Little wings of desire

One of the joys of having a patch of wildlife garden, even if it is small like ours, is sitting in the sun and watching the species that visit it. Often they are familiar - our pond attracts damselflies and dragoflies, and we try to include a wide range of pollinator-friendly plants for bees and hoverflies, but sometimes something a little different appears. In this case a little flicker of movement caught my eye and I looked closer to see two small flies waving their wings at each other. The wings had dark patterns of blotches and lines and I recognised them as being in the family Tephritidae. This family has no common name as such, but they are sometimes considered to be 'fruit flies' in the broad sense, and are also included in the informal grouping known as 'picture-winged flies'. A little more research in Smit (2010) and White (1988) confirmed the species as Tephritis neesii, which is common on Leucanthemum (e.g. ox-eye daisies as here) in southern England, where I live. So, nothing unusual as such, but I'd not seen it before; I did wonder if the 'dance' was a form of competition between males, but it is actually a male-female mating display.

Pair of Tephritis neesii during their mating dance.

It also turns out that in some tephritids, the form of the dance can indicate the genus of the fly - Tephritis such as these hold their wings flat and open/close them alternately; Urophora open/close them simultaneously while rocking from side to side; Chaetorella hold their wings sideways with the edge pointing up, then shake them. Males do fight, but it is less elegant - there was a third fly just out of shot that buzzed one of the pair later on. Though my photo shows the wing pattern quite clearly (it's the same in males and females), a video shows the dance itself, so here's one that's been kindly posted on YouTube:



References

Smit, J.T. (2010). De Nederlandse boorvliegen (Tephritidae). Entomologische Tabellen. Supplement bij Nederlandse Faunistische Mededelingen, 5: 1–159. [In Dutch]
White, I.M. (1988). Tephritid flies. Diptera: Tephritidae. Handbooks for the Identification of British Insects 10(5a): 1–134.

In spring the pond goes sproing

After a long, cold early spring, the last couple of weeks have been warm, dry and sunny - and the season has leapt at the opportunity. Butterflies are flying, birds are nest-building, bees are pollinating. All good things. As a microcosm of this rapid seasonal burst of activity the denizens of our garden pond have been distracting me from computer-based tapping and drawing me out to sit by and watch, camera in hand. Our pond's not huge, but a lot of care was taken to ensure variety of structure (and thus habitat) - here are a few of the occupants taking advantage of it.

The fly Elgiva cucularia. It is a member of the family Sciomyzidae that specialise in hunting snails - of which we have plenty. This species is associated with boggy conditions and I have recorded it several times on our pond vegetation, so the shallow, algae filled section is clearly doing its job.

A Large Red Damselfly Pyrrhosoma nymphula posing obligingly on my finger.

One of at least six smooth newts living in our pond. This shot was taken with a waterproof endoscope which I'm still new at using.

Some of this year's batch of frogspawn.

Two pond snails busily engaged in making more snails. The whitish structure top-right is indeed a snail penis AKA 'love-dart'.

Unexpected egg-flies

Back in January, my wife showed me a blackbird egg she'd found in the garden. It looked whole, but was incredibly fragile and broke almost as soon as I picked it up, clearly already being cracked. I expected maybe a whiff of something nasty, but there was more going on than I expected...

Inside the egg... lots of invertebrate action.

Naturally, instead of saying 'yuk' and throwing it away, I had a closer look. The orange inveretebrates are mostly fly pupae plus a few larvae. The black shapes are pupal skins of something already emerged, and the large larva in the middle something else entirely. A quick look in Smith (1989) jogged my memory that the smaller ones were probably juveniles of the Psychodidae, also known as moth-flies or owl-midges. The larvae of many species are associated with decaying organic matter, so the inside of a failed egg is a plausible hiding/feeding place whether the goo insode is egg material or something else that had seeped in. Beyond that I couldn't tell, so I put them in a hatchery and waited. After not too many days this is what I found...

Pupae, pupal cases and adults of a psychodid fly.

In total there were 15 pupae and these soon started to emerge as adults. The small size, their shape, and their hairy/feathery wings mean they don't look like typical flies, but that is exactly what they are - as you can see below, they have a single pair of wings, the other pair reduced to drumstick-shaped balance-organs (halteres). Psychodidae are not an easy group to work on (especially if you are not that familiar with them), and identifiying the flies to genus, let alone species, would require time, a microscope, and a copy of Withers (1989). I won't go through all the steps, but here are a few key features:

There are two veins (dashed lines) between the two main forks in the wing veins (circled).

The arrow indicates the eye-bar - an extension of the eye above the antenna. The circle indicates the pale haltere mentioned earlier - yes, these realy are flies!

 The antennae are an important feature too, but take care when keying out genera and species...

The key asks whether the antennal segments are barrel-shaped or have an elongated stalk. These look barrel-shaped but...

...if you remove a segment you can see that the barrel-shape in this case is formed of hairs that hide the real shape - the dark segment clearly has a stalk.

So, after quite a bit of deliberation, this keyed out as the genus Psychoda. I'm less certain about the species (not only can they be difficult to separate, but the taxonomy of Psychoda needs to be revised), but it might be P. alternata (the stripy larva in the first photo matches this, as does the foul habitat). Withers (1989) doesn't list Hampshire for this species, but the Psychodidae are under-recorded, and he does mentioned Wiltshire and Sussex, so it wouldn't be a surprise. That's enough for now - I shall leave you with some more juveniles, feeding/hiding merrily in the goo...

Psychoda - three pupae (complete with a pair of pupal horns for breathing) and a larva.

References

Smith, K.G.V. (1989). An Introduction to the Immature Stages of British Flies. Handbooks for the Identification of British Insects 10(14): 1-280.
Withers, P. (1989). Moth Flies. Diptera: Psychodiae. Dipterists Digest 4: 1-83.

Long-legged lovers from lakeside leaves

After holidays, after the backlog of work I returned to... it's time for flies - in particular the genus Dolichopus in the family Dolichopodidae (long-legged flies). As well as long legs, most male 'dolis' have very large genitalia, but a post title focusing on that feature might reach the wrong audience... Anyhow, I was watching what I think is D. popularis (there are several similar species in the genus) when I noticed courtship behaviour - so, out came the camera to document a romantic photo-story...

A single Dolichopus

Two males court one female (on the left)

One male is driven off, the other courts the female by standing on long legs over her and rapidly beating his wings.

He tried to mate but was rebuffed (he would dart behind her, but she moved away and turned round), so back to the courting.

This time his efforts were sufficient and the female permits mating.

Female post-mating.

Male post-mating - the large structure bent down from the rear of the abdomen is his genitalia.

Male post-mating.

Orange agents of decay

While checking a bee-log in our garden, I noticed one of the holes had a dead fly in it. I removed it and was about the throw it away when I saw tiny orange dots on the surface. Because I am a nosy ecologist I put it under the microscope to see if there was anything interesting going on, and saw what looked like a microfungus growing out of the joints and bristle-bases of the fly.

Fly (possibly in the family Muscidae) with orange fungal growths.

There are some very interesting fungi that parasitise insects and I've written about one of them before. However, this looks different - maybe something simply using an already-dead fly as a substrate.

Fungal growths showing the thin threads of hyphae between the orange fruiting bodies.

Fungal fruiting bodies at the bases of the fly's bristles.

The fungal structure is clear - hyphae and fruiting bodies - but with most microfungi, it is necessary to look at the spores, so I made a slide and zoomed in.

Fungal spores x100

The spores are clearly visible as slightly curved spindles, each split into several sections by cross-walls (septae). However, though a mycologist would probably know this fungus by sight, I couldn't find anything that matched it, so sent my pictures to the British Mycological Society's facebook group. It didn't take long for one of the BMS to tell me that this was a species of Fusarium. This at least explained why I hadn't worked out what it was - most Fusarium species are soil fungi involved in decomposition of dead organic matter but I hadn't been looking at soil-dwelling species. If so, the fungus was simply decomposing the fly - which is what it does, and very usefully too; no soil decomposers = dead soil. However, some Fusarium are insect (and plant) pathogens, so it could have killed the fly before decomposing it.

Fusarium are varied, diverse (in terms of both species and strains) and not all well understood or taxonomically clear, though some cause plant diseases and others can infect humans, while one is the main ingredient in Quorn! So, the identification stops at genus on this occasion, but has introduced me to a fungus that, although I'd heard of it, and it may be growing all around us in the ground, I've never stopped to look at before. Thanks BMS!

Syrphid detail

Sometimes I have to hunt for specimens, sometimes specimens come to me - in this case the hoverfly (family Syrphidae) Helophilus pendulus - a common species, often seen in our garden, in this case found recently dead on a windowsill. It could have been swept into the bin, but not before treating it as an opportunity to look at external hoverfly anatomy in the following series of annotated images.

Helophilus pendulus, dorsal view - note the strong, almost semi-circular, loop in wing-vein R4+5 (about a quarter of the way in from the wing-tip), characteristic of the hoverfly Tribe Eristalini. The pattern shows that the species (and genus) is a wasp-mimic. The fainter 'false vein' or vena spuria can be seen running much of the length of the wing (approximately in the middle) and is only found in hoverflies.

Helophilus pendulus, front view - the 'face' is clearly seen with its dark vertical stripe in the centre, running across two protrusions - (1) the 'knob' and (2) the 'lip' above a strong indentation.

Underside of the abdomen showing the hind legs most clearly - the hind tibia is at least half pale in H. pendulus as shown by the red bar.

The black-and-white pattern of the thorax is visible here as well as the fine bristles around the compound eyes (note the row of four relatively large dark bristled pores just behind the centre of the rear margin of the eye) and the ocelli (simple eyes) on the top of the head (red arrow).

Dorsal view. The red arrow indicates the semicircular protrusion ('scutellum') behind the thorax which covers (and presumably protects) the upper rear of the thorax and delicate membranes between that and the abdomen. The short bar top-left indicates the yellow 'gap' between the characteristic black abdominal markings and the rear of the segment.

As in all true flies (Diptera), the 2nd pair of wings is reduced to a small drumstick-like 'haltere' which has a counterbalancing/gyroscopic function beating the opposite way to the wings in flight.

The large posterior spiracle (red arrow) near the base of each wing - used for breathing along with the anterior spiracle found just above the base of each front leg, just behind the head.

One of the 'feet' - the 5th (of 5) tarsal segments is shown by the red bar - there are two claws (solid arrow), each curving past a gripping pad (broken arrow).

At the base of the wing there are various tufts of hairs which help cover the various joints between body plates etc and prevent material getting in which might cause damage or interfere with movement.

The front of the 'face' - the central vertical stripe ends at the 'lip' above a deep indentation.

The antennae are short and consist of three segments (numbered here) - the 3rd is expanded and bears a long sensory bristle called the 'arista'.

The lenses of the compound eye.

The extended mouthparts which form a three-segmented sucking/licking structure including sensory apparatus (e.g. for testing potential food), muscular pumps and so on. Liquid food is taken - dried nectar or pollen must be dissolved/suspended in saliva before it can be consumed.

There is of course more that could be covered here (and I may expand some parts with more detail in future posts), even without dissection, but if you want to know more, the following are books I regularly use:

• Rotheray, G.E. & Gilbert, F. (2011). The Natural History of Hoverflies. Forrest Text, Cardigan. Does what it says on the cover. More morphological detail/images would be useful, but still good coverage of natural history.
• Stubbs, A.E. & Falk, S.J. (2002). British Hoverflies. BENHS, Reading. Keys to adults of British species, many plates, including dissections of genitalia, detailed species accounts, and useful background information.

Enjoy!

Mites that hitchhike

While I was leading a community wildlife walk across some cattle-grazed water-meadows yesterday, one of the younger members in the group used his youthful sharp vision to spot a small dung beetle (Aphodius fimetarius) which looked a little unusual with what appeared to be tiny bumps on the elytra. Although some sort of deformation is presumably possible, the 'bumps' were (as suspected) phoretic mites of the genus Macrocheles. 'Phoretic' means they practice 'phoresy' i.e. use other species as transport rather than feeding on them as a parasite might.

Aphodius fimetarius with phoretic mites on the pronotum and elytra. 1 square = 5mm.

Aphodius fimetarius with phoretic mites on the underside, especially of the abdomen. 1 square = 5mm.

On this occasion I haven't taken microscope photos of the mites as I don't intend to identify them beyond genus. Although these mites are possibly more familiar from larger dung beetles, research in France (Glida & Bertrand, 2002) suggests that, as they are active all year, Aphodius are important in distributing and establishing populations of Macrocheles mites because these beetles are active throughout the whole year, including cold periods. At least some Macrocheles species are predatory on fly larvae (and some are phoretic on adult flies), hence being moved between manure piles/cowpats presumably delivers them safely to new hunting grounds. Also, although the beetle presumably bears some burden in carrying sometimes large numbers of mites, there may be a trade-off if the mites reduce the populations of dung-feeding fly larvae and therefore increase the amount of dung available to their dung beetle hosts. I'm sure there's a potential experiment in there somewhere...

Reference

Glida, H. & Bertrand, M. (2002). The occurrence of Macrocheles mites (Acari: Macrochelidae) in relation to the activity of dung beetles: a field study in Southern France. In: Bernini, F., Nannelli, R., Nuzzaci, G. & de Lillo, E. (eds.). Acarid Phylogeny and Evolution: Adaptation in Mites and Ticks. Proceedings of the IV Symposium of the European Association of Acarologists, pp. 199-207.

Insect slaves in a fungal nation II

I've written about the fly-killing fungus Entomophthora muscae before, way back near the start of the Ecology Spot. In that post I covered the behavioural changes it causes, and a bit about how the fungus does this (or rather, how little we understand this). I don't want to repeat it here (it's all in the original post), but when I found another yellow dung-fly (Scatophaga stercoraria) infected with E. muscae, (well, certainly this fungal genus, and E. muscae is by far the most likely) this time in our garden, I felt an update was in order.

A dead yellow dung-fly Scatophaga stercoraria infected by Entomophthora muscae. Note the typical posture adopted shortly prior to death - head down, abdomen up, wings spread - this maximises the spread of fungal spores.

With the Harvard research programme (looking at how the fungus infects hosts and changes behaviour) having closed, it does not seem that this thread is being actively pursued at present (if this isn't the case, please do let me know and I'll update this post). There has however been recent work looking at the evolutionary history of the fungus (e.g. Gryganskyi et al. 2013) and taxonomic research by Humber (2012) raises the group to full phylum status.

More on this fascinating, if often overlooked, fungus undoubtedly to come...


References


Gryganskyi, A.P., Humber, R.A., Smith, M.E., Hodge, K., Huang, B., Voigt, K. & Vilgalys, R. (2013). Phylogenetic lineages in Entomophthoromycota. Persoonia 30: 94 -105.

Humber, R.A. (2012). Entomophthoromycota: a new phylum and reclassification for entomophthoroid fungi. Mycotaxon 120: 477-492.

Murk-dwelling bottom-breathers

I've posted about our garden pond before, but may not have mentioned that off to one side of it is an old stone fountain-top which has been plugged to provent leaking. Having no outflow unless there is heavy rain and it spills over, this means it becomes stagnant with leaves and other organic matter accumulating. The temptation might be to clean this out and add clean water, but no, it is there for a reason - habitat for larvae that are adapted for such conditions. An example of this is the rat-tailed maggot, the larva of hoverflies in the genus Eristalis, in particular E. tenax, and others such as the sun-flies Helophilus sp., plus Sericomyia, Mallota, Anasimyia and Myathropa. As adults, Eristalis are are excellent honey-bee mimics (hence the common name of 'drone-flies'), but their larvae, like those of the other genera listed, are very different. The most obvious feature is the long, telescopic posterior breathing tube - essential when living in stagnant, low-oxygen water among decaying vegetation.

Rat-tailed maggot, the larva of Eristalis sp. (probably E. tenax), approx. 10mm long excluding 'tail'.

This is a young larva - my identification is a little tentative as I can't see the key features yet, but the timing is right as E. tenax were frequenting the water long enough ago for eggs to now have hatched, whereas although there are Helophilus pendulus as well, they have only just started breeding activity as far as I can tell; I will be able to confirm their identity when they are more fully developed. They are filter-feeders and some of the gut contents are visible here, as are the well-developed prolegs.

Rat-tailed maggots showing how their breathing tubes are used.

The white section of the tube forms a sheath made from one extended segment and contains complex musculature used to extend and retract the breathing tube, as well as protecting it (the tip of the tube can be seen as a short white-tipped dark segment). The larvae can also swim slowly by undulating the body and tube. They may not be the most attractive creatures, but I do think they are interesting, and they are of evolutionary interest as these larval forms appeared quite recently in hoverfly evolutionary history (Rotheray, 1993), not to mention their role in consuming waste organic material. They do of course also develop into adults - the dronefly mentioned above, which has a role in pollination, so a valuable species too.

Eristalis adult on Buddleia davidii

Reference

Rotheray, G.E. (1993). Colour guide to hoverfly larvae (Diptera, Syrphidae). Dipterists Digest 9: 1-156.

Hey hey, it's the end of May

After a long, cold spring, I've been watching all kinds of habitats and species wake up and get 2013 moving, including our garden pond. To celebrate this, I'm going with a non-technical post today, just enjoying what can be seen with a bit of careful design and construction, and a bit of patience in a small-to-medium urban back garden...

A portrait of the hoverfly Heliophilus pendulus basking on a pond plant

A small hoverfly (I haven't identified it yet) feeding on a buttercup (Rancunculus repens) by the pond edge.

A smooth newt gulping air.

Nymph of large red damselfly.

And that's it for me today - enjoy the sunshine, enjoy the wildlife and happy ecology! Back with something more technical in a few days...

Ye olde bee log

A couple of years ago (how time flies...) I wrote about the diversity of bees in our garden, including an image of Osmia rufa (the red mason bee) using a log that I had attached to our garden fence. Since then, I've made a rather more sophisticated insect hotel including new bee-blocks and have been following the development of bee diversity in our garden as the various features mature and are added to. In the meantime, the old log had become very rotten with little activity noted around it last summer, and so I decided it was time to take it down and see what was inside.

Old bee-log showing extensive fungal decay and woodworm activity.

The outsides had been heavily arracked by woodworm and many holes and crevices had suffered fungal decay with tufts of white mould clearly visible. Onto the deadwood pile with those bits... Splitting the core open provided more interesting features however.

Empty O. rufa cocoons, one in situ in the hole drilled when making the bee-log, the other removed to show the thin papery texture.

The remains of the walls/plus separating cells which are arranged in sequence along a hole.

A view through two O. rufa cocoons - because they are arranged along a hole, the outermost one must leave first, the next then passing through its cocoon to emerge.

The remains of a cocoon including frass (insect faeces), presuambly from the insect before the cocoon was formed.

These are simple enough observations but rarely seen as logs need to be split open to view them - this is of course destructive and is only being done here because the log was past its 'sell by' date given the amount of decay and lack of activity last year. The life cycle of O. rufa is well documented (e.g. here) so rather than repeat this, I simply want to show which aspects of it are readily visible with a little careful effort. For example, although not photographed, a number of holes contained mouldy yellowish masses - pollen stores created by females for their young, but which were uneaten and subsequently began to decay, presumably as the young did not develop for whatever reason (it was a cold, wet summer in 2012 which can not have helped). Others showed mere traces of pollen storage, suggesting successful emergence. Also, as holes in logs are useful shelter for other species, it wasn't too surprising to find evidence of use by insects other than O. rufa.

Smaller pupal cases inside the bee log

One of these non-Osmia rufa pupal cases removed and magnified, approx 6mm long. The red line follows the split where the insect (whatever it may be) emerged; the green arrows indicate a pair of short posterior processes (breathing tubes) typical of many fly pupae.

Beyond determining that it is a fly, I can tell no more about this species - it might be parasitic, it might simply be using a handy hole for pupation with no other link to O. rufa. However, among the various debris and evidence of O. rufa long since left, I did find one intact bee cocoon.

The one remaining O. rufa cocoon, approx 11mm long blocked in by a number of soil and wood particles.

A small female O. rufa emerging from the cocoon.

The small 'prongs' or 'tampers' (one indicated by a red arrow) on the face of the female O. rufa, used to push mud into place when sealing a hole, although they are under-developed in this specimen.

I must say I was surprised to find an intact cocoon and initially thought it was one that had failed to emerge last year. However, in the warmth of my study I noticed some movement and a bee began to emerge. Its movements were rather feeble so a helping hand (well, pin) was used to pull off part of the cocoon. The female that emerged did not move strongly and was very small with (to me) under-developed facial prongs - possibly a poorly developed specimen from last year's poor summer which had managed to hibernate successfully. She has now been released on the bee-hotel - hopefully there will be a emergence of plenty more from the many plugged holes in the newer logs.