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.

Serendipity

My photography sessions are dominated mostly by the weather, and even when the weather is half-reasonable I can still struggle to get half a dozen decent shots. Sometimes, however, everything clicks and I manage to get a good range of illustrative images.

Scaeva pyrastri is a hoverfly that can be readily identified by the abdominal markings: they are paler than most species and the inner part of the curve is further forward than the outer part. In this shot, you can also see the hairy eyes, which separate it from other similar species.

Scaeva pyrastri hoverfly

Scaeva pyrastri is thought to be immigrant from mainland Europe, and I know that there has been a mass migration of moths to Ireland in the past couple of days, so this hoverfly has almost certainly flown from France to breed here. (The brown hoverfly at top left is Eristalis pertinax).

Eristalis intricarius is one of our best bumblebee-mimicking hoverflies:

The bumblebee mimicking hoverfly Eristalis intricarius

That yellow/orange 'band' is very convincing in life, but when you see it close-up, it's clearly just a scutellum with longer than usual hairs.

And just as I was standing up from taking that shot, I saw the very bumblebee that it is mimicking:

Bombus lucorum (agg) (right) and Bombus pascuorum (left, both workers)

That's a nice shot of two of my 6 local bumblebee species.

Helophilus pendulus is perhaps the most common single species of hoverfly on the patch at the moment. I know that there are a few related (but rarer) species that might be around, so I examine each specimen very carefully just in case. Today I got that 'eureka' moment as I found this male Helophilus hybridus:

Helophilus hybridus (male)

Helophilus hybridus larvae are associated with black mud where Bulrush is present, and the adults don't disperse very far. There is a stand of Bulrush about 300m. from where this shot was taken.

Here's an archive shot of Helophilus pendulus for comparison:

Helophilus pendulus (archive)

Notice that the yellow abdominal markings are quite different, and the rear legs are yellow only at the 'knee' in hybridus, but the yellow is extensive on pendulus.

The larvae of some fly and micromoth species feed on the seeds of composite flowers such as Knapweed. The seeds are an excellent food source, and the larvae can feed inside the undeveloped seedheads in relative safety.

Notice the word 'relative'; some parasitic wasps are aware that there are larvae inside the flowerhead, and at the appropriate time (now) we can see the Ichneumonids searching the unopened flowerheads. When a larva is detected, the ovipositor is deployed and we see the drilling operation that takes place:

Ichneumonid ovipositing in larvae inside the Knapweed flowerhead

The eggs are deposited inside the body of the hidden larva and will remain there until the larva has reached full size. At this time (or soon after the larva has pupated) the ichneumonid egg hatches out and the ichneumonid larva eats the host before pupating inside the husk. This egg-laying process can be seen in perhaps three days per year.

Here's an unusual shot of the process from the rear:

Ichneumonid ovipositing

A few days ago, I showed a picture of a very atypical Square-spot Rustic. Here's one that looks as if it has read the book and followed the rules:

Square-spot Rustic

Here's a link to the original post, for comparison.

It's all interrelated

It's a bit early in the year for the fungal part of my brain to kick into action, but occasional summer specimens can stimulate the old grey matter.

This is Panaeolus ater, which is 'hygrophanous': it changes colour according to whether it is wet or dry. The dry weather has put it into this (very) dry state:

Panaeolus species are relatively easy to identify to family due to the mottled gills:

The larvae of many fly species eat the mushroom fruit-bodies, often consuming them to destruction, and you can be sure that if there are fly larvae around, then an ichneumonid won't be far behind them. This minute one was prospecting the outside of the caps, so I suppose it can detect them from there without having to go down and search each gill individually.
The timing of this parasitisation is critical: the mushroom fruitbody will only be there for a few days during which the fly larva must progress from egg to pupation. So the ichneumonid must locate the fly larva (and the mushroom!) during that very short time. That's at least a quadruple dependency: the ichneumonid depends on the fly larva which depends on the mushroom which depends on its host (usually a plant, dung or wood). And, of course, the host will have its own set of criteria for being there....

Staying with ichneumonids, this one is very numerous at the moment as it runs over and under leaves looking for caterpillars:

Bang on time

I was thinking it was time to see the summer butterflies and, sure enough, I found Meadow Brown, Ringlet, 2nd generation Speckled Wood and 2nd generation Green-veined White all within a minute of each other.

The Meadow Brown is a grass feeder, but it frequently basks on higher plants:

The Ringlet is also a grass feeder. This shot shows where it gets its name from:

That brings the number of butterfly species on this short (80 m.) section of hedgerow to 7 for this year:

• Green-veined White
• Speckled Wood
• Orange Tip
• Small Copper
• Meadow Brown
• Ringlet
• Small Heath

There's still time for Small Tortoiseshell, Peacock, Painted Lady and Red Admiral, all of which have been spotted here before. Green Hairstreak is also a slight possibility.

I have found this Bramble-eating sawfly larva for a couple of years, now. I'm still working on an id:

The first of the Ichneumonids with the longer ovipositors have started to appear. These lay eggs into moth or fly larvae in grass seedheads or in composite flowerheads such as Thistle or Knapweed. They tend to feed for a couple of days before I see them laying, so I expect to get some oviposition shots by next week. The very long rear legs on this one suggest something close to Lissonota sp., which use the long legs to keep the abdomen clear of the seedhead when swinging the ovipositor into position on grasses.

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

Bad light

Even when it isn't raining at the moment, any light that we do get is horrible, but we do what we can.

The Angelica is currently covered with insects of all kinds. Most are nectaring, but a few of them use the nectaring insects as a source of their own food in a similar way that crocodiles and lions use watering-holes as prime feeding ground.


The above shot shows:

A) Ichneumonids
B) Tenthredo sp. Sawfly
C) Ectemnius Wasp
D) Tree Wasp

This nectaring Ichneumonid poses a bit of a problem. I've seen this upward-curved ovipositor a few times, but I can't really work out the purpose of that curve. Maybe it reverses into a hole and lays its egg backwards?


Sometimes you see something and you intuitively know it's new. This Leafhopper was a bit larger than the usual ones and slightly more rounded. A quick check through the references reveals that it's Aphrophora alni, and is new to me.


Similarly, this hoverfly shouted "I'm new, too", and I managed to get a few shots before it flew off. It's certainly a Melangyna sp., but that's as close as we can get without capturing it.


These are scarce at the best of times: the larvae are specialist eaters of specific aphids.

That time of year

Specimens of this wonderful 20mm Ichneumonid have been flying hard and fast under the ferns for the past few days. This one was kind enough to give me a look. Maybe a male.


Two new micromoths. First Endothenia quadrimaculana, which is a localised species due to its dependence on Marsh Woundwort as the larval foodplant.


And a frequent species which was 'recently' introduced: Blastobasis adustella.


I suppose we're sliding down into the fungal part of the season. This is the puffball Vascellum pratense. New to me, and interestingly found in two completely separate locations on the same day.

If at first you don't succeed...

The Lissonota sp. ichneumonids have started to lay their eggs in unsuspecting moth larvae hidden inside grass seedheads. I've been following these for a week, now, and yesterday I was rewarded with a couple of shots of the egg-laying taking place:

Notice the antennae being used to pinpoint (ouch!) the location of the larva.


This shot shows the ovipositor at the moment it was being retracted. It's finer than a human hair.


This shot appears to be of a male (of a completely different species):

Staying with parasitic insects, these two Tachinids were on adjacent Bramble leaves. It looks as if they were pointedly ignoring each other. I see a great many Tachinids, and this shows just how many larvae of moths and butterflies are parasitised each year.

Some leaf-miners are very easily identified as such. This is Agromyza filipendulae, on Meadowsweet.


But the mines of Phyllonorycter species can easily be overlooked. This is Phyllonorycter rajella, on Alder. The pupa is only 2mm long, so the adult moth will never be recognised as such in flight.


That's the year half over, and it was only just new year.

Ichneumon time

This Ichneumonid was examining every grass seed looking for moth larvae. She didn't appear to find any, because no laying was noticed. Still...there's always tomorrow. For her, and for me.




Notice the antenna wrapped right round the seedhead in this shot:

Hunter hunted

I watched this red ant walking over the Dandelion flowerhead:


Then it suddenly nose-dived deeper into the flowers.


After a few seconds a tiny Ichneumonid appeared, with the ant holding onto its rear leg. A brief struggle ensued and the wasp made off, apparently none the worse for its experience.


The Ichneumonid was probably looking for moth larvae deep in the petals, but the parasite got more than it bargained for. No matter what you are in wildlife terms, you're either food for something or feeding on something else.

Updates

I have occasionally been relating the story of the Nematus pavidus larvae and their primary and secondary parasites. The latest post is here.

I have now been told that the ichneumonid that is ovipositing from under the leaf is one of the Ctenopelmatinae, possibly one of the Campodorus sp., which have been reared from Nematus sp. larvae.

The under-the-leaf oviposition technique is not in the literature, so this might be one of the first times it has been observed, and certainly the first time it has been recorded. One reasonable theory is that the larvae are very aggressive with their defence reflex (a sudden whipping of the rear of the body, pulling it up into the characteristic 'S' shape), so the Campodorus is actually protecting itself from the Nematus larva's protection reflex. This ties in nicely with the observation that the secondary parasite checks for the presence/absence of this response before it lays its own eggs from a straddle position. I suspect that the Campodorus egg subdues the Nematus larva to some extent (but why? Certainly, it differentiates an already parasitised larva from a clean one, thereby avoiding duplicate [and therefore wasteful] primary parasitisation, but it also makes it easier for the secondary parasite to detect the primary parasite and lay its own egg. A double-edged sword. )

Moving on to the Entoloma from Ards forest: it appears to be Entoloma serrulatum. These are the spores:


Magnification is 400x, the spores are mounted in water and the individual spores are around 10 microns long.

More Ichneumonids

Ichneumonids are parasitic wasps which lay their eggs directly into the larvae of butterflies, moths, flies and sawflies, although some are hyperparasites (laying their eggs into the larvae of primary parasites), and a few are paraparasites ( laying their eggs into the larvae of hyperparasites). The host is always eventually killed by the parasite, usually in the pupal phase. Most Ichneumonids lay a single egg in each host, although some lay multiple eggs, and there are over 1750 different species in UK and Ireland, ranging from 2-3mm up to the largest at 8cm long. Due to the fact that the various different families converge on a very small number of colour patterns, identification is very complex and always requires trapping, killing and microscopic investigation. There are very few people who have embarked upon the years of study required to investigate this group, so they are relatively poorly understood. If I had a spare life I would certainly give them a go, because I find them absolutely fascinating. Their form varies enormously, although they all have long antennae and a very narrow 'waist' between the thorax and the abdomen. The nature of the host can usually be determined by looking at various characteristics of the parasite: size, length of legs, length of ovipositor.

I photographed this beauty last night:

Based on the size (3 cm. from nose to tail) alone, this one requires a very large host, and it will almost certainly parasitise one of the larger moths, such as the Drinker or Northern Eggar. The larva of the Elephant Hawk Moth is parasitised by the similarly-sized black and white Ichneumon Amblyjoppa proteus. [http://homepage.eircom.net/~hedgerow14/may30.htm shows the emergence sequence]

The next is a Macrocentrus sp., and the structure of the body is very carefully arranged: she has massively long antennae, very long rear legs and a very long ovipositor. These lay their eggs into fly and moth larvae hidden deep inside the seedheads of Thistles and Knapweed. The long legs are required to give her body enough clearance to spin the ovipositor 180 degrees towards her antennae.


You can see an action shot here.

This next one is smaller, and has short legs and a medium-length ovipositor. I suppose this will be parasitic on a small larva which is exposed on the surface, rather than hidden in a seedhead.


The configuration of this one bothered me for a while. It has extraordinarily long antennae, long legs and no visible ovipositor. So what could possibly be the reason for such a shape?

(hint, wasp males usually have long antennae, and male ichneumonids are rare).

Just to complete the story from yesterday, here is the larva of the Sawfly Nematus pavidus, with its body curled in the usual defensive posture.