Page 106 - Engineering in Nature

Engineering in Nature

When light strikes a reflective surface, it's reflected at the same
angle as it arrived.
Although students of physics know these laws, many people
today are unaware of their effects on daily life and the purposes they

serve. What is surprising, however, is that there are other creatures
that put these principles to good use.
In their daily lives, butterflies make use of these laws, of which
many humans are ignorant. For example, the Colias butterfly is una-
o
o
ble to fly when its body temperature drops below 28 C (83 F). In that
event, it immediately spreads out its wings and, turning its back to
the Sun, adjusts them perpendicular to its rays. When its internal tem-
o
o
perature rises to a sufficient40 C (104 F), its turns around 90 degrees,
which minimizes the warming effect of the Sun's rays, and the butter-
fly's body temperature starts to fall.
On its wings, this species of butterfly has black spots that also
serve to collect heat in the butterfly's body. Significantly, these spots
32
are located near those regions of the body which most need to be
warmed, so that the heat is transferred over a shorter distance.
On the other hand, the Pieris species of butterfly arranges its wings
at such an angle that, just like with a reflec-
tor, it can concentrate all the heat rays
onto those regions most in need of

warmth. 33
These butterflies have certainly
received no training in physics or
optics. They are unaware of the
laws of physics and of the angle at
which solar rays can be most produc-
tive.

104