Open and shut case for insect breathing described in New Scientist, 5 Feb 2005, p19. Insects take oxygen in through tiny tubes called spiracles in the sides of their bodies. Some insects such as ants and butterflies open and close these when they are inactive, and entomologists previously thought this was a means of preventing water loss. Stefan Hertz of Humboldt University, Germany and Timothy Bradley of University of California, Irvine, have studied the amount of oxygen and carbon dioxide inside the bodies of pupating moths by inserting fine tubes into their spiracles. They found the pupae maintained oxygen levels at about a quarter of the levels in the atmosphere. Hertz and Bradley concluded that the opening and closing of the spiracles prevents oxygen accumulating when they are at rest and are not using it up. They suggested “insects’ respiratory systems evolved for heavy activity and massive oxygen consumption. So when they are resting they have to close their spiracles to prevent too much toxic oxygen flowing in”.
Editorial Comment: For those readers wondering how oxygen could be described as toxic, oxygen in the wrong place in the wrong amounts can do a lot of damage to living cells. Oxygen is used in the last step of a series of complex chemical reactions that produce energy for cells. If it is not used properly it will react quickly with other chemicals in the cell and cause damage. Therefore, all living organisms need mechanisms for not only collecting oxygen, but a control mechanism for delivering only the right amounts of oxygen to body tissues. It is good evidence of purposeful design that insects have the means of controlling how much oxygen they take in. Without this they are dead! (Ref. respiration, biochemistry, insects)