The image attached was taken of a fly in Polish amber approx 20-300 million years old. It was taken with a Zuiko 20mm on a bellows at approx 12x.There are two images.I am wondering if there is anyone who can give info about what this fly was doing during sap envelopment. It appears to me that it is sucking the membrane(please see nubulous material drifting towards the mouthparts) from an egg possibly it's own. I would be grateful of info
Without having a closer look at the actual specimen I suspect it to belong to one of the families attracted to fermenting tree sap, most likely Odiniidae but possibly Periscelididae. Many dipteran groups feeding on juices (either true juices or substances the dissolve in saliva) consume a lot of fluid/food in one go. They can then later be observed regurgitating fluids. What is exactly happening then is not clear (see the relevant forum thread on Diptera.info; I may give the exact link later). My guess is that this fly was 'caught' while regurgitating and the 'balloon' is actually contains the regurgitated food and a 'drag mark'.