This article was published originally on 8/25/2010 Alert readers
across Iowa and in neighboring states are asking, "Why are there
are so many dragonflies this summer?" I'm not sure what explains
this larger-than-normal number of dragonflies but callers are
reporting anywhere from "dozens" to "hundreds" of dragonflies
flying in swarms during late afternoon to early evening.
Excessive rainfall in this year does not explain the abundance.
Dragonflies develop as nymphs in rivers, streams and lakes. Most
take at least one year to develop from the egg to the adult
stage, and some take 2 or 3 years. So the swarmers you see now
are at least one year old and probably two. These are the
offspring of last year’s adults (if not the adults that were
flying back in 2008 or 2009). To me, that means this year’s
abundance is related to what happened 1 to 3 years ago, and not
what happened 1 to 3 months ago. In fact, I predict that
dragonfly numbers will be down in the next 1 to 3 years as
flooding of 2010 may have been detrim