Underwater life - Macroinvertebrates
Note: Sensitivity scores (e.g. S8) are shown below beside the name of each macroinvertebrate. This is because a scale has been developed to summarise the sensitivity of different macroinvertebrate groups to the water quality of streams.
- The most sensitive groups - the animals that can only survive in cool clean water - are given a score of 8-10.
- Animals that can survive in polluted or warm water are given a score of 1-3. These animals can also survive in good quality water, but if they are the most common type of animal in a sample, the water is probably degraded.
The diagram on the right is an example of the way we show the sensitivity for each animal on the site. In this example, the animal has a sensitivity of 8. This is taken from MCI (Macroinvertebrate Community Index) scores for the bug. In some places we show the information as (S8).
Acroperla - Stonefly
Hi there, my name is Acroperla...
I'm a young stonefly. You can tell I'm a stonefly by my two tails, and if you
look carefully you might see a tuft of gills between my tails. Those gills help
me to breathe under the water. I'm prettier than my cousin Zelandobius because
I've got a neat pattern of pale markings on my body and legs. Like other
stone flies I can run around out of the water, which is a trick that most stream
insects can't do.
You might see me running around the beaches of lakes, but my favourite home
is stony streams where I can climb out of the water to go exploring. I can't
live in streams that are too muddy, especially the ones that get really warm in
the sun. I also can't live in streams that have been turned into concrete drains
because there's nowhere for me to shelter from the fast water current every time
Aoteapsyche - Net-spinning caddisfly
Did you know that some stream insects use nets to fish for
I'm a net-spinning caddis called Aoteapsyche and I make small
nets that I attach to the bottom of the stream so I can catch small animals and
plants drifting in the water. When I'm not checking my net for food, I hide in
my home made of tiny stones, which I've also attached to the bottom of the
Young Aoteapsyche like me are found in streams all over New
Zealand but we are most common in streams below big lakes. Thousands of yummy
little creatures swim around in the lakes and young net-spinning caddis like me
feed on these creatures as they get washed out of the lake. When I'm grown up
I'll have to go to the surface of the water and then I'll be able to fly away to
lay my eggs in another part of the stream. I need to be very careful though,
because lots of caddis get eaten by fish when we are trying to get out of the
- Crane fly larva
You might think I'm just a maggot...
But I'm actually a baby daddy-long-legs fly called Aphrophila. I
live in streams while I'm young, but when I'm grown up I'll leave the stream and
change into a long-legged fly. I can crawl around the stream quite quickly with
feet that look a bit like the suckers that caterpillars have. I also have a neat
trick of pulling my head back into my soft body so sometimes you can't see my
head at all.
I eat other insects that live in the stream; they must get a
nasty surprise when they find that a soft wormy thing like me can catch them and
eat them! I can't live in streams that have been spoilt by people tipping
poisonous stuff into the water, because that stuff might kill me or it might
kill the insects that I feed on.
Lots of people say I'm the scariest looking insect found in our streams...
I'm certainly the biggest stream insect and I could give you a painful bite
if you annoy me. I'm a young insect called a dobsonfly or Archichauliodes and I
live in stony streams. Some people also call me the toe-biter so you'd better
wear shoes or boots if you walk around in my stream!
You might think I'm a kind of centipede because it looks like I have a lot
more than the six legs that insects are supposed to have. Most of the things
sticking out of my sides are gills though, not legs. I breathe in the water
through my gills, and I move around with the six legs just behind my head. I
live in streams with clean water because they have lots of other insects, and
these insects are what I eat.
- Double-gilled mayfly
I'm a young mayfly called Austroclima...
I live in fast-flowing stony streams, especially in the bush.
Can you see my three long tails? All of us mayflies have three tails. We breathe
through gills on the sides of our bodies and we can wave these gills in the
water to help us breathe. My flat body is designed so I can sit flat on stones
without being washed away. In fact I'm so flat that you might not see me when
I'm not moving.
I'm very fussy about where I live. I need cold water because I
find it hard to breathe in warm water. My favourite food is the thin brown slime
growing on stony surfaces, but I find it difficult to live on the streambed if
the slime gets too thick.
- Sand fly
Have you ever been bitten by sand flies?
Did you know that young sand flies live under the water in
streams? I'm a young sand fly and the scientists call me Austrosimulium. I'm
pretty small so you have to look very closely to see me. I sit on stones or
plants under the water and I catch tiny bits of plant or tiny creatures to eat.
I catch this food with a special net shaped a bit like a fan attached to my
mouth. It's a bit like having a kitchen sieve sticking out of your face!
We sand flies can live in clean stony streams and also in weedy
streams where the water is dirtier. This means that we're found in most streams
so you can be bitten by grown up sand flies almost anywhere. If I were you, I'd
keep some insect repellent handy if you're going to spend much time close to
- Spiny-gilled mayfly
I'm a spiny-gilled mayfly called Coloburiscus...
I 'm one of the biggest may flies in our streams. When we may
flies are young we live under the water, but as we get older we grow wings so
that one day we can fly away to find a nice piece of stream to lay our eggs. May
flies have three tails, but my middle tail is quite small so you might have to
look closely to see it. You can easily see my spiny gills sticking out of my
body; they make me look quite fat.
You might find lots of spiny-gilled may flies like me in clean
streams with cold water, especially in the bush. I eat small bits of plant and
small animals that float down the stream. You'll never guess how I catch this
food - I trap bits of food in the long hairs that grow out of my legs!
- Dark-headed free-living caddisfly
I'm a free-living caddis called Costachorema...
They call me free-living because I don't live in a tube made out
of stones or bits of plant like some other types of caddis. There are lots of
different types of caddis that live in our streams while we are young, and when
we are older we change into a caddisfly with wings so we can fly off to find
other streams where we think our young could grow up.
I live in stony streams, usually where the water is flowing
quite quickly. You might think I look much like my cousin Hydrobiosis but his
head isn't as dark as mine. Sometimes we live in the same place, but I can't
live in places where people have tipped dirt in the stream and made the
streambed all muddy.
I'm a young mayfly called Deleatidium...
I live under the water until I'm a grown-up mayfly. Then I'll be
able to fly away to lay my eggs in another part of the stream. I've got three
long tails and I breathe through things called gills that look like leaves on
the sides of my body. I live on the rocks in streams. Shady streams are best for
me because I like cool water. I wish people would keep my home nice and shady by
planting trees by streams that flow through cities and farms.
At night I eat the green stuff growing on the stones under the
water. I have to hide during the day because lots of fish like eating young
mayflies if they see them.
- Aquatic earthworm
Have you ever seen worms on the bottom of a stream?
Some types of worms live in your garden, and others live in
streams and rivers. I'm one of the water worms called Eiseniella and I look just
like a garden worm. Worms like me eat the very tiny critters and bits of plant
in the muddy and sandy parts of the stream. We are like little vacuum cleaners
sucking up the tiniest bits of food that everyone else has forgotten about.
Some worms are smaller than me and they live in the most yukky streams that are
quite badly polluted. When people tip wastes from cities, farms and factories
into streams, these wastes go rotten in the water, and worms help to clean up
the stream by eating these wastes. If worms are the only creatures you can find
living in a stream, the water might be polluted so I suggest that you find a
better stream to explore!
- Riffle beetle
I'm a kind of beetle that lives among the stones in streams...
Beetles like me are called Elmids. When I am young, I am long
and skinny like in the photo. When I am an adult, I will be a shiny beetle.
We live in many different kinds of streams in New Zealand, and
we are very common in gravelly streams. Sometimes there are more of us than any
other kind of insects in the water. Lots of little fish eat Elmids so we have to
hide in the gravel. That might be why you haven't seen us in the water before.
If there is one creature that lives in streams that you could
call "Rubber Man" it would be me...
I'm a freshwater flatworm. As my name suggests, I have a very
flat body, and you have no doubt noticed my eyes that look cross-eyed. We
flatworms change shape all the time as we explore the stones and plants in the
water. If you want to watch flatworms like me, you'll probably need a magnifying
glass because we're pretty small.
I'm a type of flatworm that can live in dirty streams, including
streams that run through cities and farms. Some of my cousins are more fussy
types of flatworms and you might have to look for them in nice clean mountain
streams. I even have a cousin that lives on the claws of freshwater crayfish -
he doesn't look much like me because he's shaped like a small fat hand with six
fingers, weird eh?
Have you ever seen movies where people have been attacked by
Did you know that there are lots of leeches like me in New
Zealand streams? You don't have to worry though, because most of us feed on
small creatures like water snails and worms, not people.
We leeches live in lots of ponds and slow-flowing streams. We
can stick to stones and plants very strongly using special suckers under our
stretchy bodies. Some people might think that leeches in streams are a bad
thing, but we're just minding our own business, and finding us in your stream
doesn't mean there's anything wrong with the water.
- Fresh water crab
If you think that all crabs live at the beach, you've never met me!
I'm a freshwater crab and I live in streams and lakes. My
proper name is Halicarcinus but most people just call me the freshwater
crab. If you look at bits of rotten wood in streams such as the Oratia
Stream in Waitakere City, you might see crabs like me hiding in holes in the
wood. We hide because eels and other fish would eat us if they found us. We
have pincers like the seawater crabs, but our pincers are too small to bite
people or to protect us from those hungry fish.
We need people like you to make sure that there are always trees beside our
streams because this is where those bits of wood come from. Trees also
provide the shade that we need because our eyes don't work very well in
Hydrobiosis - Free-living caddis fly
My name is Hydrobiosis and I'm a young caddisfly.
You might have seen some of my cousins that live in houses made
of sticks or stones. My body is sometimes bright green but some Hydrobiosis are
When I'm older I'll make a shelter out of small stones and I'll
hide there until I've grown wings. Then I'll climb out of the stream and fly
away to find somewhere to lay my eggs.
I live in clean streams, but sometimes people spoil my stream by
putting dirt and rubbish in the water. Remember that streams are my home so
please don't tip stuff down any road drains because that stuff will end up in my
- Fresh water limpet
Have you ever seen limpets on rocks at the beach?
Did you know that there is a kind of limpet that lives in
streams? That's me, a freshwater limpet called Latia. You might be surprised to
know that I can glow in the dark! Actually I make a sticky goo that glows bright
green and this goo gets carried away by the stream current. I only release the
glowing goo when something like a hungry eel disturbs me. Those dopey eels often
bump into me at night when they're looking for food but they get such a fright
when they see the bright green light that they forget about eating me!
You might see me attached to nice clean bits of wood or stone. I
can't live in streams with too much slimy algae on the bed, or in unshaded
streams that get too warm.
- Swimming mayfly
Have you ever seen a stream insect that looks like a small
That could have been me, the swimming mayfly Nesameletus. I have
three tails, and my tails are like small feathers that help me to swim quickly
through the water. I don't want to be eaten by the fish, so I am a fast swimmer.
When I stop swimming, the gills that look a bit like small
leaves stuck to the side of my body, beat like little fans. These gills help me
to breathe in the water. I have a close cousin called Rallidens that looks much
like me, but he's got extra little gills that I don't have. Finding us in a
stream is a sign that the water is pretty good for stream creatures, but that
doesn't mean that you can drink it because there still might be bugs in the
water that could make you sick.
- Small-headed free-living caddisfly
If you've ever seen a young caddisfly that has a big body, a
small head, and no case to hide in...
That could be a Neurochorema like me! Young caddis flies that
don't carry cases are sometimes called free-living caddis flies. I look quite
similar to other types of free-living caddis flies but my small head gives me
away. Since I don't have a case to hide in, I have to watch out for bigger
insects and fish that might try to eat me.
Like most free-living caddis flies, I crawl around on the stones
on the bottom of streams. We need people like you to look after our streams by
keeping dirt out of the water, because we can't crawl around in places full of
mud. One way that people can help is by putting fences along our streams so that
cows and sheep can't get in to the stream and make a mess.
- Smooth-cased caddisfly
I'm a baby insect called a smooth-cased caddis...
I have lots of cousins that live inside houses that look like
tubes, but my tube is the smoothest. See how nice and orange my tube is? I hide
my soft body inside the tube so no big nasty bugs can eat me.
My favourite food is rotten leaves that have fallen in my
stream, but sometimes I also eat the brown slimy stuff called algae growing on
the stones in the water. I like to live in streams that flow past lots of trees,
because those trees drop yummy leaves into the water. Trees also keep my stream
shady and this keeps the water nice and cold, just the way I like it. You may
not find young caddis like me in many city streams because city people sometimes
cut all the trees down, leaving us with no shade or food.
- True fly
Have you ever been running...
around a lake or stream in the evening and had a small insect go
into your eye, mouth or even up your nose? That insect may have been an adult
midge. Midges are a kind of fly and the young of most midges live in the water.
I'm a kind of midge called an Orthoclad and young Orthoclads like me have nice
green bodies. If you look closely you'll see that I have a head and eyes, but
I've got no legs at this stage of my life.
You might notice that I do a lot of dancing even when I stay in
one place; that dancing is helping to keep water flowing past my body which
helps me to breathe. We Orthoclads are a tough bunch. We don't mind when the sun
heats our stream and we are happy living amongst the thick slimy algae that
grows in some farmland streams. If Orthoclads like me were the only creature you
could find in a stream, it might mean that the stream water is pretty yucky so
maybe you shouldn't be playing in it!
Paracalliope - Amphipod
If you have ever put a bit of waterweed in a jar or tray with
You might have noticed lots of little flea-like creatures
swimming around at high speed. These creatures might have been little amphipods
called Paracalliope like me. You might have seen amphipods on the beach hopping
around when you lift a piece of driftwood or seaweed. I'm a kind of amphipod
that prefers to live in streams, rather than lying around on the beach.
My favourite streams are weedy ones that are slow-flowing and
these types of streams are often close to the sea. I need to hide in the
waterweeds because lots of little fish like eating amphipods. When people dig
out all the weeds from streams, creatures like me have nowhere to hide and
little to feed on so you won't find much living in those streams.
- Fresh water crayfish
If you're looking to see what's living under stones or bits of
wood in streams and lakes...
You'd better watch out for me, the freshwater crayfish. I hide
in those sorts of places during the day and if you disturb me I could pinch you
with my powerful pincers. Some people call me a koura, or a crawly, but when my
pincers get hold of your fingers you're likely to call me all sorts of names!
I live in streams where there are lots of places to hide.
Streams in cities sometimes aren't much good for us because people keep digging
out our hiding places, and spoiling our water with all kinds of nasty stuff that
gets into streams from stormwater drains. Did you know that drains along the
road and outside your house might take water straight to my stream? Please don't
tip anything down those drains!
Freshwater shrimps like me live in streams near the sea...
Because the baby shrimps live in seawater. I am quite easy to
see in the water because I'm bigger than most creatures living in my stream. I
eat the green and brown stuff growing in the water, so some people keep us in
fish tanks because we help to keep the tank clean.
I can't swim very fast so I stay in gently-flowing water, hiding
in the waterweeds. I'm a very good climber so I can climb over some waterfalls
using my sharp claws. I wish people wouldn't build big dams on my streams,
because dams can be very hard to climb over.
- Introduced fresh water snail
Did you know that some of the snails found in New Zealand
streams come from overseas?
I'm one of them and I'm called Physa. My small, round shell
makes me look a bit like a bubble and you might not notice me if I'm not moving.
We Physa snails can spread quickly in streams and ponds because we can start
laying eggs when we are only ten weeks old!
I'm one of the creatures that help to clean up our streams. I do
this by eating the green slimy stuff that grows in polluted (dirty) water. The
slimy stuff can grow really quickly if there is no shade over the stream and
when people let fertiliser from farms and sewage from cites into the water.
Sometimes there is too much of this slime for us and our snail friends
Potamopyrgus to eat.
- Pond snail
I'm a snail called Potamopyrgus but some people just call me a
pond or mud snail...
I eat the yummy green or brown slime growing in ponds and
streams. I like water that's not flowing too fast because I can't hang on in
Somebody took some of my family overseas and let them go in
streams in other countries. Now there are streams in Britain, Australia and
America that are full of Potamopyrgus just like me and we've become a real pest!
When will humans learn that taking creatures around the world and letting them
go in other countries causes lots of problems?
- Stony-cased caddisfly
You might think this is a pile of small stones, but it's my
house and I carry it around with me...
I'm a kind of stream insect called a stony-cased caddis. My
stony case helps me to hide away from some of the other stream bugs that might
try to eat me.
When I'm older I'll close the end of my case, just like a
caterpillar closes itself into a cocoon when it changes into a moth. When I
hatch I'll be a grown-up caddisfly and I'll quickly struggle out of the water
and fly away to find another home.
I live with lots of my friends in clean water streams, but
sometimes you might see us in streams in farmland and cities. I can't live in
warm water or still water; cool streams are my favourite places.
- Swimming mayfly
My name is Rallidens, and I'm a young swimming mayfly...
Like other mayflies I live in the water when I'm young but one
day I'll be able to fly away to look for other streams. See how my shape is a
bit like a fish? This helps me to swim. I breathe with gills on the side of my
body, and I can wave these gills in the water to help me breathe.
I live in pools in shady streams. Many insects like me live in
streams that are shaded by lots of trees because these streams have nice cold,
clean water. We find it easier to breathe in cold water.
- Stick caddisfly
Have you ever seen a stick walking around in a stream?
That's me, a stick caddis called Triplectides. As a young
insect, I hide my soft body inside hollow bits of stick. Sometimes I'll make a
home out of lots of small bits of plant or a collection of leaves. When I've
made my home, you won't know I'm there until you see my striped legs.
I live in slow-flowing streams, especially those in the bush
where there are lots of sticks falling into the stream. I can't survive in
streams that have lots of rubbish or other horrid stuff tipped into them. Some
people don't realise that when they wash cars on the road or tip things like
paint or oil down the grates on the road, it all ends up in my stream. This is
called pollution, and there are some streams that have such bad pollution, that
most stream creatures and fish can't live in those streams any more.
My name is Xanthocnemis and I'm a young a damselfly...
You might have seen my parents flying around streams and ponds.
They look like small dragonflies, but we can fold our wings back along our body
and the dumb old dragonflies always stick their wings out sideways. The three
things on my tail are gills and they help me breathe under the water.
While I'm young, I live in the water and I hide in the
water-plants. I catch and eat other insects in the water when they come too
close to me. I have to watch out for fish because they would find me really
I don't mind if the water gets warm in summer but lots of other
kinds of stream insects and fish die if the sun shines on the water too much. If
we don't have any trees shading our streams and ponds, there won't be many
insects or fish sharing my home.
If you find an insect with two tails in a stream, chances are
it is a young stonefly like me...
Scientists call me Zelandobius and I am one of the most common
types of stonefly. I sometimes crawl out of the water to go exploring in the
moss on the tops of stones. Most stream insects can't run around above the water
like I can.
Some of my stonefly relatives are much bigger than me and they
can be quite scary looking. The biggest stoneflies live in streams with big
stones, but since I'm smaller I'm quite happy living in gravely or sandy
streams. The biggest stoneflies can only live in very cold water, but I can live
in streams that are not so cold.
- Double-gilled mayfly
My name is Zephlebia and I've got to be the best looking
mayfly in my stream...
See the neat pattern on my body and legs? You can tell I'm a may
fly because of my three long tails and the leaf-shaped gills on the sides of my
body. If you looked very closely at my body near my tails you'd see that I have
pointy spines along my sides.
You might see me clinging to stones or a piece of wood if you
lift these out of a stream. I hold on to them so the flowing water doesn't wash
me away. I also eat the tiny plants that grow on the surfaces of sticks and
stones. You might have seen my cousin Austroclima who is a bit smaller than me
and doesn't have my pretty pattern. Both of us live in shady streams with clean
water, so please don't cut down the trees beside our streams, and please don't
tip dirty water down your drains.