I don't normally just link to ant related news without having something to say myself. However, I think that Martialis heureka warrants making an exception.
Myrmecos does a good summary of the story, with some nice photos. Other good coverage is at ScienceDaily, Nature News and Discover. The paper is available from PNAS, at a cost, though the abstract is available for free.
Tuesday, 16 September 2008
Sunday, 7 September 2008
Separating Lasius niger and Lasius platythorax workers
By popular request! Well, one person requested it anyway.
Lasius niger and Lasius platythorax are undoubtedly hard to separate. This becomes particularly difficult when you find specimens that seem to be somewhere in between. However, it is always possible to assign them to one species or another, with a bit of work.
First of all, L. niger and L. platythorax are small dark brown Lasius with outstanding hairs on their antennal scapes. In the UK there are no other species that have these characteristics, though in Europe it gets a little more complicated1.
Some people seem to base identification of the workers of these species on one or two characteristics. However, experience has taught me that it is usually more reliable to use all of the following:
Probably the most useful character is the clypeal pubescence. Quite often this can be visually assessed, with practice, though on occasions an entire nest series will have moderate clypeal pubescence and have to be assessed morphometrically. To do this you use a measuring line, as shown below. Measure the length of this line in µm (l) and then count the number of hairs that intersect it (n). Seifert (2007) gives the average distance between the hairs (l/n) for L. niger as <16µm and for L. platythorax as >19µm.
Clypeal pubescence in Lasius niger. Measuring line shown in red.
Clypeal pubescence in Lasius platythorax. Measuring line shown in red.
Whilst you're looking at the clypeus it's worth noting its shape in profile. Typically, L. niger has a rather curved clypeus, whilst in L. platythorax it is comparatively straight. The idea that they differ has been floating around in BWARS for a couple years now, though I must admit I'm one of the last to accept that this is probably a good character. I feel like I've now seen enough and have not been able to dispute it - plus Barry Bolton is apparently using it, so it must be good!
Check the shape of the propodeum in profile. In L. niger the propodeum tends to be a smoothly rounded dome, whilst in L. platythorax it tends to be more conical in shape.
Finally, look at the relative length of the setae on the mesosoma, especially the pronotum. In L. platythorax these setae tend to be distinctly longer. Seifert (2007) gives figures for the length of the longest setae on the pronotum divided by the length of the head as 0.119±0.009 in L. niger and 0.159±0.010 in L. platythorax.
The two species have distinct ecological preferences. L. niger prefers drier habitats and has synanthropic tendencies - this is the species that sometimes invades houses. L. platythorax prefers wetter conditions, and is usually the species found in woodland and wet grasslands.
I've also started noticing that the larvae in L. platythorax seem to be more slender than in L. niger. Of course, this is based wholly on my subjective observations, but might be a good indicative field character.
NB: The photomontages are of British specimens2 that show generally typical characteristics. However, both specimens show setae on the propodeum that curve forward, which is not typical. In the Scottish L. platythorax, which were collected in atypical habitat at their most northern known location in the UK, the entire series had curved forward propodeal setae.
1 American L. niger are most likely a different species again, as the images I have seen do not have the dense clypeal pubescence of L. niger, but do not appear to be L. platythorax either.
2 To be honest, I don't think that them being British matters - if anything I find the characteristics of these species to overlap more in the UK than in mainland Europe. However, I know some British myrmecologists who get funny about such things!
Lasius niger and Lasius platythorax are undoubtedly hard to separate. This becomes particularly difficult when you find specimens that seem to be somewhere in between. However, it is always possible to assign them to one species or another, with a bit of work.
First of all, L. niger and L. platythorax are small dark brown Lasius with outstanding hairs on their antennal scapes. In the UK there are no other species that have these characteristics, though in Europe it gets a little more complicated1.
Some people seem to base identification of the workers of these species on one or two characteristics. However, experience has taught me that it is usually more reliable to use all of the following:
- Density of pubescence on the clypeus
- Shape of propodeum in profile
- Setae length on the mesosoma
- Shape of clypeus in profile
Probably the most useful character is the clypeal pubescence. Quite often this can be visually assessed, with practice, though on occasions an entire nest series will have moderate clypeal pubescence and have to be assessed morphometrically. To do this you use a measuring line, as shown below. Measure the length of this line in µm (l) and then count the number of hairs that intersect it (n). Seifert (2007) gives the average distance between the hairs (l/n) for L. niger as <16µm and for L. platythorax as >19µm.
Clypeal pubescence in Lasius niger. Measuring line shown in red.
Clypeal pubescence in Lasius platythorax. Measuring line shown in red.
Whilst you're looking at the clypeus it's worth noting its shape in profile. Typically, L. niger has a rather curved clypeus, whilst in L. platythorax it is comparatively straight. The idea that they differ has been floating around in BWARS for a couple years now, though I must admit I'm one of the last to accept that this is probably a good character. I feel like I've now seen enough and have not been able to dispute it - plus Barry Bolton is apparently using it, so it must be good!Check the shape of the propodeum in profile. In L. niger the propodeum tends to be a smoothly rounded dome, whilst in L. platythorax it tends to be more conical in shape.
Finally, look at the relative length of the setae on the mesosoma, especially the pronotum. In L. platythorax these setae tend to be distinctly longer. Seifert (2007) gives figures for the length of the longest setae on the pronotum divided by the length of the head as 0.119±0.009 in L. niger and 0.159±0.010 in L. platythorax.
The two species have distinct ecological preferences. L. niger prefers drier habitats and has synanthropic tendencies - this is the species that sometimes invades houses. L. platythorax prefers wetter conditions, and is usually the species found in woodland and wet grasslands.I've also started noticing that the larvae in L. platythorax seem to be more slender than in L. niger. Of course, this is based wholly on my subjective observations, but might be a good indicative field character.
NB: The photomontages are of British specimens2 that show generally typical characteristics. However, both specimens show setae on the propodeum that curve forward, which is not typical. In the Scottish L. platythorax, which were collected in atypical habitat at their most northern known location in the UK, the entire series had curved forward propodeal setae.
1 American L. niger are most likely a different species again, as the images I have seen do not have the dense clypeal pubescence of L. niger, but do not appear to be L. platythorax either.
2 To be honest, I don't think that them being British matters - if anything I find the characteristics of these species to overlap more in the UK than in mainland Europe. However, I know some British myrmecologists who get funny about such things!
New title bar
It only took two hours of fiddling to get it right.
For those who care, the species used for the mugshots are, from left to right:
For those who care, the species used for the mugshots are, from left to right:
Saturday, 6 September 2008
Focus stacking ant images
I wish I had the kind of technology that the guys at AntWeb have for taking photographs. They use Automontage to focus stack the images, ensuring that everything is in focus. The principle of focus stacking is that you take photographs with different parts of the subject in focus and then use the software to combine the in-focus bits of all the images to create a new image.
The big issue for me is the cost, as the technology involved is pricey. The photographs that I take at the moment are done in a very low-tech way with what is now a rather dated camera, but it seems to work without costing the earth.
I recently read an article on tardigrades in British Wildlife, in which the author discussed briefly the technology he uses for photographing these tiny beasts. It turns out that you can focus stack images on the cheap, with two software packages freely available: Helicon Focus (for Macs) and CombineZP (for Windows).
I've had a bash at producing some stacked ant images in CombineZP. It's fair to say that the process involved is incredibly fiddly, time consuming and computer memory hungry, with the images produced rather variable. However, it does work fairly well, once you've learnt to keep the camera completely still whilst taking the images.
I know some people dislike focus stacking, because it makes images appear flat, so I thought I'd put CombineZP to the test.
The following photographs are of British Lasius niger (it's worth clicking on the images to view larger versions). Image 1 is the best of the original images used to create the composites below:
CombineZP produced two images (from nine original images), using different stacking techniques, that were of reasonable quality. Image 2 is perhaps the closest to the original and was produced using Pyramid Maximum Contrast methodology:
Image 3 uses Pyramid Weighted Average methodology:
I have my own thoughts on which I prefer, but I thought I'd put it to the vote:
The big issue for me is the cost, as the technology involved is pricey. The photographs that I take at the moment are done in a very low-tech way with what is now a rather dated camera, but it seems to work without costing the earth.
I recently read an article on tardigrades in British Wildlife, in which the author discussed briefly the technology he uses for photographing these tiny beasts. It turns out that you can focus stack images on the cheap, with two software packages freely available: Helicon Focus (for Macs) and CombineZP (for Windows).
I've had a bash at producing some stacked ant images in CombineZP. It's fair to say that the process involved is incredibly fiddly, time consuming and computer memory hungry, with the images produced rather variable. However, it does work fairly well, once you've learnt to keep the camera completely still whilst taking the images.
I know some people dislike focus stacking, because it makes images appear flat, so I thought I'd put CombineZP to the test.
The following photographs are of British Lasius niger (it's worth clicking on the images to view larger versions). Image 1 is the best of the original images used to create the composites below:
CombineZP produced two images (from nine original images), using different stacking techniques, that were of reasonable quality. Image 2 is perhaps the closest to the original and was produced using Pyramid Maximum Contrast methodology:
Image 3 uses Pyramid Weighted Average methodology:
I have my own thoughts on which I prefer, but I thought I'd put it to the vote:Sunday, 31 August 2008
Hygrocybe intermedia
One of the few things that the UK seems to do really well is waxcaps (Hygrocybe sp.). They are one of the more spectacular groups of fungi, coming in a range of very vivid colours. In Europe they are associated with grasslands, though elsewhere in the world they tend to occur in woodlands.
The first time I encountered Hygrocybe intermedia was in 2000, on the sand dunes just a few metres from Sizewell nuclear power station in Suffolk. At the time, the species was listed on the provisional UK red data list for fungi. Although it has since been removed, it's evidently not that common, with only 410 records on the Fungal Records Database of Britain and Ireland.
This specimen was found at Brown Robin, a Cumbria Wildlife Trust reserve near Grange over Sands, where H. intermedia was the most abundant fruiting fungus present. As fungi go, it is an unmistakable waxcap, in the Northern Europe at least, due to it's colour, squamulose pileus (cap) and fibrillose stipe (stem).
The first time I encountered Hygrocybe intermedia was in 2000, on the sand dunes just a few metres from Sizewell nuclear power station in Suffolk. At the time, the species was listed on the provisional UK red data list for fungi. Although it has since been removed, it's evidently not that common, with only 410 records on the Fungal Records Database of Britain and Ireland.This specimen was found at Brown Robin, a Cumbria Wildlife Trust reserve near Grange over Sands, where H. intermedia was the most abundant fruiting fungus present. As fungi go, it is an unmistakable waxcap, in the Northern Europe at least, due to it's colour, squamulose pileus (cap) and fibrillose stipe (stem).
Wednesday, 27 August 2008
Invertebrates from Leighton Moss
I visited Leighton Moss RSPB reserve on Saturday.
It wouldn't be surprising if over 99% of visitors go to Leighton Moss for birds, with the remainder going for dragonflies, but I'm afraid I tend to find this sort of birding boring. On the whole, I'd much rather have the birds up close and personal, even if it is just European starlings on a bird feeder. The one exception to the general reserve experience was when I visited Inner Marsh Farm for work on a day when it was closed to the public. On this day I ate my lunch in the hide in the absence of birders (who are a funny bunch) and had water rail and other waders literally metres away.
What excited me about Leighton Moss was the flora and the invertebrates.
The other rather special observation was the bug Pictomerus bidens feeding on a caterpillar. I had seen this species before in Cornwall, but had never found it feeding. It actually came as quite a surprise, as I had not realised that it was carnivorous!
It wouldn't be surprising if over 99% of visitors go to Leighton Moss for birds, with the remainder going for dragonflies, but I'm afraid I tend to find this sort of birding boring. On the whole, I'd much rather have the birds up close and personal, even if it is just European starlings on a bird feeder. The one exception to the general reserve experience was when I visited Inner Marsh Farm for work on a day when it was closed to the public. On this day I ate my lunch in the hide in the absence of birders (who are a funny bunch) and had water rail and other waders literally metres away.
What excited me about Leighton Moss was the flora and the invertebrates.
One of the things that I've known about for a long time, but saw for the first time, was the alder moth caterpillar Acronicta alni (though I will admit that it was my brother that remembered the name). The alder moth is a widespread species, but the caterpillars are rarely seen, as they apparently spend much of their time in the canopy of various tree species, on which they feed. However, the final instars of the caterpillar are fantastic,
looking like something more suited to the tropics than wet-and-dreary UK.
looking like something more suited to the tropics than wet-and-dreary UK.The other rather special observation was the bug Pictomerus bidens feeding on a caterpillar. I had seen this species before in Cornwall, but had never found it feeding. It actually came as quite a surprise, as I had not realised that it was carnivorous!
Tuesday, 26 August 2008
Mapping ant colonies
A colleague of mine forwarded this to me last week, but I went away and haven't had chance to deal with it properly until now.
Researchers at Texas A&M University used Ground Penetrating Radar (GPR) to map a colony of Atta texana, producing a 3D model of the tunnels and chambers. It's all very clever and has the advantage of being non-invasive.
I've seen some of the models that Walter Tschinkel has produced and they are very attractive (and scientifically valuable). However, these models do result in the destruction of the colony and can be very time consuming to produce. By using GPR the colony is not destroyed.
Whilst I think that this is a great step forward, I doubt how well it can be implemented in the short term. The trouble is, whilst A. texana colonies are big, most ant colonies are small with narrow tunnels, and I doubt that the GPR would be sensitive to pick up all the finer details. Maybe in the future, if the sensitivity of the equipment improves, this technique will become more valuable. It's also much harder to visualise the colony without an actual physical model, though no doubt these could be created at additional cost if needed.
It will be interesting to see how this develops (and how the technology can be used in other fields - mapping European badger Meles meles setts for a start). More information is available on the project website.
I also followed a link from the BBC web page this was reported on and discovered that a friend of mine has made the news, again... (Show off.)
Researchers at Texas A&M University used Ground Penetrating Radar (GPR) to map a colony of Atta texana, producing a 3D model of the tunnels and chambers. It's all very clever and has the advantage of being non-invasive.
I've seen some of the models that Walter Tschinkel has produced and they are very attractive (and scientifically valuable). However, these models do result in the destruction of the colony and can be very time consuming to produce. By using GPR the colony is not destroyed.
Whilst I think that this is a great step forward, I doubt how well it can be implemented in the short term. The trouble is, whilst A. texana colonies are big, most ant colonies are small with narrow tunnels, and I doubt that the GPR would be sensitive to pick up all the finer details. Maybe in the future, if the sensitivity of the equipment improves, this technique will become more valuable. It's also much harder to visualise the colony without an actual physical model, though no doubt these could be created at additional cost if needed.
It will be interesting to see how this develops (and how the technology can be used in other fields - mapping European badger Meles meles setts for a start). More information is available on the project website.
I also followed a link from the BBC web page this was reported on and discovered that a friend of mine has made the news, again... (Show off.)
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