Eristalis sp. ?

[Johnny81]

Taken today, Northampton. Resting near pond vegetation. I think it is a hoverfly of the Eristalis genus, but there is something odd about this one to me. Pics are a little dark so apologies.



Many thanks

[Jason Green]

Afternoon John,

Eristalis yes, agreed something looks a little odd. I caught a very similar-looking specimen the other day (a lot of decumbent pale hairs clothing the first tergite for one). As soon as it's set and I've identified it, I'll let you know.

Take care,

Jason

[Geoff F]

Colouration of Eristalis can be quite variable, particularly the abdomen.

It is probably E. pertinax or tenax but be really need to see the hind leg to be certain. Either way it looks like she is about to start egg laying.

[Johnny81]

Ahh I did think that protrusion from the abdomen was for laying eggs . Is the terminology; a pre-genital segment? This individual was spending a great deal of time around the pond, I presume the eggs are laid in aquatic areas and the larvae spend an aquatic life? Apologies I have limited knowledge on inverts at present.

[Jason Green]

Mine came up as Eristalis pertinax, probably just fresher than I'm used to. The points that appeared odd weren't needed by the key.

[Geoff F]

I'm no expert on the full life cycle of this species, John, but it appears that the larvae like ditches, drains and moist muck heaps around farmyards, etc. I don't know if the present trend for cleaning up farmyards is having any impact on them.

Last year, I found E. pertinax to be rather scarce although E. tenax was plentiful. Normally it is the other way around where I live. But so far this year E. pertinax is very common.

[JRsbugs]

If this was E. pertinax it would have orange front and mid tarsi, they might be as often there is some blackish colour on them but yours looks to have more than a little black.

Without seeing the hind leg properly, and other features which are needed for different species such as mid leg colour, facial features e.g dark stripe down the middle of the face, pilosity of face, colour of antennae and whether the arista are hairy or not are all needed for different species. Other than E. pertinax which can be done from the orange tarsi, and E. tenax which can be done by the all dark dilated hind leg then you don't stand a chance of an ID without good close ups of different features. Wings with dark markings can lead to an ID with other features but some species such as E. pertinax which doesn't normally have dark markings often does have them.

Janet

[Johnny81]

Thanks for everyone's input. Here is a better picture I took today of an individual (maybe the same one?) in the same location. Hope this helps, unable to get a view of the face still.

[JRsbugs]

Originally Posted by Johnny81

Thanks for everyone's input. Here is a better picture I took today of an individual (maybe the same one?) in the same location. Hope this helps, unable to get a view of the face still.

I've spent some time checking any possibilities, the only one which keys out is Eristalis similis. The hind femur gives the impression it has orange at the base but I think it's only hairs. I found an example to compare..

Diptera.info - Discussion Forum: Eristalis similis?

[Johnny81]

Thank you for spending some time on this one JRsbugs. I will run with E. similis, I take it this species is much less common than E. pertinax and E. tenax? Could it be time of year?