Monday, May 18, 2015

No Bulb Firefly

Mating Fireflies
I saw a number of these insects on May 6th, crawling on the outside wall of our house as well as nearby trees.  While some spooked, this pair was committed to mating and made only one abortive attempt at flying.  When I transferred them to a photo board where the largest one measured a whopping 12mm, they tried to walk in separate directions without success.

They looked like fireflies but in May?  They are winter fireflies, Ellychnia corrusco, and their time of appearance is only part of their interesting story.  The photograph below was taken on April 12th in Maine by Mike Lewinsky.  He reported "I was shocked to see this beetle land on the snow in front of me, and doubly so when I realized it was a firefly. We are just beginning to see the first sign of insects returning for spring."
Winter Firefly Photo - Mike Lewinski Creative Commons
 A mark-recapture study done in Massachusetts in 2000 on the Life History and Mating Behavior of Ellychnia Corrusca showed that they overwintered as adults with low mortality. 
"By dissecting males and females sampled throughout late winter and spring, it was found that adults become reproductively active in early March, when male seminal vesicles first contained sperm and female ovaries first contained mature oocytes. Both sexes mated multiply during the approximately six-week mating season (early April through mid-May), and copulations lasted up to 28 h."
The genus Ellychnia is known as diurnal fireflies, meaning that they fly during the day.  Most notably they lack the "fire," that is they have no light producing organ as adults like their nocturnal cousins in the genus Photinus.  As overwintering adults which mate in March, it is likely too cold in evenings to fly so that they have evolved a different mechanism, attracting mates instead by pheromones.  

I wanted to photograph their lack of bioluminescent organs, but when I turned them over the loss of dignity was too much for them to stand and they parted ways and flew off in separate directions.  Maybe their timer said that the 28 hours were up.

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