The Great Butterworm Controversy

Within the reptile hobby in North America there are a few well established feeder insects. I mentioned most in an earlier post, but did not talk about butterworms. The reason I avoided butterworms is that, unfortunately, they are impossible to culture outside of Chile. More on that soon.

Butterworms, like all of the popular "worms" available as feeders, are actually the larval stage of an insect. In the case of butterworms the adult stage is the Chilean Moth, Chilecomadia moorei; they are also called the Trevo- and Tebro- worm (and even a few instances of Tebo- and Trebo), and are like silkworms in that they feed exclusively on a single species of tree, the Trevo/Tebro/Trebo/Tebo, Dasyphyllum diacanthoides.

C. moorei are exclusively found in Chile, and are considered a possibly invasive species. When shipped out of Chile, C. moorei larvae are irradiated to kill parasites, and, it is speculated, to prevent them from pupating. I have seen websites contradicting this, and claiming that the reason C. moorei larvae don't pupate in captivity is that they have a nearly 6 year larval stage, but this has come from only a few small, un-notable sources. For whatever reason C. moorei can't pupate outside of Chile, the fact keeps them a lucrative export for the country, frustrates hobbyists like myself, and prevents C. moorei  from becoming one of the premier feeder insects available.

On a reptile forum last month, a member posted a cautionary tale accompanied by gruesome pictures. Two of his Rhacodactylus geckos, a crested and a gargoyle, recently developed what appeared to be burns on their snouts after being fed butterworms. This spurred a small number of following posts claiming similar problems, including two which claimed the worms had melted plastic!

The story was reposted to the forum which I frequent (requires membership to view posts), and is being contested rather strongly by my fellow RC'ers. I myself was fairly critical of this originally, primarily because there is an overwhelming glut of information that states that these worms are not harmful, and only a few recent claims to the contrary. None the less, something burned those geckos, and something melted the plastic, and if we are to believe the sources of these complaints, there were no other possible causes.

So far speculation has ranged from absurd (radiation from export treatment! OH NO!) to plausible (crushing the heads before feeding them releases stomach acid that the worms use to burrow through wood, which otherwise would not be released until inside the geckos' stomachs, or that these are actually a cousin of C. moorei, C. valdiviana which feeds on more toxic eucalyptus. Not backing either of these theories, but both are more plausible than OMG RADIATION!!!!).

In an effort to nip this potential rumour in the butt, I have written to the author of one of my favourite blogs (and my favourite invertebrate blog), Arthropoda, requesting an investigation or resources for myself. Google can only get one so far.

So far I remain on the side of doubt. I have fed hundreds of butterworms to my reptiles, including hatchling leopard geckos, and I have never once seen anything close to resembling the reported burns. Then again, I have also never seen them melt plastic, which has been reported twice since the release of this story, and once on Arachnoboards last year. It will be interesting to see where this goes, and even better if it clears up the other rumours surrounding butterworms -such as their larval duration, export irradiation, and diet- in the process.

5 comments:

  1. I wouldn't want to feed my leopard gecko butter worms; being from Chile you don't know what they ate in the wild and in captivity. If they gut load a plant that is poisonous, that could affect the geckos/lizards.

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    1. @FG
      Except you do know what they have eaten in the wild... the only food they eat is the trevo tree in Chile... clearly you haven't researched them much...

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    2. Sorry, I am very protective of my leopard gecko.
      But I could give it a try to see if my leo would eat one.

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  2. A few things: I wanted to follow this with noting that I have now personally witnessed butterworms boring through plastic. On two separate occasions. Both times the larvae were left out at a high room temperature (~80F, in a breeding room), and the larvae was found dead, having half-eaten it's way through the bottom of a flimsy plastic container.
    Clearly, they have the ability to eat plastic, but I cannot verify that the ability is due to a caustic reaction.
    FG: Butterworms are a great feeder to add a bit of fat and calcium to your gecko's diet, and as Jondor noted, they don't eat anything once they've been taken from their food source. I have fed butterworms for years with no ill effects.
    Jondor, you're absolutely correct, but please be nicer. The internet is already full of jerks (and I've contributed myself enough, I just don't want to encourage mean things here).

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  3. I fed my adult gecko some butterworms that i ordered online. They were pretty huge and it was kind of difficult for him to get the whole thing in his mouth but he chomped on one or two and softend them up before swallowing them down. Within a couple minutes of feeding he began rubbing his face against the window sill like something was attacking his face. Now when he did this his face got coated in dust. He seemed to calm down after a few minutes and I didnt really think anything of it. A couple days later i noticed the dirt from the sill was still on his face, when I washed it off I saw that he had developed a thin black line around the outside of his mouth, maybe like half to 2/3 of the border of his mouth had the line including just under his nose. I dabbed a little water and iodine solution on some gauze and cleaned his mouth and thought he would be fine, just needed some time to heal. For the three years that i had him up to this point he was never sick and I took very good care of him. He seemed very hearty until now. Anyway over the next couple days He wouldnt eat an then he became all mucousy and slime would crust his nostrils, eyes, and you could see strings of the mucous when he opened his mouth. and he was unable to see, id have to use cotton swabs and remove the film from his eyes, This was like 5-6 days after giving him the worms. he just got worse and worse. He would just sit in one spot unable to eat or see and he was suffering. I should have take him to the vet right away but whatever he caught from the butterworms quickly got the best of him, he was in almost like a vegetative state. Wouldnt eat, looked like just sitting and breathing was difficult for him. On the 7th or 8th day after he ate the butterworms I was worried, I had been giving him drops of water directly in his mouth but I was worried that he wasnt eating so, i tried to crush some soft pellet food and put it in his mouth but it just got lodged in his throat, seemed like he used up any last energy he had fighting me trying to feed him so i left him alone and within an hour later he was Dead. I think he was burned by the acidic guts of the worms. Was that what killed him or did he develop some kind of secondary infection, i cant say. It just dawned on me while writing this that there may have been internal damage too, i mean i only saw what was on his face but his insides could have been destroyed too. I dont know what got him but it all started fcuz i wanted to change up his diet a bit and give him some special treats, I am regretful. Spike, I am so sorry my friend, I hope we may meet again one day.

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