Sunday, July 18, 2021

Water Strider

A pleasant way to spend a summer afternoon is sitting in the swimming hole watching water striders skim across the surface.  Gerridae are a family of insects in the order of "true bugs," Hemiptera.  They use their front and back legs to stay on the surface, rowing with the middle pair.  The short front legs have claws to grasp prey from above and below the surface while the hind legs can serve as rudders.

Their tiny feet resist sinking due to tiny hydrophobic microhairs, more than 1000 per millimeter.  Their ability to skate on water lies in the cohesiveness of water, the same reason that you can put 36 water drops on a penny before they run off as seen here on Youtube.  This creates surface tension, the same reason that it hurts to do a belly flop into a pool.  You can see it in action in this BBC Clip.

Danger comes from above and below.  When they sense movement below the surface from a predatory fish or backswimmer, they can jump up, putting even more pressure on the surface tension. 

Females have anatomical adaptations to resist an insistent male's advances but he may hang on anyway as in this video.  A male will mount and if she resists his advances will blackmail her by beginning to tap the water to attract predators until she yields. Discover Magazine

Water striders mating - Wikipedia

Now add on the weight of a mating male on her back and that puts the female even more at risk.  Surprisingly females can actually learn to jump with the new load.  Scientists have reported in that they actually added weights onto water striders.  With time and practice females learned to jump with the load, using a slightly different technique.  Even more interesting, that is something that the weighted males in the study never learned.  My editor-wife doesn't find that surprising.

Thursday, July 15, 2021

Wren Family Album


Summer is the time when birds are raising a family.  The first clue may be a bird flying with twigs, leaves or even strings, the elements of nest construction.  By watching closely, you may be able to find their nests and watch the family develop.  Once you have found the nest, you should make your visits brief, just for a minute to avoid disturbing the family.  A quick photograph is a good way to follow their development.  Ben Caruthers sent me these photos of a Carolina Wren family.

Freshly hatched and naked

Initially they will be incubating the eggs and the parents will only be leaving the nest for a couple of minutes to avoid chilling their brood.  In some species, only the female broods the eggs while the male hangs around nearby.  Once the eggs have hatched, the pace picks up as the parents begin flying on the hunt for insects to feed their young.  The naked chicks initially sleep soundly but in a few days they may respond to your visit with open mouth, expecting a nice juicy caterpillar.

Partially dressed in downy feathers

Over the next couple of weeks they start to develop their feathers, a look that resembles a tousled look of a “bed head.”  During the third week they will lose some of their fluff and start to look more like a teenager.    

Day 14 - fully feathered and ready to fledge

Some species fledge during the third week.  It is important during this time to avoid disturbing them as a premature fledging puts them in danger, entering the cold cruel world before they are prepared.

Freshly fledged Phoebe  
If you are lucky enough to see a newly fledged bird like this Phoebe, you can still notice little remaining bits of fluff, the last remnants of their youth.

Safe nest watching pointers are available at Code of Conduct.


As I finished writing this yesterday, a tiny downy feather came floating down and landed on my keyboard.  I was sitting on the couch in our family room with no birds in sight.  Spooky! 

Thanks to Ben Caruthers for all the photos and his timeline.

Monday, July 5, 2021

Pearly-eye on the Web?

Pearly-eye in the morning - REK
On awakening, I saw a small butterfly clinging upside down on the bedroom window pane.  After considering how and why it was there, I got up and could see it was a Northern Pearly-eye, Lethe anthedon.  I photographed it with my cellphone and that got me thinking about technology and the pace of change in knowledge.

Bugguide via Creative Commons

L. anthedon was first named by A. H, Clarke in 1936 and a field guide describes the different names and spellings over time.  These would have been scattered in academic papers, known and argued over by a few experts in universities.  Finding this fact alone would have required searching through field guides 10 years ago.  Now I can find its history, lifecycle and foods on my iPad, computer, or even my cellphone if I have the patience to type on the small screen.

Black club bases - BG

At I can see its frequency in individual states as well as if it is threatened and by what factors.  Instead of thumbing through a field guide a page at a time, I can identify a Pearly-eye in seconds by sending a picture to INaturalist.*  However this gives a somewhat ranked likely identification as discussed below.

If I am still unsure, sending it to Bugguide lets experts evaluate the photograph.  This however may take weeks or months, depending on which volunteer expert checks in.  Which Pearly-eye species is it?  "Similar to other pearly-eyes, but more northern in range, bases of antennal clubs black."

In this case INaturalist ranked Pearly-eye as the first choice.  I had sent my original picture in before cropping and color correcting it to the picture above.  Su Lynn Rogers saw the blog and suggested that it might be a Hackberry Emperor.  Looking at the photo closely I discovered she was right.  I submitted the improved photo and the Hackberry Emperor moved to Number one and Pearly-eye dropped to 4th choice.

What it eats  (grass and occasional sedge species) and  how it lives have been studied and documented by academics, grad students and obsessive naturalists.  These details were recorded in scattered papers but are now available instantly on BAMONA.

Duke, the dog -Canus familaris
Need a better photograph?  Searching Bugguide images instantly brings up lots, many tagged for Creative Commons where they can be shared without a copyright.

Most of these advances in technology have occurred in the lifespan of our dog Duke, not that he particularly cares.  But we do.