The Hornet Robberfly, Asilus crabroniformis.
Aug 27, 2017 12:59:15 GMT
deliasfanatic and mygos like this
Post by nomad on Aug 27, 2017 12:59:15 GMT
The Hornet Robberfly, Asilus crabroniformis Linn 1758.
Olivier's recent find of the Hornet Robberfly, Asilus crabroniformis of the Asilidae family, in Italy, drew my interest of where to see this species in Britain. It came as no surprise to find that this impressive predator was rare in this country, being found very locally in a number of habitats, such as pasture meadows, downland and heathland. The larvae are predators of dung beetle larvae. The Hornet Robberfly is said to be our largest Diptera but having seen the Bumble-bee Robberfly, Laphria flava in the Alps of Switzerland, this species certainly rivals A. crabroniformis in size. Here L. flava is certainly the rarer species, being confined to a few ancient Caledonian pine forests in Scotland.
A. crabroniformis peaks here in mid-August but is still on the wing in September and I thought it was certainly worth trying to find this magnificent insect this year. While I was researching the UK distribution of A. crabroniformis, I found a very informative paper online by Natural England, "The hornet robberfly (Asilus crabroniformis Linnaeus) - adult behaviour at selected sites in Dorset, Hampshire and Surrey in 1997". The paper details research undertaken by Natural England from one site each from the three counties mentioned. After reading this paper, I believed my best chance to photograph this species would be to visit Thursley National Nature Reserve in Surrey.
The Thursley NNR is a large area of both wet and dry lowland Heathland with birch and groups of scots pine. Here A.. crabroniformis was said to be confined to one area of dry heath with shorter heather and gorse. I arrived early to this extraordinary and beautiful place and found that the heathland was purple with the flowering of the heathers, Calluna vulgaris and Erica cinerea, that were in some areas, studded with the yellow of Dwarf Gorse, Ulex minorareas. There can be few such colourful botanical wonders in Britain. Lowland heathland such as this, is a precious habitat that is rare throughout Europe.
I arrived at Thursley early at 8am (Saturday 26th) on what was going to be a scorching late summer's day and I am glad I did. Within an hour of arriving at Thursley, after a search of the heathland, I found two A. crabroniformis females at two different sites adjacent to each other. The light is much better for macro photography in the morning, you do not get the flat light and glare of mid-day. The two Hornet Robberflies that I found appeared quite suddenly and had flown to rest on clumps of heather and one of which I disturbed, decided the sharp spines of gorse would do just as well. They were obviously warming up to prepare for their day's hunting and they provided an ideal photograph opportunity. I was able to get very close to this magnificent beast. Although I was on the heathland for a further three and half hours, I did not find see any further examples of A. crabroniformis during my visit. I was very pleased to find that twenty years after the studies at Thursley of A. crabroniformis by scientists for Natural England, the habitat had remained suitable for this species on this heathland reserve. The scientists were concerned that A. crabroniformis had declined to an alarming extent and it is now a UK BAP priority species requiring conservation action. Thanks heavens for nature reserves, without them safe guarding our fauna, many insects in Britain would either be extinct or confined to much fewer sites. I could cite a list of what would have been lost without such special areas that would fill a good sized notebook! Habitat loss is always nearly the main reasons for extinctions and rich biotopes need safe guarding with legal protection.
A. crabroniformis at most of its English sites, lays its eggs in cow dung but there has never been grazing animals at Thursley. The scientists found that rabbit latrines were the main breeding areas at Thursley, where under the dry rabbit pellets the larvae hunt mostly Typhaeus beetle larva.
Below. Thursley Heathland NNR.
Below. Habitat of A. crabroniformis at Thursley.
Below. Asilus crabroniformis. Individual 1, female. August 2017.
Below. Asilus crabroniformis. Individual 2, female. August 2017.
Below. The Bumble Bee Robberfly, Laphria flava. Another very impressive Robberfly mimic. Simplon, Switzerland. July 2016.
Olivier's recent find of the Hornet Robberfly, Asilus crabroniformis of the Asilidae family, in Italy, drew my interest of where to see this species in Britain. It came as no surprise to find that this impressive predator was rare in this country, being found very locally in a number of habitats, such as pasture meadows, downland and heathland. The larvae are predators of dung beetle larvae. The Hornet Robberfly is said to be our largest Diptera but having seen the Bumble-bee Robberfly, Laphria flava in the Alps of Switzerland, this species certainly rivals A. crabroniformis in size. Here L. flava is certainly the rarer species, being confined to a few ancient Caledonian pine forests in Scotland.
A. crabroniformis peaks here in mid-August but is still on the wing in September and I thought it was certainly worth trying to find this magnificent insect this year. While I was researching the UK distribution of A. crabroniformis, I found a very informative paper online by Natural England, "The hornet robberfly (Asilus crabroniformis Linnaeus) - adult behaviour at selected sites in Dorset, Hampshire and Surrey in 1997". The paper details research undertaken by Natural England from one site each from the three counties mentioned. After reading this paper, I believed my best chance to photograph this species would be to visit Thursley National Nature Reserve in Surrey.
The Thursley NNR is a large area of both wet and dry lowland Heathland with birch and groups of scots pine. Here A.. crabroniformis was said to be confined to one area of dry heath with shorter heather and gorse. I arrived early to this extraordinary and beautiful place and found that the heathland was purple with the flowering of the heathers, Calluna vulgaris and Erica cinerea, that were in some areas, studded with the yellow of Dwarf Gorse, Ulex minorareas. There can be few such colourful botanical wonders in Britain. Lowland heathland such as this, is a precious habitat that is rare throughout Europe.
I arrived at Thursley early at 8am (Saturday 26th) on what was going to be a scorching late summer's day and I am glad I did. Within an hour of arriving at Thursley, after a search of the heathland, I found two A. crabroniformis females at two different sites adjacent to each other. The light is much better for macro photography in the morning, you do not get the flat light and glare of mid-day. The two Hornet Robberflies that I found appeared quite suddenly and had flown to rest on clumps of heather and one of which I disturbed, decided the sharp spines of gorse would do just as well. They were obviously warming up to prepare for their day's hunting and they provided an ideal photograph opportunity. I was able to get very close to this magnificent beast. Although I was on the heathland for a further three and half hours, I did not find see any further examples of A. crabroniformis during my visit. I was very pleased to find that twenty years after the studies at Thursley of A. crabroniformis by scientists for Natural England, the habitat had remained suitable for this species on this heathland reserve. The scientists were concerned that A. crabroniformis had declined to an alarming extent and it is now a UK BAP priority species requiring conservation action. Thanks heavens for nature reserves, without them safe guarding our fauna, many insects in Britain would either be extinct or confined to much fewer sites. I could cite a list of what would have been lost without such special areas that would fill a good sized notebook! Habitat loss is always nearly the main reasons for extinctions and rich biotopes need safe guarding with legal protection.
A. crabroniformis at most of its English sites, lays its eggs in cow dung but there has never been grazing animals at Thursley. The scientists found that rabbit latrines were the main breeding areas at Thursley, where under the dry rabbit pellets the larvae hunt mostly Typhaeus beetle larva.
Below. Thursley Heathland NNR.
Below. Habitat of A. crabroniformis at Thursley.
Below. Asilus crabroniformis. Individual 1, female. August 2017.
Below. Asilus crabroniformis. Individual 2, female. August 2017.
Below. The Bumble Bee Robberfly, Laphria flava. Another very impressive Robberfly mimic. Simplon, Switzerland. July 2016.
