Highlights of 2013

December's been a quiet month on the blogging front - a large beetle project is ongoing (status review of the UK Chrysomelidae) and then of course the whole festive-season-thing. However, there was a proper summer this year with an extended period of hot dry weather extending into a mild autumn, and this meant some fine invertebrate (and other) sightings after some truly awful, cool, wet summers. The most spectacular (for me as they were all personal firsts) were probably three Lepidoptera finds between July and September - two butterflies, a monarch (Danaus plexippus) and long-tailed blue (Lampides boeticus) and a moth, the Clifden nonpareil (Catocala fraxini). The monarch is a North American species, and although some have been known to cross the Atlantic, it is more likely that this (and one from a nearby friend's garden) had escaped from a butterfly farm, maybe on the Isle of Wight. Certainly there was a small flurry of records of this species in southern England, aided by the fact that monarchs in the UK often visit gardens to seek their foodplant, milkweed (Asclepias syriaca) which is of course also non-native. The other two are scarce migrants seen in higher-than-usual numbers due to the favourable conditions this year. Being native to NE Europe, the Clifden nonpareil is more often seen on the eastern coasts of Britain, but my sighting was in Hampshire, about 10km inland where one large and unmistakable adult was seen basking on warm brickwork near scrub including its foodplants - aspens and other poplars (Populus spp.). Also a rare migrant, the long-tailed blue can be found on various Fabaceae such as everlasting-peas (Lathyrus spp.) and brooms (Cytisus spp.) - as a Mediterranean resident, it's not often seen in this country. I'll stop there, but if you'd like an affordable and user-friendly guide to European butterflies, one of my favourites is Haahtela et al. (2011). More to come from me in 2014, but until then, here are some pics from 2013...

A flock/mob of jackdaws in spring, as seen from my study window.

Adult female smooth newt in our garden pond.

A leaf beetle larva and its defensive shield of faeces and shed skins.

And finally, just to prove that I do go out and do ecology in the field, here I am taking great created newt eDNA samples at Claylands Nature Reserve, Hampshire.

Reference

Haahtela, T., Saarinen, K., Ojalainen, P. & Aarnio, H. (2011). Butterflies of Britain and Europe: A Photographic Guide. A & C Black, London.

It's OK to be takeyai

It's time to look at a family of insects I've not written about before - the Tingidae or 'lacebugs'. These are true bugs (Hemiptera) and, though small, are distinctive due to having a lace-like network of reticulation covering the pronotum and forewings. The function of this isn't immediately obvious, but as they often look like dried seeds or similar, it may be a form of camouflage. They are also flattened dorso-ventrally, with the head, in many species, hidden beneath a hood-like or bulging extension of the pronotum. Although generally unfamiliar to non-entomologists, they can be quite common and there are over 2,000 known species worldwide (25 in the UK, 8 of which are listed as scarce or rare).

All Tingidae are plant-feeders, and being mostly host-specific, some are considered pests. One of these, a Japanese species first recorded in Britain in 1998 (Halstead & Malumphy, 2003) was found in our garden yesterday - the andromeda lacebug Stephanitis takeyai. It feeds on the 'Japanese andromeda' Pieris japonica and has been introduced into the USA and Europe via the ornamental/garden plant trade. It also uses other Pieris species, as well as rhododendrons and azaleas - as such it is sometimes considered a pest in ornamental gardens, though in ours it is welcome to eat what it can find as we don't grow these!

Stephanitis takeyai, approx 4mm long (excluding appendages)

The dark reticulation is clearly visible here and, along with the dark wing markings (which break up the outline) and leaf-coloured legs/antennae I suspect provides effective camouflage. The bulbous hood of the pronotum is visible, almost entirely obscuring the head/eyes, but can been seen more clearly from different angles.

Stephanitis takeyai, side view showing the pronotal hood and, just behind it a thin longitudinal pronotal keel. The flattening of the body is also clear.

Stephanitis takeyai, front view, again showing the pronotal hood.

Although some North American tree-pest species have been well studied, there is a lack of information about the Tingidae in more general sources. There is a short section including keys in Southwood & Leston (1959) and although Ryan (2012) updated the list in this publication, adding S. takeyai and Corythucha ciliata, identification details were not included. However, S. takeyai is a distinctive species, only likely to be confused with another rhododendron-feeding introduction, S. rhododendri which is broadly similar, but has mainly pale wings with a brown band near the base.

S. rhododendri is covered briefly in Becker (1974), Buczacki & Harris (1981) and similar publications, as well as in Southwood & Leston (1959), while Alford (2011) covers the platanus lacebug C. ciliata, a North American pest of various plane trees first found in Britain in 2006, again via the plant trade. However, there is much to learn about these insects, and it seems likely that more will be accidentally imported, so definitely a group worth keeping an eye out for, including on garden/ornamental plants.

References
 
Alford, D.V. (2011). Plant Pests. Collins, London.
Becker, P. (1974). Pests of Ornamental Plants. HMSO, London.
Buczacki, S. & Harris, K. (1981). Guide to the Pests, Diseases and Disorders of Garden Plants. Collins, London.
Halstead, A.J. & Malumphy, C.P. (2003). Outbreak in Britain of Stephanitis takeyai Drake & Mao (Hemiptera: Tingidae), a pest of Pieris japonica. British Journal of Entomology & Natural History 16: 3-6.
Ryan, R. (2012). An addendum to Southwood & Leston's Land and Water Bugs of the British Isles. British Journal of Entomology & Natural History 25: 205-215.
Southwood, T.R.E. & Leston, D. (1959). Land & Water Bugs of the British Isles. Warne, London. [there is a 2005 reprint which is much cheaper, and a CD-ROM version from Pisces Conservation Ltd.]

Beetles that keep their supercool

A few days ago, I wrote about antifreeze proteins in overwintering plants, during which I mentioned in passing that there is a similar system in some insects, and that I might write about that too. So, here goes...

Winter conditions in southern England

One of the key concepts here is 'thermal hysteresis' (TH), the difference that antifreeze chemicals (usually proteins, but there are exceptions) create between the melting and freezing points, thus inhibiting ice formation and crystal growth. In fish this effect can reduce the freezing point by up to 1.5°C, and in plants the effect is weaker, but in insects, it is much stronger, reflecting the colder temperatures experienced on land than in water (plants don't show this, but are very differently organised both morphologically and biochemically). For example, despite being intolerant to freezing, the Spruce Budworm moth Choristoneura fumiferana (family Tortricidae) can survive to around –30 °C due to the presence of antifreeze proteins (e.g. Doucet et al. 2002, Qin et al. 2007). More impressively, the Alaskan beetle Upis ceramboides (family Tenebrionidae) survives conditions as cold as –60 °C using a non-protein TH chemical called xylomannan (Walters et al. 2009) which is a combination of sugars (sacchardies) and fatty acids (Ishiwata et al. 2011) in the cell membrane where it appears to function by suppressing the freezing of water molecules within cells. Interestingly, xylomannan was already known to be present in the red seaweed Nothogenia fastigiata, and research on this has shown it to have anti-viral effects by inhibiting replication, including types of herpes, influenza and (to a lesser extent) HIV, among others (Damonte et al. 1994).

The Alaskan-Canadian 'red flat bark beetle' Cucujus clavipes puniceus (family Cucujidae) is another that can survive extremely low temperatures (some individuals 'supercooling' to -100 °C in the lab!), in this case due to the more typical TH proteins and also losing 60-70% of its water content in winter (presumably reducing the among that has to be prevented from freezing) (Sformo et al. 2010, Carrasco et al. 2012).

I could go on - there are plenty of other examples even if some of the mechanisms and biochemistry are not fullt understood - but the point is that (1) there are processes here which require more study (anti-virals anyone!) and (2) wherever we look, life is more resilient than we imagine, with tardigrades and bacteria able to survive in space and much work being done on 'extremophiles' in places such as hot springs and hydrothermal vents as well as the frozen Arctic. Maybe time for a bet at Ladbrokes on life being found in the liquid interior of Europa...

References

Carrasco, M.A., Buechler, S.A., Arnold, R.J., Sformo, T., Barnes, B.M. & Duman, J.G. (2012). Investigating the deep supercooling ability of an Alaskan beetle, Cucujus clavipes puniceus, via high throughput proteomics. Journal of Proteomics 75(4):1220-1234.
Damonte. E., Neyts, J., Pujol, C.A., Snoeck, R., Andrei, G., Ikeda, S., Witvrouw, M., Reymen, D., Haines, H. & Matulewicz, M.C. (1994). Antiviral activity of a sulphated polysaccharide from the red seaweed Nothogenia fastigiata. Biochemical Pharmacology 47(12): 2187-2192.
Doucet, D., Tyshenko, M.G., Davies, P.L. & Walker, V.K. (2002). A family of expressed antifreeze protein genes from the moth, Choristoneura fumiferana. European Journal of Biochemistry 269(1): 38-46.
Ishiwata, A., Sakurai. A., Nishimiya, Y., Tsuda, S. & Ito, Y. (2011). Synthetic study and structural analysis of the antifreeze agent xylomannan from Upis ceramboides. Journal of the American Chemical Society
133(48): 19524-19535.
Qin, W, Doucet, D., Tyshenko, M.G. & Walker, V.K. (2007). Transcription of antifreeze protein genes in Choristoneura fumiferana. Insect Molecular Biology 16(4): 423-434.
Sformo, T., Walters, K., Jeannet, K., Wowk, B., Fahy, G.M., Barnes, B.M. & Duman, J.G. (2010). Deep supercooling, vitrification and limited survival to -100 °C in the Alaskan beetle Cucujus clavipes puniceus (Coleoptera: Cucujidae) larvae. Journal of Experimental Biology 213(3): 502-509.
Walters, K.R., Serianni, A.S., Sformo, T., Barnes, B.M. & Duman, J.G. (2009). A nonprotein thermal hysteresis-producing xylomannan antifreeze in the freeze-tolerant Alaskan beetle Upis ceramboides. Proceedings of the National Academy of Sciences of the USA 106(48): 20210–20215.

No seeds, no fruit, no fungi - November!

It's been an odd year in the UK (and elsewhere) - an unusually warm early spring, then a cold, wet early spring and summer and a very variable autumn with frosts and warm periods. Unsurprisingly, this has seriously impacted some of the UK's wildlife negatively. For example, the Big Butterfly Count found declines in many common species, with 11 of the 21 target species decreasing in abundance by more than a third since 2011. There are a number of reasons - low temperatures clearly affect cold-blooded groups such as insects, which in turn reduces the food available for insectivores such as birds and bats. Plant growth is also affected by cold and water-logging, so less sugar is produced, fruit growth is reduced (and what does grow may be affected by moulds and blights and fall early or rot on the plant), leading to less seed production - bad for plant reproduction and seed-feeders such as many winter birds. This is already having visible effects as more unusual species appear in gardens - so, it is even more important to keep bird-feeders full. Poor fruit/seed growth in Scandinavia has already meant that at least a couple of thousand waxwings have flow across the North Sea to NE Britain. There are also less obvious effects. For example, the reduced sugar production means that ectomycorrhizal (externally root-associated) fungi grow poorly despite the damp conditions.

However, not all is doom and gloom. Some species have taken advantage of warm late summer and autumn temperatures to grow and breed - I have certainly seen late bird-nesting activity, and while in south Devon last week (the SW is the warmest part of the country), while some trees were losing their leaves, others were budding as seen here.

Hazel coming into bud in mid-November in south Devon

Late flowering has provided at least some extended nectar availability (apart from ivy which is always a winter source) as seen here where a small Panurgus calcaratus bee is feeding on a yellow composite flower, again in mid-November. Found in a band across SE England it is also known all round the SW coast as you can see on the map here; clearly a species needing warm temperatures as it is absent further north.

Panurgus calcaratus feeding on a yellow composite flower in warm sunny mid-November conditions in south Devon

Warm damp autumn weather has meant that some fungi have done well eventually, such as those living on damp deadwood and leaf-litter, while in our new garden pond, the pond-skaters have bred very successfully and are highly active. Slugs and snails have also had an excellent year, though this is not popular with gardeners and allotment-holders, not to mention those of us with old houses that have little holes where slugs can gain access in the middkle of the night...

Overall, there are sadly probably more wildlife losers than winners, but what does the future hold? Well, nothing is certain, but an important study by Overland et al. (2012) does give some indications. Firstly, as many people have suggested, it isn't just 2012 when the summer has been cold and wet - this is a pattern that seems to have begun in 2007 when there was what appears to be a sustained shift in early summer Arctic winds. This change is linked to increased North American atmospheric blocking which ultimately leads to the southward movement of the jet stream that has been mentioned in TV weather forecasts. The study also looked at why this has happened and has unsurprisingly concluded that climate change is a likely candidate - in particular the melting of Arctic ice (particularly around Greenland, remembering that Greenland is politically European but geographically North American) which highlights the potential connectivity between Arctic climate and mid-latitude weather i.e. the Arctic heats up, the UK gets bad summers.

This is of course an ongoing story - research is undoubtedly ongoing to finesse some of the findings and explanations. As an academic, I find this fascinating but as someone interested in wildlife and environmental issues, I also find it deeply troubling, especially when the UK government seems to be trying to pull back from its low-carbon committments. However, I'll stop there lest the Ecology Spot becomes my political ranting zone!

Reference

Overland, J. E., Francis, J. A., Hanna, E. & Wang, M. (2012). The recent shift in early summer Arctic atmospheric circulation, Geophysical Research Letters 39, L19804 (6pp.)

Tarantula anatomy III: the appendages

Having looked at the abdomen and cephalothorax, it's time for the third and final instalment of tarantula anatomy based on the features visible on a moulted skin.

Ventral view of the sternum showing articulations with legs and chelicerae

Although legs and chelicerae are the most prominent appendages and found on the cephalothorax, I want to start with the spinnerets found at the end of the abdomen. Even though this is not a web-weaving spider, it still needs to produce silk e.g. to form eggs cocoons (this is a female), and does so from the paired spinnerets. Each spinneret is linked to silk glands and is a segmented structure to allow the silk to be manipulated as it is extruded.

One of the spinnerets - note the segmentation and longitudinal groove in the last segment.

Moving forward, a key feature is of course the presence of eight legs - the source of much arachnophobia. These are clearly jointed and are dark with orange-red bands giving this species its common name. However, the part I want to look at is the end of the final segment or tarsus - the spider's 'foot' if you like. Whereas the rest of the leg (and much of the spider) is covered in a variety of bristles, the foot-pad is covered in tiny, short hairs giving it a soft, velvety appearance. More importantly, this also means that the pad has a large surface area, aiding grip - much like the almost fractal convoluted ridges on a gecko's foot (maybe more on that another time - there are electrostatic effects involved which are fascinating), as well as a pair of small claws.

The underside of the tarsus showing a velvety covering of small hairs.

Tip of the tarsus with the tiny claw (one of a pair) indicated.

Moving further forward, the next appendages are of course the mouthparts, in particular the fang-bearing structures called chelicerae.

Ventral view of the chelicerae showing fangs.

The chelicerae are articulated and can flex the fangs forward to grip prey as the fangs are hardened and sharply pointed. As the spider is not strongly venomous, it chews rather than sucks its prey, using the fangs to grip and press food against a line of smaller teeth on the front edge of each chelicera.

Chelicera showing fang, smaller teeth and flat inner surface.

The inner edges of the chelicerae are flat and relatively hairless as they fit closely against each other, with fringing hairs around the edge as shown above (these may be used to stridulate i.e. produce sound when rubbed together, at least in some species). Looking inside a chelicera, there is evidence of the mobility of this structure required in order to chew and manipulate food - connective tissues can be seen which would have been attached to muscles that move the chelicera and fang.

View into a chelicera showing the bases of small teeth, plus the remnants of connective tissue used to move the appendage and fang.

That brings me to the end of my trilogy of tarantula anatomy posts. There are of course many other structures in a live spider, but the skin is easy to manipulate and can be dissected without harming the spider which has left it behind. So, if you are a tarantula-keeper, why not have a look the next time your spider moults - there are many interesting structures the closer you look.

Tarantula anatomy II: the cephalothorax

My previous post looked at the abdominal structures seen in the shed skin of a tarantula - this time I'm moving forward a segment to look at the cephalothorax i.e. the fused head and thorax.

The thorax with the top removed

With the upper surface removed, the empty thorax shows a clear pattern - the central section (the inner surface of the sternum) surrounded by the eight cavities associated with the coxa (1st segment) of each leg. The thorax is of course empty as the spider has emerged, but a slightly different view shows how complex this must be.

The empty thorax looking forward into the chelicerae

Here the structure is clearer still - the sternum at the base, the eight cavities through which the legs will have been extracted, plus corresponding cavities at the front (top of the photo) where the chelicerae (fang-bearring jaws) and head were pulled free. The white tuft of hairs between the chelicerae remains as do some white thread-like connective tissues within the empty legs. The sternum also clearly shows small holes such as those where book-lungs were joined to the outosde air via spiracles (breathing pores). Looking inside the upper surface of the cephalothorax, further structures can be seen.

Inner surface of the cephalothorax showing sculpturing

Close-up of sculpturing within the cephalothorax

 The inner surface shows both vaulting associated with the muscle attachments of legs and chelicerae, forming a central point between the attachments of these appendages. The lower photo is a closer look and shows finer mesh-like sculpturing presumably associated with the muscle attachments and possibly the passage of bodily fluids around them and/or the locations of nerves such as those serving sensory bristles. Near the front edge, the remnants of the eyes are also visible as their surface is also part of the exoskeleton and hence moulted along with other structures. Compared to the overall size of the spider, the eyes are small and closely clustered, possibly indicating the importance of, for example, sensory bristles to an animal that spends much time in a dark burrow during the day.

Front view of the cephalothorax showing eyes

Closer view of the inside surface of the cephalothorax showing how the eyes protrude outwards.

The upper surface of the cephalothorax - this back-lit view shows that there are eight eyes arranged on a small dome.

So, although the spider has left, certain structures - as with the abdomen - remain; the third and final part will look at appendages, including legs and fangs!

Tarantula anatomy I: the abdomen

A few days ago, I was chatting with a friend of a friend on facebook after they posted a picture of the moulted skin of their pet Mexican Redknee Tarantula Brachypelma smithi. The upshot was that they offered to send me the skin so I could have a look at it under the microscope and see what interesting features were visible. It turns out that there were quite a lot - more than can fit into a single post - so here is part 1, looking at abdominal features.

Dorsal view of the tarantula skin as it arrived in the post

The skin was well packaged and in really good condition and shows first of all how the spider moults. The top of the abdomen and cephalothorax split and peel back as a long flap, and the spider emerges up and backwards, pulling its legs and other appendages free. The new exoskeleton - including the fangs - is soft and needs to harden, and hence the spider will not be able to feed for a couple of days after moulting.

Looking at the abdomen, there are the familiar long bristles that you might expect to see, but a closer view (and indeed touch) shows that the texture is actually very different. There is a dense covering of shorter, softer hairs which look and feel much like moleskin - quite unexpected if you don't know what to expect!

The soft hairs of the abdomen along with longer, coarser bristles.

The long bristles are important as they have a sensory function, whicle some others form an important defence mechanism, being brushed off towards potential predators using the legs. These 'urticating' hairs (the paler patch top left in the photo above) are much smaller but are barbed and cause irritation to areas such as the eyes. In the wild, the spider would spend most of its time in a burrow in an earth bank and use these hairs to deter predators such as coatis - though large and fearsome-looking, these spiders rarely bite and have only weak venom. In this genus, the urticating hairs are classified as Type III (there are six recognised types) which are 0.3–1.2 mm long and particularly irritating to mammals, including humans who sometimes develop a rash as an allergic reaction. The biochemistry of the hairs is poorly known - they appear to be chitnous and are certainly not made of living tissue - their irritating effects have been assumed to be physical (i.e. the effect of having barbed hairs stuck in your eyes/skin), but there may also be direct chemical effects, at least in some species.

The bases of two sensory bristles showing the attachment points that fit into 'sockets' in the exoskeleton. Mag x40

The fine hairs on the surface of a bristle. mag x100

Some of the small, defensive urticating hairs - note the thin attachment points and covering of barbs. Mag x40

Close-up of the barbs covering urticating hairs. Mag x100

The last feature I want to look at here are the book lungs, a series of flat membranes (lamellae) that spiders use for breathing via a pair of pores (spiracles) and which increase the surface area for gas exchange in much the same way as alveoli do in our lungs. They are named after their overall form which is similar to a stack of pages in a book. In this specimen, initially they were deflated and looked like quite unremarkable white masses, but when teased apart, some of the fine structure could be seen with the lamellae attached to branches leading to the spiracle and thus the outside air.

A deflated book lung.

Close-up of the book lung showing individual lamellae.

So, just a few abdominal features here - after all, the spider took its other organs with it! However, they are still interesting and there's more to come as I will be writing about the cephalothorax and appendages soon...

Why Smurfs are like slipper limpets

Yes, I do mean Smurfs, those little blue Belgian cartoon characters... and slipper limpets are marine gastropods, Crepidula fornicata. So, why are they similar? Well, you probably know that, although there are lots of Smurfs (101 in fact), only one is female - Smurfette. Now, this could easily lead into pornographic territory (and undoubtedly has, somewhere on the Internet), but that's not what the Ecology Spot is about... instead I want to be a bit speculative and look at how this might affect Smurfs biologically if they were real...

One possibility would be that they became eusocial (like ants, bees and termites for example), with Smurfette as the only reproductive female (I assume Smurfs are viviparous, but maybe there are Smurf eggs - who knows?). However, Smurfette does not appear to be a large sedentary egg-layer (or large sedentary birther-of-live-young Smurflings), nor do there appear to be non-reproductive females rendered infertile by Smurfette pheromones. This is the case in, for example, the honey bee Apis mellifera, where the queen emits Queen Mandibular Pheromone (QMP), a pheromone set which, among other functions, inhibits ovary development in other females. So, the queen bee remains on the throne, and the princesses have to wait in line.With no other females present, and Smurfette running around actively, this seems unlikely. Instead, I think Smurfs might be an example of sequential hermaphroditism (SH).

One of the best-known examples of SH is C. fornicata. Though native to the eastern coast of North America, it has been widely introduced into the coastal waters of Europe, Japan and the NW Pacific, where it is invasive (having no predators away from its original range), competing with native filter-feeders for food. For more on its British history see here.

A stack of C. fornicata (plus a small chiton on the left) - photo by F. Lamiot, and used here under the Creative Commons Attribution-Share Alike 1.0 Generic license.

They can often be found in stacks and chains, their SH reproductive strategy meaning that the largest, oldest individuals, found at the base of  the stack are female, while the younger, smaller ones at the top are male, and some in between are 'transient'. If the female(s) die, the largest male becomes a new female.

Proestou (2005) showed that C. fornicata tended towards a 1:1 sex ratio, and that as a male's distance from a female increased, his reproductive success decreased i.e. that the males closest to the female have a competitive advantage. From this, it follows that if these males suffer a reduction in reproductive success (e.g. from competition with other males) that is greater than that due toswitching sex at a small size, then they should change. Only the lowest male in a stack can change sex, a process that takes around 60 days, during which the penis regresses and the pouches and glands of the female duct develop. If a juvenile settles on an existing stack, it develops as a male and may stay like this for up to 6 years due to pheromones released by females at the base of the stack (Fretter & Graham, 1981). Presumably the death of a female means this pheromone ceases to be produced and thus the male can change sex - another process must prevent others from changing, possibly pheromones from the new female-to-be? As there are 'transients' which complicate the picture, a pheromone gradient seems plausible.

So, although the sex ratio is different in Smurfs (100:1 rather than 1:1), an SH strategy fits well. If Smurfette dies, then as the oldest male, Papa Smurf should become Mama Smurf, with some of the others (who after all, could be 'transient' and we wouldn't know by looking at them) waiting in line.

Next post - normal service will resume!



References

Fretter, V. & Graham, A. (1981). The Prosobranch Molluscs of Britain and Denmark. Part 6. Journal of Molluscan Studies Supplement 9: 309-313.
Proestou, D.A. (2005). Sex change in Crepidula fornicata: Influence of environmental factors on reproductive success and the timing of sex change. Dissertation, University of Rhode Island.

Focusing on the familiar V: dragonflies part I

A few months ago, a reader suggested I took an occasional look at some more familiar species. As my chosen remit is to popularise and familiarise less well-known species, I mused for a bit and then thought 'OK, why not?' which led to a short series on ladybirds. Now I have a garden pond, created and filled just a few weeks ago, and already interesting species are starting to appear, something I've been nattering about on facebook quite a bit. So, it seemed a good time to have a close look at one species in a generally popular group - the dragonflies - in particular the Common Darter Sympetrum striolatum. In Britain, this is probably the most commonly seen smallish red dragonfly (not to be confused with damselflies which are much more spindly), and is one of a number of species in a genus known in North America as 'meadowhawks'.

Male common darter Sympetrum striolatum on water mint.

First of all, its range is huge - from Ireland, Iberia and parts of North Africa eastwards through Europe as far as Japan, with migrations seen which can be huge in number. Like other Sympetrum, only mature males are red and it is these which I will focus on here. Females and immature males are yellowish as is typical for this genus.

The abdomen is almost parallel-sided (just a weak constriction in the front half) unlike others such as the ruddy darter S. sanguineum which has a more distinctively 'club-like' appearance. The abdomen is an orangey rather than deep red, while the sides of the thorax also have clearly yellowish patches (visible in the photo below).

Male common darter Sympetrum striolatum on Buddleia davidii.

As dragonflies can be variable in terms of depth of colour and other abdominal features, it is sometimes necessary to look more closely at the head to separate species in this genus. In S. striolatum, there is a black area above the 'face' running between the eyes, but this does not extend down the inside edge of the eyes (as shown in the photo below), unlike in, for example, S. sanguineum and S. vulgatum (which although common in continental Europe, is only found in southern Britain as a scarce vagrant).

Head of male common darter Sympetrum sanguineum showing limited extent of black facial mark.

So, if you are in Britain and see a red dragonfly of this shape and colour, there's a good chance it will be a male S. striolatum, but do take care as there are other options, and more so if you are on the continent. If you would like to find out more about this and other British and European dragonfly species, I've included a reading list at the bottom of this page - and if you'd like more info about creating a wildlife-friendly garden pond, why not download an advice booklet here (from the excellent Pond Conservation). Enjoy!

Male common darter Sympetrum striolatum surveying our new pond from his perch on water mint

I went on holiday and found an alien!

Every now and again, me, my wife, and some friends go for a short holiday on the Isle of Wight (it's not far away and there's a house we can borrow for free!). Last time, we found a fossil crocodile - this time a small alien appeared inside on one of the windowsills...

Dorsal view of the insect which is 18mm long 'nose to tail'.

As it happens, it was already dead when found, but well preserved, just missing a front leg. This made it particularly obliging and easy to photograph. It's also a distinctive species in the UK and is an adult Western Conifer Seed Bug Leptoglossus occidentalis (note the white zigzag mark across the middle of the wings), a true bug (Hemiptera) in the family Coreidae (squashbugs). A native of North America, it was first found in Britain in 2007 when a single specimen appeared in a college in Dorset, southern England. Since then, there have been numerous sightings all over the country, though most commonly along the south coast, suggesting migration across the English Channel following its introduction to continental Europe (northern Italy) in 1999, after which it spread widely and rapidly. Nymphs have also been found in Britain, indicating at least one breeding population and adults have been known to enter buildings to hibernate (possibly the source of this specimen); adults fly well, making a buzzing sound - being relatively large (but harmless to humans), this means they are often easy to detect if they enter houses.

As the common name suggests, it is associated with conifers and feeds on the cones and seeds of over 40 species, particularly trees in the family Pinaceae. In North America, it can be a serious economic pest of conifer nurseries (e.g. causing a large proportion of conelets to abort) but in Europe it is generally found in gardens and parks so such impacts have not been seen, and future effects are uncertain - nor does it attack timber. So, let's have a look at our little alien in more detail.

Close-up of the head and pronotum (the 'head cone' is about 3mm long).

Here it is clear that the reddish pronotum has a detailed pattern of yellow blotches containing tiny black spots, while the head is dark with a central red stripe and other smaller red marks. Also, the antennae which appear smooth at a distance are actually densely covered in short bristles.

Dorsal view of the wings.

Here, the distinctive zigzag markings on the forewings are clearly visible, as is the venation of the membranous hindwings, the covering of short bristles, and the black-and-white markings on the edge of the abdomen ('connexivium').

Ventral view of the head and thorax showing the pointed mouthparts (rostrum).

The long rostrum is clearly visible here and is jointed with the section lying underneath the head having fine transverse lines (striations). The rostrum is formed from mouthparts modified to peirce and feed on plant tissues and is attached to the front of the head (in other suborders of Hemiptera, the attachment might be further back). You can also see where the front right leg was attached - now missing, there is a green blob where the point of attachment sealed over.

A close-up of the hind leg.

Lastly, the hind leg provides another distinctive feature (along with the reddish colour and pale zigzags) allowing this species to be easily identified. The inner edge of the hind femur is armed with sharp teeth, but the key feature is the flattened leaf-like shape of the hind tibia which can be seen clearly here along with the tiny black dots puncturing it. Again, although the legs look smooth at a distance, they actually have dense tufts of hairs.


So, although this species has only been in Britain for a few years, it appears to be spreading rapidly and as it is so distinctive, you have a fair chance of seeing one (possibly in your house), especially in the south. For more info on it, I recommend the excellent British Bugs page which includes links to a life stages chart and a more detailed factsheet (which provided some of the info here) as well as the recording scheme for sightings of this species in the UK.

All the lonely beetles, where do they all come from?

Shortly before World War II, London’s Natural History Museum published the first edition of Common Insect Pests of Stored Food Products (Hinton & Corbet 1943), a slim volume providing a guide to the identification of such insects. Although not specifically covering beetles or non-native species, the topic is such that many of the species covered were indeed beetles, and that are number of these were introduced to Britain. However, it was not until the publication of Volume 1 of Insect Travellers (Aitken 1975) that the beetles recorded from cargoes imported into Britain were surveyed and presented comprehensively, whether or not they were seen as pest species. In Volume II (Aitken 1984), which covered insects other than beetles, the numbers, types and origins of cargoes were updated,  and extended to cover the period 1957 to 1977. The 1970s saw a shift from cargo stowage in ships’ holds towards the use of freight containers; in turn this led to the decline of ‘traditional’ ports with piecemeal unloading which allowed for easier inspection and application of insecticides. Therefore, ship and wharf inspection was virtually superceded by increased vigilance inland by the 1970s e.g. at the end points of cargo distribution such as factories, warehouses, mills and farms.

Fast-forwarding to 2010, a lot has changed. Britain now has a Non-native Species Secretariat (NNSS) with its associated Non-native Species Information Portal (NNSIP) of factsheets currently in development. In 2005, Natural England undertook an ‘Audit of Non-native Species in England’ which tabulated 2721 species and hybrids, of which 98 were beetles. Looking at these, the origins/native ranges can be approximately split as follows:

Europe 43

Australasia 16

North America 10

Asia (as a whole) 5

Eurasia 5

East Asia 3

South America 3

‘Tropics’ 3

Central America 2

Palaearctic 2

Africa 1

Europe & Africa 1

South Atlantic islands 1

Unknown 3

Although there is some doubt about the origins of some of these (e.g. a few listed under ‘Europe’ could turn out to be Eurasian), by far the most prevalent source of non-native beetle species is elsewhere in Europe, even though Asia, and especially China, is often cited anecdotally as such a source. It is true that many non-native plants originated in China, and that increased Chinese exports are likely to increase the transport of species from East Asia. However,  it should also be remembered that some Chinese beetles found in Britain and elsewhere are particularly striking such as the Asian longhorn beetle (Anoplophora glabripennis) and the citrus longhorn beetle (Anoplophora chinensis). These have in turn induced the production of many factsheets and column-inches about their invasiveness and damage to timber (e.g. Haack et al. 2010) and that the Internet allows much faster and broader familiarisation with such species than was the case when introductions were first being catalogued.

Asian longhorn beetle (Anoplophora glabripennis)

While other invertebrates may show a similar pattern (of 34 spiders on the NNSIP register, 20 are from Europe and none are strictly Asian), looking at new and potential invasive species as a whole (i.e. including all animal taxa) shows a different pattern. For example, since their 2005 audit, Natural England’s horizon-scanning (Parrott et al. 2009) highlights 63 species across its red ‘alert’, yellow ‘watch’, ‘black’ and ‘climate’ lists; of these, North America (13), East Asia (12) and Asia (9) are the key areas of origin with only 5 species originating elsewhere in Europe and 7 more widely in Eurasia.

There are many factors here, but some seem to stand out; 

• Beetles move by many means, often helped by humans, but many introductions into Britain are likely to be from Europe as their ranges expand northwards with climate change.
• Many terrestrial invertebrates, especially small species, can spread to new areas unaided – this is seen with ‘ballooning’ spiders.
• Larger species, particularly invertebrates are often spread intentionally such as fish species introduced for angling or ornamental purposes and subsequently escaping or being released.

So, to return to the title question ‘...where do they all come from?’, the answer is that they are from more-or-less everywhere, but often just across the English Channel – for those of us interested in species recording and finding new beasties, they are likely to keep us busy and there will no doubt be further striking exotics hitting the headlines as they appear in fruit shipments and imported houseplants. Meanwhile, the small and less obvious beetles will be making their quiet way from continental Europe...

References

Aitken, A.D. (1975). Insect Travellers. Volume I. Coleoptera. Technical Bulletin 31. Ministry of Agriculture, Fisheries and Food. HMSO, London.

Aitken, A.D. (1984). Insect Travellers, Volume II. MAFF Agricultural Development and Advisory Service Reference Book 437. HMSO, London.

Hinton, H.E. & Corbet, A.S. (1943). Common Insect Pests of Stored Food Products. British Museum (Natural History), London.

Haack, R., Hérard, F., Sun, J., & Turgeon, J. (2010). Managing invasive populations of Asian longhorned beetle and Citrus longhorned beetle: a wWorldwide perspective Annual Review of Entomology, 55 (1), 521-546 DOI: 10.1146/annurev-ento-112408-085427

Parrott, D., Roy, S., Baker, R., Cannon, R., Eyre, D., Hill, M., Wagner, M., Preston, C., Roy, H., Beckmann, B., Copp, G.H., Edmonds, N., Ellis, J., Laing, I., Britton, J.R., Gozlan, R.E. & Mumford, J. (2009). Horizon Scanning For New Invasive Non-native Animal Species in England. Natural England, Sheffield. (Natural England Contract No. SAE03-02-189, Natural England Commissioned Report NECR009).

Thank you to the US Fish & Wildlife Service for putting this image in the public domain. Much appreciated.