Life History & Reproduction

Like all beetles, Photinus ignitus and all other fireflies undergo an indirect life cycle of four life stages: egg, larva, pupa, and adult (Lloyd, 2005).  The egg, or embryonic stage, is where the firefly life cycle begins.  A fertilized female will deposit her eggs in the soil around mid-summer. Photinus ignitus have a preference for moist soils, so the most common place for their eggs will be under mulch (Debbie, 2013).  To learn more about the environment that Photinus ignitus lives in check out Habitat and Geography.  The worm-like hunting and eating specialist indicate the next stage of the firefly life cycle: larval stage.  Larvae are predaceous, and at night, they will hunt soft-bodied prey, such as slugs, snails, worms, and other insects.  Photinus ignitus are especially apt to target annelids (segmented worms) while scavenging for food (Lloyd, 2005).  Upon capture of the prey, the firefly larva will inject digestive enzymes that will immobilize and break down the remaining kill (Debbie, 2013).  Some snails that live in the same environment as Photinus ignitus are Stenotrema exodon and Stenotrema barbatum.  Even though in a different environment, here are a couple more interesting snails that could be prey for other species of fireflies, Praticolella candida and Praticolella trimatris. 

                     
                                      Glow worm larva eating a snail from Robin Scagell.

Larvae, also called glowworms, have a defensive mechanism of being luminescent.  The larvae glow to indicate to predators of an unpalatable, or unpleasant, taste.  They may even have lethal consequences to the predators who are not warned off (Lloyd, 2005).  To learn more about this, visit the Interactions page.  In the next stage of the firefly, we examine a remarkable transformation.  The pupal stage usually takes place in late spring, where the larvae seek or make sheltered places (Debbie, 2013).  Photinus larvae usually pupate in self-made chambers under the surface of the soil.  Pupation lasts from one to three weeks (Debbie, 2013), where the larva’s body is broken down by biochemical processes and transformed into an adult firefly (Lloyd, 2005).  An estimated 10 days to several weeks after the completion of metamorphosis, the adult firefly is ready to emerge.  The adult firefly is generally only concerned with finding a mate and reproducing (Lloyd, 2005).

The way in which fireflies find mates and reproduce is quite fascinating.  Fireflies, in general, have a diverse form of courtship signals.  The way in which the males find the females is very different depending on what part of the day the firefly is active.  The fireflies that are active during the day detect where the female is by the females’ pheromone, which is a volatile chemical signal that leads the male upwind toward the signal source, the female (Lloyd, 2005).   Photinus ignitus is a nocturnally active firefly.  Instead of using pheromones for their long-range attraction, these fireflies use discrete pulses of bioluminescence to locate their mates (Lewis & Cratsley, 2008).  In some species, only the flightless female will emit flash signals to attract the male, but in Photinus ignitus, both species produce bioluminescent glows (Lewis & Cratsley, 2008).  To increase the complexity of finding mates, the flash signals emitted from both sexes are precisely timed to encode what species the lightning bug is and also whether it is male or female.  In some species there is just a single flash of bioluminescence, but in Photinus ignitus it is a group of flashes (Lloyd, 2005).  After the female locates a male of her species producing bioluminescent courtship flashes with his lantern, the female will respond from her perched location with a flashing of her own after a critical species-specific time delay (Cratsley & Lewis, 2005).  This courtship dialogue will continue back and forth until the male, who is flying, walking and climbing towards the destination, makes contact with the female (Lewis & Cratsley, 2008).  The flashing will cease after the male mounts the female dorsally.  Copulation (sexual intercourse) occurs once the male firefly inserts his aedeagus (male reproductive organ) into the female’s genital opening (Cratsley & Lewis, 2005).  This is the first of two stages of mating.  Stage two occurs once the male rotates 180°, remaining abdomen-to-abdomen with the female.  The male then transfers a spermatophore (a sperm-containing package) into the female’s bursa.  This stage is quite long, lasting up to 8 hours (Cratsley & Lewis, 2005). 

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