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.

Further update on Ichneumonids and sawflies

In February, I posted about hyperparasitic Ichneumonids, and yesterday the story took a further amazing twist.

To summarise, the Ichneumonid I had been following was a hyperparasite, which was targetting the larvae of the primary parasite already inside the sawfly larva. Since then I have been searching for the primary parasite to complete the picture.

Yesterday I found a new Ichneumonid ovipositing in the sawfly larvae, but the ovipositing process was the most bizarre I've ever seen. This is a shot taken from below the leaf:


The Ichneumonid is under the leaf, with her abdomen curled round the edge of the leaf and ovipositing into the larva, which is above the leaf. I've seen these long-abdomened wasps before, but didn't know why the abdomen was so long. Now I know.

Just in case there's any doubt, here's the ovipositor in action:

This shot shows the Ichneumonid leaving the scene after her work was done:

The portion of leaf shown is about 8 cm. long.

You couldn't write a story like this.

More moths

It's still early days in my moth career. Some are fairly easy to identify, but others can be much more troublesome due to:

• variations within species (size, colour, pattern)
  
• similarities between species
• wear
• changes in phenology due to warming

Much of the identification process relies on experience and repeated exposure to conflicting identifications: yesterday I read a post on UKmoths where five experts gave five different suggestions for one worn specimen.

Anyway, here are my recent discoveries, with varying degrees of confidence.

First, Northern Eggar - Lasiocampa quercus f. callunae:

The Northern Eggar/Oak Eggar complex is rather interesting: the life-cycle is either 1 year (mostly southern) or 2 year (Northern/Western), but the intermediate zone (English midlands/Welsh border) has populations that vary between 1 year and two years. I rather suspect we're seeing the intermediate stage of one species becoming two. There are, however, consistent variations in size and pattern between the two subspecies. I've chosen Northern Eggar for this one simply because that's what we have in Ireland, but the rear of the main yellow band is diffuse, which ties in perfectly. It should be noted that these are day-flying moths and can often be confused in flight with larger butterflies, especially Dark Green Fritillary.

Next, Garden Carpet - Xanthorhoe fluctuata. Identification mostly based on the 3 wing patches, the largest of which fades away. Thorax and abdomen colours look good, too.

I'm a bit less confident of this one. Flounced Rustic - Luperina testacea. But I love the common name.

Maybe a bit more confident of this Shaded Broad-bar - Scotopteryx chenopodiata.


All new to me, but I'll wait for the dust to settle before I add them to my species list.

A trip to the seaside

I paid a very brief visit to the coast today, and saw some species that I only find there.

The 6-spot Burnet Moth can be very numerous in grassy areas at the coast. I've seen fields full of them.

Wild Carrot - Daucus carotta - is also a coastal plant, although I do know of one inland riverbank (on limestone) that has some.

Lady's Bedstraw is usually found at the margin between grassy areas and dunes.

Then it rained. Again.

Another Bumblebee parasite

Earlier in the year I showed the Cuckoo Bumblebee Bombus bohemicus, which is parasitic on the bumblebee Bombus lucorum s-l, by taking over the nest and using it to raise its own young.

The Conopid fly Sicus ferrugineus is another parasite on bumblees, but this time the behaviour is a bit more personal. It sits in wait beside a convenient flower:


And then leaps out to staple an egg upwards into the soft abdomen of a passing worker bumblebee. Here's a close-up of the fly, showing the upturned abdomen:

Note how the abdomen curves right round - in almost a full circle - until it's pointing upwards.

And this close-up shows the upward-pointing ovipositor.


Recent studies have indicated that a parasitised bumblebee will change its feeding pattern after the egg has been laid. Perhaps this is to make sure the diet suits the fly rather than the bee.

It's tough out there.

Moths continue

I'm still getting lots of moths coming to my front door lights on any dry(ish) night. My backlog of identifications is growing, but these two seem safe enough. Shout if I'm wrong.

First, Large Yellow Underwing - Noctua pronuba:


And Yellow-barred Brindle - Acasis viretata:

Kit

Ok...here we go...

Set up

My main set up is a Canon EOS 350D with a Canon 60mm USM Macro lens. The effective focal length of the lens is 90mm., due to the 1.5 x multiplier on small-sensor Canon SLRs. This lens gives me the possibility to capture objects 1:1 on the sensor. USM stands for Ultrasonic Motor, which I'll come back to later. This set up isn't exactly compact, but it is handy and delivers the results you've seen since January 2007. Here's a look at it:


Prior to 2007, I used the Fuji s7000 as my main camera, and I loved it dearly. It's certainly easier to use (and it's cheaper), but the images, whilst very good, don't have the wow factor of the DSLR images.

Methodology

All of my shots are hand-held, so I need to set exposure to at least 160th to eliminate handshake. That means I work almost entirely at Shutter priority, leaving the camera to work out aperture. The depth of field (DOF) on a macro lens is very small indeed, so I need as much light as I can when shooting at a relatively high speed, because the aperture will automatically be opened up to compensate for the fast exposure and, sadly, DOF only increases with smaller apertures. I've experimented with different ISO and always shoot at ISO 400: ISO 1600 gets a bit too grainy for me. Depth of field is still, however, very small even at ISO 400. In order to reduce the effect of reduced DOF, I don't go in as close as I can, preferring to stay further away and crop later. The resolution of the sensor (8 megapixel) means I can crop without losing much definition.

I shoot with autofocus when I can, and the USM motor is extremely fast and very accurate. If I have to shoot on manual focus, that is quick and easy, too, with the switch being under my left thumb, on the barrel of the lens. Another good feature of the lens is that it has manual override on autofocus. In other words, I can use autofocus to get in quick and then fine-tune the focus manually without the camera complaining and trying to refocus automatically.

I tend to shoot more frames than I need, but with Digital who cares?

For flash, I just use the built-in flash unit, and it seems to work satisfactorily. I like to soften flash when I can and I usually work with a single layer of tissue paper stuck onto the flash (I just lick it first).

Although the low DOF more or less demands that I get perpendicular to my subject, I try to make sure that the surface I'm shooting (e.g. a moth wing) is also not flat on to the lens. That helps to make sure that the glare doesn't get reflected back to the camera.

For the computer work I use Photoshop CS2, but I keep my post-processing to an absolute minimum, usually just a crop and resize, with perhaps a tiny bit of brightness/contrast fine-tuning. I really believe that getting the shot correct in the camera is the right way to go. I work entirely in .jpg. I have tried RAW, but didn't find the (very slight) increase in quality was worth all the post-processing effort.

In terms of finding material to shoot and making identifications, that would take a book to cover.

But, in summary:

• get to know your environment
• practise by taking lots of shots (they're free)
  
• watch and study trends and movements
• get your hands on the best set of books you can afford
• join a wildlife society

Maybe some time soon I'll discuss my library.