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Could anyone identify this - I think it may be a syrphidae, but it almost behaves as a predatory wasp. Seen on the island of Guadeloupe in the Lesser Antilles. There were several, visiting small holes in the sand, I don't think the sand burrows were their own, they seemed to be flying from one to another, possibly trying to find one with something in - small crabs?? when they stay underground for much longer, perhaps laying eggs on a host?

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Hello Nick Smith,

The specimen pictures is not a Diptera, but a Hymenoptera. It seems to me that this is a Sphecidae of the genus Bembix. Typical in dunes and sandy habitats.

Greetings,

Ectemnius

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These are now more often placed in family Crabronidae. Tribe Bembicini are called "sand wasps" in English. They dig burrows in sand and stock with insect prey. Diptera are common prey. I have seen a related genus carrying a leafhopper (Cicadellidae).