DIPTERA > BRACHYCERA | Higher Diptera

MUSCOMORPHA > SCHIZOPHORA > Calyptratae > Oestroidea > Tachinidae (270 species)

(subfamilies: Dexiinae, Exoristinae, Phasiinae and Tachininae)

A large family of generally robust and bristly flies that are extremely variable in appearance and where only a relatively small number can be reliably identified from photos. They are often referred to as parasitic flies, but that term is misleading as all tachinid flies are parasitoids in their larval stage. Although their egg-laying strategies vary, the females of most species target lepidopteran larvae, generally depositing their eggs on or close to the selected host or, in some cases, actually injecting into the host. Apart from butterflies and moths, other species may also be used, for example beetles, both the larvae and the adults, sawfly or cranefly larvae, or even earwigs or centipedes. And, in respect of the phasiines, various heteropteran bugs.

Adult tachinids mostly feed on flowers with many species being important pollinators. At rest they typically sit with their wings held back in a delta shape rather than flat over their back and, whilst each species will have certain habitat preferences, they may be found on sunlit foliage, or on trunks or posts.  

They vary both in size from tiny to large (2-20mm) and in colour, typically from grey to slate black, although in some cases with a marked thorax and/or abdomen, often with red or orange spots, and others which are metallic green or yellowish grey. Some will be generally bristly, others partially, and some quite bare. They have a strongly developed subscutellum, typically broadly rounded-triangular lower calypters and hyperpleural bristles. Wings can be clear or shaded, but importantly, in most cases, the median vein M1 has a noticeable bend, curving forward to either meet R4+5 to form a petiole or to adjoin the margin leaving an open cell.

There are four subfamilies and, at some point when I have a few more species to feature, I will reorganise the collection accordingly. However, for now, I've simply spread the species that I've managed to photograph to date across two pages in alphabetical order. There are a large number of genera, over 130 I believe, which is far too many to list but, nevertheless, it is useful to link species with their respective subfamily, which can be seen either when hovering over an image or as an extended caption when enlarged.

Once again, one of the most useful sources of information is Steven Falk's Flickr albums and, although other resources have been used, here's a little bit of detail in respect of the species that I'm currently able to feature.

Dexia rustica - a medium-sized, rather long-legged, bare-eyed species with short orange antennae, plumose arista and a pronounced central facial ridge. The thorax has a greyish-yellow dusted coating with four dark, often broken stripes. The abdomen has a greyish-brown to reddish colouration with darker longitudinal markings. Despite widespread distribution, the species is not particularly common.

Dexiosoma caninum - superficially similar to Dexia rustica in many respects, but without the central facial ridge. The thorax has a yellow-buff dusted appearance and the abdomen is more greyish with darker markings forming bands across the hind margins of tergites three and four. The femora and tibiae are orange, but the tarsi are darker. Usually found resting on low foliage in woodland or areas of scrub.

Dinera grisescens - a generally smallish, slim, long-legged, grey-dusted, tachinid with a few dark markings on the thorax. It is often mistaken for a Solieria species, except they have a narrower parafacial with much larger eyes. This species typically favours dry, open areas.

Ectophasia crassipennis - a medium-large, somewhat flattened tachinid that closely resembles some Phasia species, but has vein R4+5 open apically rather than stalked. Highly variable, both in size and abdominal markings. Larger males typically have broad, well-patterned wings but, in smaller specimens, they are narrower with fewer markings, similar to the females and difficult to separate. The species was previously restricted to the Channel Islands, but in 2019 it was recorded from a few mainland southern coastal areas, since which time it has slowly expanded its range. 

Eriothrix rufomaculata - a bristly medium-sized tachinid with a dark grey streaked thorax and black cylindrical abdomen with prominent, but variable, orangey-red patches on the sides that are separated by a dorsal black line. Wings are slightly shaded, yellowish at the base, have a long costal spine, and with the median vein strongly curved and meeting R4+5 to form a petiole.

Exorista rustica - one of seven Exorista species, all of which could be found locally; medium-sized, bare-eyed with a dark scutellum and three pairs of postsutural dorsocentrals. Another species that prefers more open areas. Although very rarely recorded, Exorista tubulosa is extremely similar and always a possibility particularly with specimens found in chalk downland locations. It can be distinguished by the lack of discal bristles on tergite 3, although given the rarity of the species it could only be officially considered by checking the genitalia.

Gymnocheta viridis - a distinctive metallic-green, early season tachinid that could only be confused with a couple of much rarer species although, without taking into account the different body form, wing venation and generally bristly appearance, could be initially mistaken for a Lucilia 'greenbottle' species.

Gymnosoma rotundatum - an unusual and rather rare, localised species with an almost spherical dark orange abdomen with three variable, separated or partially connected, round black spots. The thorax is black above and golden brown on the sides. Wings are slightly shaded, darkening yellow-brown towards the base, and with the median vein strongly curved meeting R4+5 near the margin to form a petiole.

Please use the forward 'next page' (>) button above to continue reading about the remaining species I've photographed

Updated Nov.24 (v.3)