Freeze to hit expanding hoverfly range?

[Roger Morris]

Hello everyone

I wonder if it would be possible to use WAB to develop a monitoring group to see how some of the hovers that were marching north have been affected.

Both Volucella inanis and V. zonaria were hit very badly by the 1963 freeze and I have a feeling they may have been badly affected this time too.

Are there enough people to make this happen? It would be really good to look at these two species.

Regards & happy new year

Roger

[Wild-Woman]

It will be interesting to see how this winter affects many of our inverts. I myself will be keen to know how our relatively new to this country, wasp spiders fare.

[Naturenutz]

what areas have they reached in the uk may i ask.I took note of many hovers last year,but these 2 have passed me by.I did find bombylans and pellucens here in bristol north.

[Ukwildlifeo]

Originally Posted by Wild-Woman

It will be interesting to see how this winter affects many of our inverts. I myself will be keen to know how our relatively new to this country, wasp spiders fare.

Ive been wondering how wasp spiders and small red eyed damsels will be affected. All this snow and cold Isn't going to help praying mantids colonise the UK either

I certainly be keeping my eyes out for these and Volucella sp. (my fav hoverflies)

[Jason Green]

Evening Roger,

An interesting question. Though I'm South I'll keep you posted if I notice any drop in numbers or other trends.

Take care,

Jason

[Dogghound]

I personally think cool wet summers are more of a problem to insect expansion. Alot depends on the summer factors like day length, summer temp, habitat quality/existance, hours of sunlight etc. Alot of insect's winter as larvae/nymphs so as long as they are frost free and not physically frozen they can survive long periods of cold temperatures. Heavy frost is a real problem of course species expanding north will suffer especially if wintering sites are not perfect. Spiders are probrably more at risk due to the fact they are always in an adult form.

[Roger Morris]

Hello

First point - see maps of these two on Hoverfly Recording Scheme - Index - both have reached south Yorkshire. Both species are well established in the Bristol area - from websites Montpelier seems a stronghold.

On the question of what is controlling these two species, I'm afraid the summer argument does not work for them. Stuart Ball and I have published several papers on the subject and we have found that there are two critical components. Firstly, summer temperatures - mid summer averages above 20 deg C. Secondly, and crucially, mid winter temperatures not dropping below zero. The crash in both species coincides very comprehensively with the 1960s cold weather - there seem to be good links with the NAO. These papers can be found at:

Morris, R.K.A. & Ball, S.G., 2004. The changing distribution of Volucella inanis (L., 1758) (Diptera: Syrphidae). British Journal of Entomology and Natural History 16: 221-228

Morris, R.K.A. & Ball, S.G., 2004. Sixty years of Volucella zonaria (Poda, 1761) (Diptera: Syrphidae) in Britain. British Journal of Entomology and Natural History 17: 217-227.

There are differences between the two. V. inanis completely disappeared from the SW and is only just getting back into that region. V. zonaria contracted to a few coastal localities and to London and Bristol - urban heat island effects are likely to be the main explanation.

In the V. zonaria paper we postulated possible range expansion from the data to 2003 and to quite a large extent this prediction has been borne out. So I think we can say we have quite a strong handle on the variables that are relevant to these two species.

The other factor that may be an issue is the abundance of social wasps and there are indications that the droughts of recent years have seriously affected these - lack of prey items.

We have not fully hit on the factors affecting one or two other species whose ranges are expanding e.g. Rhingia rostrata but there do seem to be hot summer/warm winter effects here too.

Regards

Roger

[tristanba]

On a related note, it is likely that the prolonged cold conditions this winter will impact on populations of heat-loving Heteropterans such as the Southern Green Shieldbug Nezara viridula, which has managed to gain a foothold in the UK due to the recent tendency for milder winters.

Studies in Japan have shown that a mean January temperature of 4 degrees results in an 80% drop in numbers and that for every 1 degree reduction there is a corresponding 15% increase in mortality. In the light of this the UK population is likely to be severely pruned back.

[Dogghound]

Originally Posted by Roger Morris

Hello

First point - see maps of these two on Hoverfly Recording Scheme - Index - both have reached south Yorkshire. Both species are well established in the Bristol area - from websites Montpelier seems a stronghold.

On the question of what is controlling these two species, I'm afraid the summer argument does not work for them. Stuart Ball and I have published several papers on the subject and we have found that there are two critical components. Firstly, summer temperatures - mid summer averages above 20 deg C. Secondly, and crucially, mid winter temperatures not dropping below zero. The crash in both species coincides very comprehensively with the 1960s cold weather - there seem to be good links with the NAO. These papers can be found at:

Morris, R.K.A. & Ball, S.G., 2004. The changing distribution of Volucella inanis (L., 1758) (Diptera: Syrphidae). British Journal of Entomology and Natural History 16: 221-228

Morris, R.K.A. & Ball, S.G., 2004. Sixty years of Volucella zonaria (Poda, 1761) (Diptera: Syrphidae) in Britain. British Journal of Entomology and Natural History 17: 217-227.

There are differences between the two. V. inanis completely disappeared from the SW and is only just getting back into that region. V. zonaria contracted to a few coastal localities and to London and Bristol - urban heat island effects are likely to be the main explanation.

In the V. zonaria paper we postulated possible range expansion from the data to 2003 and to quite a large extent this prediction has been borne out. So I think we can say we have quite a strong handle on the variables that are relevant to these two species.

The other factor that may be an issue is the abundance of social wasps and there are indications that the droughts of recent years have seriously affected these - lack of prey items.

We have not fully hit on the factors affecting one or two other species whose ranges are expanding e.g. Rhingia rostrata but there do seem to be hot summer/warm winter effects here too.

Regards

Roger

Cheers I shall have to have a read and tell off one of fellow local surveyors for feeding me lies

[Jason Green]

Originally Posted by tristanba

On a related note, it is likely that the prolonged cold conditions this winter will impact on populations of heat-loving Heteropterans such as the Southern Green Shieldbug Nezara viridula, which has managed to gain a foothold in the UK due to the recent tendency for milder winters.

Studies in Japan have shown that a mean January temperature of 4 degrees results in an 80% drop in numbers and that for every 1 degree reduction there is a corresponding 15% increase in mortality. In the light of this the UK population is likely to be severely pruned back.

Not good for my target of photographing one this year then! As we had been saying last year, a lot of their old strongholds don't hold adults now and subsequently they are were trouble, and that was before this...