Page 128 - Engineering in Nature

Engineering in Nature

the dissipation of heat to colder regions of the body, the moth main-
tains its vitally important thorax warmth.
But at this point arises an important question. The stomach tem-
perature of a moth that takes flight as a result of vibration registers a
2-degree rise, and the rise in thorax heat reaches 35°C (95°F).
How is it, therefore, that this insulation system can maintain a
more than 30-degree temperature difference between the thorax and
abdomen, which are only 1 to 2 millimeters (0.03 to 0.07 inches) apart
from one another?
The answer lies in another amazing design in the moth's circula-
tion system.

Winter Moths' Different Body Structures
In all moths, the blood flows in a single vein from the abdomen to
the thorax, and from there to the head, where it is warmed. On its re-
turn, it is filtered through tissue. In addition, the anatomy of the win-
ter moth is different from that of summer-flying moths—a difference
in design that lets the winter moth survive cold temperatures.
The veins extending along the winter moth's abdomen form the
heart-and-aorta section of the circulatory system. This part, which ex-
tends in the upper part of the tail, turns a 90 degree angle downwards
as it nears the heart region. It then enters this area from underneath
where the thorax joins the abdomen. So far, the blood in this area is
cold.
When the vein enters the abdomen, contraction of the muscles
there warms the blood on its way from the stomach to the chest re-
gion. Where the abdomen and thorax meet, the vein assumes more or
less a V shape. The blood in the left arm of the V is cold, and that in
the right arm warmer.
Under normal conditions, the heat of the warm blood rising in the

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