Terrestrial Invertebrates

Depending on their requirements to complete their life cycles, terrestrial invertebrates require a range of habitats. There are those that need flowers and feed on pollen or on the plant itself, others that need decaying wood to complete their lifecycle, those that live under stones and others that live on the tops of mountains!

Read on to find out more about some of our terrestrial invertebrates.

Earthworms (Phylum Annelida)

Charles Darwin said of earthworms “It may be doubted whether there are many other animals which have played so important a part in the history of the world, as have these lowly organised creatures.”

Earthworms are amazing! There are 25 species of earthworms native to the UK varying in size from 9-35 cm long. Their combined actions are astounding – it has been estimated that earthworms produce £16 billion of topsoil each year! Earthworms aerate the soil and are fantastic recyclers. Spring is a great time to celebrate worms – this is when they become more active, and as we dig over our gardens and plant seeds, we see more of them and are reminded of what they do for us.

Pseudoscorpions (Class Arachnida, Order Pseudoscorpiones)

Also known as False Scorpions, there are 30 species of these small and fascinating creatures in the UK. Pseudoscorpions are related to spiders and scorpions (although they have no stinging tail like their cousins). They are often found in leaf litter, decaying vegetation and under wood bark. There is one species that lives indoors in stables, grain stores and dusty bookcases, where it hunts booklice and dust mites. In the UK they range in size from 2-8 mm making them hard to spot.

Spiders (Class Arachnida, Order Araneae)

Spiders are fascinating invertebrates found in a diverse range of habitats – from the inside of our homes to the tops of mountains. There are approximately 670 species of spider in the UK. Spiders native to the UK have a great range of body sizes – from the tiny Minute Maro Money Spider (Maro minutus) to the huge Cardinal Spider (Tegenaria parietina) with a leg span of more than 10 centimetres. The Four-spot Orbweaver (Araneus quadratus) is one of our heaviest weighing up to 2.5 grams! Spiders play an important ecological and environmental role controlling many insect pest species. Without them there would be more flies in your house and insects damaging our crops.

Spiders are arachnids and classified in the invertebrate Order Araneae. Almost all adult arachnids have four pairs of legs unlike adult insects which all have three pairs of legs. Arachnids have two further pairs of appendages, the jaws (chelicerae) which are adapted for feeding and defence and the pedipalps which have become adapted to aid in feeding, movement and reproduction.

Snakeflies (Order Rhapidioptera)

Only four species of Snakefly are known to occur in the UK- there are no records of them from Northern Ireland. This ancient group are very distantly related to lacewings, alderflies and scorpionflies. They are predatory insects feeding on aphids and other small insects and are easily recognisable with their elongated thorax and head which looks like a snake. The female snakefly looks like it has a long stinger at the end of its abdomen, this is an ovipositor that is used to lay eggs in the cracks of bark, and completely harmless to us!

Beetles (Order Coleoptera)

A large and diverse group that all have biting mouthparts and hardened wing cases called elytra that protect the abdomen. The vast majority of the 4,100 species of beetle that are found in the UK are terrestrial. Almost 300 species of beetle haven’t been recorded in Britain since the 1970s! They live in a wide range of habitats – including several that require freshwater habitats. Beetles have a great range of sizes in the UK – our smallest beetle Nephanes titan (from the Featherwing Beetle Family Ptiliidae) is less than 1mm in length and our largest the Stag Beetle (Lucanus cervus) can grow to 7.5cm in length!

There are over 100 different families of beetle that includes the ladybirds (Family Coccinelidae), longhorn beetles (Family Cicadellidae), and the ground beetles (Family Carabidae).

Many people may be familiar with the ladybird that we often see in our gardens – the Seven Spot Ladybird (Coccinella septempunctata). The non-native and highly invasive Harlequin Ladybird (Harmonia axyridis) can now be found across the UK. This species is notorious for feeding on our native ladybirds as well as a wide range of other insect species. Ladybirds are well known as a gardener’s friend as they feed on aphids and other pest species.

Another gardener’s friend are the ground beetles. Ground beetles are predatory with long thin legs that allow them to chase their prey. Many of them are nocturnal except for the colourful tiger beetles that are often seen (and heard) buzzing by on a hot and sunny day.

Longhorn beetles are one of our most visually attractive group of beetles. This fascinating family includes the Wasp Beetle (Clytus arietis) and the Timberman Beetle (Acanthocinus aedilis). All but two species of longhorn beetle are saproxylic – the larvae require rotting and dead wood to complete their life cycles. The larvae of the other two species develop in the hollow stems of Umbellifers such as Hogweed (Heracleum sphondylium). The larvae of longhorn beetles can take several years to develop whereas the adults live only for a few weeks or months.

Bees, wasps, ants and sawflies (Order Hymenoptera)

Our bees, wasps, ants and sawflies are all included within a huge and diverse order of insects called the Hymenoptera (Hymen= membranous; ptera= wing). There are over 7,000 species within this fascinating group in the UK. We may all be familiar with the painful sting of a wasp or bumblebee. A sting is a modified egg-laying device (the ovipositor) that is used only in defence and for many to paralyze prey to take back to their nest. All females (except sawflies) within this group have a sting, but the vast majority aren’t strong enough to pierce our skin, plus they are so busy going about their business.

Sawflies are a primitive group – the larvae are similar in appearance to butterfly and moth caterpillars, except with legs on nearly all segments. The larvae feed on the leaves of plants and include many that feed on specific species of plant such as the Solomon’s Seal Sawfly (Phymatocera aterrima) that feeds on Solomon Seal (Polygonatum species). There are even some species that make galls on leaves and those with larvae that live in decaying wood- such as the larvae of the Giant Woodwasp (Urocerus gigas). They are important pollinators with adults of several species visiting flowers for nectar. There are nearly 500 species of sawfly in the UK.

Parasitic wasps are important biological pest controllers with over 6,000 species in the UK! These wasps are parasites of other invertebrates (technically parasitoids since they often kill the host) or their larvae develop in living plant tissue where they may form galls. This is an immense and complex group of wasps with many different life histories. They are abundant and play a vital role in the checks and balances in populations of other invertebrates.

There are over 250 species of bees (including bumblebees and solitary bees) in the UK. Bees are our most efficient and important insect pollinators, they feed on nectar and gather pollen to feed their larvae.

Wasps are a fascinating group of insect and like the bees also include both social and solitary species. There are about 350 species of wasp in the UK and only nine of these are social (with a single queen and many workers). Most feed their larvae on other insects and are efficient pest controllers.

A single ant can carry 50 times its own bodyweight, and they will work as a group to move larger objects! Most ants are colonial and have nests with a few hundred to thousands of workers depending on the age of nest and species concerned. Some species of ant can live for over 30 years, and they are our longest living insect! Some species of ant collect seeds to eat, but most are predatory on other tiny creatures or found feeding on honeydew secreted by aphids; some even manage and protect aphid colonies, milking them like a herd of cows.

Snails and slugs (Class Gastropoda, Phylum Mollusca)

The vast majority of our 150 or so species of terrestrial snail and slug are vital in recycling nutrients. Known as detritivores, they feed on dead and decaying plant material, fungi and animals returning nutrients to the soil. Many of our species are nocturnal and have poor eyesight- they use their tentacles and the soles of their foot to detect smells and taste. Snails and slugs are related to octopus and squid that live in the sea. Almost all species are hermaphrodites, meaning they have both male and female sexual organs and can fertilise each other when mating. Most importantly- snails and slugs are important prey for a number of other animals, including Hedgehogs (Erinaceus europaeus) and Song Thrush (Turdus philomelos).