A typical tachinid wing

This is a photograph of a Tachina grossa wing, annotated to show the commonest features that are used in the keys:

I always orient myself by looking for the smallest vertical vein called r-m, the little one in the middle – it links the last true radial vein (r4+5) to the median. The median vein is probably the most important in tachinids because it often bends in different ways and either joins or doesn’t join r4+5. If the median vein joins r4+5 before the wing edge then it forms a small stalk called the petiole (not on this photo). Sometimes the bend has a little stalk (appendix – not in this photo) or crease that extends towards the wing margin. If you go up from r4+5 the next radial is r2+3 and these 2 veins meet together, near the body, at another important areas called the node. The node has varying numbers of hairs on it and sometimes these hairs extend along r4+5 towards or even beyond r-m. Above r2+3 you will see r1 and then to the left sc, the sub-costal vein. Along the leading edge is the costal vein (annotated in sections – CSx) – these sections are of varying relative lengths and this can be important. The last section (CS6) extends to a notional point that is the tip of the wing. Below the median vein the next radial is called the cubital vein and it is linked to the median by m-cu. The point where m-cu joins the median is important in some species, as is the length of the section of the cubital beyond m-cu. The final vein that is of interest to us is the anal vein – we are usually just asked to see whether it extends to the edge of the wing, but watch out – make sure that it isn’t just a crease that meets the wing edge! đŸ˜‰

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