Mangrove Shore Fly

Size variable between 6 and 9mm. These red flies have been observed hunting in or near mangroves. The closer to shore the more abundant and active they were. They deliberately target marine matter that attaches to mangrove leaves. They definitely prefer the underside and can as a result can be hard to photograph. One individual was targeting barnacles (I always struggle to recognise them as crustaceans), liking the opening. Maybe it is just salt that or detrius that they are after. None of these flies were found further inland but that is not to say that they are coastal only. The red body had my hopes go high that it was a wasp, but I am pretty confident that it is a fly. It has two white markings on its dorsum. I don't think they are the wing stumps. They look like indents, similar to an apple that has two bite marks. ALA has not been checked yet and googling flies is cumbersome. Update 24/2/2017: Still no proper identification. Looking through photos the apple bite marks seem not to affect all animals. Also, the ocelli are unusual, only one centred or several small ones merging into one. The horseshoe nose is unusual, too, looking like a night high beam, cup-shaped rather than two (hairy) branchs.