Naturally-occurring treefall gaps are an important part of forest ecology, playing a prominent role in the regeneration of both pioneer and non-pioneer tree species. Nate Lemoine is setting out to understand how insect herbivory plays a role in the growth and health of plants at treefall gaps. By caging small plots within gaps, he is deterring deer and other animals from eating the plants. He is also using herbicide to deter insects from some plots to compare to controlled plots where only water is sprayed.
By Dejeanne Doublet, intern Conducting research with insects means that you must take on the roles and duties of a caretaker.
This summer we worked with the caterpillar species Spodoptera exigua (beet armyworms) and their close relative Spodoptera frugiperda(fall armyworms). Both species were shipped to us in sheets of eggs containing roughly 1,000 caterpillars. Most caterpillars start out their lives as eggs on leaves. They usually don’t get to pick and choose their food at the beginning of their lives, and are usually forced to eat from the plant or tree where they hatched.
Some caterpillars will enter a wandering stage once they’re big enough. They may wander about from plant to plant, picking and choosing what they like best or they may stay put at one type of plant for the rest of their life.
The first step involves mixing the agar into boiling water until it is completely dissolved. Then, the temperature should to reduced to 85 degrees before adding in the remaining ingredients.
An array of the ingredients that make up Lepidoptera food including wheat germ, agar, cellulose, fructose, vitamins, etc.
The cooled down mixture hardens and molds to its container.
When you’re a caterpillar shipped to a lab with 999 other caterpillars, though, you don’t necessarily get to have an all-you-can-buffet of cuisines. Our lab doesn’t quite function like a Subway and you can’t always have it your way. However, we do make sure you’re eating all your nutrients and vitamins with a homemade concoction of Lepidoptera food.
The recipe consists of more than a dozen ingredients that are simply mixed into boiling water. Click here for the full recipe. Once the ingredients are mixed together, they form a thick substance that cools down to form a tapioca pudding-like concoction.
We poured the finished food goo into 8 oz. plastic containers, allowed it to cool, then placed small pieces of the sheets containing caterpillars eggs on top of the food. We then placed the containers in a 30 ºC chamber under lights that mimic a 16-hour day and 8-hour night cycle. The caterpillars usually begin to hatch a day from when they arrive as eggs. Within a few days, they’re growing and eating and growing and eating.
Monarch caterpillars are not easy to come by. In the last five summers I’ve spent at the Smithsonian Environmental Research Center in Maryland, I’ve only come across several caterpillars per season. This year, our lab is full of monarch caterpillars with a count currently up to 13 caterpillars, three of which are forming their chrysalis shells and undergoing metamorphosis.
I’ve been working with caterpillars, and I needed to find a way to keep the caterpillars on the leaf for a few days so I can come back and get them later. Clip cages are great for this. Bio-Quip sells them, but they are small (1″ inner diameter) and expensive ($40 for a pack of 10). Here’s a step-by-step guide of how to make your own clip cages. These cages are great for hobbyists wanting to rear insects, teachers who want to raise insects in a classroom, or researchers who need a way to do experiments (cheaply) with bigger insects.
1. Purchase the appropriate foam tube and supplies
I used both trampoline pole padding (1.5″ inner diameter) and pool “super-noodles” (2″ inner diameter). Either one works well, is cheap ($3 – $5), and light (no more petri dishes that overload the leaf and cause sagging). A single tube can get about 15 full cages. Other than the tube, you only need window screening (cheap at home depot), contact cement ($4 per bottle), and long staples ($3 – $5 for 100). I like Powershot cable staples because they are wider than normal staples, but you need to pull the plastic end off to make them useable.
2. Chop up the tube
The tube should be cut into 2″ wide slices. You can use scissors, a razor blade, Exacto knife, or anything else. I used a chop saw to slice through six tubes in a matter of minutes. Also, the chop saw gave me a nice clean, straight cut. A band saw would work even better than a chop saw.
3. Glue the slices onto window screening
You can do this however you like. My preferred way is to lay the window screen on a table, coat one side of the foam slice with contact cement, and simply lay the slice onto the screen. Wait a few minutes for the cement to dry. This works incredibly well if you’re mass producing hundreds of clip cages like I was. Make sure you do this in a well-ventilated area. You’ll want to give the glue several days to dry and air out all of the fumes before putting insects inside.
4. Cut the foam slices out of the window screen
This is pretty self-explanatory.
5. Use staples to connect two slices
I use three staples per clip cage. Put the two halves together (window screen facing out on both sides), and use the staples to fasten them together.
6. Place on plant with insect. Enjoy
Here is the final product in action. Each cage should cost about a dollar, if that.