Insects are perhaps the most familiar invertebrates. They belong to a group of animals known as arthropods. Adult insects have six legs and a body made up of a head, thorax and abdomen. Many also have one or two pairs of wings; they are the only invertebrates that can fly. Their bodies are supported by a hard exoskeleton made of chitin. Just like the crustaceans rule the oceans, the insects rule the land. They exist in almost every terrestrial environment, and in an enormous array of colours, shapes and sizes. Many of them have fascinating life histories.
Insects – the basics
Vile or vital?
Insects often have a bad reputation for being creepy, scary or just a complete nuisance. Whilst bees may sting us if we sit on them or get too close to their nests, we rely on them to pollinate our crops. Without them performing this vital role it would be very difficult to produce food – the bees are the farmers’ best friend!
Other insects are responsible for keeping the soil fertile (e.g. dung beetles), eating smaller insects which damage the plants we grow (such as the ladybird eating greenfly), and some very insignificant-looking bugs called scale insects have been used to produce carmine (a red dye used in foods, textiles and cosmetics) since the time of the Aztecs.
Insect diversity is far greater than any other group of animals and the sheer numbers of species and of different insect groups is mind-blowing. Insects also outnumber most other animal groups in terms of individuals, and colonies of the social insects such as ants may number in the millions. Insect collections allow us to monitor and study insect biodiversity.
RAMM’s insect collections
RAMM’s insect collections are divided into the main orders of insects. This arrangement allows us to locate a particular type of insect quickly for reference.
|Lepidoptera||Butterflies and moths|
|Hymenoptera||Bees, ants and wasps|
|Orthoptera||Crickets and grasshoppers|
|Odonata||Dragonflies and damselflies|
|Phasmida||Stick and leaf insects|
They are stored in drawers that have a tightly fitted lid to keep out pests such as the carpet beetle which will feed on the dead insects and destroy the collection. Most of the insects have a pin through them which allows them to be viewed from all angles and holds them in place. The pin is held in place by the cork or plastazote drawer lining.
The pin also holds labels that give information about the specimen such as collection location and date. The information that accompanies a specimen is very important, particularly where and when it was collected. Other information such as whose collection it came from can often be deduced from the handwriting or type of label if this information is not given.
Butterflies and Moths
Butterflies and moths (order Lepidoptera) are among the most majestic of insects. Their vivid colours and striking patterns are mesmerising both in nature and in museum collections. Transient, fluttering and fragile, or adept flying machines, these wonderful creatures are one of the highlights of RAMM’s natural history collections.
Thanks to past curators
The size and quality of our collections is largely thanks to the dedication of Major Bertie Gay and Anthony Adams who painstakingly sorted the specimens into consolidated collections that were arranged in taxonomic order. Major Gay also purchased, from his own pocket, a considerable number of rare and tropical specimens for the collections as well as numerous cabinets for their storage.
We have over 120,000 Lepidoptera specimens making ours one of the finest, most extensive and scientifically valuable Lepidoptera collections of any provincial museum in the country.
Butterflies and moths undergo complete metamorphosis. Tiny larvae (caterpillars) hatch from the eggs and most start feeding immediately. They shed their skin several times in order to grow. The larvae pupate, sometimes inside a silken cocoon, before emerging as winged adults. The juvenile stages are very different from the adults.
All life stages have been preserved in our collections.
Empty pupal cases and cocoons are relatively simple to preserve, but larvae are much more difficult due to their soft bodies. If the larvae were just left to dry naturally they would become shrivelled and lose the appearance they had in life. The easiest way is to store them in a fluid such as alcohol, but this can make them difficult to study and cause them to lose their colour.
As a result collectors had to come up with an ingenious method of preservation. The insides of the larva would be squeezed out of a small puncture in its rear end. A very fine glass tube would then be inserted through the puncture allowing the larva to be inflated while drying the skin over a heat source. It would then be mounted on a piece of wire for display in the cabinet. These larvae are extremely fragile – they are a little like a tissue paper balloon.
The literal translation of Lepidoptera from ancient Greek means ‘scaly wing’. The beautiful patterns on a butterfly’s wings are made up of thousands of pigmented (coloured) microscopic scales. In some cases, however, the colour is not produced by a pigment, it is generated from the way the structure of the scales reflect light. This is called iridescence. Many butterflies show iridescence but the best known are those in the genus Morpho. Some butterflies lack scales on their wings making them transparent.
The beetles (order Coleoptera) are the most diverse insect order with over 300,000 species described and many thousands still to be described and discovered.
From the tiny to the tremendously large, beetles exist in all shapes and colours. One of the largest beetles in the world is the goliath beetle (Goliathus regius) which can measure up to 11cm in length.
Some species are known as jewel beetles because of their beautiful metallic wing cases (elytra) that protect the flight wings beneath them. This metallic colouration is not caused by a pigment but by iridescence. Iridescence is also seen in some butterflies and is caused by the way the structure of the beetle’s exoskeleton reflects light. Due to this, the beetle’s colouring will not fade even after many years in our collections.
Beetles undergo complete metamorphosis. They hatch from eggs as larvae that range from soft, legless grubs to fierce, fast-running or swimming predators. Once large enough they pupate and then emerge from the pupal case as an adult beetle.
Our collections and collectors
Larvae are most frequently preserved in fluid, such as alcohol. Adult beetles are usually preserved as dry specimens. They have a pin passing directly through the body that allows us to store them securely in drawers. However, some of the smaller beetles are fixed to a piece of card using water-soluble glue, and the pin passes through the card so that the beetle is not damaged.
The majority of our beetle collections exist thanks to the efforts of three collectors:
Philip Le Hardy de la Garde
De la Garde collected many beetles and other natural history specimens during his Naval career, particularly from the Plymouth area when he was based at Devonport. During his retirement he made collections in Teignmouth and Braunton. His collections were left to the Museum in his will in 1913.
John Joseph Reading
John Reading is one of the most famous Plymouth entomologists. He was a curator of entomology at the Plymouth Institution from 1861 to 1863. He left Plymouth in the early 1870s and his collections came into the possession of Brooking Rowe who later presented them to RAMM in January 1904. This donation included a 40-drawer entomological cabinet. Reading kept extensive and accurate records of his captures and sightings and he was involved with several important (re)discoveries.
S.G. Rendel, then living in France, donated his collection of British beetles to the Museum in May 1928. Many of the specimens were collected in the Tiverton area. Unfortunately we know little of his life history.
The true flies belong to the order Diptera. This literally means ‘two wings’ and all true flies have just one pair of wings. What were once hind wings have evolved into halteres which are tiny peg-like structures that keep flies balanced in flight.
Only flies by name
This means that though many types of insect have ‘fly’ in their name, they are not true flies. Butterflies (order Lepidoptera), scorpionflies (order Mecoptera), mayflies (order Ephemeroptera), caddisflies (order Trichoptera) and dragonflies (order Odonata) all have two pairs of wings, not one. Fireflies are actually a type of beetle.
Flies in disguise
Many types of fly including hoverflies mimic the warning coloration of bees and wasps to avoid being eaten. Bees and wasps use this coloration to warn predators that they can sting. Flies are unable to sting, but by mimicking the appearance of a bee or wasp they fool predators into thinking that they too are harmful.
Flies and nature
Flies are often seen as a nuisance with no useful role at all. However, many species of fly including the hoverflies are nectar feeders and hence are important pollinators of plants. These flies are a harmless and welcome sight in gardens, more so since their larvae may be feeding on greenflies (…which confusingly are actually a type of bug, and not a true fly).
Adult and larval flies are a vital part of nature’s clean-up team because they feed on dung and dead animals.
Flies are also an important food source for small mammals, birds and other invertebrates.
Flies and man
Flies are an important consideration in human medicine. They often have mouthparts that are sharp and designed to pierce skin in order to suck blood, or that are like a sponge to mop up liquids such as nectar or dung. The mosquito is responsible for transmitting the deadly diseases malaria and yellow fever and the tsetse fly for the spread of sleeping sickness.
Houseflies and bluebottles can transmit harmful bacteria to humans as they are not fussy feeders and will happily feed on uncovered human food after just having visited a cow pat (or worse)!
Bees, ants and wasps
Insects in the order Hymenoptera are among the most social and industrious of all insects. Wasps, ants, hornets, bees, sawflies and parasitic wasps all belong to this order, though not all show social tendencies.
The old saying about bees being busy is certainly true. Bees, and many wasps, travel from flower to flower to gather pollen or feed on sweet nectar, and in doing so they quite unintentionally pollinate the flowers. This allows the plants to grow fruit and seeds in order to reproduce.
The honey bee (Apis mellifera) is responsible for pollinating the vast majority of our crops. Albert Einstein is said to have predicted that ‘if the bee disappears from the surface of the earth, man would have no more than four years to live’. Although he was not an entomologist, today’s insect specialists agree that without the bee it would be extraordinarily difficult for humans to grow food.
We are family
Many species of ants, bees and wasps live in large colonies. For example, ants can form colonies and super-colonies that contain many millions of individual ants. At the centre of each colony is a queen who is cared for by large numbers of her female offspring. The queen is the only member of the colony that will reproduce; all the other members cooperate to carry out specific roles within the colony.
Going it alone
At the other end of the spectrum are the solitary wasps which include woodwasps, sawflies and parasitic wasps. Species that do not live in vast colonies greatly outnumber those that do. Some species live in almost complete isolation and don’t even need to find a mate.
Most wasps are probably so small you wouldn’t even notice them but you might notice the effects they have on other organisms. One species is responsible for forming a gall known as the robin’s pincushion which is bright red in colour when first formed. This grows after the female wasp has laid her eggs in the plant stem. Other parasitic wasps may parasitise their young…and these parasites may even be parasitised! It has been estimated that up to 14 different species may be found inside one robin’s pincushion gall.
Ants, bees and wasps are masters of construction. The honey bee makes honey comb, which is a plate of hexagonal wax cells, in order to house their larvae and stores of pollen and honey.
Some wasps produce elaborate paper nests to house entire colonies which are often suspended from tree branches. They use their powerful jaws to scrape away wood fibres from trees and fences which they turn into a pulp using their saliva. The pulp is then carefully reformed into the walls of the nest.
Ants excavate large ‘cities’ underground consisting of hundreds or tiny tunnels and chambers. Some wasps also dig underground nests and construct the internal structure from mud.
A sting in the tail
Only the female ants, bees, wasps and hornets can sting. This is because the sting has evolved from the female’s ovipositor (egg-laying tube). Not all species are able to sting, even though their long ovipositors might make it look like they can. The parasitic wasps use their long, sharp egg-laying tubes to implant their eggs into plant tissues and other organisms such as caterpillars.
Crickets, grasshoppers and katydids
Insects in the order Orthoptera include the grasshoppers, crickets and katydids. They are often well camouflaged for the environments that they live in – some have wings that look like leaves, others are long and thin like twigs. These insects are famous for their jumping ability and many species have extremely powerful, long hind legs enabling them to jump a long way.
Grasshoppers and crickets are renowned for their ability to ‘sing’. Their songs are produced by rubbing one body part against another which is called stridulating. The legs and wings may be rubbed together or against the body to produce sound.
RAMM has several unusual specimens in its collections. The predatory bush cricket (Saga pedo) is probably one of the most fascinating crickets in our insect collection.
Why are these bush crickets so fascinating? Firstly, they are large! This specimen is over 15cm in length from the tip of its antennae to the end of its body – considerably larger than anything you will find in the fields around Exeter!
Secondly, almost all crickets of this species are female – males are very rare. The females do not need to mate with a male cricket in order to reproduce because they are able to produce young that are genetic clones of themselves (i.e. they will all be female). This is called parthenogenesis and is a common reproductive method in the insect world.
Finally, whilst grasshoppers are vegetarian and crickets are omnivorous, Saga pedo is unusual in that it is entirely carnivorous. She will lie in wait for a smaller insect such as a grasshopper to pass by and ensnare it in her spiny forearms (very similar to how praying mantids catch their prey) and then devour the unsuspecting insect with her powerful jaws.
RAMM has two specimens of this species. Both were collected by Major Bertie Gay during his service with the Royal Artillery in Macedonia in 1917. He was awarded the Military Cross for bravery in action during the First World War, as well as an MBE for staff services and the Territorial Decoration in the Second World War. Later in life he was a curator at RAMM for over 20 years.
The mole cricket is also an oddity in this order. As the name suggests the cricket physically resembles a mole and burrows underground. Like a mole it has enlarged front legs and ‘hands’ with which to dig down beneath the surface. The mole cricket’s hind legs are relatively short as underground it has little need to jump and large hind legs would make it more difficult to burrow.
We often refer to any number of different types of small invertebrate as ‘bugs’. However, a more appropriate general term might be to call them ‘minibeasts’ or, less affectionately, ‘creepy-crawlies’. This is because only insects belonging to the order Hemiptera can technically be called a ‘bug’.
There is an enormous diversity in the body shape of bugs, and in features such as their wings, antennae and eyes. The word Hemiptera literally means ‘half-wing’ which refers to the fact that their wings, where present, are often hard at the base and membranous at the tip.
The life histories of bugs also differ enormously. Some, such as aphids and shield bugs, feed on plant sap, whereas others, including water boatman and pond skaters, feed on other small insects and sometimes small fish and tadpoles.
The feature that groups all of these different insects together is the structure of their mouthparts. They have a piercing and sucking function and are like a straw with two channels, one for taking in food and the other for saliva. They use this sharp ‘beak’ to pierce the stem of a plant, or the skin of an animal, and then suck out their liquid contents.
Bugs undergo incomplete metamorphosis – they do not pass through a pupal stage. Bug nymphs increase in size by shedding their skin until they reach adulthood.
RAMM has some weird and wonderful bugs in the collections.
One exotic bug from Trinidad (known as the toe-biter bug!) is particularly scary. At a terrifying 10cm in length this bug will give a painful bite if handled. It swims using its hind legs, while its forelegs are used for grasping prey. The toe-biter will inject digestive juices into its prey (possibly your toe!) and then suck out the contents using its straw-like mouth parts.
The cochineal bug is a type of scale insect found in South America and Mexico where it feeds on the sap of cactus plants. It may not look like much in the photograph, but this insect has been very useful to us. The Aztecs used these bugs in enormous quantities to make a dye called carmine which is crimson red in colour. We still use cochineal today for colouring food, fabrics and cosmetics.
Dragonflies and damselflies
These stunning creatures belong to the order Odonata, which is split into two suborders: the Zygoptera or damselflies and the Anisoptera or dragonflies.
They often have striking vivid and metallic colouration and are quite a spectacle to see on a sunny day by the river. They are outstanding aviators – dragonflies can hover, and fly at great speed, and are the only insects that can fly backwards! The damselflies perform elaborate aerial courtship dances over the water, and insects of both suborders can feed and mate whilst on the wing.
The most striking feature of both the dragonflies and the damselflies is the enormity of their eyes. They have very large compound eyes that provide them with excellent eyesight.
Dragonflies and damselflies undergo incomplete metamorphosis. Juvenile (nymphal) stages live in feshwater streams and ponds where they are voracious predators. The regularly shed their skins as they grow larger and their wing buds become more obvious. Once they have grown sufficiently they climb out of the water and shed their skin to reveal the winged adult insect.
Whilst the skins are very fragile, they are easy to incorporate into pinned collections. Nymphs, particularly damselfly nymphs, are best preserved in alcohol. Dragonfly nymphs are much more sturdy and can be dried and pinned with care.
RAMM’s collections of Odonata
Due to their extraordinary eyesight and flying capabilities adult dragonflies and damselflies can be very challenging to catch, even with a net. Therefore it must have taken a lot of dedication and patience to capture the specimens in our collections.
The vivid colours that these insects have in life often fade quickly after death, and so Odonata collections can seem drab and dull in comparison. Special preservative techniques can help reduce the colour loss, but in turn this can make them very brittle.
One small but particularly well preserved collection was donated to us in 1960 and the images are of specimens in that collection.
Stick insects and mantids
Stick and leaf insects (order Phasmida) and praying mantids (order Mantodea) often physically resemble plants. Their wings, bodies and limbs may mimic the shape and colour of dead and living leaves, twigs and even flowers. Though insects from these two orders have very different habits, they both use their camouflage to remain hidden in their natural environments.
Insects from both orders undergo incomplete metamorphosis. Stick and leaf insects hatch from individual eggs that closely resemble plant seeds. However, female praying mantids lay a foamy egg case called an ootheca on a leaf, branch or other hard substrate from which many tiny nymphs will hatch. Phasmid and mantid nymphs look very similar to the adults and must shed their skin as they grow. Only adults will have fully functioning wings, although these are not present in all species.
Praying mantids are so called due to the pose they often hold. They will stand with their forelegs raised and bent appearing as if in prayer. They adopt this position so that their barbed forelegs are ready to grab any passing insect or animal because, unlike the stick and leaf insects who are vegetarian, they are entirely carnivorous. They are voracious predators and hence they are often wrongly called preying mantids. Mantids have excellent eyesight.
Camouflage is the first line of defence for many species. As their name suggests, stick insects are often long, thin and twig-like, but some can be very large and prickly. Leaf insects are usually very flat and wide. Mantids take on a variety of shapes and colourations but are also capable of blending in perfectly with the background.
However, some species display warning colours. The Peruvian fern insects, for example, are either bright red, orange or yellow with black stripes. These colours warn predators that the insects will taste foul.
Other stick insects, such as the jungle nymph, have brightly coloured hind wings. These are hidden by the fore wings while the insect is at rest, and can be flashed to startle predators. Mantids frequently have brightly coloured hind wings, some with eye spots.
Many of the stick insects in RAMM’s collection are from the collection of Major Bertie Gay who was a curator at the Museum. Unlike the mantids which are usually quite small, some of our stick insects are over 30cm in length (including legs), and require very large drawers to store them in.