Page 126 - Engineering in Nature

Engineering in Nature

covering grew cold faster than moths
with one. He performed an experiment to
determine to what extent that layer could
retain heat. Moths with their normal pro-
tective coverings and others deprived of
them were subjected to various wind tun-
nel speeds. He measured the rates of
chilling of the moths' bodies and ob-
served that at a wind speed of 7 meters a
Prof. Bernd Heinrich second (22 feet/second)—roughly the
speed at which a moth flies—moths with-
out protective coverings grew cold twice
as fast as those with their scales intact. 41
This layer is an important piece of the moths' makeup, yet it is still
not enough to meet all the insect's needs. In humid environments,
moths can survive only down to -2°C (28°F), which is their standard
freezing temperature. But as we've already seen, temperatures where
they live can fall to as low as -20°C (-4°F). In such extreme cold, the
scaly layer's protective function will of course be insufficient.
Therefore, the moth needs an additional system.
From there, scientists began to examine of the winter moth's heat-
ing systems in greater detail.

Another Proof of Flawless Design
When the air temperature during flight falls below zero, the winter
moth has to overcome yet another problem. The moth will vibrate its
wings to maintain heat in its thorax, since the emerging heat will be
lost in due course, the moth won't be able to maintain the required
heat level. It will thus expend all its energy on vibration, and then die.
But contrary to this likely scenario, the winter moth stays alive be-

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