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Seb, reading your "tropical pacific region" I imagined something much simplier, Kuala Lumpur like. Even Hercule Poirot would not deduce that it is the remotest place in the World, the French Polynesia!
Now (also due to new images) the situation is clarified:
1. On the 1st image and upper-left one on the 2nd - Atherigona ustipennis
2. the lower left and right one on the 2nd images is Atherigona orientalis