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#1 2018-10-04 00:07:12

meega
DF Members
Name: Rob Zloch
From: Lancaster
Registered: 2013-09-18
Posts: 4

Empididae: Empis scotica or tumida

I have a female Empis specimen that is either scotica or tumida: axillary wing excision acute, episterna hairy, whole prosternum hairy, eight scutellar bristles, abdomen black-haired. Occiput has a large bare area on either side.

I have not come across either species before and am using Collin, 1961 and Chvala FES 29 Genus Empis, 1994. I'm not sure about the determining characters...

I have found the colour of the palpi and the halteres not easy to correspond with the keys.

The palpi are within the mouth area - one slightly protruding - and a reddish-brown colour with a bit of lighter pubescence which is particularly noticeable towards the tips. They have a few black bristles which are about the length of the antennal styles.
The halteres have dark, dirty yellow stems, with yellow (orangey-yellow) knobs. The colour becomes clearer yellow towards the end of the knobs.

In particular there are two characters that I would like help with:

Tergite 8 is black shining with just a slight dusting. Both Collin and Chvala specifically mention this for scotica but not for tumida.

Tergites 3 to 7 have only the shortest of black hairs/bristles and are virtually bare. Tergites 1 and 2 are quite long-haired at the sides. They start as very short near the middle and get longer progressively towards the sides. Their maximum length and strength being the same as the episternal hairs, for instance. This is seen in the photos. The only mention that describes longer abdominal hairs at the sides is by Chvala for tumida. I find both authors' use of the word 'pubescence' tricky.

This individual was taken in disputed territory between Cumbria and the Yorkshire Dales. Apologies that the photos are pretty basic - perhaps they'll help a bit.


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#2 2018-10-06 17:56:53

pbrighto
DF Members
Name: Phil Brighton
From: Warrington
Registered: 2011-10-21
Posts: 363

Re: Empididae: Empis scotica or tumida

It will be a good one to take along to the next February Dipterists Forum workshop, which is covering this very family.   I've got a few tricky specimens saved up for it myself!

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#3 2018-10-13 20:41:50

meega
DF Members
Name: Rob Zloch
From: Lancaster
Registered: 2013-09-18
Posts: 4

Re: Empididae: Empis scotica or tumida

It is Empis scotica. E. tumida does not have the black shining 8th tergite. E scotica has the colour of palpi and halteres as I described while E. tumida has quite yellow palpi with very short hairs and halteres coloured the other way round, i.e. yellowish on the stalk and more dusky on the knob.

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