(work in progress)
The orientation of the scutellar bristles is a very important feature in the keys and these bristles can be misaligned very easily during capture so it usually produces a lot of consternation in novices. This need not be the case if you just follow a few simple rules of thumb.
Here are some examples of specimens with crossed apical scutellars:
Notice that in species with crossed bristles both bristles usually curve slightly inwards. In species with diverging or parallel scutellars they are usually straight or even curving outwards – this is a very useful fact when the bristles have been misaligned.
Here are examples with diverging or parallel bristles:
[insert photo – diverging & erect bristles – Meigenia]
No apicals at all – note the lack of empty sockets at the tip of the scutellum, showing that this is not a damaged specimen:
Erect apical scutellars – not a great shot but you can see that they are about 45-degrees to the horizontal when viewed laterally. These are from a Phryxe so if you could view them dorsally you would see that they are also crossed:
[insert photo – hair-like apicals – Blondelia nigripes]
Some examples of damaged bristles, starting with a missing crossed apical scutellar – note the remaining one is strongly curved inwards:
[insert photos of more mangled bristles]