Thursday, 5 November 2009

Rat-tailed Maggots

A few months ago we decided to build a wildlife pond in our back garden and already wildlife has started to move in. From the goldfinches and sparrows who drink and bathe in it, to the almost microscopic mites that swim around.  
However, I have recently noticed an abundance of a new species....

Having posted the pictures on the Wild About Britain Forum, they have been identified as Rat-tailed Maggots, the larvae stage of the Hoverfly (Eristalis tenax), also known as Drone-fly.
A quick search of the internet reveals some fascinating facts about the creature:
The part that looks like a tail is actually a breathing tube acting as a type of snorkel, although it does seem to be used for manoeuvring.  Apparently they can reproduce 'paedogenetically', where the larvae themselves produce more offspring without having to become adults - which may explain the sudden abundance of them in the pond.
They also prefer  oxygen-deprived water, with a high organic content (or 'foul' as English Nature would describe it), this may suggest the pond is not in good health...

When this larvae stage has completed it will pupate out of the water and then turn into one of these splendid insects: 

Picture by Fir0002/Flagstaffotos and is reproduced under the GNU Free Documentation License

Wild About Britain Forum:
North Carolina State University:  


  1. Did you know Pond Conservation UK ( are interested in surveying garden ponds to assess their importance for wildlife? You can DIY or contact them (based locally).

  2. I am aware of Pond Conservation (my wife works on the same corridor at Brookes).
    But I have not checked their website for a while and now I'll certainly be doing their Big Pond Dip

    And I'll post the results here, but I expect it will be in the 'your pond could do better' category.
    What will be interesting is to see if it improves each year.
    Thanks very much for the link.