How would giant, secluded, underground-cave-dwelling insects get enough food?

In my world, there are underground ruins from an ancient civilization. There are giant insect creatures living in these underground cave-like ruins, ranging from the size of a large dog to the size of an elephant. They are attracted to these ruins due to a magical aura it gives off, and have a natural resistance to it. The attraction is so strong that they don't leave the underground caves to gather food from the surface, or for any other reason. The same aura makes other animals die.

There is no light coming into the underground caves, but there is a natural supply of water that makes its way down into these underground caves. Plants don't die from the aura, but since there's no light, plants have a hard time living there.

Are these conditions too unrealistic for such a creature to thrive?

What else would need to be present in this environment for giant insect creatures to have sufficient food so that they could thrive in large numbers?

Edit: Thank you everyone for the great answers! You've all given me a lot of really interesting things to consider. This community is awesome.

posted over 6 years ago

anwen‭

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