If your toddler is prone to putting things into his or her mouth, be careful that they don’t try tasting these toxic insects and related organisms.
The bright glow of a firefly adult or larva is thought to be a warning that these insects are full of potent steroid chemicals called “lucibufagins.” The compounds are a close relative of toad toxins. You wouldn’t lick a toad, so don’t try a firefly, either.
Blister beetles (family Meloidae) are unfortunately non-descript, and diverse in their appearance. They are most abundant in deserts, prairies, meadows, and agricultural lands. Squeeze one and it exudes an oily liquid from its leg and body joints. The liquid contains the toxin cantharidin, and it can raise painful, scarring blisters on sensitive skin. Ingested, it can be fatal, even to horses and other large animals.
Monarch Butterfly Caterpillars
Insects that feed on toxic plants, like milkweed, often sequester those toxins, incorporating the poisons into their own bodies for self-defense. Steer clear of insects with bold patterns of black or metallic blue and white, red, yellow, or orange. This is the bug’s way of advertising that it is dangerous to eat.
Bombardier beetles (Brachinus spp.) are not common, but you might find them under stones or boards in fields or near water. Bother a bombardier beetle and it will literally blast you with hot acid. Two chemicals stored in separate glands inside the beetle come together in a “reaction chamber” in the beetle’s rear, creating a minor explosion.
Most millipedes, class Diplopoda, have defensive chemical secretions that they deploy when threatened by a potential predator. Among the over 30 toxins known from various millipedes are hydrogen cyanide, acetic acid (vinegar), formic acid, benzaldehyde, and phenol. Most millipedes coil up before excreting such chemicals.
Remember that inquisitive cats, dogs, and other pets can also suffer from encounters with toxic insects, millipedes, and other invertebrates. Keep cats indoors, and watch what Fido gets into. Livestock owners need to beware that blister beetles can be inadvertently baled in hay.