Firefly By Day

Everyone can recognize a firefly at night when they light our night landscape with their bright flashes. During the day, fireflies are not actively flashing signals to prospective mates and are more difficult to recognize. Fireflies can be found on foliage and visiting flowers where they feed on pollen.

Pollen is higher in protein content than other parts of a plant. Insects may feed on pollen to increase their protein intake which is needed to produce more eggs. Many plants make excess pollen to attract insects to feed. Some pollen attaches to the feeding insects and the insects carry pollen and help fertilize the plants. For plants, pollination by insects is more efficient than wind pollination. Even though the insects consume some of the pollen, pollen is delivered to other flowers by the insects much more efficiently than the wind could blow the pollen to another flower.

Fireflies are not easily disturbed and will allow people to approach very closely. Most fireflies are toxic to birds and other predators. Fireflies of the genus, Photinus produce toxins called lucibufagins. The toxins allow the fireflies to feed and rest undisturbed. Fireflies advertise their toxicity with their black and red warning coloration. If disturbed, they will secrete a milky liquid that contains the bitter and toxic chemicals.

Predators that live in areas with fireflies are naturally cautious about eating them and will reject them. Some exotic predators, such as the Australian bearded dragon lizard, are not conditioned to avoid fireflies. Entomologist and chemical ecologist, Tom Eisner, reported on two cases of lizards, fatally poisoned by Photinus spp. fireflies. Pet owners must control the food their pets can consume.

Do not let children put fireflies in their mouths (or put them in your own mouth). Fortunately, most toxins are intensely bitter and the innate reaction is to spit them out. A bitter taste is nature’s way of letting us know that something is not good to eat.

Firefly, Photinus spp., Feeding on Cilantro Pollen

About jjneal

Jonathan Neal is a retired Associate Professor of Entomology at Purdue University and author of the textbook, Living With Insects (2010). This blog is a forum to communicate about the intersection of insects with people and policy. This is a personal blog. The opinions and materials posted here are those of the author and are in no way connected with those of my employer.
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5 Responses to Firefly By Day

  1. Pingback: Firefly | Living With Insects Blog

  2. Pingback: Firefly Lights | Living With Insects Blog

  3. Pingback: What a Firefly Taught me about Impermanence | Sweeping ZenSweeping Zen

  4. Hi jjneal, do you happen to know of a reference that documents the claim that “Fireflies advertise their toxicity with their black and red warning coloration”? thanks, Peter Andolfatto (

  5. jjneal says:

    Offhand I cannot name an article that addresses color pattern. There are articles that discuss aposematism in fireflies including bioluminescence in immatures, clicks by adults to deter bats as well as chemical signals. You might try searching the lit using “firefly aposematism”. Hope this helps.

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