A Light Snack
While our firefly male is flying and flashing, his mind set on sex,
other nocturnal creatures are out here, too – and they’re intent
upon dinner. This meadow is home to hundreds of wolf spiders
and their orb-weaving cousins, all eager to put firefly filet on
tonight’s menu. They’ve strung webs between the tallest grass
stalks, invisible traps waiting to ensnare careless flyers. Lots
of unlucky male fireflies will get quietly filtered out of the air
tonight, and so will meet their sticky ends wrapped up tightly
and hanging limply (see photo at left). Yet even as he dies, the
unfortunate male’s flash may live on. Our field notebooks are
filled with observations of fireflies shrouded in spider’s silk that
continue their rhythmic flashing long after they’ve been immobilized. Their flashing attracts other fireflies, and sometimes
these newcomers wind up trapped in the web too. Perhaps these
spiders have figured out how to turn their captives into bioluminescent fishing lures.
What are the odds in this gamble between sex and death?
Jim Lloyd decided to find out. He headed out from Gainesville,
Florida, to a grassland hotspot for Photinus collustrans fireflies.
Equipped with his sharp eyes, a surveyor’s wheel, and a tally
– one at a time – as they cumulatively logged more than 10
frequent flyer miles and gave nearly 8,000 flashes. Only two
males wound up finding females, while the same number found
themselves in a predator’s deadly embrace. For a Photinus male,
the search for mates is certainly a high-stakes game of reproduc-
Back in our New England meadow, our male fireflies are still
aloft. They’ve been patiently searching for nearly 20 minutes.
Now, at last, one male glimpses a flashed reply from below. The
time delay is just right for his species – finally, a female has
answered his calls! He swiftly drops from the air to land nearby.
A flirtatious flash exchange strikes up as he scrambles toward
the female on foot. He runs partway up a grass blade, stops, and
flashes. Will she answer him this time? No. He runs farther up
the blade, stops, and flashes once more. Now she does reply, but
rats – it looks like he’s been traveling in the wrong direction.
He’ll need to retrace his steps. This intermittent courtship dialogue continues while the male runs frenetically up and down
grass blades searching for the female. Another hour passes
before he sees her response directly above him – she’s right here
on the same grass blade! Rushing upward, he climbs onto her A mating pair of Photinus fireflies (female left, male right).