Page 18 - The Book of Caterpillars: A Life-Size Guide to Six Hundred Species From Around the World

FROM EGGS TO PUPATION

right Two caterpillars
of the Checkered
White (Pontia
protodice), a tiny
second instar and
a much larger fifth
instar, demonstrate
how fast these larvae
grow. The fifth instar
is just nine days
older than the
second instar.

FEEDING AND GROWING
16
16
Caterpillars are programmed to eat as much as possible in order to grow
and mature. The period from egg hatch to pupation may be as little as ten
days, although in species with multiple dormancies caterpillars can live for

two to three years, with one Arctic species taking up to seven years to
complete development. An approximate doubling of length occurs in each
successive instar. Between 60 and 80 percent of the total plant mass eaten
by a developing caterpillar is consumed in the final instar. Size is relative,
however, as the largest saturniid silkmoth and hawkmoth caterpillars grow
up to 6 in (150 mm) in length, while the final instars of “micromoths” may

reach only 3/16 in (5 mm).
Species also grow at different rates and in different seasons, depending
on their preferred food. Some feed only on leaf buds, others on young
leaves, mature leaves, flower buds, flowers, seeds, or even stems. Buds,

flowers, and seeds are more nutritious (generally with more nitrogen) than
leaves or stems, promoting faster growth but within a shorter growth
period. Food sources such as grasses and evergreen needles are low in
nutrition but hugely abundant over vast areas, so caterpillars exploiting
these resources grow slowly but with little competition.

DEALING WITH ENVIRONMENTAL EXTREMES
Caterpillars, like all insects, are cold blooded and depend on environmental
conditions to achieve the optimum body temperatures for development.

For the majority of species, the range of body temperatures favoring
development is 59–86ºF (15–30ºC). When temperatures remain below
41ºF (5ºC), with periods below 32ºF (0°C) and limited, low-angle
sunshine, many caterpillars are unable to develop. To survive long, hard
winters, they have to change their physiology and enter a dormant state of