Venus flytraps can eat gnats, but they’re surprisingly bad at it. Gnats are often too small to reliably trigger the trap’s closing mechanism, and even when a trap does snap shut, many gnats slip out through the gaps before the trap fully seals. If you’re hoping a Venus flytrap will solve a gnat problem in your home, you’ll likely be disappointed.
Why Gnats Are a Poor Fit
A Venus flytrap closes when an insect brushes against tiny trigger hairs inside the trap. But the system has a built-in safety check: two separate hairs must be touched within 30 seconds for the trap to snap shut. A deflection of just a few degrees and a tiny amount of force is enough to fire one signal, meaning even an insect as light as a 3-milligram mosquito can set off a single trigger. The problem with gnats isn’t necessarily their weight. It’s that they may not contact two hairs quickly enough before wandering back out.
Even when a gnat does trigger closure, there’s a second problem. The trap doesn’t seal instantly. It snaps into a loosely closed position first, and the interlocking “teeth” (called cilia) along the edges still have gaps between them. These gaps act as a filter: insects large enough to be worth digesting can’t escape, while tiny ones slip right through. Fungus gnats and fruit flies are often small enough to crawl out before the trap tightens down.
The Energy Problem
Every time a Venus flytrap closes, it pays a metabolic cost. Research published in plant physiology journals found that trap closure temporarily reduces the plant’s ability to photosynthesize while also increasing its energy expenditure. The plant essentially shifts resources away from growing and toward digesting. Each trap can only close and reopen a handful of times in its life before it dies and is replaced by a new one.
This means a trap that closes on a gnat and comes up empty, or digests one successfully but gets almost no nutrition from it, is a net loss for the plant. Studies tracking nitrogen absorption in wild Venus flytraps found that the total amount of nitrogen gathered from very small insects like ants (comparable in size to gnats) is low. The real growth payoff comes from larger prey like crickets, spiders, and grasshoppers, which can deliver a burst of nitrogen significant enough to fuel new trap growth. A gnat weighing less than a milligram simply doesn’t offer much return on that investment.
Can It Happen? Yes, Sometimes
To be fair, Venus flytraps do occasionally catch and digest gnats. If a gnat is large enough or moves around enough inside the trap, it can trigger the full closure and digestion sequence. Once sealed, the trap stays closed for anywhere from a few days to several weeks while it breaks down the insect and absorbs nutrients. So it’s not impossible. It’s just unreliable and not particularly beneficial for the plant.
If you’re hand-feeding your Venus flytrap, flies, spiders, crickets, and even small slugs are all better choices. The insect should be roughly one-third the size of the trap or smaller. Anything too large can prevent the trap from sealing properly, which can lead to bacterial growth and cause the trap to blacken and die.
Better Carnivorous Plants for Gnats
If your real goal is controlling a fungus gnat infestation, other carnivorous plants are far more effective. The Venus flytrap’s snap-trap design evolved for larger, faster insects. Gnats call for a different strategy entirely.
- Butterworts (Pinguicula): These are the top recommendation from university extension programs for fungus gnats. Their leaves are covered in a sticky, glistening surface that works like flypaper. A gnat that lands anywhere on the leaf is stuck immediately, with no trigger mechanism required and no chance of escape. The University of Illinois Extension specifically suggests butterworts for anyone dealing with fungus gnats around houseplants.
- Sundews (Drosera): Sundews use a similar sticky-trap approach. Their leaves are covered in tentacle-like hairs tipped with drops of dewy adhesive. When a gnat lands, the tentacles slowly curl inward, pressing the insect against the leaf surface. Sundews are highly effective against small flying insects and come in dozens of species suited to different climates and growing conditions.
Both of these plants passively catch gnats throughout the day without wasting energy on missed closures. A single butterwort leaf can trap dozens of gnats, while a Venus flytrap has perhaps five to eight active traps at any time, each of which might close on a gnat and fail.
The Bottom Line on Flytraps and Gnats
A Venus flytrap will occasionally catch and eat a gnat, but it’s poorly suited for the job. The gnats are often too small to trigger the trap, too small to be trapped once it closes, and too small to provide meaningful nutrition when they are digested. If you already own a Venus flytrap, don’t worry if it snags one. It won’t hurt the plant. But if you’re buying a carnivorous plant specifically to deal with gnats, a butterwort or sundew will do what a Venus flytrap mostly can’t.