Monday, 21 August 2017

Water Quality Surveys for Citizen Scientists

I received the following email today. I know some dipterists have taken part and it is really easy. If you are interested in finding out more or taking part just follow the links. Many diptera species are aquatic in their larval stages. Some are very tolerant of high levels of pollution, for example Eristalis hoverfly larvae feed on bacteria in polluted water and have the 'rat-tail' breathing syphon that allows them to breathe fresh air whilst remaining in oxygen depleted water. On the other hand some soldierfly larvae are very sensitive to water quality and can be eliminated from a site by even minor pollution.

 Good Morning,


I’m writing to you from the Freshwater Habitats Trust to request your help to find clean unpolluted ponds, streams and ditches where wildlife can thrive.


Through our citizen science survey, Clean Water for Wildlife, we are supplying volunteers with simple kits that rapidly measure the water quality of local ponds, streams and ditches. Through the survey we hope to build a map of water quality across the country, find amazing clean (unpolluted) freshwater habitats where wildlife can thrive and to raise awareness of the true extent of nutrient pollution. Would you be able to help promote the survey to your group members? I hope this is something that is of interest.  


Why is the survey important?

Clean unpolluted water supports rich and diverse communities of freshwater plants and animals, including many of our now rarest species. It is often the best indicator of a thriving waterbody. Despite its importance very little is known about the water quality in most freshwater habitats, particularly in our smaller waters. Until recently it was only possible to measure water quality through expensive laboratory tests, now with simple kits it takes just a few minutes. With new technology it is now possible to fill in the gaps in our knowledge and it presents an opportunity to find many more really special clean waters where wildlife can flourish.


The kits

The kits rapidly measure the levels of two widespread nutrients pollutants, nitrate and phosphate, and can be used in all type of freshwater habitats (garden ponds, ditches, streams, fens, rivers and more). With these quick kits people can now actively participant in current scientific research into water quality and help to discover clean water habitats where wildlife can thrive. You can see the kits in action in our short ‘How to Video’ (


For more information please visit


Please don’t hesitate to get in touch if you have any questions.


Kind regards,



Hannah Worker
Freshwater Habitats Trust Project Assistant

(Please note I work on several projects and may be away from my desk for periods of time. This may mean there is a delay in my response)



Freshwater Habitats Trust, 1st Floor, Bury Knowle House, North Place, Headington, Oxford, OX3 9HY


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Friday, 21 April 2017

April 2017

The season is now well underway. Bee-flies have been seen regularly around the county. My earliest record was on the 29th March in Rothwell but Graham Warnes saw them the previous week in Northampton. In Northants we only have the one species of bee-fly, the dark-edged bee-fly Bombylius major.

Bombylius major  (c) John Showers

Two other species may yet occur in Northants. The spotted bee-fly Bombylius discolor is expanding its range northwards. It has a dotted pattern on the wings rather than the intense dark front edge of B. major.  The anthracite bee-fly Anthrax anthrax was found for the first time in Britain in Cambridgeshire last year. This latter species has been expanding its range in Europe and regularly visits bee hotels where it parasitizes the guests!

Although it is still rather cold, the dry and often sunny conditions at present create microclimates in sheltered areas and these are good places to find hoverflies, especially if there are nectar sources present. A walk round West Lodge Farm near Desborough on 19th April revealed 9 species of hoverfly. I managed to photograph a few and have attached the photos below together with the species distribution map up to the end of 2015 for Vice-county 32 - Northamptonshire and the Soke of Peterborough (historical Northants). The maps were supplied by Stuart Ball who jointly runs the UK Hoverfly Recording Scheme with Roger Morris. My thanks go to them for supply the maps and encouraging the study of hoverflies.
Rhingia campestris the Heineken Hoverfly on red campion (c) John Showers

(c) Stuart Ball

Cheilosia illustrata, a bumblebee mimic  (c) John Showers
(c) Stuart Ball

Epistrophe eligans, a typical Spring species of woodland edges (c) John Showers
(c) Stuart Ball

Eristalis pertinax, a common species whose rat-tailed larvae live in wet conditions (c) John Showers
(c) Stuart Ball

As you can see from the maps, these are widespread species. The gaps probably reflect lack of recording effort rather than real gaps in the distributions.

In addition to hoverflies I did find a number of other interesting flies:

The parasitic fly (Family - Tachinidae) Gymnochaeta viridis. A Spring species whose larvae parasitise grass stem-boring Noctuid moth caterpillars. (c) John Showers

The long-palped cranefly (Family - Tipulidae) Tipula varipennis. A common Spring species.
(c) John Showers

Monday, 13 March 2017

Norellia spinipes

Today I was looking for my first beeflies of the year on primroses but failed to find any. However I also looked at some clumps of naturalised daffodils on the roadside at Blatherwycke. The first few clumps had nothing on them but then one clump had six small, brown flies that I suspected were Norellia spinipes, a dung fly, Scathophagidae. These lay their eggs on daffodil leaves and the larvae mine the midrib of the leaf, leaving a characteristic pale line where they have been. I took one specimen home and confirmed its identity. A picture of the species can be found here:

More information is available on the British Scathophagidae Recording Scheme website here:

The species status is notable but that is likely to change as it seems to be increasing. It is probably an introduced species, coming in on imported bulbs. The first UK records were in 1965. 

I would be interested in hearing from others who have found it in Northants. It is fairly easy to identify, having the rounded head typical of a Scathophagid,  brown body with dark thoracic stripes; two rows of spines below the front femora and one row below the front tibia, giving a mantis-like appearance. It has dark shading over the cross veins and wing tip but this shading can be very feint. Look for it on daffodil leaves where daffodils are well established such as in parks, mature gardens and roadside verges.

Thursday, 16 February 2017

First hoverflies of year in Northants?

I received an email today from Lisa at the Wildlife Trust at Lings House, Northampton to say she had seen a marmalade hoverfly Episyrphus balteatus there. 

Coincidentally, I too saw my first hoverfly of the year today. It was a drone fly Eristalis tenax in Sane Copse, Yardley Chase. I am sure this mild spell will bring more out. Meliscaeva auricollis is another species that overwinters as an adult so can be found once we have some mild, sunny spells.

The winter months are the time to catch up with unidentified specimens from the previous season and I have been doing just that. Two less common species have turned up in the samples I looked at this week. One was a long-legged fly Dolichopodidae, found at Ditchford Lakes and Meadows in early July. The species was Poecilobothrus principalis. The closely related P. nobilitatus is a very common doli fly where the males display to the females on pondweed by flicking open their white-tipped dark wings and hopping from one side of the female to the other. P. principalis is much scarcer as can be seen from the NBN Gateway map -
It seems to be a coastal species from the map but a number of primarily coastal species have been found in the Nene Valley.

The second uncommon species was the Scathophagid fly Cordilura aemula. Details of the species can be found on Stuart Ball's excellent Scathophagidae Recording Scheme website at
This was found at Abington Meadows, Northampton in September. Its distribution is mapped here

I still have quite a few flies to identify from last year so I am hoping to turn up some more interesting species.