Methodology

It has been suggested (and rightly so) that I don't say very much about the techniques that I employ in order to get some of my shots. Yesterday I managed to get this rare shot of an Ichneumonid ovipositing into fly larvae hidden inside the Knapweed flowerhead:

Ichneumonid ovipositing

Ichneumonid close-up

These shots are very elusive, so it occurred to me that it might be useful to explain what went on before, during, and after the photography session.

Firstly, background information is required. Ichneumonids are parasitic wasps that lay their eggs into the bodies of the larvae of other insects: the most commonly targeted species are flies, moths, butterflies or sawflies. Timing is crucial: if the target larvae are too small, then the egg-laying process will be too difficult, but if the larvae develop too much they might already have pupated, or become too mobile, or even be able to defend themselves.  The timing is also often dictated by the foodplant of the target larva: if the plant isn't in the correct state then the female of the target species won't be able to lay her eggs. So we clearly have (at least) two timing dependencies. This means that the opportunity to take these photographs is severely limited - to perhaps a few days in each year. So in order to plan for this kind of photograph, we have to be aware of the potential timing of these events, and to monitor relevant food-plants at the appropriate time. I noticed that some females were investigating the Knapweed on Saturday, so I planned the photography session for the next day.

The female operates by flying from flower-head to flower-head, quickly testing each one with her antennae. If nothing is detected, she will quickly fly to a nearby flower-head and start to test again. The ovipositor is stored in a sheath that is held behind her, and if she detects a target, she will quickly unsheath the ovipositor and position herself so that she will insert it in the correct direction. This unsheathing and positioning takes less than a second. She then follows the unsheathing with a series of thrusts, each a little deeper, as she reaches the target larva. This thrusting might take two or three seconds: this is the opportunity for the shot. So we have to follow the female from flower to flower and take great care to observe when she appears to be taking a little longer than usual to inspect the flowerhead: this is a sign that she might be about to deploy. That's the clue to get close and be ready to focus. A fast-focussing lens is essential at this point, and I have my focussing system set to a single point. If you are focussing on a scatter system, the lens will have difficulty focussing on the insect and will get distracted by background leaves, stems or flowers. I use a Canon ultrasonic macro lens, which can focus in less than a second: essential for this kind of shot. A quick press of the shutter release when near the subject will prime the lens to be suitably-focussed: it is already nearly in the right position. As soon as she starts the injection, I am already in place with the camera primed and the lens in approximate focus. Then I take repeated shots, perhaps two shots in three seconds, so that I might get five or six opportunities from each injection sequence. Just occasionally, she will make more than one attempt in the same flowerhead - presumably to target further larvae: those are the best opportunities for a shot like this.

Most of the shots are bad: either out of focus or blurred due to hand movement, or obscured by stray, windblown leaves, or the female might have suddenly turned to get a better direction of injection. This photograph took 20 minutes to get, with probably 50 shots that went straight to the recycle folder when I was sorting the photographs later. Fortunately digital shots are cheap, so we can take as many as we like. Another reason for the long time is that the female might well decide that the local area has nothing left for her, and vanish over a hedge. This means that we have to wait for another female to come along. In addition, because we don't want to lose sight of the female, we can't pay too much attention to where our feet are going, so tripping is a frequent hazard, especially with Bramble runners nearby. Finally, when she's finished laying, she will quickly seek another flowerhead. Since we are down and close to the previous flower, we need to quickly refocus our attention to follow her movement. These can all add up to missed opportunities for the shot.

I think I might have achieved perhaps half a dozen good opportunities for a decent shot in those 20 minutes.

One final tip enables us to get that elusive shot: I call it plant-twisting. When the injection is taking place, the female is so focussed on the process that you can hold the plant stem and rotate it for the best angle for the shot without alarming her and scaring her off. (She actually couldn't fly away if she wanted to: she is firmly attached to the plant). That gives us the opportunity to rotate the plant, not only to achieve the best angle, but also to select the best background for the shot. It is no coincidence that the yellow flower at the rear of the shot highlights the ovipositor: I selected that background as I held and rotated the stem.

So all-in-all a very tricky process to get that elusive shot.

It's worth noting here that there are many hundreds - probably thousands - of species of Ichneumonid in the country, each with a unique or severely restricted range of target species. Many of the target species live in places that simply can't be photographed, but there are a few species that use prominent and available plants: these are the ones that present us with photographic opportunities.

To complete the story, the wasp's egg will hatch out, and the wasp larva will eat the host larva. The wasp larva will then pupate and hatch at the appropriate time next year (more synchronisation!). The requirement to fool the host's rejection mechanism ( the egg has to resist rejection when inside the target's body) explains why most parasitic wasps have such a small range of target species: it would be too difficult to trick all the rejection mechanisms. This is analogous to the restricted range of host plants for leaf-miners.

Small gaps

The rain is still more or less continuous, with very short gaps between showers, and I have had to adopt a new tactic for getting some pictures: I watch the sky to the southwest and wait until I see a gap in the weather some 12-15 km away. I then rush out and hope to reach the fringes of town before the gap in the rain reaches me. That means I'm in place when the temporary stop occurs. This is fine for getting photographs of plants and mines, but not so good for insects because it takes them a little while to realise that the rain has stopped and they have warmed up enough to fly to the nectar sources that I'm watching at the moment.

Tufted Vetch is an odd plant: it grows in only a few places on my patch, but wherever it grows it is rampant. There appears to be no similarity amongst the places it chooses and there are places that appear to be ideally suited, but the plant is absent. It must have some very particular micro-climate requirements.

Tufted Vetch

A few more late summer portraits:

Knapweed or Hardheads

Red Bartsia

Devilsbit Scabious

Taphrina alni is a parasitic fungus on female Alder cones:

Taphrina alni gall on Alder

The tongue-shaped growth reaches 4-5 cm. long and turns red before releasing its spores. Note that the growth is caused by the fungus, but is made by the Alder tree for the benefit of the fungus.


Alder is a good food source for Sawflies: these are multiple mines of Acidia cognata. The broad-shouldered larva can be seen in each of the mines:

Mines of the sawfly Acidia cognata on Alder

This next shot shows just how attractive Angelica is for insects at this time of year. I counted 7 ichneumonids, 2 sawflies and 2 dungflies on this flowerhead:

Angelica with Ichneumonids, Sawflies and Dungflies

One of the few Ichneumons that can be identified by sight: Amblyteles armatorius, which is parasitic on larger moths.

Ichneumon Wasp Amblyteles armatorius

Harvestmen are related to spiders, but they don't make a web. They hide instead in plants, waiting for some unsuspecting insect to come wandering along.

Harvestman Mitopus morio on Angelica

I like how the Angelica echoes the shape of the legs.

The social wasps are divided into two main families: Dolichovespula and Vespula. Dolichovespula species (Dolichovespula sylvestris shown) can be readily identified by the 'malar space', which is indicated by the arrow below:

Dolichovespula sylvestris, a Tree Wasp

The malar space is the distance between the lower edge of the eye and the upper edge of the mobile mandible, or jaw. In Dolichovespula sp., the gap is large, making the face very elongated, whilst in Vespula sp., the gap is virtually non-existent. Most of the wasps that can be seen moving leisurely over Angelica at the moment, including the one above, are males.

The Potato Capsid, Closterotomus norwegicus, is commonly found on Knapweed and other composite flowers. I have never found it on potato:

Potato Capsid on Knapweed

Late purple

Three late flowers from high bog fringes:

Devilsbit Scabious:


Marsh Thistle:



And Knapweed:


I wonder if it's a coincidence that they're all purple.

The urge to reproduce

I never cease to be amazed at the attempts of disadvantaged plants to reproduce. This tiny (5 cm. tall) Knapweed had managed to produce viable flowers despite having seeded in the middle of a road.


This Willow had been damaged much earlier in the year, and the new shoot has a catkin on the end of it:


I suppose the urge to make offspring is an essential part of the make-up of any successful species.

This blue Sawfly is quite numerous at the moment. The curved antennae - somewhat reminscent of horns - are quite distinctive.

Murder most foul

I've been stalking a female ichneumonid laying eggs in larvae inside Knapweed seedheads for a couple of days.

First, she explores the seedheads to find one that is occuped - usually by fly larvae, such as picture-wing flies:

Then she flips the ovipositor out of its sheath (note that the sheath splits along its length):


Then we have the repeated act of positioning the ovipositor and laying the egg:


This process is carried out for a minute or so, then she moves on to explore other flower heads.

I stapled together a few photographs of the process into a video of sorts:




Here's a different species exploring Creeping Thistle:


The fungal season has started, so I'll be making some trips to older woodland very soon. This is what I've always known as Bolbitius vitellinus, but I seem to remember its name changed in the last year or two.

Another new micromoth: Acleris emargana, which is a feeder on Salix sp.

Identification updated 13/9/2011

Gap in the rain

During my searches for specimens to photograph, I begin to notice subtle things that would normally not be seen. A number of fly and moth larvae live inside the seedheads of flowers such as Knapweed, or Hardheads. This is a good place to hide, since there is a ready supply of food and the larvae are protected from the weather and from most predators or parasites. Notice the word 'most': I have found carnivorous beetle nymphs inside these seedheads and, of course, the relevant ichneumonids are equipped with long ovipositors that can reach inside the deepest seedheads. I like to find out which larvae are living inside the seedheads, and the best way to find out is to open them. But, of course, I have lots of failures: many seedheads are empty.

I have noticed, though, that there appears to be an external sign of the presence of some of the inhabitants. The first picture shows a 'normal' seedhead. Notice the shape and thickness of the stem as it approaches the seedhead:

This is another seedhead, where the stem is noticeably thicker (to my eyes). I know the difference is subtle, but I can detect it very clearly in the field:

Experiments have shown that the thicker ones are usually occupied, and the thinner ones are not, so I broke open the two shown above. The thin one was unoccupied, and the thicker one had a few larvae of Tephritid (Picture wing) Flies. Not conclusive, but it's just a trend, and it saves me from bursting open dozens of potentially empty seedheads. Of course, this makes me wonder why this should be, and I suppose I wouldn't be too surprised to find that the fly larvae have some effect on the formation of the seedhead which is beneficial to them. Perhaps something like making the seeds slightly further apart, to make movement easier?

It's seed time, and I wonder if anyone else sees skeletal hands in these empty seedheads of Cow Parsley.


My survey and study of the Nematus pavidus sawfly larvae continues. This almost-mature larva is moving between leaves, having polished off the lower one. The sun was directly behind the shot, hence the glare.

Incidentally, the picture shows one absolute and one subjective feature that separate sawfly larvae from lepidopterous (moth and butterfly) ones. The number of prolegs (the stumpy ones at the rear) is 6 (the anal claspers count, too). So this is certainly a sawfly larva, since 6 or more prolegs are indicative of the sawfly. Subjectively, I can see that the larva has a round-shouldered appearance: another feature of many sawfly larvae.

Does anyone else remember these?