Lizard bitten by its feeder insects: crickets, stings and the invertebrates that are dangerous

Quick answer

The insect problem most lizards actually meet is not a sting. It is a hungry cricket left in the enclosure overnight with a sleeping gecko.

Owners worry about their lizard being stung. In practice the common injury runs the other way: uneaten feeder insects chew on the lizard. Crickets are scavengers, and a cricket with nothing to eat in an enclosure will feed on a sleeping, shedding, ill or hatchling reptile.

The fix is immediate and free. Remove every live insect from the enclosure after each feed, check the animal over, and treat any wound as a route for infection rather than as a scratch.

• Never leave live crickets, locusts or worms in an enclosure overnight.
• Check toes, tail base, vent, eyelids and the skin folds. Those are where the bites appear.
• Any wound in a reptile is an infection risk. Move the animal to paper towel and keep the enclosure clean.
• Never feed wild-caught insects. Fireflies in particular are lethal to bearded dragons.
• Swelling around the face or mouth after an outdoor sting is an emergency, because swelling there can obstruct breathing.

:::danger
Never feed a firefly, or any glowing insect, to a bearded dragon or any other lizard.

Fireflies contain defensive compounds that are highly toxic to reptiles, and ingestion of even a single one has been associated with rapid death in bearded dragons. Signs include head shaking, darkening of the body, open mouth breathing and collapse within a short time. There is no home treatment. This is a same hour emergency, and the only reliable protection is that feeder insects come from a captive-bred source and never from the garden.
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Decide in 60 seconds

Why the feeder is the danger

Crickets eat what they can find.

A cricket is not a passive food item. It is a scavenging omnivore that needs moisture and protein, and in a bare enclosure the only source of both is the reptile. Left in overnight, crickets congregate on the warm animal and start feeding on the softest available tissue.

The lizard is asleep and often cannot respond.

Leopard geckos, crested geckos and other nocturnal species are inactive during the day, but so are many diurnal lizards at night, when the lights are off and the crickets are most active. A lizard tucked into a hide has nowhere to retreat to.

Shedding skin is an invitation.

Loose or retained shed is soft, moist and easy to chew, and the skin underneath is thin and newly formed. Lizards in shed should not be left with live insects at all.

Weak animals are the ones that get bitten.

Hatchlings, animals recovering from illness, gravid females, brumating lizards and anything that has stopped eating are all far more likely to be attacked, because they neither eat the crickets nor move away from them.

The bite is small and the consequence is not.

A cricket bite is a puncture in skin that is difficult to keep clean, in an animal whose immune response is temperature dependent, in an environment full of bacteria. The wound is trivial. The abscess it becomes six weeks later is not.

Where to look, and what a bite looks like

Small wounds are cleaned with sterile saline on paper towel, not with human antiseptic creams. Anything that seals the surface traps bacteria underneath.

Toes and toe tips.

The commonest site. Look for missing tips, crusted ends, and swelling of a single digit.

Tail base and vent.

Soft skin and folds. Bites here are easy to miss under the tail.

Eyelids and around the eye.

A serious site. Geckos are particularly vulnerable, and eye injuries in reptiles progress quickly and can cost the eye.

The vent and cloacal area.

Moist and attractive to a scavenging insect.

Along the flanks and skin folds.

Especially in animals with loose skin or in poor condition.

Anywhere with retained shed.

Bites cluster where the skin is already compromised.

What the wound looks like.

Early, a small red or dark spot, sometimes with a bead of dried blood. At a day or two, a crusted point. If it becomes infected, the area swells, changes colour, may discharge, and the animal may stop using a limb or stop eating.

The response, step by step

One. Remove every insect.

Take the enclosure apart if you need to. Crickets hide under decor, in substrate, and behind heat equipment. Removing the cause takes priority over treating the wound.

Two. Examine the whole animal under good light.

Toes one at a time, tail base, vent, eyelids, mouth. Note and photograph what you find.

Three. Switch to paper towel.

Loose substrate sticks to wounds and is the main reason a small bite becomes an infected one. Keep the animal on plain paper until the skin is closed.

Four. Clean gently, with the right thing.

Sterile saline, or cooled boiled water if that is all you have, applied with clean gauze or a cotton bud. Nothing else without veterinary direction.

Five. Do not seal it.

No ointments, creams, oils, honey, petroleum jelly or plasters. They trap bacteria against the skin and make assessment harder.

Six. Get the temperature right.

Reptile healing is temperature dependent. A wound in an under-heated enclosure heals slowly and becomes infected more often. Check the gradient with a probe at animal level.

Seven. Watch, daily, for a fortnight.

Swelling, discharge, colour change, a firm lump, reduced use of a limb, reduced appetite. Any of these means an appointment.

Stings, and what actually happens

Wasp and bee stings do occur, mostly in lizards given outdoor time or in enclosures near an open window, and occasionally when a lizard catches and eats a stinging insect.

What to expect.

Local swelling and pain at the site. Most lizards deal with a single sting to the body without drama.

What is genuinely dangerous.

Swelling in or around the mouth, throat or face. Reptiles have narrow airways and a fixed skull structure, and swelling in that area can obstruct breathing. Any facial swelling after a suspected sting is an emergency.

What not to do.

Do not give antihistamines or any human medicine. Dosing in reptiles is not scaled from human or even mammal doses, and the wrong drug or amount is dangerous.

What is not documented.

The dramatic whole-body allergic reaction that people worry about is a mammalian pattern, and it is not something reptile keepers should be planning for. The realistic risks are local swelling, airway obstruction if the sting is in the mouth, and infection at the site.

The invertebrates that are dangerous

Fireflies and glow worms.

Toxic to lizards, and bearded dragons are particularly well documented. Never offer them, and never let a lizard hunt outdoors where they occur.

Wild-caught insects generally.

Garden and field insects may carry pesticide residues, internal parasites, and pathogens that captive-bred feeders do not. Wild grasshoppers and crickets are a known parasite source.

Ants.

A serious hazard for hatchlings and immobilised animals. Ants find enclosures by following spilled food and can swarm a small or weak reptile. Some species also sting.

Centipedes and spiders.

Venomous bites, and some are large enough to injure a small lizard directly.

Brightly coloured beetles and bugs.

Ladybirds, boxelder bugs and stink bugs all carry defensive chemicals. As a rule, insects that advertise themselves with bright colours are advertising that they are unpleasant to eat.

Anything from a treated area.

Insects collected near a treated lawn, a sprayed crop or a flea-treated pet carry residues that can be harmful in a small animal.

The safe position is simple: feeders come from a captive-bred source, and the garden is not a food supply.

Feeding practice that prevents all of this

Clean towels, gauze and a carrier, ready before you need them. Most of what an owner does for a feeder bite is prevention plus a clean environment.

What else it could be

A lump or a swelling on a lizard is not always a bite, and the alternatives matter.

Abscess.

Firm, often well defined, developing days to weeks after a wound. Reptile pus is solid, so it does not burst and drain the way a dog abscess does, and it usually needs surgical removal.

Retained shed constriction.

A ring of unshed skin on a toe or tail tip cutting off circulation. The tissue beyond it swells, then darkens and dies. Easily mistaken for a bite injury.

Metabolic bone disease.

Swelling of the jaw and limbs, a rubbery lower jaw, tremors and difficulty walking. Nothing to do with insects, and a husbandry emergency of its own.

Thermal burn.

Reddened or blistered skin from contact with an unguarded lamp or a heat rock, often on the back or belly rather than the toes.

Mouth infection.

Redness, discharge or cheesy material in the mouth, reluctance to eat, and swelling of the jaw line.

Tumours and cysts.

Common in older lizards, and best assessed early.

If you did not see insects on the animal, do not assume a bite. Take a photograph, note when it appeared, and let the vet work through the list.

What the vet will want to know

What never to do

Do not leave live feeder insects in an enclosure overnight.

Do not feed insects collected outdoors, and never a glowing one.

Do not apply human antiseptic creams, ointments, petroleum jelly or plasters to a reptile wound.

Do not use hydrogen peroxide on tissue.

Do not give antihistamines, painkillers or any other human medicine.

Do not leave a wounded lizard on loose substrate.

Do not offer live insects to an animal that is shedding, brumating or unwell.

Do not squeeze or attempt to drain a firm swelling at home.

When to get help

The outcome to aim for: a calm lizard on clean substrate, with the feeding routine corrected so it does not happen again.

Go immediately for facial or mouth swelling, breathing difficulty, collapse, or any sign of illness after a wild insect has been eaten. Take the insect or a photograph with you.

Go the same day for an injured eye or eyelid, a wound that is swelling or discharging, a lizard that has stopped using a limb, or a hatchling with multiple bites.

Book an appointment this week for a firm lump developing after a bite, a darkening toe or tail tip, missing toe tips, or a wound that has not closed within a couple of weeks.

While you arrange help, keep the lizard on clean paper towel at the correct temperature gradient, leave the wound alone apart from gentle saline cleaning, and make sure there is not a single live insect left in the enclosure.