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BYB visits a Scanning Electron Microscope

Here at Backyard Brains, we often get the question “Is that leg really still alive?” to which we respond “Why yes… that’s why you hear the Spikes”. The follow up question “How does it stay alive?” was often replied with similar authority: “They have tiny holes called spiracles that allow them to ‘breathe’ through their skin”. However, that last statement never sat well with us. We’ve never seen these holes, only read about them in passing in the text books.

Enter John Mansfield from the University of Michigan Electron Microbeam AnalysisLaboratory. We met John through his daughter Betsy who caught our eye a cockroach expert during an outreach event on campus. He was kind enough to let us take a closer look at the leg to see if we could find these spiracles.

John Mansfield readies a cockroach for scanning in the SEM

The first thing John did was place the leg in the SEM and pressurize the chamber to around 1.5-2 Torr. We could look inside the SEM from a computer that was used to control the scope.

Before long, John was able to zoom in closely and snap some beautiful images of our leg… but we couldn’t find the spiracles we were searching for. Below are some of the pictures that we saw (kind of… they were B&W, so we colored the legs here to make them look cooler).

After searching for about an hour, nothing. We even brought in an expert to help us look over the images, but to no avail…

We then flipped the leg over and tried again.The spiracles had to be on the backside! Right? No! We didn’t find any. The reason, it turns out, is that there are no spiracles on the leg at all! They are only contained on the main body of the cockroach.

This remains a mystery at Backyard Brains. How can a leg stay alive and fire spikes for up to 48 hours after it has been detached? With no way to exchange CO2 and O2? We still don’t have an answer for this. We’d like to hear your theories. This could be the makings of a great science caper.


  1. While this is in no way scientifically backed it is easily testable. It may be that at the point of removal, there are open blood vessels (highly likely) which allow oxygen to be passively transmitted into the body. as far as the removal of CO2, for the most parts cells will remove that, and that it moves via osmotic properties out through the cut in the leg. Like I said it could be easily tested by finding a way to seal the leg.

    Hope this helps!

    Comment by Anthony W. McCoy — 2011-Mar-03 @ 22:46

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