Monday, June 10, 2013

Monarch Butterfly Egg Hatching

 Here is the picture of the Monarch Butterfly egg that I posted a couple of days ago.  The egg looked like this for 3 days, but then changed overnight to look as it does below.  The egg "shell" below has become transparent and the baby caterpillar can be seen inside.  The large black area is its head and the black body hairs can be seen also.

While I was photographing it the baby caterpillar could be seen moving around inside the egg!
 The egg could be seen moving a bit, bulging and swaying as the caterpillar prepared to find its way out.

At almost exactly 96 hours from being laid, the little caterpillar began chewing a hole in the top part of the egg, as can be seen in the picture below.
 At this point small mouth parts with several rough "teeth" like claws could be seen tearing at the egg shell and the caterpillar seemed to be eating the small pieces.
 In this picture the left big black "eye" can be seen, with little tiny eyes, the ocelli, in a half circle to the lower right of the large black eye, in addition to the mouth munching on the egg shell at the bottom.

In the picture below the caterpillar sticks its head out for a quick first view of the world.

In the following pictures below, the caterpillar leaves the egg completely.

 At this point it became difficult to determine a focus point, as the caterpillar kept moving out of focus, which was less than a tenth of a millimeter.

It took the caterpillar less than one minute to leave the egg, once it decided it was time to go.
 Here the three right side "true" legs can be see.

I think the caterpillar is thinking hard here trying to figure out how to make the other legs work.
 In this picture three of the right pro-legs are out, waiting for the next to last pair to begin to function.

The egg is only one millimeter wide, so the newly hatching caterpillar, measured with a ruler, was exactly 3 millimeters long.
"Finally!  Whew! That was hard work, think I'll take a little rest for a minute."  At least that is what I would have been thinking  if I was the caterpillar.

The beginnings of the 4 black "antennae" can be seen on the caterpillar's back.  Two in front and two in back. These will become tentacles and function as sense organs but not actual antennae.
 The caterpillar turned around and ate part of the egg for a few minutes, and then seemed to loose interest.
 The entire hatching process from first chewed opening to this point took about an hour of pretty steady work. But the caterpillar left to explore within a few minutes.

All three eggs I was watching hatched within an hour of each other, but the ones outside on the plants took two more days, so colder temperatures must make a difference in how fast the eggs hatch.
 Exploring is fun, but this caterpillar is looking for a safe place to begin eating.
 "Hmmmm, I wonder if I can crawl upside down without falling off. "  Which is exactly what this one did.
 Twentyfour hours later the caterpillar was doing a good imitation of the book title of "The Very Hungry Caterpillar."  Small dark bands can be seen on the caterpillar now.

48 hours old in the picture below and the black and yellow and white bands are beginning to show.  And much larger holes where it has been eating. 

At 48 hours the caterpillar is now 6 millimeters long, twice as long as at hatching.


  1. Dear Siah,

    I am writing because I have seen some of the monarch egg hatch images you posted on your nature blog. I am writing a popular science book on monarchs and milkweeds and wanted to know if you would be willing to share some of these photos for the book?

    Many thanks for considering this. –Anurag Agrawal,

  2. I've been "farming" Monarchs on my kitchen counter this summer and am fascinated by you photos of the hatching eggs. I can see with my naked eye when the eggs turn black, but that's it, so these pics are wonderful!

  3. What camera did you use for these pics? Exquisite !