Page 41 - Design in Nature

The housefly's eye is composed of 6000
hexagonally arranged eye structures,
called ommatidia. Since each
ommatidium is directed in different
directions, e.g. forwards, backwards,
beneath, above and on all sides, the fly
can see everywhere. In other words, it
can sense everything within a 360-
degree visual field. Eight photo
receptors (light-receiving) neurons are
attached to each one of these units
therefore the total number of sensor
cells in an eye is about 48,000. This is
how it can process up to one hundred
images per second.

The design of its wings gives a fly its
superior flying skills. The edges,
surfaces and veins of these wings are
covered with highly sensitive sensory
hairs which enable the fly to detect
airflow and mechanical pressures.

flight, these muscles and wing movements become automatic after a while.
Sensors under the wings and on the back of its head send information about
the flight immediately to its brain. If the fly encounters a new airflow during flight,
these sensors promptly send the necessary signals to the brain. The muscles, then,
start to direct the wings according to the new situation. That is how a fly can detect
another insect creating extra airflow and can escape to safety most of the time. The
housefly moves its wings hundreds of times a second. The energy spent during
flight is roughly a hundred times that spent during rest. From this point of view, we
can say that it is a very powerful creature because human metabolism can only
spend ten times as much energy in emergency situations in comparison to during
the normal tempo of life. In addition, a human can maintain this energy expenditure
for a maximum of only a few minutes. In contrast, the housefly can sustain that
12 s
rhythm for up to half an hour and it can travel up to a mile at the same speed. ›