<<Back to this week's update   What is the larva doing — and
why?  Eating its Shed Exoskeleton This monarch larva just shed
its exoskeleton and is now eating the remaining portion, called
the exuvia. Like all insects, a monarch must shed its
exoskeleton at various stages to make room for growth. (Each
stage of growth is called an instar. The process of shedding is
called molting.)  Why Eat the Exuvia? The most likely reason for
eating the exuvia is to recycle the nurtients it contains,
especially hard-to-get nutrients like nitrogen. Dr. Alex Mira
studied this behavior in cockroaches. He found that animals
raised on low-protein diets ate the exuvia most often. Females
also ate the exuvia more than males, probably because of the
need for nitrogen in egg-production. (Female monarchs are known
to get nitrogen from males during mating, in a packet called the
spermatophore.)  Nitrogen is a building block for proteins and
genetic material, so it is essential for life. Nitrogen is
abundant in the earth's atmosphere b