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We bought a Venus fly trap about a month ago and it doesn't eat, we put a dead fly inside one of the traps and it closed, but after a while it opened up with the fly the same as it was before. This happened several times, the trap closed but the plant does not digest the bug. What could be the problem? Why is this happening?

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The plant evolved to eat live insects and spiders, and not dead ones. So you have to trick it by making it think it's caught live bait...

To feed a dead bug to your plant, first drop it into the trap so the trap closes. Easily done. Next, ever so gently squeeze the two lobes of the traps between your thumb and forefinger, as if you were trying to pick up a delicate bit of...something delicate. Squeeze it a few times more, making sure the two lobes come into gentle contact with each other. This will flex all the trigger hairs inside the trap. Another method is to carefully insert a toothpick or blunt bit of wire (like a straightened paperclip) through the gaps in the loosely closed trap. Wiggle your tool a little, so the trigger hairs inside the lobes are stimulated.

http://www.sarracenia.com/faq/faq2460.html

  • Good point. I kind of assumed that the OP triggered the hairs “enough” when feeding the plant. – Stephie Sep 24 '18 at 9:56
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Venus flytraps “digest” their prey differently than you may expect - the fly and it’s chitin carapace will not dissolve completely, but remain seemingly unchanged when the trap opens again. If you look closely, you will notice that the remains look “empty” or “flat”, not as plump as a live fly. Chitin is a pretty stable substance whereas the inner organs can be dissolved and absorbed by the leaf.

Plus, it’s not the chitin carapace that contains the “nutrients” the plant needs, so there is no need to develop mechanisms to break down the chitin.

Practical hint:
You don’t need to actively feed the plant, the insects are not the main “food source”, but merely like a mineral supplement that makes up for the fact that they naturally grow in low-nutrients soil like bogs. (Which is also the reason why you should not add fertilizer or use pre-fertilized substrate for them.) I am not saying that you shouldn’t feed the plant, just that you don’t have to worry about them and that the occasional fly now and then is enough, whether it’s caught by the plant itself or by you doesn’t matter.

A trap leaf can also just open and close a few times, then it will wither and die. So as tempting as it is, don’t play with the traps too much...

  • Although Graham's answer has useful advice, I think this answer gives the real reason. A dead "eaten" fly looks much like a dead fly. I wouldn't feed them either. There's a tendency to feed too many and flies that are too big. – winwaed Sep 24 '18 at 13:22
  • Not sure about that. The plant can detect chitin products as they are degraded. – Graham Chiu Sep 25 '18 at 4:52

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