I have a world that consists of hundreds of different caverns inside an earth-sized planet. Each of these many caverns consists of many different biomes, such as plains, Jungles,deserts,etc.

However since the plants and trees in these caverns are photosynthetic, I created a carnivorous light producing plant only found on the ceiling in these ecosystems to ensure the trees below survive.

Majority of the plant's mass is just a cluster of vines and roots that cling to ceiling but what makes it interesting is they grow strange bioluminisant bulbs. The Bulbs are 8 meters wide and are usually 50 to 20 meters away from each other. The color of these bulbs shift from white to blue depending on certain hours.

(You can see I'm trying to make a portray of day and night)

The Purpose of these bulbs is to attract Airbourne prey that rely on their own Bio-luminescence to attract mates. Once prey lands on the bulb and realizes it's a trap, their body is then absorbed into the bulb and kills the prey via suffocation. This usually happens in the "nighttime" when bulbs produce a blue or white light not bright enough to blind someone's eyes.

During the day, the bulbs release huge amounts of light and heat in order to steer away larger flying animals from consuming them, this in turn causes the plants in the bottom to rely to this bright light to grow. During this state, looking at them too long may cause blindness.

To sum it all up, how intense should the light of these bulbs be in order to sustain the plant-life below? And if so, how much prey should these bulbs consume in order to sustain enough energy to glow brightly for 24 hours?

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    $\begingroup$ An ecosystem cannot work without constant energy input. On land and in the euphotic ("well-lit") part of the ocean, this constant energy input is in the form of light (and heat) from the Sun; this powers photosynthesis, and then the biomass produced by photosynthesis feeds all the other organisms, either directly or indirectly. The energy received from the Sun is huge; most inhabited places receive 3.5 to 7 kWh / day / square meter. You must replace this constant input of energy with something. What's that something? $\endgroup$
    – AlexP
    Commented Jul 29, 2017 at 7:22
  • $\begingroup$ How about bulbs lined with unobtainium oxide on the inside allowing for fusion reaction to take place? what-if.xkcd.com/151 $\endgroup$ Commented Jul 29, 2017 at 15:26
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    $\begingroup$ @AlexP geothermal energy could work, though it's one hell of a messed up ecosystem. Geothermal feeds worms, worms feed airborne beasties, airborne beasties feed bioluminescent predators, bioluminescent predators feed trees. The energy transfer required to get any reasonable level of light to the trees means that most of the cavern will be filled with worms. $\endgroup$
    – Joe Bloggs
    Commented Jul 30, 2017 at 10:35

3 Answers 3


You need some energy to come into the system from outside.

The bulbs get their energy by eating insects. The insects get their energy from eating plants, animals or dung. The energy in the animals and dung all came from plants or from things that get energy by eating plants. The plants get their energy from the bulbs, so it's all a big closed loop.

A bit of energy is lost at every point in the loop. More is lost every time a life form walks, flies, grows tall, or in any other way expends energy on something other than being delicious. The ecosystem will quickly die out unless there is some kind of energy coming in from outside the cave. The more energy comes in, the richer the ecosystem can be.

It could be chemicals seeping up from deep underground, or an underground river that brings food from the surface.

If stuff is going in to the cave then you will also need a way for stuff to leave the cave, so it doesn't fill up.


I am afraid your world cannot work in the way you envision.

First of all, assuming your plants are no better that our real plants, we have that if your globes produce so much energy in form of heat that it is disturbing for other animals, it's pretty hard to have the globe cells withstand it, mainly because you require them to produce heat, not only light (bioluminescence is normally "cold" light).

Then you also want to sustain a biome with this light. Keep in mind that when it comes to photosynthetic efficiency

For actual sunlight the theoretical maximum efficiency of solar energy conversion is approximately 11%. In actuality, however, plants do not absorb all incoming sunlight (due to reflection, respiration requirements of photosynthesis and the need for optimal solar radiation levels) and do not convert all harvested energy into biomass, which results in an overall photosynthetic efficiency of 3 to 6% of total solar radiation

But where do these globes producing plants take the energy to sustain themselves and produce also light? You say they grow in caves, so sunlight appears to be ruled out. Since you mention other biomes, I tend to rule out also volcanic activity as energy source. Feeding on insects won't work, because insects are supported by the same plants using the globes to grow.

As a reference, our Sun drops on Earth aboout 1000 W per square meter, and that is enough to sustain life as we know it. Yet this is not enough to disturb insects, which fly during the day with no problems.

  • $\begingroup$ Thank you for the feedback and a few sources you presented me I can use to answer some of the questions myself. $\endgroup$
    – Red_Wasp
    Commented Jul 29, 2017 at 3:42
  • $\begingroup$ Also to answer your question on to where they can acquire the energy off give off light. I mentioned earlier in order for them to do so would be going into a carnivorous diet to attract flying insects, like giant moths or glow flies and then absorbing their bodies for that energy during the "nighttime". And sense you said that it takes 1000 W per square meter to support plant life, does it drop 1000 W per day or per hour in that time frame? $\endgroup$
    – Red_Wasp
    Commented Jul 29, 2017 at 3:52
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    $\begingroup$ The animals are supported by the biomes which are supported by globes... what you envision is called perpetual motion... $\endgroup$
    – L.Dutch
    Commented Jul 29, 2017 at 3:58
  • $\begingroup$ @Red_Wasp, you are probably new here, as sign of appreciation you can upvote any useful answer (and even accept the best one) $\endgroup$
    – L.Dutch
    Commented Jul 29, 2017 at 4:10

If the caves are open (to the outside) you can say that flying creatures that came from outside the caves (that feed on usual plants or phototrophic ecosystems under normal sunlight) are lured in by the bulbs’s Light in the caves, flying into the caves and getting consumed, thus providing the ecosystem with energy. For waste, water and airflow into and out of the caves would probably get rid of it.

Or, the plants get its energy from parts of itself that photosynthetizes outside the caves, connecting to the parts that’s inside the caves in order to lure the insects within for things like fertilizers or minerals (like real carnivorous plants do) you basically need some external power supply and a mean to transport this power into the caves, just like real world hydroponic farms that uses electricity from wires to power their lights.

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    $\begingroup$ Hi! Welcome to Worldbuilding! You may want to add paragraph breaks into your answer somewhere, it will make it easier to read! $\endgroup$
    – Rob Rose
    Commented Jun 5, 2018 at 2:08

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