Identification Information

Worms (thin brown/red)

Scientific name(s): Mainly Tubifex
Range of sizes: 2-6 cm long, about 1mm diameter
Features to look for: Thread-like worms, reddish in colour.
Where: Almost always in mud or silt in degraded lowland streams; sometimes in great numbers. Don’t confuse them with “bloodworms” (chironomid larvae) which are shorter, brighter red and with definitely segmented bodies


Flatworms, leeches

Scientific name(s): Platyhelminthes, Hirudinea (respectively)
Range of sizes: up to 1 cm
Features to look for: Small, brownish, undefined shape; they move with a creeping motion. Leeches are less common. They have a sucker at each end and you should be able to see that the body is segmented (use the lens).
Where: Better known as internal parasites, the Platyhelminthes also have freshwater species. Flatworms and leeches are fairly tolerant.


Snails (pointed end)

Scientific name(s): Potamopyrgus
Common name(s): Water snails
Range of sizes: Typically 1-4 mm across
Features to look for: Obviously snail-like, but tiny and often almost black; sometimes lighter brown. The top of the spiral is pointed.
Where: Found in range of stream types, usually where the water is quite enriched. Often on the undersides of stones, also on water plants. Potamopyrgus is sometimes extremely abundant.


Snails (rounded)

Scientific name(s): Physa and others
Common name(s): Water snails
Range of sizes: Usually 4-6 mm across
Features to look for: Again clearly snail-like; colour from light beige to darker brown, with markings. The shell is quite rounded with the top of the spiral a small peak. You’ll sometimes see clear, jelly-like blobs of snail eggs in the same areas.
Where: Mainly found in enriched (degraded?) water, on upper and undersides of stones.


Small bivalves

Scientific name(s): for example, Pisidium sp.
Range of sizes: 2-4 mm wide
Features to look for: Tiny, grey-brown or whitish double shells, like miniature mussels or clams.
Where: At the margins of silty, slow-flowing streams.


Limpet-like molluscs

Scientific name(s): Latia sp. (freshwater limpet)
Range of sizes: 2-8 mm wide
Features to look for: Dark coloured shells adhering to rocks. When empty, the shells appear a lighter russet-brown colour. Often very abundant.
Where: In relatively clean streams. This mollusc is not known to occur in South Island. It is widespread in North Island and can be extremely abundant.


Freshwater crustaceans (amphipods, water fleas)

Scientific name(s): Crustacean orders Amphipoda and Cladocera
Range of sizes: 1-10 mm long
Features to look for: Amphipods are up to 10 mm long and look like tiny shrimps, grey in colour. Water fleas are tiny, grey-brown flea-shaped creatures; very active and often in great numbers. The legs are clearly visible (especially if you use a hand lens to look at them.)
Where: At the margins of slow-flowing streams.


Ostracods (“seed shrimps”)

Scientific name(s): Ostracoda
Range of sizes: 1-2 mm long
Features to look for: These shrimps are tiny, grey-brown or whitish, oval shaped, like little seeds.
Where: At the margins of silty, slow-flowing streams.


Beetle larvae and adults

Scientific name(s): e.g., Elmidae
Common name: Riffle beetles
Range of sizes: Adults 2-3 mm long , larvae up to 7 mm long
Features to look for: Small black beetles. The larvae look a bit like some chironomids; but they have a “striped” appearance and have a more crawling type of movement.
Where: Adults clinging to the underside of rocks in faster-flowing water; larvae on top of stones.


Midge larvae

Scientific name(s): Chironomidae (family)
Range of sizes: 2-5 mm long, very slender
Features to look for: Tiny, white, brownish, bright red or transparent wriggling larvae. Body diameter more or less uniform. Red chironomids (“bloodworms”) can be distinguished from worms by their movement, their brighter red colour, and their legs.
Where: Often in large numbers on the tops of rocks, in the periphyton mat, as illustrated. Not always noticeable straight away: but scrape off the algae you should see them move using a looping motion. Red chironomids (“bloodworms”) occur in silt.

Cranefly larvae

Scientific name(s): e.g., Aphrophila sp.
Range of sizes: up to 2.5 cm
Features to look for: Cranefly larvae are fat greyish or light green grubs. The head is usually retracted into the body. The body is segmented and may have “false legs” that look like ridges visible on the body between each segment.
Where: Cranefly larvae are moderately tolerant and are found in stony streams of varying quality.


“Axehead” caddis larvae

Scientific name(s): Oxyethira albiceps
Range of sizes: Up to 3 mm long
Features to look for: A tiny cased caddis larva with a wedge-shaped case, something like an axehead. The pupae are a similar shape and are firmly attached to rocks.
Where: Axehead caddis larvae are found attached to stones or other substrate in streams with slow-flowing, relatively enriched water; or among periphyton growth. Because of its tolerance to enriched waters, Oxyethira is in a category separate from other caddisfly larvae.


Caddisfly larvae

Scientific name(s): Trichoptera (family); various taxa (see below)
Range of sizes: Up to 2 cm long.
Features to look for: Most caddis larvae build cases in which they live. Some types move around taking their cases with them. Others are free living, but may build “houses” of small stones to which they can retreat. The next three descriptions illustrate common types of caddisfly larvae. For SHMAK, they are all counted in a single category of invertebrate.
Where: These types of caddis are found in a range of water and stream types in moderate-to-fast flowing water, amongst or on stony substrates.
Common name: Common stony-cased caddis
Scientific name(s): e.g., Pycnocentrodes sp.
Range of sizes: 2 - 10 mm (length of case)
Features to look for: A caddis which moves around inside its case. The case is a slightly curved cylinder tapering towards one end. It is made of tiny stones or particles of sand and is dull brown in colour. Very common in stony-bedded streams in a range of water types.
Common name: Free-living caddis larvae (stony houses)
Scientific name(s): e.g., Aoteapsyche sp.
Range of sizes: Up to 2 cm long
Features to look for: A free-living caddis which builds itself a stony retreat for pupation. You’ll notice the stone “houses”. The larva itself has a brown head, brown plates on the upper side behind the head and short legs. The rest of the body is fat, light brown and grub-like.
Common name: Green caddis (another free-living caddis larva)
Scientific name(s): e.g., Hydrobiosis sp.
Range of sizes: Up to 2 cm long
Features to look for: A free-living caddis larva which builds a stony house only when it is about to pupate (transform into an adult). Dark, flattened, head; pincer-like legs; slender, bright green, grub-like body. There are also brown-coloured taxa.


Smooth-cased caddisfly larvae

Scientific name(s): Olinga feredayi
Range of sizes: Up to 10 mm long (with case)
Features to look for: Olinga is a cased caddis with a distinctive trumpet-shaped, smooth, chestnut-coloured case. It is not as common as the stony-cased caddis.
Where: Mostly in clean streams, under stones. Olinga is treated as a separate category because of its preference for clean streams.


Spiral caddis

Scientific name(s): Helicopsyche sp.
Range of sizes: Up to 3 mm across (with case)
Features to look for: A cased caddis with a flattened spiral house made of sand grains and fine grit; light brown in colour. Can be very common. Don’t confuse these with snails! Look for the gritty appearance of the case, compared with the smooth shell of snails.
Where: These caddisfly larvae occur only in really clean streams, hence their high score. Again they are treated in a separate category.


Mayfly larvae

Scientific name(s): e.g. Deleatidium sp.
Range of sizes: Body up to 2 cm
Features to look for: Mayflies make quick, distinctive movements - they seem to undulate side-to-side. Even very tiny ones can be picked out from this. They have three long tail filaments and well-developed legs.
Where: Almost always found on the underside of stones, in clean water. Mayflies are an important part of fish diets because they drift in the currents where trout can easily prey on them.


Stonefly larvae

Scientific name(s): e.g. Stenoperla, Megaloptoperla
Range of sizes: Up to 2.5 cm long
Features to look for: Stonefly larvae have two “tail filaments” and long antennae. The legs are prominent and stick out like elbows. S. prasina has a distinctive green body.
Where: Stonefly larvae are found in clean, stony streams.


Sandfly larvae

Scientific name(s): Austrosimulium sp.
Range of sizes: 2-5 mm long
Features to look for: These are small larvae, fatter than chironomids, with a characteristic bottle-shaped base; attached to rocks. You may also see pupae (resting stage) of sandflies: about 2-3 mm across, shield-shaped, with a pair of protrusions at the top.
Where: You are bound to come across these at some stage. They have not been included in this assessment because these rather tolerant insect larvae are widespread in many streams, from pristine forest flows to impacted lowland waterways. Therefore they are not particularly good “indicators”.