Cassius and Ceraunus Blue Butterfly Eggs and Caterpillars; How to Find Them in Your Yard

Continuing to answer the question about finding eggs and caterpillars in one's yard, we move to Cassius Blue and Ceraunus Blue butterflies. Both are beautiful little butterflies. The males are brilliant blue on the inside of their wings. The females have less blue.

Ceraunus Blue butterfly, first photo. Cassius Blue butterfly, second photo.

Marc and Maria Minno, in their book Florida Butterfly Gardening, share a tip to find these caterpillars. Simply gather flower buds of their host plants, place the buds in a plastic container, and check for frass (caterpillar excrement) the next day. If there is frass, there is a caterpillar!

Eggs of the Ceraunus Blue butterfly are pale blue and will be found on Hairy Indigo and other Indigofera sp plants. Eggs of the Cassius Blue butterfly are cream/white and will be found on the flower buds of Leadwort (Plumbago sp) plants.

The green caterpillar blends in with the flower buds so well that it is nearly impossible to see these tiny caterpillars. Fully grown and ready to pupate, they may be as large as one inch long. An intense study of the flower buds can still fail to reveal the caterpillar.


Once flower buds of the host plant are placed into a plastic container, wait one day. If frass is evident the next day, you know a caterpillar is also in the container.

The paper towel was added to absorb moisture from the flower buds.

Happy Hunting!

Find Viceroy and Red-Spotted Purple Butterfly Eggs and Caterpillars

"How can I find butterfly eggs and caterpillars in my yard?"



Wow! What a wonderful question. The answer can take days to write so we'll take them one or two species at a time.

Viceroy and Red-Spotted Purple butterflies can be attracted to your yard with fruit. They will feed on flower nectar and decaying fruit. A bird suet feeder, an apple, a fruit tree; nearly any type of fruit is acceptable to these beautiful winged creatures.

Viceroy butterflies lay eggs on willow leaves. Red-Spotted Purple butterflies lay eggs on willow or black cherry leaves.

The female butterfly of these two species lands on a leaf, turns around, and backs down until her abdomen touches a point of the leaf. The point is normally the tip of the leaf. If a leaf has been torn, the point could be another tip of the leaf, on the side of the leaf. When searching for eggs, look on the tips of the leaves as well as jagged edges. Almost all eggs will be found on the tip of the leaf.

The egg is green. Through a microscope, the egg resembles a sand spur. It has points all over the outside of the egg.


A young caterpillar will start eating the tip of the leaf. It will take its frass (excrement) and add a small bit to the tip of the leaf vein. When not eating, the caterpillar will rest on the extended leaf vein (excrement) and as it grows, it rests on the leaf vein.

As the caterpillar continues to grow (multiplying its hatchling weight by 2,500) it grows too large to rest upon a leaf vein. It begins to eat so much, it will eat several leaves per day. At this point it will rest on the twig of the tree. A larger caterpillar may be brown or green. It blends in well with the tree itself and is difficult to spot until one develops an 'eye' for caterpillars.

In the fall, before the leaves drop, a Viceroy or Red-Spotted Purple caterpillar that is approximately 3/4" long will eat a little over half a leaf. It will then sew the leaf to the twig with silk from its spinnerets (located under its mouth). It will next lay a thick layer of silk from side to side of the leaf, starting with the petiole, where the leaf 'stem' joins the leaf itself. As the silk dries, it contracts and draws the edges of the leaf together to form a tube that is open at one end. The caterpillar will crawl into this tube when days become very short (and nights become long). By this time, fall has arrived and leaves have started falling off the trees. The tube, called a hibernaculum, will not fall from the twig simply because the caterpillar literally sewed it to the twig.
It survives freezing temperatures for days at this point because it has gone into diapause. Sorbitol and glycerol are in the caterpillars blood, preventing it from freezing, like anti-freeze. When the days become longer (and nights shorter) fresh leaves will grow on the tree. The caterpillar will crawl backward out of the hibernaculum to eat these fresh leaves. It will return to the hibernaculum when resting until it grows too large for the tiny leaf tube.

So ....
~ Eggs; look on the tips of leaves, first checking younger leaves before looking at older leaves.
~ Caterpillars spring and summer and early fall; look on the tips of leaves for a young hatchling caterpillar and on the leaf vein for caterpillars a little older. Look on twigs for larger caterpillars.
~ Caterpillars in late fall and winter; look for hibernaculums on bare twigs. If a hibernaculum is found, a small ribbon can be tied 12 - 24 inches from the hibernaculum. In the spring, when fresh leaves are growing, the area around the hibernaculum should be checked almost daily for a young caterpillar. If a hibernaculum with a caterpillar is taken indoors in the winter, the caterpillar can become dehydrated from the dry indoor air and/or the longer periods of light indoors may cause it to come out of diapause. Without fresh leaves to eat, it will starve.

Happy hunting for Viceroy and Red-spotted Purple butterfly eggs and caterpillars!
(Watch for a post soon detailing how to tell the difference between Viceroy and Red-Spotted Purple caterpillars. Hint; it's the spikes on the humps!)

Caterpillar Instars

"I hear the term 'instar' often when people talk about Monarch caterpillars. What does this term mean, 'first instar' or 'second instar'?"

A caterpillars' skin doesn't grow. When the caterpillar grows too large for its skin, it must crawl out of its old skin (actually a cuticle, not a living skin)to continue to grow. Underneath its old skin is a loose baggier new skin that will stretch only to a certain point before the caterpillar must crawl out of it.

Looking at the photo with a large caterpillar and a tiny one on the right, it is very evident that the tiny caterpillar on the right could never grow to become the larger caterpillar if its skin didn't grow OR if it didn't crawl out of its old skin and have a larger skin underneath. The smaller caterpillar is first instar. The larger caterpillar is fifth instar, about to become a chrysalis.

Caterpillars crawl out of thier skin four times. This process is called 'molt'.

The time period between molts is called an 'instar'. Because Monarch caterpillars molt four times, they have five instars.

1st instar; hatched out of its egg
2nd instar; after the first molt
3rd instar; after the second molt
4th instar; after the third molt
5th instar; after the fourth molt and before becoming a chrysalis.

The last time it sheds its skin is when it pupates into a chrysalis.

The instar of a Monarch caterpillar is measured by its head capsule, not the size of the caterpillar. If a caterpillar doesn't eat much, it will be smaller during an instar.

Tiny caterpillars, hanging by an invisible string ...

"I have a milkweed plant in my garden, and im sure that there arent any pesticides on it or anything. A monarch comes and lays her eggs on the leaves, and i check on them and they look fine. The caterpillars hatch, but they look tinier than i think they're suppose to be. Then a couple of hours later, i look and the baby caterpillar is hanging from an invisible string, and its either dead, or will be in the morning. I'm not sure if its because of wasps, i know there are some lingering around the plant, but i really need some help. How can I save the eggs from the wasps? I cant afford a $30 sock/net thing to put around the plant. PLEASE help! Thank you very much. I would appreciate your suggestions. I am very concerned about the poor little caterpillars."

It's wonderful to hear from someone else who is so concerned about caterpillars. That concern is what turned me into a butterfly farmer. Welcome to the world of worrying about nearly invisible caterpillars and monsterous predators.

On the dime above, two Monarch eggs rest and one hatchling Monarch caterpillar crawls around. If you take a dime out of your pocket and look at it, you can realize how tiny the hatchling really is!

BUT ... a hatchling caterpillar is so tiny it is nearly invisible. I has to be small to fit inside the egg. It eats its way out and doubles in size nearly every day. In fourteen warm summer days, it gains weight over 2,500 times its original hatchling weight. At first, though, it is tiny.

The invisible thread is webbing from its spinnerets. The spinnerets are located under its head, where we have a neck. It lays a line of silk when it travels. When the plant is bumped or a predator comes by, it can drop from the leaf and suspend by its silk thread. It will slowly crawl back up the thread, an amazing sight to watch.


Wasps will kill caterpillars and eat them or carry them away. The only ways to protect them is to enclose the plant in a fine net (like sheet curtain material) or move the caterpillars and some leaves indoors. If you move them indoors, you need to either give them a safe milkweed plant to eat (like you are growing) or add leaves to the container every day. Sleeves can be expensive so simply make one with glue and a piece of fine material. Slide it over the plant or a branch with the caterpillars inside and tie it tightly shut on both ends. When the caterpillar(s) eat the leaves, move the net and caterpillars to another branch or plant.

Nature only allows one or two eggs laid to become adult butterflies. We should expect to lose caterpillars in our gardens. We should expect to see wasps, spiders, lizards, praying mantis, and other predators to carry away our caterpillars. But it is not something that many of us can accept. So we fight it!