Thursday, June 21, 2012

Flatheads, Small Minnows, and -- Oh Yes -- a "Whirligig Beetle": Buck Mt. Creek

One of the strangest critters we see in our streams -- some of them -- in the summer: a whirligig beetle larva (Gyrinidae), genus, Dineutus.  The genus ID is determined by the shape of the head: if it's "elongate" it's Gyrinus; if it's "semi-circular" it's Dineutus.   Hard to believe that this odd-looking thing turns into a black beetle that, as an adult, swims on the surface.  (For pictures of Dineutus adults, go to:  The key feature in family ID is the four terminal hooks on the final abdominal segment -- which you can see in this photo if you click on it to enlarge it.
Actual size -- around 1" long.

Gyrinidae larvae inhabit the tangled, coarse vegetation that grows on a lot of the rocks in Buck Mt. Creek in the summer.  So too do immature brushlegged mayflies and common netspinners, the two most common insects that I saw this morning.  On the bottoms of the rocks, on the other hand, it was all flatheaded mayflies and small minnow mayflies.  There are still a lot of Epeorus vitreus flatheads in Buck Mt. Creek -- they'll probably be here most of the summer -- and the Heptagenia marginalis nymphs are also showing up in pretty good numbers.

E. vitreus (a young one):

H. marginalis, also a young one:

On the small minnow mayflies -- I found the same two species I've been finding in my other "small minnow" streams: Baetis intercalaris and Beatis pluto.

B. intercalaris (male):

B. pluto

But, as the song says, "I still haven't found what I'm looking for": the small minnow mayfly Acentrella nadineae.  This one (found in the Doyles River last year on June 23).

They're very distinctive with the orange/red splotches on the terga and the thorax, and by now, I've been to every stream where I found them last year: Powells Creek, the Doyles River, the Lynch River, and Buck Mt. Creek.  I've not yet seen a one.  Just have to keep looking.

Below:  one of several small, common stoneflies -- genus Acroneuria -- that I found this morning.  This one will mature over the winter.


  1. I am just amazed at the clarity of your photos. What are your methods? I keep some insects in a tank and have control of lighting but all my pictures end up blurry or the colors are distorted.

    1. Just have to be patient, I guess. I take all of my photos at the stream, and good sunlight is a must. I use the Canon EFS 60 mm macro lens and set the shutter speed at 1/60 so I can get as much "depth-of-field" as I can. The other thing to do is use "manual" focus -- not automatic. That means you have to find a way to hold the camera as still as possible.
      I'm usually down on my hands and knees, and push my elbows into the ground to be still. I put the nymphs/larvae into a petri dish with water, get positioned directly above them and follow them around with the camera until they stop: I never shoot an insect that's moving. So, sometimes it takes awhile to get a good photo. You have to wait until they stop moving, "quickly" get sharply focussed, and get some shots before they take off again. My point of focus is always the head and eyes: I want to see them sharply in the view finder before I push the button.

      Hope that helps. I think it's something at which you get better the more you do it.

      Thanks for asking,