but they are all hugely important to the functioning of the eco system. They are fundamental to many food chains and food webs, (see food webs) they are important in recycling nutrients, they are important predators and pollinators. Without them life would not be possible!
When out and about it is easy to find and observe them – just keep your eyes open! Some are found in particular habitats e.g. dragonflies are usually found near water, scorpions under rocks (so take care lifting up rocks) bees and butterflies on and around flowering plants…..
A good way to start learning about insects is to start to learn about a particular group, identify and find out about the common species. In the following pages two groups are looked at in some detail; the butterflies and dragonflies (and damselflies). Because they are large, often colorful insects a lot is known about them and you can identify them quite easily. Scientists often use single groups like this to monitor the overall health of an ecosystem. If dragonfly numbers are down something is probably wrong with the water. Follow the links to find out more: