keithbayless's Identifications

Body length around 2mm. Via McAlpine (1983), keys out to N. corticeus, and matches largely the description. The thorax chaetotaxy agrees with the figure provided of that species (Fig. 10), but differs principally by the apical scutellar bristles being perfectly erect (instead of almost erect) and both pairs of scutellars subequal in length, and clearly longer than the length of the scutellum.
Behaviour also similar to that of N. corticeus as described by McAlpine – this fly, and possibly another observed walking head down on smooth barked trunk in a zig-zag fashion. The fly photographed in a rough crack of the trunk where it had settled.
McAlpine (1983):
“Adults of Nemo species while observed in various habitats spent much time walking on the substrate, only occasionally taking flight, particularly when disturbed. It is interesting to compare the mode of progression of these with other asteioid flies, some of which (e.g. Neurochaeta, Stenomicra and Cyamops) are at times also seen on Alocasia leaves (McAlpine 1978). N. centriseta and N. kentae walk rather slowly forwards without any tendency to reverse the direction of movement and without keeping a constant orientation to direction of gravity. This behaviour accords with that of Cyamops (family Periscelididae) and many other kinds of flies. N. corticeus and N. phaeotylos, while capable of the same behaviour pattern as the above species, spend much time walking short distances with abrupt reversals of the direction of movement, thus tending to move in a zig-zag course with, for short periods, a constant orientation of the body in relation to gravity. In the long term the orientation is not maintained, so that on the vertical bark surface the insect may be facing upwards, downwards or horizontally. This is a major point of difference from Neurochaeta, which consistently faces downwards, and Stenomicra, which faces upwards, when moving on a vertical surface, though the frequent change of direction is reminiscent of the former.”