[cobirds] A gentle rain in Fort Collins (Larimer)

This morning as I sat on my apartment complex stoop, the sun was out, the sky was clear blue, and it was gently raining, a drop here, a drop there.  As the coffee allowed my eyes to focus, I discovered the "raindrops" writhing on the sidewalk in response to their newfound freedom were pale "worms".  The "rain" was actually larvae of the Elm Leafminer (Profenusa ulmi, member of the wasp group called "sawflies") and lapping them up were robins, grackles, a black-capped chickadee family, house finches, bushtits and a white-breasted nuthatch.  The larvae mine Siberian elm leaves, like the European Elm Flea Weevil (Orchestes alni) we saw being preyed upon at the Lamar CFO Convention by the Golden-winged Warbler and many other species, but much more extensively and in a different pattern (see the next installment of "The Hungry Bird" in "Colorado Birds").  After completing their wide, brown mine that angles at a 45 from the leaf midvein, often flanked by similar mines of siblings that collectively may involve essentially the entire leaf surface, they exit the leaf and fall to the ground.  There, if overlooked by hungry birds, they wriggle into the soil, overwinter, and transform into a quarter inch-long blue-black, non-stinging wasps the following May.

                                                                                    

 

Larvae of the Elm Leafminer collected today from a 4 square-foot area under a Siberian Elm in Fort Collins.  Each larva is about 3/8ths of an inch long

Dave Leatherman
Fort Collins