Caterpillars, Biodiversity, and You!

On June 8, 2022, CREA hosted Sam Jaffe from NH-based Caterpillar Lab for a program packed with LIVE caterpillars and stories about their life cycles, defenses against predators, and key ecological role in our landscapes. Sam was captivated by caterpillars from a young age, raising them since he was four years old, and he now shares his passion for these creatures through research and education.

The program, which you can watch here or access at the end of these highlights, included lots of ‘Show and Tell’. Sam delivered his presentation surrounded by clear plexiglass boxes filled with live caterpillars, waiting for their moment of fame. He uses an HDMI microscope connected to a large screen TV – a set up that he highly recommends for parents hoping to entice their children with the wonders of the natural world.

Magnification reveals so much. First up were tiny leaf miner caterpillars. Then the beating heart and tracheal breathing tubes of transparent leaf roller caterpillars! Leaf rollers wrap themselves in vegetation to defend against predation by birds and other insects. Then the spectacular Cecropia caterpillar, green with red, blue, and yellow spines sticking out from its body. We got a close-up view of its mouthparts as it crawled around Sam’s fingers. In Maine, look for this caterpillar on larch. The Cecropia moth is North America’s largest flying insect with a wingspan of 5-6 inches!

Two themes dominate the life of a caterpillar. First, its primary goal is to eat and grow up so it can become a butterfly. Second, it needs to defend itself against the many creatures that want to eat it. Caterpillars have many strategies for keeping predators at bay.

Can you find the caterpillar in this photo?

Some will throw up on you if you touch them (this has happened to Sam) – a very clever strategy indeed! Many use camouflage – their coloration makes them look like a twig, or a leaf. Some move around at night when it’s harder for predators to see them. Others use quick release with a silk lifeline.

Still others, such as the Eastern tent caterpillar, are quite poisonous if eaten. Tent caterpillars eat only apple and cherry leaves, which leads to a concentration of hydrogen cyanide in their bodies. But as is so often the case in the natural world, some predator usually evolves a way to overcome these defenses. For example, the yellow-billed cuckoo can eat tent caterpillars despite their toxicity.


Don’t touch this caterpillar – its spines sting!

There are also some venomous caterpillars that sting, such as the spiny oak slug caterpillar. These caterpillars often have bright colors that clearly identify them and serve as a warning to potential predators. So don’t touch the really colorful, spiny caterpillars!

Caterpillars play a key ecological role in our landscapes. As herbivores – creatures that eat plants – they play a vital role in moving energy around. Plants capture the sun’s energy and use it to grow leaves. When caterpillars eat the leaves, they use that energy to grow and reproduce. Or, they’re eaten by other creatures which move that energy to different parts of the food web.

Sam reminded us that in the natural world, pretty much everything has something that eats it. Nothing is wasted, and everything has a role to play.

Some people worry that caterpillars will defoliate trees and shrubs. Sam emphasized the importance of distinguishing between native and non-native species. Plants and caterpillars that are native to an area live in balance with each other. Occasionally, a native caterpillar may experience a minor population explosion and defoliate some trees. When this happens, predators will increase in proportion to the increased food supply and nature bring things back into balance.

Non-native species are an unfortunate exception to this, especially invasive species that outcompete native species. The spongy moth (formerly called gypsy moth) and the browntail moth are two local examples of this. Because they aren’t native to this area, they have no natural predators so their population growth is unchecked.

In some cases, predators of non-native species are brought in to control them, but sometimes those predators also reduce populations of native species. It’s helpful to understand the difference between ‘specialists’ and ‘generalists.’ Specialists are creatures that require or have a strong preference for a particular food. Generalists will eat pretty much anything. Specialists do the heavy lifting when it comes to keeping populations in balance.

Zombie caterpillar with parasitoid wasp.

Sam shared some fun facts about parasitoid wasps that qualify as fodder for horror movies. Some lay eggs inside caterpillars, grow inside them, then hatch. (Sam reported that he’s seen tiny wasps swim by inside a caterpillar, when viewing them under the microscope!) As you might guess, the host caterpillar does not survive this assault.

Other wasps eat caterpillars from the inside out. Then there’s the ‘zombie caterpillar’, in which the wasp larva lives inside the caterpillar, immobilizes it, then pops out as an appendage so it can defend the caterpillar from predators, essentially protecting its home and food source. Although the host caterpillar does, ultimately, die.

The takeaway of this program is that you don’t have to travel far to see the wild, the wonderful, and the crazy! Sam recommends bringing a caterpillar friend inside, in a jar, with some leaves of the plant you find it on. Get to know it for just a few days, then return it to the wild.

For more information about The Caterpillar Lab programs, caterpillars, and the cool stuff they sell in their online store (caterpillar trading cards, stickers, puzzles, t-shirts…), check out their website! They also have open house hours at the lab on Saturdays from 12 – 5 pm!