The life story of the monarch: The caterpillar

Monarch hatching  ©Janet Allen
A caterpillar just emerging

Here are three pages showing the life cycle of monarchs.

Just hatched ©Janet AllenJust hatched

Here's a monarch that has just hatched—so small compared to the dime!

It's eating its eggshell.

As environmental designers say, in nature "Waste = Food," or as people used to say, "Waste not, want not."

Monarch caterpillar molting  ©Janet AllenMonarch caterpillar molting and eating the shed skin

The caterpillar goes through five stages called instars. In other words, as it gets too big for its skin, it sheds it so it can continue to grow. Before each molt, it just sits around for about a day.

Then, just as the eggshell doesn't go to waste, neither does this old skin.

If you look closely, you can also see that (what I call) its "helmet" is discarded behind him (on the left).

Two instars ©Janet AllenTwo of the five instars

Here are two of the five instars. I'd guess that the little one is a third instar and the big one is a fifth. (I haven't learned all the signs of each stage.)

The fifth stage is the last one. Soon it will become a chrysalis.

Notching the milkweed ©Janet AllenMaking a notch in the milkweed leaf

This caterpillar has notched the stem of the milkweed leaf. This makes the leaf hang down, protecting the caterpillar somewhat, and reducing the flow of latex, minimizing the chances of this sticky stuff gumming up his mouth.

Creating a silk pad ©Janet AllenCreating a silk pad.

It becomes very restless as it searches for a place to attach. Outdoors, it would travel quite far from its host plant. Inside the aquarium, it just crawls around and around until it's ready.

The caterpillar is creating a silk pad (see the mouth end). It will later turn around and attach its rear end to this pad. (I'm raising this one inside, so what you see is the screen on the top of the aquarium.)

Caterpillar in a j shape ©Janet AllenCaterpillar in a j shape

Here's a caterpillar attached to the underside of a leaf stem in its characteristic "j" shape. It's just hanging here and is no longer eating.

Caterpillar with droopy tentacles ©Janet AllenCaterpillar with droopy tentacles

This one has hung around for a while (the higher the temperature, the shorter the time) and is soon going to pupate.

How do I know? Look at its droopy tentacles (compare to the preceding photo). I assume that means that it has detached from its soon-to-be-discarded skin.

Note: Contrary to common belief, it does NOT spin a cocoon!

Monarch pupating  ©Janet AllenMonarch caterpillar pupating

Here the caterpillar is starting to pupate. It's NOT spinning a cocoon—it just splits its skin (see the bottom of the photo) and the chrysalis begins to appear.

Note how the skin at the top is starting to wrinkle.

Monarch pupating  ©Janet AllenThe skin is almost ready to drop off.

A few minutes later, the skin is near the top. Progress!

Monarch pupating  ©Janet AllenWiggling, wiggling

After a LOT of wiggling, the old skin drops off.

It still doesn't look like the chrysalis you usually picture, though.

Monarch pupating  ©Janet AllenAlmost there

The wing area (the broad smooth part near the bottom) is moving up. The ridges at the top are the abdomen area. The head is at the bottom.

Monarch pupating  ©Janet AllenThe chrysalis

This is the "finished product" at least for the caterpillar stage. Now we have to wait about two weeks, though the exact timing depends on temperature.

It's amazing how much faster it goes through these the stages when it's especially warm—a noticeable difference.

(And how will global warming affect this whole process?)

Different sizes
They come in different sizes

Just as with people, pupae come in different sizes.

(The one on the right just happens to be darker because the butterfly will soon emerge. It has nothing to do with size. )

Ready to emerge ©Janet AllenReady to emerge

It's always exciting to see the orange dotted wing when we come down in the morning. It will soon emerge (or "eclose" to use the technical term).