pond life part 2
Created | Updated Jan 2, 2013
Pond life part 2
Members of the crab family, or crustacea are very prominent.
The diversity of this family througout nature is extrodinary with some specis so bizzare that is is almost impossible to classify them; however one characteristic holds true throughout the crustacean family and that is they all posess 2 pairs of antennae.
in fresh water the most commonly found crustacean is Daphnia,http://en.wikipedia.org/wiki/Daphnia
Cyclops,http://tinyurl.com/omroa
and Cypris.http://tinyurl.com/yw6peb
Daphnia are water fleas. Looking a little like a very fat old man, they move by the means of 2 arms or antennae which are jerked up and down. They reproduce mostly by a fertilized egg but parthenogenesis is known.
The eggs can often be seen inside the brood pouch well protected inside the body.
Cyclops have 2 eyes but they are so close together they look like one. They move on the horizontal plain again by using the antennae, the Daphnia on the other hand jerk up and down.
Cyclops are commonly found with 2 egg sacks hanging from the tail.
Cypris are a little unusual. The body is made up of 2 shells looking like a tiny bean, hinged along the top. Motion is produced by sticking the legs out through the gap and scrabbling around, they are not good swimmers and are found mostly in horse troughs and the like, Daphnia in good warm ponds and puddles whilst cyclops mainly in open water.
Relatives of cyclops and cypris are found in huge numbers in the sea where they form a very important part of the food chain. The largest cyprid was found in the atlantic and measured over 5 milimetres.
The hog louse or Aselus
http://www.hainaultforest.co.uk/4AquaticMinibeasts.htm
is a aquatic wood louse. They dont get to much of a size but are very common. This family is interesting because they inhabit nearly anywhere damp or wet. On the sea shore the sea slater (up to 60 mm) is quite common - in the sea itself huge numbers of a giant relative are found at great depths this creature grows to some 30 centimetres plus and could possibly be a food source.
Fresh water shrimp or Gammarus.
http://www.4qd.org/Aqua/Gammarus.html
There are some 4 species commonly found in the uk.
Found in all kinds of ponds and streams they prefer mostly running water.
Closely related to salt water species they provide an important source of fish food.
There are several larger members of the Crustacea family found in the uk worth mentioning, but they are mainly river and not pond creatures.
The insects are very well represented though to a large extent by larvae.
Most midges or mosquitoes are water borne in the younger stages and some are most unusual.
The common mosquito
http://tinyurl.com/2fmpdo
is laid as a bottle shaped egg in a raft of eggs. The raft is slightly curved and of irregular shape. These rafts can often be seen floating in water buts and the like.
The larvae are up to about 8 millimeter's long; there is a tube or tail at one end, this is usually somewhere near the surface as this is used to breathe through, at the other end is the head with several bristles protruding. The body is cylindrical and made up of several joined together bulges.
There are quite a number of fairly similar species one of which is only found in the puddles formed where branches in a tree join the trunk.
Another specis of interest is
Chaoborus,
http://tinyurl.com/yuvcl6
otherwise known as the phantom midge.
The larvae is completely transparent. It is less that 1 centimetre long and prefers large open bodies of water.
At one end is the head, a bit like the head of a dragon,but with one big tooth and without a jaw, near each end are 2 bumps each housing 2 gas bags which keep the creature afloat.
It moves by tying its body in a knot then releasing itself. It is an active hunter.
Other species build tubes and live in mud, others cling to rocks in streams.
May flies
http://en.wikipedia.org/wiki/Mayfly
are very common, the adult has 3 fine hairs protruding from its rear - flies a little fitfully and is supposed to live for only a day - thence the name day fly. The body is usually held in a curve when at rest.
There are quite a few species in our waters, the smallest of which is about 5 mm long as an adult, going up to about 2 cms.
The may fly is unique amongst all insects in having a second moult once adult.
The larvae feed mostly on very small creatures in the water, some however are predacious but as they have feeble mouthparts are not as active as most of the other insects.
The larvae have 7 pairs of external gills beside the tail and like the adults 3 hairs protruding from the end.
The larval stage generally lasts for up to a year whilst the adult can last as long as 2 days but most only a few hours.
Alder fly,
http://www.plantpress.com/wildlife/o409-alderfly.phpOtherwise known as Sialis has 3 species resident in the uk. The larvae are predacious as is the adult - The body of the larvae is cylindrical with 7 pairs of tubes protruding which act as gills.
The adult is a distinct in that its wings are large and lacelike and when at rest cover the body like a cape. Other relatives are the snake fly and lacewing - they all have the same distinctive wing pattern.
Stoneflies or plecoptera. http://en.wikipedia.org/wiki/Stonefly
The larvae are mostly found in flowing water - the body of the larvae is clearly divided into head thorax and abdomen - ha 2 tails as opposed to 3 and has no external gills. The legs are held characteristically out from the body in a crabwise fashion. It is more often found clinging to rocks in running streams
The adults wings fold over the back but lie flat rather than tent like with the alder fly. There are 34 specis found in the uk.
The Caddisfly
http://en.wikipedia.org/wiki/Trichoptera
is a little unusual in the water world in that he usually builds a house and carries this around. The house is sometimes a leaf simply curled around, sometimes the caddis builds a web around its body and decorates it with sticks and other debris; at the extreme several species build a cylinder of fitted together pieces of sand, carefully chosen to be of the same colour and size then glued together.
Others are naked to the world – in this group one species copies spiders and builds a net on the bottom of streams catching debris and other insects as they flow past.
The larva is cylindrical - usually pale white and has rows of gills down each side.
The adults are usually poor filers and provide easy prey to insectivores.
Moths.
The china mark moth http://www.ukmoths.org.uk/show.php?id=2599&detail=true
is entirely aquatic in its pre adult stages.
Its presence is often first noticed by cut outs on the edges of water lilies.
The larvae make a 2-sided pouch from these cases and use them as a home. Their food is plant matter.
The adults are called China mark moths because of markings on the wings supposedly resembling the marks made on china by makers.
Dragon flies. Odonata.
There are some 64 species in the uk.
Anax imperator http://delta-intkey.com/britin/odo/www/imperato.htm
is 70/80 mm long making it our largest dragonfly.
Because of its size it can slow down considerably on a cloudy day, or even when in shadow.
There are two main body shapes in the large dragonfly world – the darter shape, which is essentially broad bodied and the hawker which is the better known needle like shape.
Of the darter shape the largest is the libelula depressa. This dragonfly is probably the most acrobatic being able to fly backwards and upside down.
The larvae of the larger dragonflies live in water for up to three years.
They are creatures of science fiction.
Staying absolutely motionless for extended periods of time the jaws will suddenly shoot out to capture a passing creature. The Jaws are mounted on a hinge under the head; perhaps it would be more accurate to describe the jaws as a mask as the affair is really independent of the mouth,
If disturbed the abdomen can contract to shoot the creature forward out of harms way – in truth they have jet propulsion.
When the larvae are ready to emerge, the nearest plant stem is laboriously climbed. The back in between the wings splits and out climbs a pale looking dragonfly. The wings slowly unfurl and gradually the dragonfly’s colour emerges.
If during this process it is disturbed it can drop into the water and drown.
A major feature of dragonflies are the eyes. They have the largest number of omatidia (lenses) of any insect, but in spite of this visual acuity they eyes are designed to be sensitive to movement and do not focus well. Dragonflies can be caught by hand if the hand moves slowly enough.
They have (for an insect) a reasonably good memory so it is possible to stalk them and sooner or later your slow movements just become another part of the background
Some of the best pictures of dragonflies on the net are on
http://www.mattcolephotography.co.uk/.
Of the smaller and less stronger flying dragonflies there are two main types; the larger demoiselles represented in the uk by Agrion splendens http://delta-intkey.com/britin/odo/www/splenden.htm and Agrion virgo, http://delta-intkey.com/britin/odo/www/splenden.htm and the more numerous smaller damselflies.
The Demoiselles are very striking. The male of splendens has a blue patch on its otherwise clear wing, the female is just brown, Virgo, the male has blue(or purple) wings whilst the female is again brown.
The Damselfly is a much daintier creature with a matchstick thin body usually a striking colour reds, golds, blues and more, there are quite a number of specis present in the uk. (some 36?)
The Larvae are quite different from the dragonfly nymph. The body is slimmer and has external gills on the tail in the form of 3 small vertical plates; it also has the capacity to “inhale” water but cannot as in the dragonflies release it as a jet. When swimming it moves its body from side to side in a flipper like motion. Like dragonfly larvae it has the mask which it ejects from the face to grasp prey.
Dragonflies and damselflies have a unusual reproductive system in that the sexual organs are under the thorax in the female and on the end of the tail in the male. This means that when mating the male has to curl his body in a loop.
When ready the eggs are let free in water, sometimes by a swoop and drop, other times by a careful immersion and paste onto a plant stem, some are laid in wet moss.
Often during egg laying the pair are still together held by the males pair of claspers which are situated on the end of its tail.
There are between seven and nine moults before the adult emerges.
Hover fies Syrphids
These are truly amazing creatures. Often seen in the summer, the wings a complete blur. Their eyes are probably the largest in relationship to body size of any insect. Their activity is so fast as to be allmost invisible, its as if they just dissapear between places.
The most common specis mimic flies and bees, they are let down by the eyes which are larger and more wrap around than either.
Their larvae are the rat tailed maggots commonly seen in farmyards. They have the distinction of being able to live in water so foul as to nearly deficient in oxygen, their respiration taking place through their "tails" which penetrate the surface; these are made up of 3 segments and are telescopic.
Spiders are represented by Argyoneta aquatica. http://www.naturegrid.org.uk/biodiversity/invert/spiderw.html
This amazing creature makes a diving bell out of silk and spends its time under water. It eats pretty much anything that it can get, its main prey being various mosquito larvae. When moving around the air it breathes is trapped in fine hairs under its abdomen. There is not much to distinguish this spider from any other spider in looks.
It is the only representative of the ordinary house type spider that has taken to the water in Europe.
Water mites.
http://www.watermite.org/
Link to water mites site
http://tinyurl.com/25jyfr
The most common example of these interesting creatures are bright red velvet cushions buisily scrambling up the calls of canals or horse troughs on a warm sunny day.
The maximum size is in the region of 5 mm.
Their food is the fluids of other insects or plant life. Fuller biography can be gained from the site mentioned above but the general picture is that this is a bit of an elusive group as far as knowledge is concerned.
Water Beetles
http://tinyurl.com/2frasj
are amongst the most striking group – mainly black with similar body shapes.
Size from 3 mm to our largest the great silver diving beetle or
Hydrophilus piceus
http://www.zin.ru/animalia/coleoptera/eng/hydpic.htm
At some 40 mm though as you can see from the web ref it can grow larger. The same family has examples which grow to over 10 cms in Australia.
This particular beetle has become rare as in the 1930s it was much sought after as an aquarium pet and virtually wiped out.
The adult is entirely omnivorous munching quite happily on a piece of Canadian pondweed or chewing a piece of meat.
Unique to this species are the 2 horns which project from the front of the thorax and are used as breathing trumpets. Most water beetles store air under the wing covers and refresh it by simply sticking their bum above the surface. Hydrous hangs below the surface with just its two horns piercing the meniscus. It can quite easily drown if caught in a tangle of weed.
The larvae are entirely predacious feeding mostly on water snails.
Next in size is the biggest representative of the dytiscidae, the great diving beetle.
http://tinyurl.com/2guqfc
This has got to be one of the most vorociously caniverous of all our water beetles. The adults are about 27/35 mm long whilst the larvae are up to 60mm.
The sexes in the adults are distinguished from one another by the ridged wing cases and clasping pads on the ends of its legs with the male, whilst the female is much more sophisticated with smooth wing cases.
The Larvae is a mean eating machine. It digests its prey by piercing the prey’s body with its sickle like jaws, injecting digestive fluid and inhaling the resulting mess.
Whilst the great silver diving beetle will live quite happily with other water creatures in a fish tank this creature must be kept on its own.
The Dytiscids
http://en.wikipedia.org/wiki/Diving_beetle
are quite a large family with several smaller representatives easily recognised by the shape and movements.
The Whirlygig beetle.
http://tinyurl.com/2hnawh
This amazing creature is probably the most prominent of our water beetles in that its natural haqbitat is the surface and can be seen rapidly swimming in circles. Its eyes are probably unique in being divided into two, the upper for viewing above water and the lower for under water – it is predacious but eats dead creatures as happily as live ones.
It is quite small, being no longer than 7 mm.
The larvae are busily predacious and a little unusual with long projections on each body segment –
(Site for list of specis and more http://www.davebentleyecology.co.uk/18.html)
WATER BUGS
Bugs are often a term used to describe any small creature or insect, however the true "bugs" are divided into two groups - they are distinct from ordinary insects in that they all suck fluids.
The Hemiptera are the most commonly found in water and range from Ranatra lineris or the water stick insect
http://www.boxvalley.co.uk/nature/sns/wad58/w58-06.html
up to and just over 50mm, and the water scorpion Nepa cinerea, just a little less,
http://tinyurl.com/34r4gf
to
The Tiny Hydrometra aquatica or water measurer measuring around 6 mm in length with tiny stick thin body.
The water stick insect has a long cylindrical body with 3 pairs of long tapering legs the first pair of which is modified into a pair of claspers. The wings are tightly furled around the body. As can be seen from the internet link they quite often leave the water either by land or air.
The body shape of the water scorpion is a little like a very thin violin, 3 pairs of legs, and the first pair modified to form clasper's. The reason for the name is the siphon (snorkel) on its tail.
How these creatures feed is literally by ramming the food with the beak and clasper's, and holding on.
One of the most common water bugs is the Pond skater Gerris Najas,.
http://tinyurl.com/3cgkhy
this is the most prominent of our surface tension using water bugs. Their food is pretty much anything they can get including carrion. They can often be seen feeding on the bodies of such creatures as crane flies which have fallen into the water. Their habitat being the surface layer of water their movements are a bit like someone walking on giant plastic bag.
Another who may be seen looking up at Gerris is the water boatman. This is an ace predator whose natural habitat is under the surface. Probably the fastest of all our water bugs .
His name is Notonecta
http://tinyurl.com/37sed4
His very streamlined body is propelled by oar like feet, he literally rows himself about. The body is so streamlined that coulour is the best way of differentiating body parts.
Strangely enough his normal position is upside down; apparently this is not determined by gravity, but by light.
Over all the Hemipteran family is sizable with probably the largest of all water insects (12 cms plus) as one of its members (far eastern)
This particular insect, also known as the toe biter is also regarded as a delicacy and eaten widely.
Members of the crab family, or crustacea are very prominent.
The diversity of this family througout nature is extrodinary with some specis so bizzare that is is almost impossible to classify them; however one characteristic holds true throughout the crustacean family and that is they all posess 2 pairs of antennae.
in fresh water the most commonly found crustacean is Daphnia,http://en.wikipedia.org/wiki/Daphnia
Cyclops,http://tinyurl.com/omroa
and Cypris.http://tinyurl.com/yw6peb
Daphnia are water fleas. Looking a little like a very fat old man, they move by the means of 2 arms or antennae which are jerked up and down. They reproduce mostly by a fertilized egg but parthenogenesis is known.
The eggs can often be seen inside the brood pouch well protected inside the body.
Cyclops have 2 eyes but they are so close together they look like one. They move on the horizontal plain again by using the antennae, the Daphnia on the other hand jerk up and down.
Cyclops are commonly found with 2 egg sacks hanging from the tail.
Cypris are a little unusual. The body is made up of 2 shells looking like a tiny bean, hinged along the top. Motion is produced by sticking the legs out through the gap and scrabbling around, they are not good swimmers and are found mostly in horse troughs and the like, Daphnia in good warm ponds and puddles whilst cyclops mainly in open water.
Relatives of cyclops and cypris are found in huge numbers in the sea where they form a very important part of the food chain. The largest cyprid was found in the atlantic and measured over 5 milimetres.
The hog louse or Aselus
http://www.hainaultforest.co.uk/4AquaticMinibeasts.htm
is a aquatic wood louse. They dont get to much of a size but are very common. This family is interesting because they inhabit nearly anywhere damp or wet. On the sea shore the sea slater (up to 60 mm) is quite common - in the sea itself huge numbers of a giant relative are found at great depths this creature grows to some 30 centimetres plus and could possibly be a food source.
Fresh water shrimp or Gammarus.
http://www.4qd.org/Aqua/Gammarus.html
There are some 4 species commonly found in the uk.
Found in all kinds of ponds and streams they prefer mostly running water.
Closely related to salt water species they provide an important source of fish food.
There are several larger members of the Crustacea family found in the uk worth mentioning, but they are mainly river and not pond creatures.
The insects are very well represented though to a large extent by larvae.
Most midges or mosquitoes are water borne in the younger stages and some are most unusual.
The common mosquito
http://tinyurl.com/2fmpdo
is laid as a bottle shaped egg in a raft of eggs. The raft is slightly curved and of irregular shape. These rafts can often be seen floating in water buts and the like.
The larvae are up to about 8 millimeter's long; there is a tube or tail at one end, this is usually somewhere near the surface as this is used to breathe through, at the other end is the head with several bristles protruding. The body is cylindrical and made up of several joined together bulges.
There are quite a number of fairly similar species one of which is only found in the puddles formed where branches in a tree join the trunk.
Another specis of interest is
Chaoborus,
http://tinyurl.com/yuvcl6
otherwise known as the phantom midge.
The larvae is completely transparent. It is less that 1 centimetre long and prefers large open bodies of water.
At one end is the head, a bit like the head of a dragon,but with one big tooth and without a jaw, near each end are 2 bumps each housing 2 gas bags which keep the creature afloat.
It moves by tying its body in a knot then releasing itself. It is an active hunter.
Other species build tubes and live in mud, others cling to rocks in streams.
May flies
http://en.wikipedia.org/wiki/Mayfly
are very common, the adult has 3 fine hairs protruding from its rear - flies a little fitfully and is supposed to live for only a day - thence the name day fly. The body is usually held in a curve when at rest.
There are quite a few species in our waters, the smallest of which is about 5 mm long as an adult, going up to about 2 cms.
The may fly is unique amongst all insects in having a second moult once adult.
The larvae feed mostly on very small creatures in the water, some however are predacious but as they have feeble mouthparts are not as active as most of the other insects.
The larvae have 7 pairs of external gills beside the tail and like the adults 3 hairs protruding from the end.
The larval stage generally lasts for up to a year whilst the adult can last as long as 2 days but most only a few hours.
Alder fly,
http://www.plantpress.com/wildlife/o409-alderfly.phpOtherwise known as Sialis has 3 species resident in the uk. The larvae are predacious as is the adult - The body of the larvae is cylindrical with 7 pairs of tubes protruding which act as gills.
The adult is a distinct in that its wings are large and lacelike and when at rest cover the body like a cape. Other relatives are the snake fly and lacewing - they all have the same distinctive wing pattern.
Stoneflies or plecoptera. http://en.wikipedia.org/wiki/Stonefly
The larvae are mostly found in flowing water - the body of the larvae is clearly divided into head thorax and abdomen - ha 2 tails as opposed to 3 and has no external gills. The legs are held characteristically out from the body in a crabwise fashion. It is more often found clinging to rocks in running streams
The adults wings fold over the back but lie flat rather than tent like with the alder fly. There are 34 specis found in the uk.
The Caddisfly
http://en.wikipedia.org/wiki/Trichoptera
is a little unusual in the water world in that he usually builds a house and carries this around. The house is sometimes a leaf simply curled around, sometimes the caddis builds a web around its body and decorates it with sticks and other debris; at the extreme several species build a cylinder of fitted together pieces of sand, carefully chosen to be of the same colour and size then glued together.
Others are naked to the world – in this group one species copies spiders and builds a net on the bottom of streams catching debris and other insects as they flow past.
The larva is cylindrical - usually pale white and has rows of gills down each side.
The adults are usually poor filers and provide easy prey to insectivores.
Moths.
The china mark moth http://www.ukmoths.org.uk/show.php?id=2599&detail=true
is entirely aquatic in its pre adult stages.
Its presence is often first noticed by cut outs on the edges of water lilies.
The larvae make a 2-sided pouch from these cases and use them as a home. Their food is plant matter.
The adults are called China mark moths because of markings on the wings supposedly resembling the marks made on china by makers.
Dragon flies. Odonata.
There are some 64 species in the uk.
Anax imperator http://delta-intkey.com/britin/odo/www/imperato.htm
is 70/80 mm long making it our largest dragonfly.
Because of its size it can slow down considerably on a cloudy day, or even when in shadow.
There are two main body shapes in the large dragonfly world – the darter shape, which is essentially broad bodied and the hawker which is the better known needle like shape.
Of the darter shape the largest is the libelula depressa. This dragonfly is probably the most acrobatic being able to fly backwards and upside down.
The larvae of the larger dragonflies live in water for up to three years.
They are creatures of science fiction.
Staying absolutely motionless for extended periods of time the jaws will suddenly shoot out to capture a passing creature. The Jaws are mounted on a hinge under the head; perhaps it would be more accurate to describe the jaws as a mask as the affair is really independent of the mouth,
If disturbed the abdomen can contract to shoot the creature forward out of harms way – in truth they have jet propulsion.
When the larvae are ready to emerge, the nearest plant stem is laboriously climbed. The back in between the wings splits and out climbs a pale looking dragonfly. The wings slowly unfurl and gradually the dragonfly’s colour emerges.
If during this process it is disturbed it can drop into the water and drown.
A major feature of dragonflies are the eyes. They have the largest number of omatidia (lenses) of any insect, but in spite of this visual acuity they eyes are designed to be sensitive to movement and do not focus well. Dragonflies can be caught by hand if the hand moves slowly enough.
They have (for an insect) a reasonably good memory so it is possible to stalk them and sooner or later your slow movements just become another part of the background
Some of the best pictures of dragonflies on the net are on
http://www.mattcolephotography.co.uk/.
Of the smaller and less stronger flying dragonflies there are two main types; the larger demoiselles represented in the uk by Agrion splendens http://delta-intkey.com/britin/odo/www/splenden.htm and Agrion virgo, http://delta-intkey.com/britin/odo/www/splenden.htm and the more numerous smaller damselflies.
The Demoiselles are very striking. The male of splendens has a blue patch on its otherwise clear wing, the female is just brown, Virgo, the male has blue(or purple) wings whilst the female is again brown.
The Damselfly is a much daintier creature with a matchstick thin body usually a striking colour reds, golds, blues and more, there are quite a number of specis present in the uk. (some 36?)
The Larvae are quite different from the dragonfly nymph. The body is slimmer and has external gills on the tail in the form of 3 small vertical plates; it also has the capacity to “inhale” water but cannot as in the dragonflies release it as a jet. When swimming it moves its body from side to side in a flipper like motion. Like dragonfly larvae it has the mask which it ejects from the face to grasp prey.
Dragonflies and damselflies have a unusual reproductive system in that the sexual organs are under the thorax in the female and on the end of the tail in the male. This means that when mating the male has to curl his body in a loop.
When ready the eggs are let free in water, sometimes by a swoop and drop, other times by a careful immersion and paste onto a plant stem, some are laid in wet moss.
Often during egg laying the pair are still together held by the males pair of claspers which are situated on the end of its tail.
There are between seven and nine moults before the adult emerges.
Hover fies Syrphids
These are truly amazing creatures. Often seen in the summer, the wings a complete blur. Their eyes are probably the largest in relationship to body size of any insect. Their activity is so fast as to be allmost invisible, its as if they just dissapear between places.
The most common specis mimic flies and bees, they are let down by the eyes which are larger and more wrap around than either.
Their larvae are the rat tailed maggots commonly seen in farmyards. They have the distinction of being able to live in water so foul as to nearly deficient in oxygen, their respiration taking place through their "tails" which penetrate the surface; these are made up of 3 segments and are telescopic.
Spiders are represented by Argyoneta aquatica. http://www.naturegrid.org.uk/biodiversity/invert/spiderw.html
This amazing creature makes a diving bell out of silk and spends its time under water. It eats pretty much anything that it can get, its main prey being various mosquito larvae. When moving around the air it breathes is trapped in fine hairs under its abdomen. There is not much to distinguish this spider from any other spider in looks.
It is the only representative of the ordinary house type spider that has taken to the water in Europe.
Water mites.
http://www.watermite.org/
Link to water mites site
http://tinyurl.com/25jyfr
The most common example of these interesting creatures are bright red velvet cushions buisily scrambling up the calls of canals or horse troughs on a warm sunny day.
The maximum size is in the region of 5 mm.
Their food is the fluids of other insects or plant life. Fuller biography can be gained from the site mentioned above but the general picture is that this is a bit of an elusive group as far as knowledge is concerned.
Water Beetles
http://tinyurl.com/2frasj
are amongst the most striking group – mainly black with similar body shapes.
Size from 3 mm to our largest the great silver diving beetle or
Hydrophilus piceus
http://www.zin.ru/animalia/coleoptera/eng/hydpic.htm
At some 40 mm though as you can see from the web ref it can grow larger. The same family has examples which grow to over 10 cms in Australia.
This particular beetle has become rare as in the 1930s it was much sought after as an aquarium pet and virtually wiped out.
The adult is entirely omnivorous munching quite happily on a piece of Canadian pondweed or chewing a piece of meat.
Unique to this species are the 2 horns which project from the front of the thorax and are used as breathing trumpets. Most water beetles store air under the wing covers and refresh it by simply sticking their bum above the surface. Hydrous hangs below the surface with just its two horns piercing the meniscus. It can quite easily drown if caught in a tangle of weed.
The larvae are entirely predacious feeding mostly on water snails.
Next in size is the biggest representative of the dytiscidae, the great diving beetle.
http://tinyurl.com/2guqfc
This has got to be one of the most vorociously caniverous of all our water beetles. The adults are about 27/35 mm long whilst the larvae are up to 60mm.
The sexes in the adults are distinguished from one another by the ridged wing cases and clasping pads on the ends of its legs with the male, whilst the female is much more sophisticated with smooth wing cases.
The Larvae is a mean eating machine. It digests its prey by piercing the prey’s body with its sickle like jaws, injecting digestive fluid and inhaling the resulting mess.
Whilst the great silver diving beetle will live quite happily with other water creatures in a fish tank this creature must be kept on its own.
The Dytiscids
http://en.wikipedia.org/wiki/Diving_beetle
are quite a large family with several smaller representatives easily recognised by the shape and movements.
The Whirlygig beetle.
http://tinyurl.com/2hnawh
This amazing creature is probably the most prominent of our water beetles in that its natural haqbitat is the surface and can be seen rapidly swimming in circles. Its eyes are probably unique in being divided into two, the upper for viewing above water and the lower for under water – it is predacious but eats dead creatures as happily as live ones.
It is quite small, being no longer than 7 mm.
The larvae are busily predacious and a little unusual with long projections on each body segment –
(Site for list of specis and more http://www.davebentleyecology.co.uk/18.html)
WATER BUGS
Bugs are often a term used to describe any small creature or insect, however the true "bugs" are divided into two groups - they are distinct from ordinary insects in that they all suck fluids.
The Hemiptera are the most commonly found in water and range from Ranatra lineris or the water stick insect
http://www.boxvalley.co.uk/nature/sns/wad58/w58-06.html
up to and just over 50mm, and the water scorpion Nepa cinerea, just a little less,
http://tinyurl.com/34r4gf
to
The Tiny Hydrometra aquatica or water measurer measuring around 6 mm in length with tiny stick thin body.
The water stick insect has a long cylindrical body with 3 pairs of long tapering legs the first pair of which is modified into a pair of claspers. The wings are tightly furled around the body. As can be seen from the internet link they quite often leave the water either by land or air.
The body shape of the water scorpion is a little like a very thin violin, 3 pairs of legs, and the first pair modified to form clasper's. The reason for the name is the siphon (snorkel) on its tail.
How these creatures feed is literally by ramming the food with the beak and clasper's, and holding on.
One of the most common water bugs is the Pond skater Gerris Najas,.
http://tinyurl.com/3cgkhy
this is the most prominent of our surface tension using water bugs. Their food is pretty much anything they can get including carrion. They can often be seen feeding on the bodies of such creatures as crane flies which have fallen into the water. Their habitat being the surface layer of water their movements are a bit like someone walking on giant plastic bag.
Another who may be seen looking up at Gerris is the water boatman. This is an ace predator whose natural habitat is under the surface. Probably the fastest of all our water bugs .
His name is Notonecta
http://tinyurl.com/37sed4
His very streamlined body is propelled by oar like feet, he literally rows himself about. The body is so streamlined that coulour is the best way of differentiating body parts.
Strangely enough his normal position is upside down; apparently this is not determined by gravity, but by light.
Over all the Hemipteran family is sizable with probably the largest of all water insects (12 cms plus) as one of its members (far eastern)
This particular insect, also known as the toe biter is also regarded as a delicacy and eaten widely.
