The breathing tube

Most lagoon-dwelling hoverflies have a characteristic breathing tube extending out the rear end, which acts like a snorkel giving them the name long-tailed larva or rat-tailed maggot. The larva is capable of extending out and retracting this snorkel into its body, which it will often do as it moves deeper into a Lagoon or if the water surface is disturbed (as if a predator were fishing for maggots).

Here you can see a larva (of many!) shunt out it’s breathing tube, pushing it out to the water surface (if you have sound on, the noise is a Myathropa florea female coming to investigate).

The tube has little hairs at the tip, which rest on the surface tension of the water keeping it at the surface allowing the larva to breath.

The tip of a Myathropa florea breathing tube
Close up showing the hairs around the tip which holds it at the surface of the water