Naturespeak A naturalist's view of the world

May 17, 2008

Mr. Four Eyes

Filed under: Uncategorized — wykes @ 8:10 pm

 

  As a kid who grew up wearing glasses, I never took great offense at the term “Four Eyes.”  When I later had to switch to bifocals I became slightly more worried about what that term really meant.  I was faced with the prospect of literally looking at the world through two sets of eyes and became worried that it would hinder my view of the world.  As it turned out, there was no need to worry because it actually enhanced my view of the natural world (and shortened my arms considerably!).

  With this background explained, perhaps you’ll understand why I have something in common with Whirligig Beetles. These common water beetles are also endowed with “four” eyes and they benefit greatly from them.   

  Just in case you have never heard of a Whirligig Beetle, let me remind you that these are those random little swimming things that you see on the surface of a pond (see above).  Looking like so many bumper cars at a carnival, these shiny black bugs gather into large social groups and appear to spend a lot of time swirling around in random confusion. I too spend an inordinate amount of time doing random things, so I see yet another parallel between our worlds.

  “Gigs” are members of the beetle clan. As card carrying members of God’s favorite type of insect, they have a set of hard exterior wing covers called elytra (see here). They are exceedingly streamlined for their aquatic lifestyle with a body shaped like a black metal pumpkinseed (and about the same size as one also.)  These beetles can dive – holding a bubble under their wing covers for an air supply – and fly great distances from water if the need arises. Their front legs are modified as long grabbing appendages and their third set of legs are converted into oar-like paddles for swimming (see here). They are best known, however, for their whirling behavior.

  The aquatic world is already chock full of fully aquatic beetles and the aerial world has an ample share of insects also.  Whirligigs, therefore, are specialized to live at the interface of these two worlds. They whirl about on the surface film and keep in constant vibratory touch with each other using wavelets to communicate. Take a look at this picture and you’ll see the pattern of vibrations emanating from each ‘gig expressed as a shadowy pattern on the bottom.  Their short stubby antennae have 2 scoop-like segments at their bases which pick up the surface vibrations (see here). This telecommunication behavior alerts them to danger and to the presence of food – they scavenge anything that falls onto the surface of the water.

  Aside from the fact that Whirligigs smell like apples when handled (I just had to throw that in somewhere), perhaps the single most unique feature is their divided eye. Gigs have only two large compound eyes, but a face plate separates each one into an upward facing “sky eye” and a downward facing “water eye.” They have bifocals, in other words.  They keep an eye on both worlds at the same time with the waterline always at mid-level.

  There are hundreds of species of Whirligig beetles in the world and all pretty much do the four eye thing. Recently, that species list was bolstered by the discovery of a new type in India. This new bug was named after legendary Rocker Roy Orbison, believe it or not – one of the more famous four-eyes in music history.

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