Your mantis won’t eat. You’re dropping flies into the enclosure and it’s ignoring them, or swatting them away, or just sitting there staring at nothing. A mantis refusing to eat — or one that’s suddenly stopped eating after weeks of healthy meals — is one of the most common concerns I hear from new keepers, and the answer is almost always one of three things.

Reason 1: It’s about to molt (pre-molt)

This is the most common reason by far. A mantis in pre-molt will stop eating anywhere from 2 days to over a week before it sheds. It’s not sick. It’s preparing.

Signs of pre-molt:

  • Refusing food it normally takes eagerly
  • Hanging upside down more than usual
  • Abdomen looks fuller/swollen (a darkening abdomen alone is not reliable on its own — read it alongside the other signs)
  • Moving less, staying in one spot
  • Eyes may look slightly cloudy

What to do: Nothing. Remove any uneaten prey from the enclosure (live crickets can bite a molting mantis) and leave the animal alone. Make sure humidity is adequate — mist the walls, not the mantis. Most will resume eating within a couple of days of a successful molt, once the new exoskeleton has hardened — give it up to several days before worrying.

Read our molting guide for the full protocol, and if a molt goes wrong see praying mantis molting problems.

Reason 2: It’s too cold

Mantises are ectotherms. Their metabolism is directly tied to temperature. If your enclosure is below the species’ minimum, your mantis will slow down — eating less, moving less, and eventually refusing food entirely.

How to check: Put a thermometer inside the enclosure, not outside it. Room temperature at your thermostat might read 72°F, but the enclosure on a shelf near a window could be 65°F.

What to do: Bring the temperature into the species’ ideal range. Most tropical species we sell do best around 75-85°F during the day; a few degrees of natural night cooling is fine, but keep nights above ~68-70°F for tropical mantises. Temperate species (Carolina, European, Chinese) tolerate cooler nights. Always check the care guide for your species. A small heat pad on one side of the enclosure works well. Don’t use heat lamps directly on plastic enclosures — they can melt or create hot spots.

Check your species’ specific temperature needs in our care guides.

Reason 3: The prey is wrong

Prey that’s too large is threatening. Prey that’s too small might not trigger a feeding response. Prey that’s too fast might stress the mantis out. Getting the size right matters.

The rule: Prey should be roughly 1/3 to 1/2 the mantis’s body length. A tiny L2 nymph doesn’t know what to do with a full-size cricket. An adult female doesn’t care about a single fruit fly. If you’re looking for a species that rarely refuses food and eats eagerly at all instars, our Spiny Flower Mantis is one of the most reliable feeders we’ve worked with.

What to do: Size down. If your mantis is ignoring house flies, try fruit flies. If it’s scared of crickets, try something less aggressive like a blue bottle fly. Some mantises also have prey preferences — orchid mantises tend to prefer flying insects over crawling ones.

For the full rundown on what to feed at every stage, see feeder insects for praying mantises, and our feeder cheat sheet for a size-by-instar breakdown.

Less common reasons

Just shipped. A mantis that arrived in the last 24-48 hours may refuse food from transit stress. This is normal. Give it time. See our unboxing guide and the shipping and arrival care guide.

Dehydration. A dehydrated mantis may be too weak to hunt. Mist the enclosure walls and watch for drinking behavior. If you see the mantis drinking, that was the problem.

Old age. An adult mantis near the end of its life will gradually eat less. If your mantis is an adult female who’s been laying egg cases, or an adult male well into his adult life (often 2-3 months past his final molt), declining appetite is part of the natural cycle. For typical lifespans by species, see praying mantis lifespan by species. If you’d like to start fresh with a younger nymph, browse our current stock — we list the exact instar for every mantis so you know how much growing (and eating) is ahead.

Illness or injury. Rare in captive-bred mantises, but it happens. If your mantis has a visible injury, discoloration that isn’t pre-molt, or hasn’t eaten in 10+ days with none of the above explanations, reach out in our Discord with photos and we’ll help diagnose.

The golden rule

A mantis refusing food is almost always telling you something is about to happen (molt) or something is wrong with the environment (temperature, humidity, prey size). Don’t force it. Don’t panic. Investigate the why.

If you’re stuck, post in #new-keeper-help on Discord — someone has seen your exact situation before, and the median response time is under 4 minutes.