Restoring Bottomland Prairie, May 2015, Part2: How Many Flies Can a Catchfly Catch?

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Mid-May 2015 was a lush growing time!  

In the tangle of vegetation in the "Postage Stamp" (a half-acre on the south side of the bridge, between the driveway and the creek), appeared these interesting but puzzling plants.   I was familiar with Saponaria officinalis, AKA Bouncing Bet, and these looked like Bouncing Bet writ large.  But where Bouncing Bet is low & leafy, these plants were tall & rangy, with lots of naked stem.   Still, those opposite leaves, the five petals, the tube-like capsule below the bloom--this had to be a relative.   I pored over descriptions of Bouncing Bet's family, the Pinks (Caryophyllaceae), and found a few likely candidates--but always one detail or another didn't fit.   Finally, I turned to Mark Mayfield at the KSU Herbarium.  Mark quickly identified this sweet little plant:  It is Sleepy Catchfly, Silene antirrhina.  

Sleepy Catchfly is a native plant, unlike its
European cousin Bouncing Bet.

Insects might not think it's so sweet.   There is a sticky substance on its stem that traps flies and other arthropods.  

This annual plant
loves disturbed ground.

The ability to trap insects makes this plant "protocarnivorous" or "paracarnivorous"--on its way to becoming carnivorous or similar to carnivorous plants in some ways.    Silene antirrhina catches insects but it doesn't digest them, as far as anyone knows.    

Is it evolutionarily on its way to developing the enzymes needed to digest insects?    Or did it once have that ability and discard it along the way?  Or does it retain a quality that is currently of no use to it but might be needed in the future--if it should grow on soil too poor, for example, to provide it with enough nitrogen?  

Why would Catchfly bother to catch flies if it doesn't get any benefit out of it?

Some other species trap insects which in turn draw predatory insects whose feces provide the host plant with nitrogen.   Could my Catchfly be doing the same?

Others trap crawling insects on their stems with the result that only flying insects reach the blossoms--providing possible advantages for pollination, seed-protection, or seed-dispersal.   The "catchiness" certainly slows down plant-eating crawlers as well.

So maybe my sticky plants do derive some benefit from trapping bugs--some benefit we have yet to discern.

That's for Catchfly to know and us to find out!