I have a large terrarium where I grow various types of moss. I keep springtails in there to handle any mold that pops up, but some creature (fungus gnat larvae?) was killing off the springtails. So I captured a jumping spider, thinking it would gobble up the fruit flies/larvae. The fungus gnats have disappeared, so it seems like the spider might have done the job, but now I’m worried about it getting hungry.

I gave it a mayfly a couple days ago, and that evening it was sitting in the corner of the terrarium like a toddler with a juice box, so it obviously likes those. Are there any specific things that are good to feed it, or can I give it anything that I catch that isn’t predatory? For example, would a “regular” sized moth be dangerous? It’d be like 2-3x the size of the spider.

  • SalamanderMA
    2·
    2 years ago

    A moss terrarium! That’s super cool!

    I don’t think the moth would be dangerous, but I would be surprised if the jumping spider actually attacks it. I did find a few images like this one, so it is not impossible. But my bet is that it won’t attack it.

    Jumping spiders are quite generalists, so my strategy would be to first find out which insects are easily available to me - either because I can find them near my place or because I can attract and catch them (flies, pill-bugs, earwigs, worms, millipedes, etc). Then I would search specifically whether each of those insects is safe or not for a jumping spider - but I would think that anything that won’t eat the jumping spider is fine.

    As to the ecological succession that you have observed of spring-tails -> fungus gnats -> jumping spider. It is possible that your interpretation is correct - that the gnats ate the springtails and the spider ate the gnats. However, judging by my experience with plants, fungi, and worm bins, it is usually the environmental conditions that usually cause the dramatic changes in populations.

    For example: A sudden increase to high humidity can cause a population of springtails to boom and entice gnats to deposit their eggs. As the environment dries up, the population of spring tails decreases and as the gnats turn into adults they become more noticeable. Since the environment as not as humid as before, the gnats then fly away to find a more humid place to lay their eggs. And so you might observe a succession like the one you have observed even without predation. Humidity is one variable, but temperature, light, fresh air (CO2), and pH are other important parameters that can be difficult to keep track of.

    Just my two cents!