Wednesday 25 September 2013

Alopecosa barbipes (Sundevall, 1833)

Have I mentioned lately that I'm really quite fond of spiders?

Alopecosa barbipes, Kingley Vale, West Sussex, UK
On Kingley Vale, West Sussex, UK, March 2013. Photographed using the same-old-same-old of Olympus E-420 with Zuiko 40-150mm lens and three KOOD magnifiers.
This charming little fox spider - one of four similar species resident to the UK - is fairly limited in its habitat preferences to chalk downland and heath.

Which brings us to our discussion for the day.

The monstrosity which is managed heathland. 

Heathland, for those who don't know, is an ecologically interesting slow-transitional phase vegetation assemblage naturally occurring in areas where fire and the resultant changes to the soil have eradicated the dominant assemblage.

Which is to say, it turns up after fire has killed the trees and made the soil uninhabitable to them. It is predominantly composed of the heathers, hence the name 'Heath', and lasts for a couple of hundred years until the soil is de-acidified and more competitive vegetation crowds out the heather.

Because nature abhors a vacuum, there are all sorts of animals and plants that thrive on heathland and - in cases such as this particular spider - in other transient habitats.

This might seem unlikely - evolution doesn't produce novel species overnight, and any specialist is dependant upon the continued existence of a particular niche. If this niche is by its very nature transient, the expectation is that if specialists do have time to develop, they'll be wiped out a couple of centuries down the line.

They're not constantly being wiped out, however, because even England is a fairly big place, and in a big place (formerly) covered in forest, large swathes would burn down frequently enough that the specialists had plenty of time to colonise new tracts before the old habitat was swallowed up by forest again.

This, by the way, is called a dynamic mosaic. Its the nature of, well, nature; over a large enough area, rare events happen frequently enough that, although precisely where it is changes, 'unique' habitats pop up frequently enough to be a constant feature of the landscape.

Britain is not, it is important to note, currently covered in forest.

At this point I would like to be able to console you that the 12% forest cover is averaged over the entirety of the UK, including the far north where many trees haven't yet caught up with the habitat that opened up when the glaciers left.

However, although the Forest commision seems oblivious to the fact that our forests are in a grossly unnatural state, they also give state-based percentages. Scotland, which would naturally host the (almost extinct) Caledonian Forest, has 16% cover; much of which is non-native (and ecologically almost useless) plantation conifer. England and Wales, both of which would, naturally, be almost entirely forested, have only 9% and 12%, respectively.

As a result, our dynamic mosaic is fractured - farmland and sprawl separate what remains of flammable forest and re-growing heathland, and most, if not all, of that forest is being used as a profitable resource, and so natural spread of fires is even more restricted. Taking everything into account, our native forest becomes almost as scarce - perhaps scarcer still - than the formerly rare, transitional environments that make up many of our national parks.

So environmental management has taken the rather controversial step of forcing these dynamic environments to be static. A national park once a heathland must not be allowed to return naturally to forest, but must be maintained as heathland. To preserve the unique habitat and assemblage, among other things.

And how, pray, is much of this maintenance done?

It might seem intuitive; controlled burning.

Spiders - along with insects, lizards, snakes and a surprising number of heath-dependant plants - do not survive fire in any stage of their life-cycle. As much as they may thrive in the area where a fire has formerly altered part of a larger habitat, they can neither escape nor tolerate the flames.

It is worth noting that not all heathland is managed by controlled burning; some is grazed - however, for many profitable grazing birds and mammals, heather is only palatable in young growth, a state which is encouraged by management by... yes, burning.


I'm not going to pretend to have a solution to this problem; I simply wish to make a note of the paradox that environmental management in the UK has become.

And, having done so, on with the taxonomy:

This spider - for a reminder,

is

Alopecosa barbipes
(Sundevall, 1833)

Which is a fox spider. Fox spiders, it's important to note, are a genus (Alopecosa) of wolf spider (Lycosidae).


- Lycosinae 
- Lycosidae   
- Lycosoidea   
- Entelegynae    
- Araneoclada      
- Neocribellatae     
- Araneomorphae     
- Opisthothelae           
- Araneae                      
- Megoperculata              
- Micrura                            
- Arachnida                           
- Chelicerata                             
- Arthropoda                                

- Ecdysozoa                                      
- Protostomia                                      
- Nephrozoa                                          
- Bilateralia                                                
- Eumetazoa                                                 
- Animalia                                                       
- Eukaryota                                                        
                                                       
And that's all, folks!


Many great resources exist for British spiders, but one very handy online tool is the Spider and Harvestman recording scheme. Most species - of spiders, at any rate - have a complete description and at least one photograph; those that don't are typically extremely rare to extinct in the country. It could be more user friendly, but for that there are pages like the Sherwood-centric Eakring Birds and the Leicestershire/Rutland site NatureSpot

Thursday 19 September 2013

Metisella willemi (Wallengren, 1857) and the use of flash...

So this is actually going to be a post with a little more information than the taxonomy and where the subject was taken, for a change. Here is that subject:
Metisella willemi, Chongwe, Lusaka, Zambia
Captured in Chongwe, Lusaka, Zambia in February 2013, using Olympus E-420 DSLR with Zuiko 40-150mm lens and 3 KOOD magnifiers.
and here it is again:
 
Captured same place, same time, same camera but one less magnifier and one or two other key differences.


The key point here is that I like both of these images.

They were both captured, as a point of note, of a subject from the same population, five minutes and less than five metres apart, and in more-or-less the same pose.

They have been cropped differently, but aside from this, they are really quite similar. Consider here the original, uncropped and un-touched up images






and compare the edited versions:














The wings-open image was taken with partial on-camera flash (1/4 of full), and a very low ISO (100). This directly reflected flash reduced the three-dimensional appearance of the insect and gives it an unrealistic shadow, as well as a more generic atmosphere.

On a more positive note, it allows the animal to be seen in its full, vibrant colour, and, in the original, untouched up version, separates the animal from its background much more readily. This is the sort of image I might include in a handguide (and, in due course, plan to).



The wings-closed image was taken with a higher ISO and only natural light. In the original , this creates a lot of noise, and the later editing essentially put it back to the state it would have been with a lower ISO, turning the noisy areas to shade and darkness.

The higher ISO has no real positives, which is why its effects were edited out. Without flash, the environment is much less generic; the butterfly is sitting in patch of sunlight through a gap in fairly thick foliage. The angle of the light makes a difference - here, with a hundred or so degrees separating the light from the lens, the texture of the leaf upon which it has settled is exaggerated, with the fine hairs on the leaf lit up for all to see; the butterfly itself is put mostly into shadow, but highlights pick out the head and the top of the eyes.

All in all, the more dramatic lighting, although it obscures many crucial identification features, creates a more pleasing image, such as someone fond of insects might frame on the wall.


This is not to say that flash flattens images - off-camera flash is often used to exaggerate textures, and a diffuse natural light coming from the direction of the photographer can often create just as flat an image; and flash can - used properly - create the illusion of any natural lighting condition. But when one's flash is limited to the on-camera, for drama, you're best off sticking with natural light. 

Anyway, back on topic.

This lovely little butterfly is the Netted Sylph,

Metisella willemi
(Wallengren, 1857)
which is a member of the:

- Heteropterinae
- Hesperiidae         
See also Acada biseriata
- Hesperoidea          
- Rhopacera               
- Bombycina                 
See also Laelia robusta 
- Cossina                          
- Ditrysia                             
- Heteroneura                        
- Neolepidoptera                      
- Glossata                                   
- Lepidoptera                               
- Amphiesmenoptera                      
- Panorpida                                       
- Endopterygota                                 
- Eumetabola                                        
- Neoptera                                                
- Manopterygota                                         
- Pterygota                                                      
- Dicondylia                                                       
- Insecta                                                               
- Hexapoda                                                             
 - Arthropoda                                                              
- Ecdysozoa                                                                  
- Protostomia                                                                   
- Nephrozoa                                                                        
- Bilateralia                                                                            
- Eumetazoa                                                                             
- Animalia                                                                                    
- Eukaryota                                                                                      

You may note that two of the three butterflies featured thus far on this blog are skippers in the family Hesperiidae. You may also come to suspect that, of the butterflies, skippers are my favourites. Was I so biased as to have favourites, you would not be wrong; they are featured because a) they, with the Lycaenids, comprise the largest portion of the diverse Central African scrub butterfly fauna and b) they are in my opinion given less coverage than larger, more conspicuous species. 


And that's all, folks! 

Saturday 14 September 2013

Oedemera nobilis (Scopoli, 1763)

To ease you back after one post where certainty is currently impossible, here's one where it's unavoidable:

Oedemera nobilis, Bosham, West Sussex, UK
Photographed in August 2012, in Bosham, West Sussex, UK, using Olympus E-420 DSLR, Zuiko 40-150 mm lens and three KOOD magnifiers.

This colourful character is a male of the common European species

Oedemera nobilis
(Scopoli, 1763). 

also known as, in the UK, the swollen-thighed beetle, a pollen-feeding species seen frequently on almost all flowers from June through to August.

Where many pollinators have vastly different early diets, the larvae of these beetles are also herbivorous, feeding on Broom and Thistles, and for their overwintering, presumably require the dead stems of these plants to be left uncut. Certainly in the area where this was photographed, abundance has increased dramatically since a half-acre or so of land on the edge of the salt-marsh has been set aside from farming and mowing, and turned to rough grassland.

 Here's another angle to illustrate the thigh in question, on a more evenly coloured individual:


And with that, once more into the taxonomy:

- Oedemerini
- Oedemerinae
- Oedemeridae  
- Tenebrionoidea 
- Cucujiformia       
- Polyphaga              
- Coleoptera                
- Coleopterida                
- Endopterygota                
- Eumetabola                       
- Neoptera                               
- Manopterygota                         
- Pterygota                                      
- Dicondylia                                       
- Insecta                                                  
- Hexapoda                                                 
- Arthropoda                                                   
- Ecdysozoa                                                        
- Protostomia                                                          
- Nephrozoa                                                               
- Bilateralia                                                                    
- Eumetazoa                                                                       
- Animalia                                                                              
- Eukaryota                                                                                 
                  

Friday 13 September 2013

Metadon inermis (Loew, 1858)

NOTE - I'm saying that this is Metadon inermis, but in truth I was told that it was either this or Metadon mynthes (both previously Microdon, but with the genus revision being put forward this year by the person who identified it, I'm being progressive). I'm going with M. inermis because not only did the secondary-contact specialist note that it was more likely, but it is also much more widely recorded, while M. mynthes, so far as I can tell, is limited to Guinea. Which is a good half-continent away from where this one was photographed. 

A not-very-good photo for you today:
Metadon cf. inermis, Chongwe, Lusaka, Zambia,
Photographed in Chongwe, Lusaka, Zambia, in March 2013. It's not a good enough picture to warrant telling you what with.
You may ask why, when this photograph doesn't exactly give great character, this image is being uploaded. Perhaps, as with Enoplognatha ovata, generally considered to have been formally described before the start date for formal descriptions of animals, it is of taxonomic note? 

No. It's more along the lines of Dolichotachina caudata, Megistocera filipes and
Synagris proserpina, although not quite so dramatic. A good picture it may not be, but it is the only picture I can locate on the web of a living member of either species that this could be*. And I'm still not dismissing that it may not really be


Metadon inermis 
(Loew, 1858)

because that would be foolish.

One interesting aside, though, comes in comparison. Behold:


 This is a bee, Sphecodes, displaying a colour form common in Central African stinging insects. 

Look again at our (harmless) fly:





The size is different, closer in the fly to the similarly coloured Megachile bees from the same area, but the similarities between these two individuals was too much for me to pass up showing you Sphecodes.


Anyhow, onwards with the taxonomy: 


Microdontinae
Syrphidae         
Syrphoidea         
Aschiza                
Muscomorpha       
Brachycera              
Diptera                      
 Antliophora                 
Panorpida                       
Endopterygota                  
Eumetabola                           
Neoptera                                  
Manopterygota                           
Pterygota                                      
Dicondylia                                     
Insecta                                             
Hexapoda                                          
Arthropoda                                          
Ecdysozoa                                               
Protostomia                                               
Nephrozoa                                                   
Bilateralia                                                        
Eumetazoa                                                        
Animalia                                                             
Eukaryota                                                             

                                                                  
And that's all, folks!








* Reemer's article revising the oversized genus Microdon does also contain images of M. inermis pinned specimens, among other things.


For anyone trying to identify members of this subfamily, Reemer's key, mentioned above, is not only the most up-to-date resource I am aware of, but also available free. Happy times.