What's That Bug? does not endorse extermination

Pupal case embedded in decaying rat?
June 1, 2010
Hello! I have long loved your website and need your help! This large, hive-shaped brown growth is emerging from the throat of a large brown rat my cat killed. You may be able to see the significant maggot population under the forearm, but the corpse is still intact for the most part. It appears larger than most of the fly pupae I have found descriptions of on the internet. Can you help? I am very curious – almost mistook it for a cancerous growth! Thank you!!
W. Barker, huge fan!
Sierra mountains, Northern CA

Thing on a Dead Rat

Dear W. Barker,
If we had just read your letter and there was no photo, we would have argued that the creature was a Rodent Botfly in the genus Cuterebra, but the thing on your dead rat looks nothing like the Rodent Botfly Larva pictured on BugGuide.  We are going to post your letter and photos and request assistance from our readership.

Thing on a Dead Rat

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What's That Bug? does not endorse extermination

6 Responses to Mystery: What's Growing on the Dead Rat???

  1. ThreeBarks says:

    Thrilled to have earned a spot on your site! I have additional photos (w/tape measure for comparison) and can send them if you are interested. The end of the pupal case (?) has gone from circular with clear liquid inside to flat – perhaps because I manipulated it gently? The rat is an 8″ Norway Rat and the embedded case is very large – 3/4″ to an inch across. Thanks again!

  2. lttlechkn says:

    Actually, I think you were right with the original assumption of this being a rodent botfly… Check out the photos on this documentary http://www.fcla.edu/FlaEnt/fe91p706.pdf I am not sure of the exact botfly that this would be, but I think you were all in the correct area.

  3. ThreeBarks says:

    One last detail: while the shape is nearly identical to that of the botfly pupa, it is smooth – none of the bristles shown on all botfly pupal cases I have seen so far.

  4. Suzanne Garofalo says:

    My cat killed some kind of medium size rodent and left it for me to find in the driveway – he is vocal about his kills so I found it with in minutes – and by that time two large – say about 1 inch long and 1/2 inch wide brown “things” were making their way to the carcass – they really gave me the willies. I scooped up the lot and tossed it well over the fence in to a fallow field adjacent to my property.

    Two nights later, cat kills another rodent. I get to it before any creepy crawlies appear and toss this one into a dense shrub (thinking cat can’t get to it). The next morning the cat brings me the rodent again and TWO of those nasty things have burrowed into its lower belly close to its haunches -one on either side.

    I started reading the above mentioned article on Bot flies but stopped when it described the larvae exiting the dead rodent as the bugs I am looking for info on appear to have attached themselves after death.

    WHAT ARE THEY??? I wish I’d never seen them!

  5. Cynthia says:

    This morning my cat caught a rat and brought it into the house for me. It was still alive and I didn’t have time to deal with it before work so I managed to get it into my enclosed shower and closed it in until after work. When I got home tonight it was dead and a large dark brown wiggly larva thing exactly as you described had exited through the rats groin area. It was alive and still near the rat. I flushed it but am also wondering what it was. Ewwwww

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