Head Rush PDF Print E-mail
Written by Gordon Wilson   
Friday, 07 May 2010 15:52

We all look at house flies with considerable distain. This is largely due to their disgusting habit of greedily landing on various forms of filth for dinner, and then not having the good sense to wipe their feet before they land on ours. But despite their unhygienic habits they are a marvel of divine engineering.  Let me take you on a short Tilt-a-Whirl ride and introduce you to one weird wonder of life in Lilliput.  House flies belong to a group called the Schizophora. This includes the flesh flies, Tsetse flies, stable flies, botflies, and blowflies (blue and green bottles).  They all share an anatomical feature of a curved seam situated between their two large compound eyes (on their forehead). This crack marks the spot where the door of their face once closed.  “When was this door opened?” you might ask.  I’m glad you did.  Don’t buckle the seat belt of your credulity.  Believe me, it’s true. I’m a Christian and I wouldn’t tell you falsehoods.

We all know that house flies begin life with more disgusting looks and habits than when they grow up. They don’t just visit squalor; they’re immersed in it. During these juvenile and adolescent weeks we called them maggots, a disgusting name to match their nursery. These pallid writhing worms consume their share of the earth’s refuse.  As they do, they grow and go through several molts (sheddings) and finally begin metamorphosis. During metamorphosis the fly is within a little brown sausage-shaped container.  This dry leathery casing is formed from the skin of the fully grown maggot when it shed to become the pupa. This cocoon-like bag, called the puparium now houses the pupa. Another transformation occurs. The innards of the pupa liquefy and an adult body forms within the pupal skin (This is starting to look like Russian dolls).  There is an adult body inside the pupal skin which is inside the maggot skin. Now the fun begins. When the adult is ready to immerge it easily slips out of the pupal skin but it requires a lot more oomph to break out of the more protective puparium. Almost like it was planned (ha!), the maggot skin (a.k.a. puparium) has a circular seam forming a pop-off lid at the end where the adult is to immerge.  It doesn’t actually say “tear here” because flies don’t need directions to open containers like we do. Even though it is pre-weakened, a simple nudge won’t budge it. To make its grand appearance, muscles in the fly’s abdomen contract forcefully shoving blood to its head. This is a head rush of dramatic proportions. The trapdoor on the fly’s face pops open under the pressure and a balloon-like thing called a ptilinum (the p is silent) inflates and billows out of its forehead. This blood bag pushes against the lid of the puparium, popping it open. Like Houdini, the fly immerges triumphant from both its pupal and maggot skin. The bag deflates and is withdrawn into its noggin. Its face closes back up never to open again. The exoskeleton of the fly stiffens to the right firmness and then it flies away. It’s in a hurry to carry out its God-given job of waste management.

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Last Updated on Friday, 07 May 2010 15:55