Welcome to the new TRS website – a one-stop-shop for anyone interested in studying UK tachinid flies. The site has the very latest news & information from the recording scheme plus the most up to date species list and key updates.

Currently the Species Accounts page allows you to search for anything on the British list; view the data we hold on it, including excerpts from all of the major works; view any photos we have of specimens or insects in the field; and also to link to the NBN mapping database, which currently hold 15,000 of our recording scheme records plus records from other regional and national recording projects.

Tachinids that look like Eriothrix rufomaculata

Eriothrix rufomaculata is an incredibly common fly in mid-summer, especially on any flowery meadows. The species is very easy to identify from the red abdominal side-patches, silvery face with projecting mouth edge, long costal spine, slightly shaded wings with a small petiole on the median vein. The only problem is that several other, rarer, species can easily be confused for Eriothrix.

In this confusion group I will include: Mintho rufiventris, all Cylindromyia spp., Aphria longirostris & Bithia spreta. All of these confusion species have some nice clear features that you should be able to pick up in photos and I’ll bring those out below:

  • Two broad longitudinal black bars on the thorax and the abdomen laterally compressed (higher than it is wide, though this can be difficult to judge) but always wider nearest to the thorax, tapering to the tip and about as long as the head+thorax; strong median discal bristles present; wing with very short petiole. [if you have a fly with 2 dark bars on the thorax; longer, forward-pointing petiole; and long cylindrical body then suspect Cylindromya (below)] = Mintho rufiventris
  • Thin black longitudinal bars on the thorax numbering 2-4 but usually thin; abdomen various shapes:
    • Proboscis long, projecting forwards further than the antennae and extending beyond the face for at least as long as the depth of the head; median discal bristles absent; heavily pale-grey dusted = Aphria longirostris
    • Proboscis can project from the face a little but never as long as in Aphria
      • Abdomen cylindrical and longer than the head+thorax; median discals usually absent; wing with a forward-pointing petiole, longer than vein r-m = Cylindromyia
      • Abdomen normally-shaped and usually as long as the head+thorax; median discals always present:
        • Wing veins r1, r4+5 and cu all have little hairs along them; no petiole on the median vein; wings clear; basicosta pale; body heavily grey-brown dusted with faint orange abdominal side-patches = Bithia spreta
        • Wing veins bare with a tiny petiole, shorter than vein rm (can be as short as r4+5 and median vein touching at the wing edge); wings often slightly shaded; basicosta dark; body black with dark grey dusting and with red abdominal side-patches … but these can vary from occupying the whole length of the abdomen to almost absent = Eriothrix rufomaculata

Here are a few free-to-use images trawled from the web to illustrate some of the features described above:

A quick guide to the new UK phasiines

This year we have been lucky enough to receive records for 2 new species to the UK – Ectophasia crassipennis & Phasia aurigera. These both bear a resemblance to Phasia hemiptera and have been confused with them in the past so I thought I’d put together a few pointers on how to spot them.

  • Phasia hemiptera is very easy to spot in both sexes because they have tufts of ginger hair on the side of the thorax, just behind the head, which are usually very visible and only present in this species. It has a small petiole on the media vein but is it usually visible through the dark blotches. Females usually have clear wings but they can be found in a black-winged form. Male wing colour concentrated at the tip and along the base of the leading edge but it is very variable and completely shaded examples are known.
  • Phasia aurigera is only known from 1 record in Kent and again it will have a petiole on the media vein but they lack any ginger hairs and the male has a lovely rectangular, golden spot in the middle of the thorax. Females are clear-winged, and look very similar to Phasia hemiptera but without the ginger hairs, of course. Male wing colour is dark towards the furthest edge and orange towards the body.
  • Ectophasia crassipennis is known from 4 records (so far) along the south and east coast. They have no petiole on the median vein and both sexes have golden dusting across the width of the thorax, with more coverage on the males. The females have a single dark patch on the wing. Male wing colour is dark around the edges with a small central spot in the middle of the wing.

Abdomen colour in all species is quite variable with more or less orange.

How to split Tachina fera type tachinids in photos

One of the most difficult problems is how to confirm/verify the identification of photos of flies that look quite like Tachina fera. I’d include in that group any of the following species: Tachina fera, Tachina magnicornis, Nowickia ferox, Linnaemya vulpina, Peleteria rubescens, Peleteria iavana & male Nemoraea pellucida. They’re all fairly large, bristly flies with a brown thorax and orange-sided abdomen and in this article I’ll try to knock them down one by one by removing the easiest first.

This is a very basic draft key that should help when identifying from photos but treat with care as it is just a first draft. Send me comments if you agree or disagree:

  • Hairy eyes?
    • Protruding mouth edge, slim-bodied fly, usually found on heathland = Linnaemya vulpina [common on heathland]
    • Flat face profile, slightly smaller head than usual, very wide abdomen, hairy calyptrae (but this is hard to spot) = Nemoraea pellucida [very rare in southern England – few modern records]
  • Bare eyes?
    • Black legs, sometimes with a slightly paler tibia?
      • Two strong black “Peleteria” bristles on the lower parafacial area; body ground colour basically dark brown; abdominal mid-stripe fairly parallel sided?
        • Second antennal segment orange; strong dusting across most of each tergite; reddish-orange abdominal side patches = Peleteria iavana [was called varia, restricted to the Channel Isles]
        • Second antennal segment dark/black; weak dusting on the posterior of each tergite; abdominal side patches distinctly orange = Peleteria rubescens [very rare in southern England – few modern records]
      • Lower parafacial bare; body & leg ground colour dark black; abdominal mid-stripe usually jagged and made from distinct overlapping black diamonds = Nowickia ferox [common in southern England]
    • Orange or light brown legs?
      • fore tarsus brown/orange; frons generally narrower (M 0.68-1.08x, F 0.94-1.28x one eye); abdominal mid-stripe tapers towards the end of the abdomen; males: fore tarsal claws as long as the last 2 tarsal segments & usually without any outer orbital bristles (rarely 1) = Tachina fera [very common across the UK]
      • fore tarsus black/brown; frons wider (M 1.10-1.39x, in F 1.27-1.55x one eye); abdominal mid-stripe widens towards the end of the abdomen; male fore tarsal claws shorter than last 2 tarsal segments & 1-2 outer orbital bristles present = Tachina magnicornis [restricted to the Channel Isles]

The most difficult splits are still between the very similar Tachina species but I think these will always be difficult. You only have to examine DNA barcodes of these species to notice that they are often wrongly identified.

It can also be a bit tricky to split Peleteria rubescens from Tachina fera/magnicornis where the insect’s face is obscured and the legs are fairly pale or obscured. I’ve noticed that in this case the Peleteria tend to have heads that are ever so slightly wider than the thorax and the abdomen isn’t much wider than the thorax; while the Tachina have narrower heads and wider abdomens. Also the Peleteria tend to have whiter/greyer thorax dusting on a slate-grey/black ground colour, while the Tachina dusting is yellowish-brown on a dark brown ground colour.

What follows is a little gallery of open-access images to help you visualise the features I’ve used above.

Dexiosoma caninum vs Dexia vacua

I always find that one of the hardest identifications to make from photos is the split between Dexiosoma caninum and the much rarer Dexia vacua. Dexia vacua is so rare that many experts thought that it was extinct in Western Europe so getting good, reliable records from photos is very important because it seems that the UK is its last stronghold.

I have been examining the few specimens I have for Dexia vacua and under the microscope they are very easy to split because Dexia all have a very pronounced central facial ridge and Dexiosoma don’t, but this is often very difficult to see in photos. Instead you have to look for other features, in what seems to be quite a variable fly. I should also add that male vacua are fairly easy to identify because they usually have orange abdominal side patches but the females are grey-brown and can look virtually identical to Dexiosoma.

So, here is a tentative list of features that I think are fairly stable. The median discal bristles aren’t always easy to see unless you get a good lateral shot but combined with the other features you should be able to get a good ID:

FeatureDexiosoma caninumDexia vacua
Central facial ridgeabsentpresent
Median discals on T3 & T4absentpresent
Median vein appendixlongshort
Median vein from m-cu to the bend lengthless than or equal to the distance from the marginlonger than the distance to the margin
Pre-sutural acrostichalsabsentpresent

These are photos that I have decided are Dexiosoma caninum:

These are photos that I have decided are Dexia vacua:

All images are (c) copyright Graham Watkeys

Thelyconychia solivaga

Recently I have been working on adding a new species to the British list to our key. Thelyconychia solivaga is a small tachinid that seems to live on fairly stony/rocky coastal sites and is very rare in the UK – in fact only 3 specimens have been found so far (by Laurence Clemons in Kent and Ivan Perry in Sussuex). These are just a few photos to show how it looks but it is a rather nondescript species that looks superficially like a small Meigenia but the apicals are crossed and the propleuron is not hairy.

They are actually so rarely collected that the Natural History Museum has 6 specimens – mostly collected in Jordan!

The problem with Phryxe …

The genus Phryxe contains a few common species (nemea, vulgaris & heraclei) and a few very rare ones (magnicornis & erythrostoma). The key pulls out nemea first by the wide gap between the facial-ridge bristles and the descending parafrontals – wider than the width of antenna-3 plus the mustardy/yellow frontal area. Splitting off heraclei has always been a matter of looking for extra bristles along the underside of costal wing section 2, which indicate heraclei – without this would mean moving on to magnicornis (split off using male genitalia), erythrostoma (big with long claws) & vulgaris (the rest). So it’s clear that male genitalia are important (once you get past nemea) but recently I have found several specimens that have vulgaris-type genitalia but which have the extra bristlets along wing section 2.

The first pair of photos shows a standard male Phryxe heraclei – the wing edge section has a scattering of extra bristlets on the underside of the vein between the leading edge and the wing membrane. The genitalia have very rounded surstyli and a smoothly rounded cercus:

The next photo shows the troublesome Phryxe vulgaris – the wing edge also has stray bristlets and the genitalia are of the usual vulgaris/nemea type with more elongate surstyli and a more angled cercus:

This means that once nemea has been excluded you really need to have a male specimen to prove vulgaris, magnicornis or heraclei. Phryxe erythrostoma is much larger and the claws are also quite distinctive. So, in summary:

Female specimens:

1. The gap between the descending parafrontal bristles and the ascending facial ridge bristles is about as wide as the width of antenna-3 and the colour of the parafrontal region is a yellowish-grey … Phryxe nemea

–  The gap narrower and the colour of the parafrontal dusting is more a blue-grey … other species

Male specimens:  (continuing from above):

2. surstyli rounded and cerci smoothly curved underneath; underside of costal section 2 with 1 or more additional tiny bristlets along the vein between the continuous row of bristlets on the leading edge and the wing membrane … Phryxe heraclei

3. surstyli extremely narrow … Phryxe magnicornis

4. fore tarsal claws longer than the last tarsonomere [large species 8-10mm] … Phryxe erythrostoma

5. surstylus moderately elongate – between that of heraclei and magnicornis (as above) and cercus with a distinct angle to the underside … Phryxe vulgaris

In reality if you have a male and the genitalia look like nemea/vulgaris type then you just have to decide which species it is from the facial bristle gap and the colour of the dusting – you don’t have to progress to the other species.

Gonia face colour

In the keys to Gonia one of the couplets asks you to consider the shininess of the face but this can be a confusing thing to judge when you only have one specimen. In this mini article I have taken photos of the 2 choices to make it clear. The first thing to do is to make sure that you are looking from the front with even light.

Gonia capitata (female) CMTR 15-01-20_153850_M=A_R=8_S=4 Gonia divisa (male) CMTR 15-01-20_154609_M=CThe first photo shows Gonia capitata (but also ornata looks like this) and these are the species described as “reflective yellowish-white” while the last photo shows Gonia divisa, which is the species described as “matt orange”. Really both species have an orange face but capitata/ornata are highly dusted with reflective scales while divisa is not shiny..

Linnaemya picta, tessellans & rossica confusion features

For many years Linnaemya picta had been confused with rossica because early workers (e.g. Fonseca) hadn’t tried using the European keys. Since the ‘discovery’ of picta in Kent it has spread across southern England as far as Bedfordshire, Oxfordshire & Berkshire and so now we have another fairly common black-legged species to confuse with tessellans. I have occasionally been confused myself by 2 couplets in the Linnaemya keys and so I have posted here some photos of the various species and illustrated the features that you need to look out for.

Firstly, both picta & tessellans have dark hairs on the gena but picta has bristles mixed in with them. The bristles should be fairly obvious because they arise from sockets, while the hairs go directly into the integument.

Secondly, both picta & rossica have a scattering of small black bristlets on top of the head, behind the post-ocular row. But rossica is distinctive in having many more bristles in multiple rows and at least a few of them are as large as medium-sized post-ocular bristles. This feature is actually very easy to find but can cause confusion if you only have a picta and don’t know whether your bristles are big enough.

Siphona urbana or geniculata?

In Andersen’s 1996 book “The Siphonini (Diptera: Tachinidae) or Europe” he made several changes to the names of Siphona spp., which have proved a bit confusing. The changes (and subsequent reversions) illustrate a few nice aspects of modern taxonomy and so I thought I would write a little piece on what happened.

Every species is based on what’s called a type specimen – ideally a specimen that the author considers to be the archetypal individual, which he uses to describe what the species looks like – a holotype. Later on if anyone wants to revise a group or they want to be absolutely sure of their identification they can hunt down the holotype and compare it to their own specimens, safe in the knowledge that the holotype is the definitive example of the species. In fact I have at times joked that the only ‘correctly’ identified specimen is the holotype – anything else is just an opinion!

When Andersen researched Siphona for his book he examined the types and noticed that actually what we had all been calling geniculata did not match the type specimen. When he examined all of the types he came to the conclusion that what we knew as geniculata should actually be called urbana and what we called cristata should be known as geniculata. This is not as unusual a situation as you might think because types are often hard to examine (being locked away in far-off museums) and people are fallible and they assume that they know what they are talking about!

Siphona geniculata and cristata are very common flies and it was quickly noticed that such a confusing change of names would cause massive problems for workers in the group. In 1999 Tschorsnig, Herting & O’Hara petitioned the International Commission on Zoological Nomenclature (ICZN, the body that defines the rules of naming and arbitrates on nomenclature in animals) and asked them to agree to redefine geniculata by reallocating a new type specimen to it. Their argument being that, although Andersen was strictly correct, the old names should be retained due to common usage. After much debate and time for reflection, in 2001 the ICZN voted on and decided to accept the suggestions.

The lectotype of geniculata was officially replaced by a new type specimen (neotype) held in the Museum of Lund University, labelled ‘Sk. Dalby, O. Molla, 21.VII.1989, leg. R. Danielson’. This action allowed cristata to be reinstated and we returned, full circle, to the situation prior to Anderson’s shake-up.

Exorista rustica vs. tubulosa

I always find this species-pair really difficult to split – even when you flip out the male genitalia. The cerci are actually quite distinctive but without good photos you can try to convince yourself that a rustica (the common one) is a tubulosa (the uncommon one). The key is that tubulosa should be really very parallel-sided while rustica is rounded and then the tip is quite pronounced.