Caterpillars Gone Wild

There is something addictive about hunting for caterpillars.  We walk along lush roads and trails, inspecting the undersides of every leaf.  Usually, nothing turns up.  But occasionally, a fantastic mega-caterpillar is revealed.

The little thing next to this green monster is its shed skin!

We bag the caterpillars and a healthy portion of the host plants' leaves so they have food.  The caterpillars get catalogued, photographed, and raised at the field station.  

It gets challenging to photograph caterpillars from just the right angles.

Every container has a caterpillar inside.  We had to photograph all 131 of them!

As the caterpillars develop, scientists measure and observe them carefully to help answer these questions:

• How do caterpillars evade predation or parasitism?
• Are some caterpillars more susceptible to parasitoids?
• Do particular caterpillars get infected with particular parasitoids?
• Does the caterpillar's diet affect how well they can fight off parasitoids?
• Is a caterpillar's diet broad or specialized?
• How does elevation influence the caterpillar-parasitoid interaction?
• Are there parasitoids that parasitize other parasitoids?

This caterpillar has been attacked by parasitoids.  You can see one parasitoid larva upon the caterpillar's body and the rest have already hatched and begun to live independently.

Sometimes the caterpillars are itty bitty.  Can you find the caterpillar in this photograph?

Don't worry.  The team had trouble finding it too!

What is a parasite?

A parasite is an organism that lives in another organism, called the host, and often harms it. It is dependent on its host for survival - it has to be in the host to live, grow and multiply. A parasite cannot live independently.

How does a parasite differ from a parasitoid?

Parasites may harm their hosts, but they depend on their hosts to survive, so they don't kill them.  A parasitoid is an organism that has young that develop on or within another organism (the host), eventually killing it. Parasitoids have characteristics of both predators and parasites.

In general, parasitoids share the following features:

• Parasitoids are usually smaller than their selected host.
• Parasitoids are very selective and only attack a particular life stage of one or several closely related species.
• Adult parasitoids are generally either nectar feeders or predators.
• Only female parasitoids are involved in finding and using the host.
• Generally the host does not die until the young are fully grown and ready to become adults.
• Parasitoids can sometimes prevent larval hosts (e.g. caterpillars) from developing, until the parasitoid is fully developed.