Eristalis tenax, a crafty maggot

The story of a larva breathing through its elongated butt.


Picture yourself in a thick layer of decaying matter goo.

[sounds of bubbles in thick liquid fade in]

It might not sound very pleasant, but you are a hover fly larva, and that is just where you need to be.

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So, you are a hover fly larva, Erystalis tenax. You are one of the species some call rat-tailed maggot, a name that fits you very well. At the end of your body, a series of telescopic anal segments allow you to reach far up for fresh air, while you stay down here in the goo, hidden and surrounded by food. Like a little blobby submarine, you feed, with your air tube barely visible at the surface. You have a specific trick to make it emerge just as little as you need: a set of oil-producing glands. These glands ensure that the opening of your butt-(breather/snorkel) is well covered in hydrophobic material, and prevents wetting or inundation. This way you can keep it right at the surface. Anybody who want a piece of you would have to get into a mud fight for sure.

Safely hidden in your layer of goo, you can focus on the current objective: filter this organic matter to get your food, and turn into a nice adult hover fly. Then you will be a flying beauty, and the flowers will have to thank you for their pollination.


Dolley, W.L. and Farris, E.J. (1929) ‘Unicellular Glands in the Larvæ of Eristalis Tenax’, Journal of the New York Entomological Society, 37(2), pp. 127–134.

Rotheray, G.E. (2019) Ecomorphology of cyclorrhaphan larvae (diptera). Cham, Switzerland: Springer.