This week we had two caterpillars on our rush milkweeds.
At first glance they look quite similar.
Both have bands of color and filaments (also called tubercles) that look like antennae.
Looking more closely, it is apparent that this caterpillar has two pairs of filaments, one pair in front and one pair in back. In addition, its bands of color are unbroken.
This caterpillar has three pairs of filaments and some of the dark bands have droplets of yellow in them.
Do you know what species of caterpillars these are?
Note on the filaments (tubercles): These threadlike projections are often mistaken for antennae. Caterpillars do have antennae, but they are only tiny bumps on the front of the head near the mandibles. The filaments vary in length and are occasionally missing.
Caterpillars like these can move their filaments, sometimes in a jerky motion.
Answers: The caterpillar in the first and third photographs will turn into one of these. The caterpillar in the second and fourth photographs is one of these.
This weekend we were inspired by an absolutely gorgeous new picture book, A Butterfly Is Patient by Dianna Hutts Aston and illustrated by Sylvia Long. (See review at Wrapped In Foil.)
Aston and Long have collaborated on two other wonderful books, A Egg is Quiet and A Seed is Sleepy. If you are familiar with those books, you will know to expect extraordinary illustrations and accurate, age-appropriate information written in lyrical text. In this book all about butterflies, they have outdone even themselves. A Butterfly Is Patient is definitely inspiring!
Activities to learn more about butterflies:
1. Study Caterpillar and Butterfly Anatomy
Have you ever spent time actually studying the parts of a caterpillar or butterfly? I know, it may be hard to look past the bright colors and beauty, but studying how these animals go together helps you appreciate them in a different way.
Try to find a smooth caterpillar like this tobacco hornworm (some of the fuzzy or spiky ones have stinging hairs, so don’t pick up those.) Gently coax it onto a leaf or stem where you can observe it with a hand lens. See if you can find the following organs and structures.
In this side view of a moth caterpillar, we can see the thorax (the three segments right behind the head), and the abdomen quite clearly. The thorax is where we find the six true legs, which are the identifying characteristics of insects. What are those fleshy appendages on the abdomen, aren’t those legs? From a scientific perspective, those are not true legs, but are called prolegs. They are used for walking and clinging to leaves just like legs, but they lack the joints of a true leg. As you will see, the adult will have only the true legs.
The small circles on the sides of the caterpillar are spiracles, the openings through the insect’s exoskeleton that allow it to take in air.
In this view, we can see the caterpillar’s head. At the bottom of the head are the mandibles, the pruning scissor-like jaws that it uses to cut food. Slightly above and to the side of the jaws are the ocelli, which are simple eye spots. The caterpillar probably doesn’t see much with those tiny spots, maybe only whether it is light or dark out. This photograph shows a better view of the jointed legs.
After the caterpillar transforms into a pupa and then a butterfly, we see different structures.
What a transformation!
Instead of tiny ocelli on its head, the butterfly has large compound eyes. The mouth has become a long tube for sucking nectar from flowers (some butterflies actually lack a mouth altogether). There were antennal buds on the head of the caterpillar, but now the butterfly has full blown antennae.
The true legs are long and delicate and the prolegs are gone. Attached to the thorax are the wings. If you read a book about how to identify butterflies, it will probably describe markings on the upper or forewings, or the lower hind wings. The raised structures in the wings, called wing veins, are also important for identification.
Can you find the mouthparts and the spiracles on this giant swallowtail butterfly?
Activity 2. Butterfly Life Cycle
Butterflies go through a complex series of changes during the life cycle, a process called complete metamorphosis.
Let’s explore the life cycle of the queen butterfly, and then make a poster.
The queen butterfly starts out life as an egg laid by the female butterfly on a milkweed plant.
A caterpillar emerges from the egg, and begins to feed on the plant.
When it has reached its full size, the caterpillar transforms into a chrysalis.
After a week or so, out comes the adult butterfly.
Have you guessed which picture is a caterpillar from the previous post on Butterflies Everywhere? The real caterpillar is the lowest photo. The photo above it is a bird-dropping sitting on a nearby leaf.
The caterpillar, sometimes called an orange dog, is thought to mimic bird-droppings to avoid being eaten by birds.
We are quite excited because this caterpillar turns into the beautiful giant swallowtail butterfly (photo at Butterflies of Southeastern Arizona website).
Another interesting thing about the orange dog caterpillar is that it has an unusual defense. When alarmed, it shoots out a smelly orange, horn-like structure called an osmeterium.
This one is pretty small because the larva is still small. I found an even better shot of an orange dog osmeterium at the BugGuide website.
Not six feet away we have a pair of caterpillars on our desert milkweed. These are the larvae of the queen butterfly. They resemble monarch larvae, but have three sets of spiky appendages and the stripes are red rather than black.
I caught a picture of the adult queen butterfly as it was laying eggs a few days before on another desert milkweed.
By the way, it is not an accident that we have so many caterpillars and butterflies in our yard. When we planted our landscape, we purposely chose plants that are food for caterpillars. Butterfly gardening is something that the whole family can enjoy. If you are interested in learning more, just let me know.