Wednesday, November 25, 2015

Pigmy Backswimmer

Pygmy backswimmer with a ballpoint pen - REK
While looking at life in a pond at the WOLF school, the students noticed that some of the tiny black specks were actually swimming in the thick mat of duckweed. They started chasing them in a drop of water with a handheld microscope but photographing them proved elusive. It took me even longer to get these blurry images as they wiggled around on damp paper. This video of it swimming on a single drop of water shows it better.

I sent these pictures with apologies to Dr. David Bowles at Missouri State University who responded patiently "That is a pygmy backswimmer (Heteroptera, Pleidae, Neoplea striola). They are by no means rare, but often overlooked due to their small size. Nice find." * Kind words for a blurry picture. According to Dr. Andy Hamilton at, Neoplea striola is the only common member of the family Pleidae (pygmy backswimmers) in eastern North America.

Hanging just below the surface, watching its reflection  -  Lonny
As the name implies, these bugs hang upside down on the surface of the water, using their oar-like legs to swim. These predatory Hemiptera (true bugs) voraciously attack mosquito larvae while avoiding mosquito predators so they would seem to be a good choice to introduce for mosquito eradication. This was attempted in California but they found that N. striola requires cold overwintering conditions to reproduce according to

I had to go four levels in Google to find any more information about this insect that lacks a good press agent. describes its underwater hibernation in New England lakes, awakening only when the water temperature reaches 54 degrees Fahrenheit in the spring.  They have fine hairs which carry air when they dive, allowing them to reach deeper depths before the bubble collapses.  The bad news is the denser the hair, the less surface area the insect has to absorb the air.

Dorsal view - Lonny
None of this is important in our shallow pond.  I will have to measure the water temperature this winter to see how cold it gets, but it appears to have found a good home in this haven far from other ponds.  How it got this far into the forest, only its ancestors know.  

*  This blog depends regularly on the patience of expert friends reviewing blurry photographs.  Thanks to all of them for humoring us.

Update-June 12, 2017  
More from the Bug Lady

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