What's That Bug? does not endorse extermination

cocoons in comfrey tea
January 23, 2010
I just found clear, wriggling cocoons in my comfrey compost tea. you can see the bug inside the cocoon, a long black object with wings wrapped around. they have long stringy tails and are all bundled in a mass together. they do not look like maggots and they are roughly 1 cm in length. can you help me? i could not really get good shots as my camera is not much of a close up one.
shayni
New zealand, north island

Rat Tailed Maggots in Comfrey Tea

Dear shayni,
Our first thought on this is that we need to research exactly what the pupa of the Rat Tailed Maggot looks like, and then we need to see if comfrey tea is the name for the liquid fertilizer that is made by brewing manure in water.  You are right about your photo being blurry, but it does give a general idea of this mass of insects, but alas, the details must remain in our imagination, though that has been known to be rather vivid at times.  We see we were wrong about the comfrey tea, which is made from the plant comfrey, Symphytum officinale, and is applied externally to a number of conditions including bruises, cuts and acne, and that it might be used as an organic fertilizer.  It appears you have brewed it outdoors in a large bucket, which is why you have what we suspect your insects are Rat Tailed Maggots.  Rat Tailed Maggots are the larvae of Drone Flies, Eristalis tenax,  According to Charles Hogue in Insects of the Los Angeles Basin:  “the larvae live in water, usually in sluggish streams or small stagnant ponds that are foul with organic matter; they may also breed in fresh liquid cow manure.  Because of their extremely long, extendable posterior breathing tube, the larvae are called ‘Rat-Tailed Maggots.'”  We then found an online article entitled Eristalis tenax and Musca vomitoria in New Zealand by G.V. Hudson, F.E.S. that was read before the Wellington Philosophical Society on the 2nd October 1889.  Suddenly, your simple letter opened up an entirely new can of worms since the Drone Fly was reported in New Zealand prior to 1889:  Is the Drone Fly a truly cosmopolitan species because its range expanded naturally?  Or was it spread by man?  Mmmmmmm.  BugGuide has some excellent images of Drone Flies mating and BugGuide indicates the Drone Fly was introduced to North America prior to 1874.  We can’t help but wonder why and how Drone Flies were introduced to North America.  This could be a graduate thesis topic, but alas, at some point, we need to stop and respond that you have Rat Tailed Maggots in your Comfrey Tea.  According to Wikipedia:  “When fully grown, the larva creeps out into drier habitats and seeks a suitable place to pupate. In doing so it sometimes enters buildings, especially barns and basements on farms. The pupa is 10-12 mm long, grey-brown, oval, and retains the long tail; it looks like a tiny mouse.
”  We should also mention that the adult Drone Fly is a perfect mimic to the adult Honey Bee, and this mimicry is in itself interesting in that both the Honey Bee and the Drone Fly are connected to human agriculture and animal husbandry. Mmmmmm.

What's That Bug? does not endorse extermination

2 Responses to Rat Tailed Maggots in Comfrey Tea

  1. Sally Crimp says:

    Are these maggots pollutants when left in liquid to decompose. I have made my own fertiliser from seaweed cow and horse manure. Putrud smell, decided to revove lumps from tubs and noticed quite pklum looking maggots with a tan coloured tail appendage. Can you identify what they are and if they are poisoning my intended liquid fertilizer. Also should I add blood mnd bone, lime??? to assist decomposition process. Ta

    • bugman says:

      The Rat Tailed Maggots are attracted to the decomposition in the concoction you have made. The Rat Tailed Maggots are not harmful and they will not have a negative effect on your fertilizer, but rather they are a sign that the fertilizer is fertile. If it was our garden, we would add the lime and blood meal if needed to the soil when mixing in your decomposing fertilizer, not during the manure seasoning process.

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