Tuesday, May 1, 2012


I've poking around along the Mississippi River with my kids this spring.  Our favorite spot is along Boom Island across the river from downtown Minneapolis, because we've found a few fossils there.  So most of our poking around is under rocks, looking for more fossils.  Almost every rock we turn over has at least one stonefly under it, if not more (and many more Isopods, maybe a later post).  The first time we found one I recognized it as a stonefly, but realized I didn't much of anything about them.  So what follows is a random assortment of stonefly facts.

  • Stoneflies make up the insect order Plecoptera.  
  • According to the USGS, there are nineteen species of stoneflies in Hennepin County,and 53 species in all of MN.
  • They are usually found along streams and rivers.
  • Stonefly adults feed on soft plant parts such as young leaves, buds, fruit, flowers, and pollen.
  • Stonefly nymphs (young) live in the water and either feed on dead plant material, or on other insect larva, depending on the species.
  • Stonefly adults are pretty secretive, hiding under rocks, in crevices, or under debris pushed up onto the shore.  They rarely fly, preferring to crawl, and are nocturnal.
  • Stoneflies find mates by "drumming", tapping their abdomens against something, which can be felt by another stonefly.  Each species and each sex of each species has its own drumming pattern.  Since the sounds just travel through the substrate they are drumming against, we can't detect them (too bad). 

We've had a enjoyable times at this little rocky shoreline.  It's strangely isolated for being within close view of downtown; we've been there four times and have never even had a person peek down at us.  I'd like to return throughout the summer and see what else hatches out and/or is living under the rocks.