Caterpillars and Climate Change: What's the Connection?

Hi All,

Before I bring you out to join me in the Pearl River Wildlife Mangement Area close to Slidell, Louisiana, where we will be collecting caterpillars, I should probably explain why Dr. Dyer and his graduate students are studying caterpillars here. He is very interested in biodiversity*. For one thing, they want to record the diversity of caterpillars (Lepidoptera- this is the scientific name for the family of butterflies and moths) and parasitoids (in this case wasps-Hymenoptera-and flies-Diptera- who lay their eggs inside the caterpillars or around where they are feeding on a plant). Parasitoids lay their eggs in or near the caterpillar, the eggs hatch, and the larvae eat the caterpillar and kill it. So it's also useful to understand how caterpillars defend themselves against their enemies.

*Biodiversity: bi·o·di·ver·si·ty
(bī'ō-dĭ-vûr'sĭ-tē) n.
1. The number and variety of organisms found within a specified geographic region.
2. The variability among living organisms on the earth, including the variability within and between species and within and between ecosystems.

Challenge Question 1: Can you find Slidell, Louisiana on a map? What bodies of water is it close to?

Caterpillars have many enemies, not just parasites. These baby stink bugs we saw in the field jab their swordlike mouths into the caterpillar and suck out it's insides. What a way to go!

The scientists also want to examine the connection between climate change and the interactions between caterpillars and parasitoids. Some believe that climate change will cause changes in caterpillar populations. Maybe some rare species of butterflies and moths will become extinct, or maybe parasitism will go down and some caterpillar populations will go way up. This could be trouble for the plants caterpillars eat. But one of the main reasons to study caterpillars and their interactions is out of curiosity. Learning about natural history is an important part of understanding the world around us.

Challenge Question 2: What might happen to the caterpillar's host plant (the plant they live on and eat) if the population of caterpillars increases?

Life Cycles

A little background on the life cycles of butterflies and moths will also help you here. Do you all know that caterpillars undergo metamorphosis to become butterflies and moths? Well, before they pupate (form a pupae that will become an adult) they have to grow. They go through several instars (check out this link!). When we collect caterpillars in the field we have to identify which instar they are in. The instar is kind of like their age.

Habitat
One of the places we are looking for caterpillars is called Honey Island Swamp. The habitat here is bottomland hardwood swamp. You find a lot of the same kinds of trees here as we have in Maryland, oak, sweet gum, sycamore, maple. And the caterpillars live on these and other plants like honeysuckle and wild carrots. There are lots of other animals that live in this habitat, too.

Here are a couple we saw today.

Eastern River Cooter. This one was taking in some sun on a log. There are many species of turtles here.

Baby copperhead snake. This one was curled up in the leaves of an oak tree. My colleague reached in to get what she thought was a caterpillar and saw this at the last mintue. She pulled her hand out before the snake knew she was there! The moral of this story is, always use a stick to explore for caterpillars.

Broad-headed skink. We saw many of these amphibians along the path near a wet marshy area. They were quite shy but this one came out for a photo.