I believe this hoverfly was laying eggs on a mutton lemon plant that is infested with the Asian citrus psyllid. These tiny insects have infested several mutton lemon bushes on our street, and other hoverfly species on the island have larvae that are aphid predators. I guess I will have to keep an eye on these bushes and see what strange stuff turns up next.
Nice syrphid! This should be either Allograpta radiata or Allograpta limbata; both are in range and morphologically very similar (the characters used to tell them apart aren’t easily visible in photographs, and the abdominal pattern of this fly is intermediate between the two). The larvae generally do prey on aphids, though some are herbivorous instead. Nice shots!