Page 118 - Engineering in Nature

Engineering in Nature

Resilient Winter Moths
A great many species of moth die in winter. Yet some manage to
survive —for example, the 50 or so species of the Cuculinae sub-
group of the moth family Noctuidae are able to survive through even
the harsher months of the winter. For that reason, Cuculinae moths
are also known as "winter moths," which have a life cycle the exact
opposite of other members of their species. Their caterpillars feed on
tree seeds in early spring and then remain motionless throughout the
summer. They grow to adulthood at the end of autumn or in the win-
ter. And during the cold days of winter, they feed, mate and lay eggs
for subsequent generations.
Scientists studying the winter moth's interesting life cycle came up
with surprising and thought-provoking conclusions.
First of all, to survive these creatures need to fly. Yet in order to do
so, the temperature of the thorax region where their wing muscles are
located must be at least 30°C. Where the moths live, however, the am-
bient temperature is generally below freezing.
Scientists therefore began seeking to answer how winter moths
survive despite the cold. How is it that they don't freeze when they
are motionless? Despite the cold, how do they manage to fly, feed and
reproduce?
Researching all these questions, scientists discovered that winter
moths have a marvelously engineered heating system. This system,
the product of the most delicate planning and superior creation, is an
assemblage of complementary stages.

Stage 1: Heating by Shivering Their Wings
In the winter moth's body, the main muscles are connected to the
wings. Before flight, the moths shiver their wings by constantly con-
tracting these muscles, causing the temperature of their thorax region

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