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Contents
Introduction ...................................................................................................................................... 3
Mini-beast hunt ................................................................................................................................. 4
Collecting ...................................................................................................................................... 4
Log and stone turning .................................................................................................................... 5
Invertebrates of St Helena ................................................................................................................. 6
What are invertebrates? ................................................................................................................ 6
Feeding ............................................................................................................................................. 7
Invertebrates mouthparts.............................................................................................................. 7
Plant and animal feeders and scavengers .................................................................................... 10
Plant feeders - Herbivores ........................................................................................................... 10
Animal Feeders - Carnivores ........................................................................................................ 10
Scavengers/recycler – Omnivores/decomposer ........................................................................... 10
Movement ...................................................................................................................................... 11
Senses ............................................................................................................................................. 14
Reproduction and Growth ............................................................................................................... 15
How to treat bugs with care and sensitivity ..................................................................................... 16
Pollination ....................................................................................................................................... 17
Taxonomy- Classification and variation ............................................................................................ 18
Habitats........................................................................................................................................... 21
Cloud Forest ................................................................................................................................ 21
Dry Forests .................................................................................................................................. 21
Streams and ponds ...................................................................................................................... 22
Semi-deserts................................................................................................................................ 23
Leaf litter and Soil ........................................................................................................................ 23
Adaptation ...................................................................................................................................... 28
Colours and camouflage .............................................................................................................. 28
Mimics......................................................................................................................................... 28
Defence - Stalked eggs and backpacking waste ............................................................................ 30
Food Chain, food webs and trophic levels ........................................................................................ 32
Social and solitary invertebrates ...................................................................................................... 34
Migration ........................................................................................................................................ 35
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Light and sound ............................................................................................................................... 36
2
Introduction
St Helena is a unique island. The isolation of it has over millions of years enabled
invertebrates to evolve and develop into new species. Many of these are found nowhere
else in the world - they are endemic to St Helena.
Sadly many of the endemics are on the brink of extinction and urgent action is needed. In
February 2013 the project “Laying the foundations for invertebrate conservation on St
Helena” also known as the “Bugs on the Brink” was established. The project is raising the
profile of St Helena’s unique and important wildlife, kick starting the conservation of these
endemic bugs and making sure that everyone realises how special St Helena is for them.
It was funded by the UK Government’s Darwin Initiative and supported by Buglife UK (the
Invertebrate Conservation Trust), the Centre for Ecology and Hydrology UK, St Helena
National Trust and St Helena Government.
I have created this invertebrate education pack to raise awareness of the special endemic
and other invertebrate species found on the island and include St Helena’s unique wildlife in
the school curriculum.
Along with the education pack is an equipment loan box, which you can borrow from the
National Trust for free so it is possible for you to carry out mini beast educational activities
yourself. It can be adapted to suit the needs of each age group right from the early years to
Key stages 1-4.
The education pack aims to give both you and your students a better understanding of St
Helena’s invertebrates and their habitats. In this document “science”, I provide you with
teaching tips and suggestions as well as related worksheets,
activities, equipment and crafts so you can easily and
confidently talk about the unique wildlife of St Helena.
Address
The loan box will have all the necessary equipment to
conduct bug hunts, microscope work and research.
Please book a week in advanced to borrow the loan box for
free from the National Trust by contacting us on the
following:
St Helena National Trust,
Broadway House,
St Helena Island,
South Atlantic Ocean,
STHL IZZ
I hope you will enjoy this education pack and loan box.
Telephone
Buglife office: 22569
Main office 22910
Liza Fowler
Email
[email protected]
Invertebrate Education Officer – “Bugs on the Brink”
project.
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Mini-beast hunt
You don’t have to go far to have a mini-beast hunt. Most of the schools on the island are
situated in the countryside and mini-beast hunts can easily be conducted in the school
grounds.
Collecting
Bug hunts is a great way in which children of all ages can engage and understand the
diverse range of invertebrates on St Helena - both for land (terrestrial) and aquatic
habitats.
There are many different ways to collect invertebrates; two of the methods are given
here: sweep net collecting and pitfall trapping.
The sweep net techniques are suitable for children to conduct a hunt in woodland or
grassland habitats and pitfall trapping can be used anywhere.
Please refer to the equipment session for more detail.
St Pauls Primary
Pilling Primary
Year 1 Pupils are having a closer look at their
invertebrates, collected in their pooter and looking
through a handheld magnifying glass.
Teaching tips for Outdoors
For Early years
The reception class are having a look under a log and
discussing what’s living there.
For KS 1-4
First demonstrate to the children how
to use the equipment. See equipment
booklet for instructions on how to us:
I gave each child a pooter and split
This age group can either work
them into smaller groups with one
individually or in pairs, one can sweep
sweep net per group to avoid
net and the other can collect the
overcrowding. I sweep net the
invertebrates with their pooters. This
Sweep nets pg. 2
vegetation for them as they find it
depends on the amount of equipment
Pooters Pg. 3
difficult to use the nets with the right
available.
pressure to collect the invertebrates
The size of your group and the ages of
from the vegetation. They collect the
the students will influence how you do
invertebrates from the nets with their
this……..
pooters themselves. Nearing the end of
the lesson give the children each a turn
with the nets so they can get a feel for
them.
Equipment needed: Sweep nets, Pooters, Magnifying hand lens or pots and a spoon for scoop up large invertebrates for
early years and forceps for the older students.
Worksheets: Bug hunt investigation (all ages) Pg.3, My mini-beast Pg.4 and pitfall trap investigation sheet Pg.9
4
Log and stone turning
There are many different types of invertebrates living under logs and stones and
even in leaf litter. You can always find a log or stones on the ground.
To collect these invertebrates you can use a spoon to scoop up bigger species (for
the younger children) or forceps (for the older students) and place them into
magnifying pots, jars or the port a bug to have a better look.
But, be sure to return the logs and stones back to how you found them, and remind
students to do the same.
Prince Andrew School
Here the students are studying what invertebrates are
in the debris, sucked up by the bug-vac machine, while
entomologist, David Pryce explains what they are and
the importance of invertebrates.
The students learn how to use entomology equipment and collecting techniques with pooters and sweep nets.
Teaching tips for Research
Questions
Invertebrate conservation projects are a
good opportunity for students (KS3-4) to get
involved with and research.
1. Where did the data first come
from? (History)


2. We know there are 455 endemic
species of invertebrates recorded,
now find out how many native and
non-native invasive species there
are by using the species list that can
be found on the South Atlantic
Environmental Research Institute
(SAERI)
www.south-atlantic-research.org


Some examples of questions are here with
cross defences in brackets:
3. Make charts from your findings
(Maths)
4. Research what has caused
invertebrates to decreases or
increases in population sizes? e.g.…
Questions
Habitat loss
Increase in predatory
invertebrates
Habitat restoration
Climate change
5. From the species list (found on
the SAERI website), pick a name at
random and research:

Its taxonomy

Is it a carnivore,
herbivores or omnivore?
6. What is the rarest species of
invertebrate on St Helena and when
was it last seen? And there are 320
insects, find out what kinds they
are?
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Invertebrates of St Helena
There are 455 endemic invertebrate species that have been recorded on St Helena to date.
These species are unique to the island and the unusually high number of endemic species
found here means that St Helena is internationally important.
What are invertebrates?
Invertebrates are animals without a backbone and they make up the great majority
of animal life. They are a unique and very diverse group of animals on earth.
Invertebrates are classified into taxonomic groups such as Arthropods which includes
Insects, Arachnids and Crustaceans and other groups like Molluscs, Echinoderms and
Annelids.
Here are the statistics on the endemic invertebrates of St Helena in their taxonomic
groups. See the Species list for more information by downloading it from the South
Atlantic Environmental Research Institute (SAERI) website www.south-atlanticresearch.org
The basic groups are in bold.
Taxonomic name
Common name
Total
Insecta
Insects
320
Arachnida
Arachnids
95
Chilopoda
Centipedes
3
Crustacea
Crustaceans
10
Turbellaria
Flatworms
3
Mollusca
Molluscs
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First, let us take a brief look at some of the different types of invertebrate’s mouthparts and
how they have adapted to obtaining their food.
Feeding
On St Helena there are about 1350 species of invertebrates. There are ones that consume
plants, animals and a variety of other things.
A few feed on only one particular kind of food, they are known as 'specialists', while some
have a more diverse diet and are called 'generalists' and others can change their diets
during the different stages of their life (e.g. they may eat plants as a larvae and animal as an
adult or vice versa).
A range of invertebrates eat either the inside or outside of different parts of plants. Some
actually eat the plants themselves, while others just suck sap and some feed only on nectar
and pollen.
Another specialised group of invertebrates feed on blood, often from large animals,
including humans, by biting or sucking from the outside. Others feed from the inside of the
body of animals these are called internal parasites.
Some invertebrates are scavengers – nature’s recyclers. They eat plants and animals that
are already dead and decaying, also feeding on the dung of animals.
Invertebrates mouthparts
Chewing
There are many invertebrates that have complicated jaws made up of three parts.
They consist of a large pair of jaws called mandibles that are used to bite off food, a
smaller pair called maxillae and a third pair similar to fingers that help put food into
the mouth. This includes beetles, grasshoppers, wasps, centipedes and woodlice.
Sucking and piercing
The structures of many other invertebrates have adapted into a tube where they can
suck up liquid food. Butterflies and Moths for example, suck nectar from flowers
with a straw like tube called a proboscis. When not in use it is coiled up. Butterflies
and Moths do not have any mandibles.
Bees have a long tongue to drink the nectar deep in the flowers but have kept their
mandibles for eating pollen.
Many of the invertebrates that suck up liquids pierce plant stems and leaves to
obtain the sap inside. Predatory bugs suck out the insides of their prey. Flies have a
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sucking pad to feed on liquid food and spiders liquefy their prey with their digestive
enzymes and ‘drink’ the liquid from inside their victim's body. Other predatory
invertebrates pierce the skin of animals and suck their blood like mosquitoes.
Some aquatic invertebrates are filter feeders; they sieve plants, animals and other
particles from the water. Clams, Barnacles, Water fleas as well as aquatic insect
larvae are some examples of this behaviour.
Arthropods
Cricket mouthparts
Butterfly mouthparts
Maxilla
Mandible
Proboscis
Maxilla
Bee mouthpart
Mosquito mouthparts
“Tongue” glossae
Mandible
Piecing mouth (labrum)
Fly mouthparts
Sucking pad
(labellum)
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Annelid mouthpart
Molluscs mouthpart
Arachnid mouthpart
Fang
Poison gland
Teaching tips for observation
Take your students out into the school grounds near some
flowering plants. Observe invertebrates feeding on the nectar
(this also covers pollination).
This is a good way in which children can see how the mouthparts
of bees and butterflies have adapted for feeding from flowers.
Check plants for holes and see if you can find what’s
been eating them. Caterpillars and snails might be
found, put them in a glass jar or magnifying pot to see
its mouthparts close-up.
Look out for spiders webs; if they are hungry they might
be feeding on their victims trapped in the web and be
careful not to squash soft invertebrates!
Equipment needed: Magnifying hand lens or magnifying pots or glass jar
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Plant and animal feeders and scavengers
Here are examples of the different types of endemic feeders.
Plant feeders - Herbivores
Piecing and sucking
Chewing
This endemic Vultureine leafhopper (Nehela
vulturina) is one of 41 species of True bugs that have
piercing mouthparts. This leafhopper sucks the sap
from plants and is a common sign on Diana’s Peak
The Spurred grasshopper (Tinaria calcarata) has
mouthparts adapted for chewing, they can be seem
in lush areas like Peak Dale
Animal Feeders - Carnivores
Piecing and sucking
Piecing and sucking
The endemic Golden Sail Spider (Argyrodes mellissi)
liquefy its prey and drinks the insides out, its habitat
is Diana’s Peak.
The Wollaston's Bug (Vernonia wollastoniana)is a
predatory True bug with piercing mouthparts to feed
on its victims insides
Scavengers/recycler – Omnivores/decomposer
Chewing
Some beetles, like this Leleup's darkling beetle(Tarphopphasis leleupi) are general decomposers, they eat
decaying leaves, sticks, grasses, insects and faeces and occasionally new plant growth. The habitat of this
beetle is Prosperous Bay.
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Movement
All invertebrates have their own particular ways of moving. These include walking and
running, jumping and hopping and swimming.
Slugs and snails movement is known as sliding or gliding.
Spiders and some other invertebrates throw out several strands of web to form a parachute,
which is caught by the slightest breeze allowing them to move from one place to another;
this is called ballooning. Worms wiggle through the soil and most insects fly.
Here are examples of the different invertebrates and how they walk, run, jump, hop and
swim.
Walking on land
Walking on water
Most insects have long tin legs, which are all alike,
they move three legs at a time and balance on the
other three
Lesser water crickets, they are very light bugs and
have long spread-out legs and their feet are wax,
preventing them from becoming wet, which they use
to walk on the surface tension of water.
Running
Jumping
This Prowling wolf Spider has very long leg, allowing it
to run very fast
The long hind legs of grasshoppers and plant hoppers
enables them to leap. They straighten their legs very
quickly,pushing themselves high into the air.
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Hopping
Swimming
The Jellico flea beetle has strong hind legs almost like
a grasshopper that allows it to hop like a flea.
Ostracods are of the crustacean family and swim in
freshwater. Inside its body is a complex set of
appendages, which have a range of functions
including swimming.
Here is another example of movement.
Looper caterpillars
Looper caterpillars have a set of six true legs at the front of its body and a set of four false legs at the back, but
none in-between. They move forward by bringing forward their hind ones, curling up the middle of its body into
a loop, then stretching out its front legs to move forward.
Insects are the only invertebrates that can fly and most of them have two pairs of wings.
Flies have a rear pair converted into tiny sense organs. Beetles and True bugs have their
forewings changed to hard protective wing cases which they hold up and out of the way
when flying.
Dragonflies are almost the only four winged insect which are very fast manoeuvrable fliers
and others like lacewings are slow fliers. Most other four winged insects have some way of
hooking their fore and hind wings together when flying.
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Here are some examples of different fliers.
Flying
Butterflies
Beetles
Butterflies have fairly square shaped wings that are
flapped slowly.
When beetles are at rest, their wings are folded under
a stiff wing casing. When it flies it holds up its casing
to let its wings move easily.
Flies
Hoverflies like the Loveridge's Hoverfly are very manoeuvrable fliers; they can hover, dart very fast and even fly
backwards!
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Senses
Invertebrate’s senses do not work quite in the same way as ours.
Touch
Insects and spiders have tiny, sensitive bristles and hairs all over their bodies
(sometimes including their antennae, which are wrongly called feelers). These hairs
connected to nerves and they can sense whenever they are moved by wind or in
contact with something.
Taste/Smell/Sensing Moisture and heat
The antennae of insects, woodlice, centipedes and millipedes are mainly for,
smelling, tasting and sensing heat and moisture. Some moths can smell each other
or their food plant from a very long way away. Many insects are also able to ‘taste’
with the undersides of their feet. Butterflies, bees and blow flies immediately put
out their proboscis and start feeding when they land on something sweet.
Eyes
Insects, woodlice, centipedes and millipedes have compound eyes, made up of
thousands of separate lenses, each pointing a slightly different direction so that they
can detect even the slightest movement. Unlike us, they cannot focus their eyes at
all. Some, with very large bulbous eyes, can see forward, backwards and downwards
all at the same time. Some insects also have simple eyes called ocelli which have a
single simple lens. Spiders have as many as eight of these, usually in two rows, e.g.
the jumping spiders have two ocelli that are larger than the rest and provide them
with excellent vision.
The eyes of molluscs are much more similar to ours; with a lens which some of them
can actually focus. Those of slugs and snails are on stalks which can be pulled back
into their bodies
Hearing
Not all invertebrates can hear (try shouting at a spider or a slug!). Some insects hear
through ears in surprising places where they have tiny organs called tympana organs.
These are often at the base of their wings but on some crickets their ears are half
way up their legs.
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Reproduction and Growth
Reproduction in invertebrates differs depending on species.
A few can reproduce asexually which is having no sex at all or even not having any sexual
organs. There may be no males involved and females lay eggs or give birth asexually; aphids
are a good example of this kind of behaviour.
Aphids
Egyptian Hoverfly
Asexual
Sexual
Sexual reproduction is more typical. Hermaphrodites are sometimes found amongst
invertebrates. This means that both male and female sexual organs are present in
one individual. Individuals can be either both male and female at the same time
mating, or act as a male or female. Almost all slugs and snails are hermaphrodites.
Growth
In order for invertebrates to grow bigger, they must shed their exoskeleton and grow
a new one. Depending on the type of life-cycle involved, the invertebrate can
become progressively more like the adult as it grows or goes through a pupal stage,
where it undergoes a complete re-build before hatching.
Hemimetabolism / incomplete
metamorphosis
Holometabolism /complete metamorphosis
Worksheets: Life cycle 1 Pg.7 and Life cycle 2 Pg.8
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How to treat bugs with care and sensitivity
Invertebrates are a delicate group. Even though some of them are covered in a hard outer
shell, they all need to be treated with respect.
When discovering bugs on plants, under logs and stones, observe them without touching
them and you can avoid getting stung and bitten. Some invertebrates will defend
themselves if they feel threatened and many will run away to hide or fly away if suddenly
approached, so make sure you move slowly and carefully.
Almost all species of larvae have soft bodies, like caterpillars. Handle them gently so they
won’t get squashed and if you would like to take a closer look at any species, put them in a
glass jar.
Use sweep nets to collect bugs and use a pooters to suck them up. This way you won’t use
fingers and the pooter will allow you to observe closely. For larger invertebrates that can’t
fit through pooter tubing, place in a jar or vial.
If you are collecting invertebrates like centipedes, spiders or scorpions, carefully catch them
by using the forceps and place them in large jars.
Always return the creatures back into their habitats and put logs or stone back as they were
found.
Help to encourage invertebrates around your environment by making habitat piles, bug
hotels and sanctuaries for them.
Do invertebrates need food and water to
stay alive?
Invertebrates do need water to survive, but how
they eat or drink depends on their diet and their
mouthparts.

Herbivorous bugs get most of their
water from plants because plants
contain a lot of water.

Carnivorous bugs often have to get their
water from somewhere else other than
their prey, at the edges of puddles and
ponds, from dew or rain drops on leaves.
Drugs and medicines
Many of our drugs and medicines come from
plants.
However many invertebrate scientists have
researched and developed invertebrate products
or chemical compounds to treat illness.
Refer to PDF article bugs as drugs
For example Bees can be seen sucking the nectar
from flowers and they have also be observed
sucking liquid from fizzy drinks like coke.
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Pollination
Pollination is a process in which pollen lands on the stigma of a plant and travels down to
the ovaries where fertilization takes place.
The colours on flowers attracts all sorts of invertebrates, both flying and crawling, to drink
the sweet nectar from the flowers. At the same time the pollen sticks to the hair on their
bodies and is carried away and transferred to another flower; hairy species like bees are
very good at this.
The colours of flowers can tell us a lot of what type of invertebrate visits them, for example
all of our endemic flora have white flowers except one, Boneseed which has yellow flowers.
This indicates that most of our endemics are pollinated by moths: they are more visible at
night, they don't need bright colours and often produce a moth-specific scent. Many of the
moths are endemic and so they were the main pollinators of the endemic flora before nonnative species got here.
Common Honey bee
Living with invertebrates
Human society immediately recognises invertebrates as pests. Many of them however are our
friends, helping and benefiting us in many ways.
Some species of moth and beetle cause a lot of damage to plants and crops. Some get into our
stored foods like cereals, flour and rice, but everything needs to eat to survive.
Good invertebrates that help us are species such as ladybirds and lacewings; they eat aphids and
help to control their populations. Without these helpful creatures, a lot of plants would be far less
healthy.
Moths, butterflies and Honey bees pollinate plants so that they can reproduce. Bees produce honey
from the flowers nectar making it a food source for other animals, including humans and other
invertebrates.
Invertebrates may be very small, but they have very important roles in ecosystems, contributing to
cycles, food chain and webs and many other things. One in three mouthfuls of food depends on
pollination! Without invertebrates we wouldn’t have chocolate, strawberries and silk.
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Taxonomy- Classification and variation
Invertebrates are put into different taxonomic groups of similar types to help identify them.
Keys are used to identify similarities or differences in the varieties of species. For example
all invertebrates that have six legs and a three part body – head, thorax and abdomen - are
classed as insects.
However, insects are also placed inside another group called Arthropods. There are two
other groups also classed as arthropods, the arachnids (invertebrates like spiders) and
crustaceans which are creatures like woodlice and crabs. These groups share similarities in
body parts, like eight legs (arachnids) or more than eight legs (crustaceans) along with other
basic differences in shape and segmentation.
Another major group has a shell found either externally on their bodies, like snails, or
internally like octopuses, these are classed as molluscs.
Invertebrates which can regenerate themselves and usually have five points such as starfish
and sea urchins and have spiky skin are echinoderms. Invertebrates that have their bodies
divided into segments and use muscles in the body wall for locomotion are called annelids,
this includes species like earthworms.
There are other taxonomic groupings which are more complex, but this is beyond the scope
of this document.
Below is a key for terrestrial invertebrates
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Habitats
Habitats are places in the environment that provide animals with food and shelter. St
Helena has a wide range of habiats including forests, ponds and stream and semi-deserts.
Here are some examples of our habitats and what invertebrates can be found in them.
Cloud Forest
Diana’s Peak is a cloud forest; this means that a large proportion of its moisture
comes directly from clouds, fog or mist covering the hillsides. This is one of a few
sites that the endemic plants flourish and habitat restoration is taking place. Some of
the endemic species of invertebrates are common on the Peak, whereas others can
only be found in small patches associated with one particular endemic plant species.
Here are some examples of invertebrates that are common, scarce and rare in this habitat.
Common
Scarce
Rare
Vulture leafhopper
(Nehela vulturina)
Golden sail spider
(Argyrodes mellissi)
Edith's leafhopper
(Chlorita edithae)
Dry Forests
These are forests that are found all around the island, but they differ from site to
site. They may have only one type of tree species or consist of a mixture, like the
Eucalyptus and Pine tree species, or the Gumwood trees at the Peak Dale.
In these forests there may be invertebrates that have adapted to all types of
environments like the Blushing snail; it can be found on Dianna’s Peak right through
to the edges of the coastal areas. An important group of endemic species that can be
found in these habitats are weevils; they are very small (usually <5 mm) and
specialize in eating dead wood and fungi, other endemic species here include
hoverflies and moths.
21
Here are three examples of endemic species that can be found in this habitat.
Common
Scarce
Rare
Small chimney-sweep grass moth
(Helenoscoparia nigritalis)
Minute weevil
(Pseudomesoxenus minutissimus)
Gumwood Bullet weevil
(Isotornus retractilis)
Streams and ponds
There are many streams that run from the highest points on the island, down into
the valleys towards the sea, and there are isolated catchments (natural and manmade) scattered around the island where life flourishes.
In and around streams there are different species of invertebrates living. Crane flies
generally like moist habitats and their larvae live near the edges of streams in the
soil or in swampy places.
Ostracods are small Crustaceans, also known as seed shrimps that can be found in
isolated rock pools or where the backwaters of streams.
Fresh water shrimp are also found, but only where the water is slightly salty
(brackish). This occurs as freshwater absorbs salts from rocks as it flows through
them, thus making it slightly salty. Many streams fail to reach the sea as in the drier
areas they evaporate away or soak down into the sediment or rocks along their
beds.
Common
St Helenian crane fly
(Dicranomyia sanctaehelenae)
Rare
The larvae of a Crane fly
Helenian large ostracod
(Herpetocypris helenae)
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Semi-deserts
These are the dry areas that occur at the edges of the island where there is
scrubland vegetation like cactus (Tungi), aloes and other bushes.
Although these environments look quite barren and lifeless, there are many different
invertebrates occupying them. Crickets, jumping spiders and beetles, can be seen
during the day, jumping and running out of the way if disturbed. Most of the time,
they might go unnoticed because of their spectacular camouflage colours that blend
them into their surroundings. For example:
Common
Scarce
Rare
Dryland grasshopper
(Primnia sanctaehelenae)
Leleup's darkling beetle
(Tarphiophasis leleupi)
Prosperous Bay Plain ground
beetle (Harpalus prosperus)
Leaf litter and Soil
Leaf litter supports millions of invertebrates and microscopic organisms which are
very important to ecosystems. They breakdown dead and decaying plants and
animals, so that the nutrients can be taken up again by other species, this is called
the nutrient cycle.
All sorts of invertebrates live in leaf litter such as spiders, beetles, millipedes and
woodlice. Other smaller Invertebrates include mites (there are 41 endemic species of
these tiny invertebrate) and springtails which inhabit the micro world, along with
bacteria and fungi.
Further decomposition is taking place below the soil surface. Dead matter is taken
deep into the ground through tunnels; along with water and air which flows through
the tunnels made by earthworms.
There are many invertebrates that use the soil for shelter. One that is now extinct
was the Giant earwig (Labidura herculeana), it made a tunnel almost a metre long
and we also have unique and very rare Mole spider that tunnels its way around in
soft rocky soil.
23
Here are examples of invertebrates that live in the micro –world
Common
Rare
A typical mite
An illustration of the Napoleon bug
(Napoleon vinctus)
Here is a piece of the Giant earwig's pincers next to a Seaside Earwig for scale (specimens
are at the Museum of St Helena along with the Giant ground beetle).
Extinct
Grant earwig (Labidura herculeana) fragment with a Seaside earwig (Labidura riparia)
Teaching tips for making habitat piles, bug hotels and sanctuaries
There are ways which we can all help to encourage invertebrates around our schools and home, try making habitat pile,
bug hotels and sanctuaries. These structures are very similar and have the same principles. They are designed to provide a
refuge, hunting ground and shelter for invertebrates that are over-wintering or hibernating and they help to encourage
communities of invertebrates that naturally control pests for our benefits.
Activities booklet: Make bug hotels & wood piles. Pg. 5 and Make bug sanctuaries. Pg. 14
Worksheets: Life cycle 1 Pg.7 and Life cycle 2 Pg.8
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Here are example maps of the areas in which some invertebrates can be found and how
common, scarce and rare they are.
Common
Blushing snail
(Succinea sanctaehelenae)
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Scarce
Leleup's darkling beetle
(Tarphiophasis leleupi)
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Rare
Gumwood Bullet weevil
(Isotornus retractilis)
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Adaptation
Invertebrates are everywhere, they have adapted to their habitats to survive. Many
invertebrates have special features, e.g. some have colours that help them to blend into
their surroundings and other can only be seen when in flight, resting or feeding.
Colours and camouflage
There are many invertebrates that are plain in colour like grasshoppers; some
beetles are grey, black or brown which helps them blend into their surroundings, and
many other invertebrates are covered in assorted colours and patterns.
Some invertebrates have bright colours to indicate warnings to predators to stay
away. The majority of the endemic invertebrates aren’t brightly coloured, this
indicates that they are probably harmless, though there haven’t been any studies to
test this.
At the other end of the spectrum is the African Monarch butterfly which often
migrates to St Helena where it lays its eggs on the Milkweed plant. The larvae
consume the plant along with its toxic chemical compounds and store it in their
bodies for the rest of its life cycle to protected them from predators; predators have
learned not to eat either the caterpillar or the adult because of their brightly
coloured bodies that indicate they are distasteful.
Larva of the African monarch butterfly
African monarch butterfly
(Danaus chrysippus)
Mimics
Some invertebrates have evolved to mimic other stinging or poisonous species; this
helps save them from predators.
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Here are examples of mimics.
Helenian Ant Spider
(Myrmarachne isolate)
A typical ant
This endemic spider mimics an ant.
Bright Hoverfly
(Simosyrphus aegypticus)
Common wasp
(Vespula vulgaris)
The indigenous Bright hoverfly mimics a wasp
Drone Fly
(Eristalis tenax)
Honey Bee
(Apis mellifera)
The indigenous Drone fly is mimics a bee
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Diadem
Hypolimnas misippus
Female
Male
The female Diadem butterfly mimics the Monarch butterfly; however the male has a completely different
appearance.
Looking like another invertebrate is only one of their survival strategies. Some
invertebrates smell like other invertebrates to survive.
The indigenous Deaths head hawk moth (Acherontia atropos) mimics the scent of
the Honey bee so they can crawl into their hives and steel the honey from the bees
without getting stung.
Death's-head Hawk moth
(Acherontia Atropos)
Defence - Stalked eggs and backpacking waste
There is one invertebrate that has adapted in an unusual way of ensuring it is safe
from predators.
When adult green lacewings lay their eggs it is attached to plants by a long thin stalk.
This is so it will be out of the reach of predators like ants; that have not yet learnt
that if they cut the stalk they will get the egg.
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Brown lacewing larvae collect their waste matter on their backs all held together
with silk; this is so it can suddenly be thrown in the face of predators so they get a
mouthful of distasteful material instead of a nice juicy insect.
Green lacewing egg
(Chrysopa sp.)
Brown lacewing larva
(Micromus atlanticus)
Many invertebrates have a means of defence, some sting like wasps and bees and
some bite like spiders and some can administer venom, causing pain and discomfort
or even death.
Other invertebrates discharge horrible deterrent odours for defence.
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Food Chain, food webs and trophic levels
A food chain shows how energy is passed from one organism to another organism by being
eaten. Food chains can link together to form food webs, this happens when animals chose
to eat more than one plant or animal.
Food chain example:
Food web example:
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Each species occupies a certain position in a food chain; this position is called a trophic level,
there are producers and consumers, a plant is a producer because it makes its own food by
photosynthesis.
The animals are the consumers; however there are different consumers at each level of
consumption because energy is lost at each level. Above producers are primary consumers
(herbivores) above these are secondary consumers (carnivores) and at the top of a food
chain is the top consumer or top carnivore.
There are also decomposers (bacteria and fungi) which feed on decaying matter; they help
speed up the decaying process to release nutrients back into the environment, for plants to
absorb all over again.
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Social and solitary invertebrates
Most invertebrates are solitary, living and feeding on their own and only coming together
when it is time to mate, but there are a few invertebrates that are social and live together in
colonies.
Bees, ant and termites are social insects; they live in colonies, sharing shelter, food, water,
and work.
A colony is highly organized, for example in a Honey bee hive there is one bee larger than all
the other bees and this is the Queen who lays eggs. Next there are male bees called Drones
which mate with the queen to fertilize her eggs which produces bees called workers. The
workers are all females, but they don’t mate, their job is collecting nectar and pollen to feed
the developing larvae and if a queen becomes old or sick, the workers will start to raise a
queen larva to replace her when she dies.
Not all species of bee and wasp are social, indeed most are solitary; most of these species
are parasites that lay their eggs individually in their prey species.
The solitary White-faced bee
(Nothylaeus sp.)
The solitary wasp
(Solierella scrobiculata)
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Migration
Most animals need to migrate to suitable environments to find food and water. This can be
because the seasons are changing and food and water are becoming scarce.
Some of our more frequent visitors to the island are the Painted lady and Monarch
butterflies and a dragonfly called the Globe skimmer. These species are from sub-tropical
regions, and usually arrive here from Africa as this is where the prevailing wind direction is
from.
The Monarch butterfly is originally from Africa, it seeks out the Milkweed plant which its
larvae feed on and the Painted Lady butterfly seeks the Least mallow or “bread and cheese”
plant for its larvae.
The Globe Skimmer dragonfly on the other hand, uses weather systems high in the
atmosphere to sense moist conditions and follow them to where the rain forms. When
ponds and puddles are formed they descend to them and release their eggs into suitable
waterbodies and continue on their way to other places with the weather system.
African monarch butterfly
(Danaus chrysippus)
Painted lady butterfly
(Vanessa cardui)
Globe skimmer dragonfly
(Pantala flavescens)
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Another migratory species is the Death's head hawk moth; as this species raids hives for
honey in order to migrate it is a problem for beekeepers. In the 19th century all of the bees
on the island died out and it was noticed that the Death's head hawk moth vanished too.
About five years after bees were re-established on the island the moth had arrived again
and established a breeding population.
Death's-head Hawk moth
(Acherontia Atropos)
Light and sound
All invertebrates have different times of the day in which they are active or inactive. In
daylight hours we can see many different types of invertebrates feeding, resting or flying.
There are many species however that hide during the day to avoid predators and only
become active at night; these are called "nocturnal".
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