Bioblitz 2 - The Hatching

Earlier in the summer I helped out with identification at a bioblitz, and one of the things I was given to look at was a cluster of pupae attached to an oak leaf. It didn't take long to work out that they were a species of small parasitic wasps in the genus Eulophus, but they needed to be reared to adulthood to be identified to species. So, that's what I did...

Now empty, the ring of pupae that surround the host caterpillar (removed), giving this stage of Eulophus the name 'tombstone pupae'.

Side view of Eulophus - note the metallic green colour, much reduced wing venation and long pale legs. The body, excluding legs, wings and antennae is around 2mm long.

Note the bulges on the mesoscutum just in front of the wing bases. The line around the bottom of a bulge is called the notaulix (pl. notaulices) and is only sharp in the front half. This is diagnostic of the subfamily Eulophinae.

The antennae are inserted level with the base of the eyes, not halfway up. This is one characteristic of the genus Eulophus.

The scutellum (the upper surface between the wing bases here) is only slightly convex, not strongly bulging. This is another characteristic of Eulophus.

More characteristics - the front coxae (basal segments) are pale and the mid coxae are metallic.

These (and some other hard-to-photograph) features mean that this species is Eulophus larvarum. It is common in the UK and has two forms - the spring form (April-June) and the summer form (June-August). The summer form has a pale spot near the front of the gaster (the broad or 'main' part of the abdomen) which is seen here.

The pale/yellow spot on the gaster showing this to be the summer form of E. larvarum.

This species is a parasite of the exposed caterpillars of moths in several families in the UK. Being so tiny they are often overlooked, but careful searxching may produce specimens and they were easy to both raise (in a  ventilated lidded pot) and (to my surprise) identify, using Askew (1968) which is now available as a free download - see below.


Reference

Askew, R.R. (1968). Handbooks for the Identification of British Insects 8(2b). Hymenoptera: Chalcidoidea Section b. RES, London. [free download here]

Bioblitz bits AKA things in other things

I've done a couple of bioblitzes as entomological geek-in-residence for the day, identifying things that are a little tricky, and the most recent was just a couple of days ago in Southampton, around the Southampton University campus. This involves me looking for specimens myself, but during busy periods such as when groups come back from recording sessions, I'm at a table with a microscope and a pile of books. A lot of different species passed through my hands that day, but here are a couple of less familiar one that are both endoparasites...

The species of interest here isn't the aphid, but the disc-shaped structure below it. The aphid is a mummified husk at this stage because it has been parasitised by the small wasp Discritulus planiceps. This lives inside the aphid, then exits through the body wall and develops into an adult inside the disc-like cocoon it builds beneath the host skin. Wasps of the genus Praon do something similar but their cocoons are tent-shaped.

This cluster of pupae was attached to the underside of an oak leaf. They are each a few millimetres long and have small blobs of what I assume are dried faeces at one end. A bit of research indicated that they are probably wasps of the genus Eulophus. They are now in my hatchery to see if I can confirm the species once they emerge. They will have emerged from a caterpillar host before pupating and the fragments to the left of the cluster are probably where it was attached before falling off the leaf. A more familar species is the braconid wasp Apanteles glomeratus that has a similar lifestyle, parasitising the caterpillars of white butterflies like Pieris.

A close-up of a Eulophus pupa - various structures are quite clearly visible such as eyes and mouthparts.

At the end of the day, Lizzy from HBIC announced the total number of species recorded on the day - 257, an increase of about 30 on last year's event, although more records will trickle in a specimens like the Eulophus above are identified.

Little larvae that love leaves

As you may know, I specialise in leaf beetles (Chrysomelidae) and quite often get sent specimens to identify as I run the national recording scheme for this family. These are usually adults, but now and again juvenile stages which are more difficult, but also useful reference material, especially as I (eventually) intend to write a guide to their identification. Some months ago I was sent some larvae preserved in alcohol to see if I could confirm whether they were Chrysolina marginata. It took me a while to find the time for this (it's been a busy year), but here's the process.

Tube of preserved larvae.

Contents of the tube. The larvae are of different stages (instars) and the largest ones are around 7-8mm long. The anal proleg is visible (especially in the specimen top right) and this is a feature of Chrysolina.

Sensory structures on the head. There are no compound eyes, but in Chrysolina there are six ocelli (simple eyes) on each side of the head as indicated by green arrows, four in a rough square and two the other side of the antenna which is circled in blue. The segmentation of the small antenna is clearly visible, including the small segments/structures at its tip.

Side view of one of the larger larvae. The blue lines show the joints between segments. The green lines show sclerites (hardened patches) arranged in irregular rows.

The end of one of the legs, showing the tarsal claw. The inset shows that the outline (solid) has no protrusion at the base. This is a feature of C. marginata with some other species having a protrusion (dotted line).

Close-up of the body surface. Sclerites are shown in green circles. The pale blue arrows show intermediate secondary bristles with small dark patches at the base of each. Between these there are tiny dark dots of microsculpturation as shown within the dark blue outlines. This mixture of features is seen in C. marginata.

So, the combination of features, along with the keys in Marshall (1979) and Zaitsev & Medvedev (2009) confirms that these larvae are C. marginata - easier than larval identification often is, and provides information that is due to be used in a report later this year.

References

Marshall, J.E. (1979). The larvae of the British species of Chrysolina (Chrysomelidae). Systematic Entomology 4: 409-417.
Zaitsev, Y. M. & Medvedev, L.N. (2009). Larvae of Leaf-beetles of Russia. KMK Scientific Press, Moscow. [In Russian]

Looking after Spiny Norman

OK, in case you've not heard of him, Spiny Norman is a giant hedgehog from the Monty Python 'Piranha Brothers' sketch. I'm not going to write about offbeat-comedic imaginary hedgehogs, just the real ones you might see in your garden - more precisely the European hedgehog Erinaceus europaeus (there are seventeen species worldwide but only this one is found in Britain and last summer it was voted Britain's national species).

Months before I saw a hedgehog in our garden, I knew there was at least one around because of its droppings - black with invertebrate remains in it.

Traditionally a common and familiar species, hedgehogs have undergone a serious decline in Britain - this is difficult to measure but has been achieved with work such as the PTES Mammals on Roads Survey and the BHPS 2011 State of Britain's Hedgehogs report. The national population is estimated at around 30 million in 1950 but only 1.5 million by1995, and a further halving by 2001 in some areas. The reasons for this major decline are not entirely clear. However, some likely causes include:

• Agricultural intensification, in particular larger field sizes and losses of hedgerows and permanent grassland – also pesticide use which reduces prey availability.
• In urban areas (even small ones such as villages), smaller and tidier gardens with impassable fencing is likely to have reduced the amount of suitable urban habitat. 
• (Over)development, not only direct habitat loss, but fragmentation by buildings and roads which leads to  local populations becoming isolated and vulnerable to local extinction. 
• Increased road use - tens of thousands of hedgehogs are killed by vehicles each year and may be an importance cause of local decline in some areas.
• Competition with badgers (Meles meles) - where habitat provides effective cover and foraging opportunities, badgers and hedgehogs can coexist. However, badgers are a natural predator of (and competitor for food with) hedgehogs which therefore avoid sites with large numbers of badgers. The badger cull is still a stupid, unethical and politically motivated idea though. 
• Increased disease levels.

So what can you do?

• If you have a garden, don't be too tidy - allow leaves to accumulate, have a scruffy wildlife area and put in a hedgehog house. I made one out of scrap wood last autumn and it's already got a hedgehog in it (oh yes). I wouldn't have known except that the current bad weather damaged the roof and I found the hedgehog during (subsequently very careful and quiet) repairs earlier today. It really is important to resist the temptation to lift the lid for a peek... 
• Also, if you have a pond (as we do), make sure the sides are not steep all the way around as hedgehog will drown if they fall in and can't climb out - flatten/shallow out at least some of the edge and/or install slipways if you need to. 
• If possible, avoid using plastic mesh/netting or leaving plastic bottles, pots etc lying around as hedgehogs can get tangled, or get their heads stuck in them (their foraging behaviour means they are naturally inquisitive). Also, don't burn piles of grass mowings or other cut vegetation without checking first for hedgehogs (the same goes for bonfires). Similarly check compost heaps before turning them with a fork to avoid stabbing hedgehogs. 
• Also avoid using garden chemicals, including slug pellets, especially the more toxic versions (some are more mammal-friendly). 
• Leave some gaps/holes in fencing so hedgehogs can move between and in/out of gardens. 
• Don't feed hedgehogs with bread-and-milk - they can't digest it and it makes them ill. If you want to feed them, cat-food is fine. In dry conditions, shallow dishes of water are important too.

Our garden hedgehog house (note the staggered entrance-way and pile of dry leaves) with the waterproof roof removed.

I could go on, but there are plenty of online resources like this leaflet about 'Gardening with Hedgehogs', as well as opportunities to get more involved such as the Hedgehog Street project where you can become a Hedgehog Champion, and a variety of voluntary PTES surveys.

Garden hedgehog enjoying cat food and a dish of clean water. Nom.

Focusing on the familiar VI: ladybirds part 4

It's a year and a half since I started my occasional series looking in a little more detail at familiar species. In that post I looked at the 'typical' 7-spot ladybird Coccinella 7-punctata, including the yellow colour it shows when newly emerged as an adult, and compared it with the Harlequin ladybird Harmonia axyridis. This time, I decided to go back to the 7-spot and look in a little more detail at its external anatomy.

Dorsal surface of the 7-spot ladybird Coccinella 7-punctata

The dorsal surface is fairly straightforward and is what we usually see - the pair of wing cases (elytra) showing the familiar orange-red colour with seven black spot, the black and white pronotum in front of this, covering the thorax, and the head which is mostly hidden, although you can see the antennae protruding here. The ventral surface is a little more complex, and it's useful to become familiar with the standard terminology.

Ventral surface of the 7-spot ladybird Coccinella 7-punctata

I have ignored the appendages (legs, antennae and mouthparts) on this occasion but have numbered some of the other features that may be less familiar as they illustrate how the plates fit together to for the exoskeleton:

1. Epipleuron - the folded-under edge of the elyton which fits against the body.
2. Prosternum - the front section of the thorax (analagous to the sternum or breastbone in humans), which has a small keel running front to back (here a greyish line).
3. Mesosternum - the middle section of the thorax.
4. Metasternum - the rear section of the thorax.
5. The front section of the abdomen - you can see the curved join against the metasternum.
6. The 6th (and rearmost) abdominal segment. Ladybirds can be difficult to sex, but the shapes of these segments can be useful and there is more detail in Randall et al. (1992).

You will see the prefices pro-, meso- and meta- used elsewhere to mean 'front', 'middle' and 'rear' e.g. 'profemur' for the femur of the front leg. The plates have elastic membranes between them - the abdomen is particularly flexible in males as they need to curl it beneath in order to mate, and this affect the shape of the abdominal segments and membranes, leading to subtle differences that can be used to tell males and females apart.

That's all for now (maybe I'll write an intro to beetle appendages some time) - if you want to know more about ladybirds, especially from a UK perspective, have a look at the further reading list below, and why not get involved in the UK Ladybird Survey - new volunteers always welcome!


Reference

Randall, K., Majerus, M.E.N., & Forge, H. (1992). Characteristics for sex determination in British Ladybirds (Coleoptera: Coccinellidae). The Entomologist 111: 109–122.

Further reading

Brown, P., Roy, H., Comont, R. & Poland, R. (2012). Guide to the ladybird larvae of the British Isles. FSC, Preston Montford. A fold-out laminated sheet perfect for beginners.
Majerus, M.E.N. (1994). Ladybirds. HarperCollins, London. A classic - part of the New Naturalist series.
Majerus, M., Roy, H., Brown, P. & Ware, R. (2006). Guide to Ladybirds of the British Isles. FSC, Preston Montford. A fold-out laminated sheet perfect for beginners.

Roy, H., Brown, P.,  Comont, R.F., Poland, R. & Sloggett, J.J. (2013). Ladybirds (2nd ed.). Pelagic, Exeter. Much updated from the 1989 edition (which of course didn't have the Harlequin which wasn't in the UK then), an excellent little book with detailed keys to species, including the 'micro-ladybirds'.

Roy, H., Brown, P., Frost, R. & Poland, R. (2011). Ladybirds (Coccinellidae) of Britain and Ireland. FSC, Shrewsbury. Details of all species including maps, identification features, ecology and so on.

Pondnet diary day 2

Continuing the Pondnet survey that began about a week ago, having done a preliminary survey of the main environmental features and whichever species could be spotted from the side, this time a net and white tray were required.

My wife/field-assistant doing some pond-netting.

the first thing we notcied was the great increase in frog tadpoles - not only in number (from a couple of hundred to at least a thousand as a rough estimate) but in size. A week previously the ones we saw were newly hatched - these had developed their typical fat-headed shape. They hadn't all hatched in the last week, so many must have been well hidden. The net also meant that we could confirm the species of the numerous small fish seen previously - they looked like sticklebacks but it's always worth checking, and all the ones we caught (and yes re-released) were indeed three-spined sticklebacks (Gasterosteus aculeatus).

A three-spined stickleback Gasterosteus aculeatus - the dorsal spines are just visible

Of course, it wouldn't be a proper sampling day (for me) if there weren't invertebrates involved. The netting meant we could see beyond the larger surface-dwelling species and maybe find some that, even if common, are less immediately familiar.

The water-slater or hog-louse Asellus aquaticus

The water-slater or hog-louse Asellus aquaticus is an isopod crustacean i.e. related to woodlice, and is common and widespread in Britain. It can be found in a very wide range of water bodies and qualities, but especially under aquatic foliage, stones and wood (Gregory, 2009), so is rarely seen by the casual observer without a net. It can be separated from the similar Proasellus meridianus by the head pattern although the photo doesn't show it as clearly as could be seen on the live specimen.

Another common-but-overlooked species is Plea minutissima, the 'least water-boatman'. It is broadly similar to other water-boatmen seen 'rowing' beneath the water's surface, but is tiny (around 1.8 - 2.8mm long) and its domed shape means that it is initially more likely to look like a small beetle than a water bug at a glance (Denton, 2007) - it certainly did to me when seen among the debris and other small species from the net. However, under the microscope (or even a squinted eye) it is quite different and the pointed mouthparts can be seen.

The least water-boatman Plea minutissima is the sole British species in the family Pleidae.

Lastly, I'd like to keep moving down the size scale to look at the water mites - arachnids of the suborder Hydracarina. These are mostly bulbous and the body in not separated into separate sections (cephalothorax and abdomen) as would be seen in the suborder Oribatei. Identification is tricky, but Hopkins (1961) can be downloaded from free here and is very useful for those beginning to study this tricky, and again often-overlooked, group. I won't go into detail about the identification here, but the water mite I investigated was Piona coccinea - a red species around 2-3mm long, red and globose in form.

That's where I'll leave pond-related matters for today - more soon!

The water mite Piona coccinea.

References

Denton, J. (2007). Water Bugs and Water Beetles of Surrey. SWT, Woking.
Gregory, S. (2009). Woodlice and Waterlice (Isopoda: Oniscidea & Asellota) in Britain and Ireland. NERC/BRC, Wallingford.
Hopkins, C.L. (1961). A key to the water mites (Hydracarina) of the Flatford area. Field Studies 1(3): 45-64.

Pondnet diary day 1

Pondnet is a new Pond Conservation volunteer survey aiming to identify trends in pond quality and associated species. I was recently allocated a pond in Milkmead Copse in Hampshire's Itchen Valley Country Park, and now spring's arrived, I decided that today was a good opportunity to make my first visit to the site.

The pond in Milkmead Copse

It was good to see some frogspawn had survived the cold conditions as there were at least a couple of hundred recently hatched tadpoles, plus one adult newt. However, something else (yup, an invertebrate) caught my eye - a water scorpion (Nepa cinerea) that came to the surface.

Water scorpion, Nepa cinerea

This is a predatory true bug (Hemiptera) and the raptorial (hunting) front legs used to grip prey are clearly visible, plus the breathing tube at the rear. Although this appears to be a single thin tube, it is actually formed from two halves (they separate if a specimen is dried) - air flows from it along two grooves which have small water-repellent hairs and the spiracles open into these grooves (Denton, 2007). Being a bug, it has piercing/sucking mouthparts rather than the jaws/mandibles seen in beetles. It is a large insect by UK standards at around 20mm in length, excluding appendages. It is an active hunter, taking small fish and various other invertebrates. However, I was surprised to see it tackle a larger (approx 25mm) dragonfly nymph, itself an active and powerful predator.

N. cinerea attacking a dragonfly numph.

N. cinerea on the back of the dragonfly nymph

This is not behaviour I've seen before and the nymph struggled for a few minutes before managing to dislodge its attacker by dragging it against a piece of vegetation. Presumably the position of N. cinerea allowed it to pierce the nymph while remaining out of direct reach. Certainly, the water scorpion swam away after this encounter and the nymph came back to the surface. I'm not 100% sure which species it is as it is coated in silt which obscures key features. However, the size, head shape and silty coating are typical of the black-tailed skimmer (Orthetrum cancellatum) so that is my identification for now.

Dragonfly nymph, possibly Orthetrum cancellatum, the black-tailed skimmer. Note the hairs on the legs and body, coated in silt.

The same dragonfly nymph - note the protruding eyes and the 'mask' showing the mandibles.

So, an interesting start to a new survey programme. More to come from the pond!


Reference

Denton, J. (2007). Water Bugs and Water Beetles of Surrey. SWT, Pirbright.

Leaf beetle key - write, edit, plug

If you are a regular here, you'll know that I have a considerable interest in invertebrates and that they form a large proportion of the topics I write about (a glance at the 'tag cloud' in the right margin will confirm that). However, you might not know that I specialise a little more than that and that one of my areas of specialism is in the Chrysomelidae - the 'leaf beetles', which include the 'seed', 'reed', 'flea' and 'tortoise' beetles - and the two small closely related families, the Orsodacnidae and Megalopodidae. You may be familiar with these groups having a slightly different taxonomic arrangement, such as the Bruchinae being accorded full family status, but recent cladistic work (e.g. Reid, 1995) suggests otherwise.

A few years ago I became interested in this group as a voluntary species recorder for the UK's Biological Records Centre (BRC), and later as organiser of the related UK Recording Scheme. I soon found that, even with the excellent Atlas to British and Irish species having been published (Cox, 2007), I needed to collect a large number of individual journal articles in order to be able to reliably identify adults of the British chrysomelid fauna and that even then there were gaps. The last key covering all species was Joy (1932) which, although excellent, was unavoidably out of date (and hard to find affordably until the CD-ROM version appeared), while the update (Hodge & Jones 1995) was out of print. Grr. Although the BRC were extremely helpful, sending me copies of the articles I needed if they had access to them, it became clear that a lack of readily available user-friendly identification literature was a major barrier to expanding interest in this beetle group. Such a barrier needed to be overcome, especially as the Chrysomelidae includes many charismatic (shiny, colourful and metallic such as the green dock-beetle Gastrophysa viridula) species as well as a number of considerable economic importance (horticultural and agricultural pests) such as the unpopular Lily Beetle (Lilioceris lilii) and the notorious potato pest, the Colorado Beetle (Leptinotarsa decemlineata) although the latter is currently unable to colonise Britain due to low winter temperatures. There is also a conservation component as accurate identification is needed to provide useful distribution and monitoring data. For example, there are a number Biodiversity Action Plan (BAP) and Red Data Book (RDB) species, such as the Pashford Pot Beetle Cryptocephalus exiguus which provides an (unfortunately) excellent case study of ineffective landscape-scale conservation, while the flea beetle Psylliodes luridipennis is a UK endemic known only from Lundy Island where it is threatened by over-grazing and invasive rhododendron.

Consequently, I made the decision that 'the book' would only appear if I wrote it, and so I began, aiming for an intermediate audience as I wanted to cover all British and Irish species, and many require dissection under a low-power microscope - not something for beginners maybe... I won't go into too much detail other than to say it was difficult - really, really difficult. The initial draft wasn't too bad to write, but - as expected - had many errors and omissions which were discovered during testing. However, many testers provided excellent tips and suggested changes - some extensive - which greatly improved the final version. The difficulty came where species were not covered reliably by existing literature, and this happened a lot while trying to write keys for the notoriously tricky flea beetle genera such as Longitarsus. I was aided in many cases by the excellent images (including genitalia) on the European Chrysomelidae website, but in the end there is no substitute for going to a museum or other institution, and consulting specimens in their reference collections such as those held in Winchester (Hampshire County Council), Oxford (Oxford Uni Museum of Natural History) and at the BENHS HQ near Reading. This is what sampling and collecting is for - it ain't decoration or 'train-spotting'!

A tray of beetles from the Oxford Uni MNH collections

So, after editing, re-editing, adding a few species that had been newly found in Britain, and making changes following taxonomic updates, the final version - complete with cover photo - went off to the publisher and then the printer. I was expecting it to be ready in mid to late November, but - much excitement - a courier delivered a box of my author's copies this morning - whoop! I think they are great (obviously) and a bargain at only £8.50 - available here - enjoy! All the many many hours of beetle-scrutiny was worth it - now, I seem to remember there's no general textbook covering this family...

Woo hoo! A box of brand new copies of my key to British and Irish leaf beetles.

References

Cox, M.L. (2007). Atlas of the Seed and Leaf Beetles of Britain and Ireland. Pisces, Newbury.

Hodge, P.J. & Jones, R.A. (1995). New British Beetles: Species not in Joy's Practical Handbook. BENHS, Reading.

Joy, N.H. (1932). A Practical Handbook of British Beetles (2 vols., 1976 reprint). Classey, Faringdon.

Reid, C.A.M. (1995). A cladistic analysis of subfamilial relationships in the Chrysomelidae sensu lato (Chrysomeloidea). In: J. Pakaluk & S.A. Ślipiński (eds.) Biology, Phylogeny, and Classification of Coleoptera: Papers Celebrating the 80th Birthday of Roy A. Crowson. Muzeum i Instytut Zoologii PAN, Warsaw, pp. 559-631.

Pond bugs - the long and short of it

As you may have noticed if you're a regular, since building my own garden pond, I have been pretty enthusiastic about all things lentic (I like that word) and this post is no exception. During a recent Southampton Natural History Society field trip (hosted by Naomi, an ecologist from Pond Conservation) to look at invertebrates associated with New Forest ponds, numerous fine creatures were found, including a couple of spindly beasts that are probably unfamiliar to most people who don't regularly wade around in the mud and reeds, pond net in hand. The first of these is the Water Stick-insect Ranatra linearis.

Water stick-insect Ranatra linearis

The first thing to say is that this isn't a stick-insect, it's a true bug (Hemiptera) in the same family (Nepidae) as water-scorpions, and as such has piercing/sucking mouthparts. The long 'tail' is its breathing tube 15-20mm long at the end of a 30-35mm long body (not including the legs) - quite a striking creature, and though locally common in southern England and wales, rarely seen as it tends to lurk in dense pond vegetation, where it is an ambush predator (like a mantis for example) grasping prey with its raptorial front legs. If caught in a pond net, it tends to look like a bit of twiggy detritus until it moves - the occasional human has been known to jump in surprise at pond-dipping events and the like...

The raptorial front legs of Ranatra linearis

Here you can clearly see how the legs can shoot out mantis-like and grab prey (often small newts and fish) which will then be pierced by the pointed mouthparts (also visible). It is able to fly - useful if a pond dries up, and they also hunt on land - and although I have never seen one doing so, apparently it looks similar to a damselfly when in flight. The eggs are a peculiar sight too - when laid on leaves of water plants such as reedmaces and bur-reeds, breathing tube emerge into the air, and the eggs look like little rows of surgical stitches; there are good photos in Denton (2007).

Moving onto something smaller, at 9-12mm long (excluding legs and antennae), the Water-measurer (Hydrometra stagnorum) is another true bug common in much of lowland England and Wales (less so in Scotland and northern England) and is especially elongate, having the longest length-to-width ratio of any British insect - even the head is elongate, protruding well in front of the eyes which can be seen about half way between the antennae and front legs.

The Water-measurer Hydrometra stagnorum

It tends to be found around the edges of ponds and streams, including bankside vegetation as well as the water surface, and are also known from ephemeral waters where they can be found under debris during dry periods. Although they are generally unwinged, individuals with wings do occasionally occur. Attracted by ripples of movement (Savage 1989), they feed on smaller invertebrates such as water-fleas (Cladocera e.g. Daphnia) and mosquito larvae, piercing them through the water surface with their mouthparts, and sometimes pulling them up through it - Fitter & Manuel (1994) includes a photo of prey being consumed. Unlike R. linearis above, the front legs are simply used for walking and are not involved in catching prey - their very regular tip-toe gait gives them their common name as they appear to be pacing out distances. There is a second slightly smaller species, H. gracilenta, but this is very rare in Britain, known only from a handful of locations in southern and eastern England. Back in the 1950s, it was apparently found in the New Forest, but the account was never published and so the alleged location remains a mystery (Huxley 2003) - to find one there would be an entomological highlight!

Although both of these species are fairly common, this is not true of all our aquatic bugs - many (most) ponds in lowland Britain are polluted to some extent, especially by nutrients from our intensive agricultural system, and this has seriously impacted the biodiversity of pond ecosystems. With both point and diffuse sources being a problem, it can be difficult to ensure good ecologicsl water quality, but advice (on managing existing ponds or creating new ones) can be sought from organisations such as Pond Conservation. Garden pond ponds are a little different as few of us have enough room for the metres of shallow muddy margins that a really good pond needs, but some of the same advice applies and they are really important oases - and excellent fun to watch as the wildlife colonises it and does its thing!

Naomi from Pond Conservation hard at work looking for aquatic invertebrates in a shallow pond in the New Forest.

References

Denton, J. (2007). Water Bugs and Water Beetles of Surrey. Surrey Wildlife Trust, Woking. [Covers a good range of species; lots of useful info and excellent photos even if you're not in Surrey].
Fitter, R. & Manuel, R. (1994). Lakes, Rivers, Streams & Ponds of Britain & North-West Europe. HarperCollins, London. Also published in 1986 as Field Guide to the Freshwater Life of Britain and North-West Europe. [Both versions are out of print, but worth tracking either down online as they can be quite cheap.]
Huxley, T. (2003). Provisional Atlas of the British Aquatic Bugs (Hemiptera, Heteroptera). BRC, Huntingdon.
Savage, A.A. (1989). Adults of the British Aquatic Hemiptera Heteroptera: A Key with Ecological Notes. FBA, Ambleside. [The standard identification guide].