Breaking Swallowtail Diapause in Chrysalises

How can I make my swallowtail butterfly emerge? How long does it stay in chrysalis?

Some species of butterflies spend the winter as a chrysalis. They live for months as a chrysalis, almost in a type of ‘suspended animation’. They aren’t developing inside. Instead they are waiting for the essential triggers that will take them out of diapause, restarting metamorphosis. A swallowtail butterfly may stay a chrysalis for over a year.

Diapause is triggered before the caterpillar pupates. One cannot cause an already-formed chrysalis to go into diapause. A chrysalis can be taken out of diapause, however, causing them to continue developing as if it were spring and to emerge as adults.

The following pertains to caterpillars/chrysalises that are raised/stored indoors. Remember, if you leave your chrysalises outdoors, nature will take care of this for you.

How can you trigger a butterfly to break (come out of) diapause?

The answer is simple. We need to change their surroundings to make them ‘think’ it is spring! How do we do that?

We begin with these two questions: 1) What are the triggers that causes a caterpillar to pupate into a chrysalis in diapause? 2)What are the triggers that bring them out of diapause? As we answer these questions, we’ll explain what you can do in your home to break diapause for your chrysalises.


1) Light: One of the triggers that causes a swallowtail caterpillar to go into diapause is the length of night (the dark period of a 24 hour day) while they are a large (5th instar) caterpillar. When caterpillars are raised indoors, they often go into diapause because of longer ‘nights’ (dark periods). Most of us tend to turn off lights when we leave a room. As fall begins, nights lengthen. In the spring, they shorten. When nights begin to shorten and temperatures warm a bit, they emerge. To encourage an adult butterfly to emerge, place the chrysalises in an area where they will be in light for 14 hours.

2) Temperature: Caterpillars normally pupate into chrysalises that are in diapause when temperatures are cooling down in nature. In our homes, we use air conditioners and heaters, changing the temperature to something totally different than nature’s temperatures. To trigger a chrysalis to emerge from diapause, we should place them in an area with warmer temperatures, above 70, preferably in the mid to upper 70′s, if possible.

3) Humidity: Spring and summer rains encourage a butterfly to come out of diapause. In colder temperatures, there is less humidity in the air. As air warms up, humidity increases. You can increase humidity by either a) spraying your chrysalis with warm water, b) dunking it under the faucet every day, or c) placing it in a humid area. Natural humid areas in our homes and offices are by our kitchen sinks and in bathrooms.

What is THEIR perceived season?

It is to their perceived season that they respond. When we are raising caterpillars indoors, we often think of their surroundings as ‘spring’, ‘summer’, ‘fall’, or ‘winter’, whatever is going on outdoors in nature. Remember, when chrysalises are indoors, they are not responding to nature’s settings outdoors. They are responding to the settings of our homes/offices/classrooms. The reality is that we may have winter with several feet of snow outdoors yet the chrysalis may be in ‘summer’, with lights on for long periods of time because it becomes dark sooner than in the summer and it is too cold for us to go out. We leave lights on in the house longer because we want to see what we are doing. Temperatures may indicate that it is a warm spring day to the chrysalises that are located indoors when it may be below freezing outdoors, with several feet of snow on the ground. It may be the opposite. It may be 90 degrees outside and our caterpillars/chrysalises may be in air-conditioned temperatures in the mid to upper 60′s and exposed to light less than 10 hours a day.

On the flip side, if you want swallowtail butterfly chrysalises to go into diapause or want to keep them in diapause, you can arrange their (indoor) environment for that purpose. How?

If you are *sure your chrysalises are in diapause, they may be stored in the refrigerator in a hard sealed plastic box. We recommend that you line the box with paper towels or tissue to prevent them from banging around as the box is moved. A hard box is recommended to prevent anything from falling over and squishing them in the refrigerator. Sealed is recommended because frost-free refrigerators take moisture out of the air. (It is the moisture in the air that creates frost in a refrigerator.) Frost-free refrigerators can kill chrysalises through dehydration. If the chrysalises are in a SEALED plastic box, your refrigerator can’t dehydrate and kill your chrysalises. They are easily stored by placing your sealed chrysalis box in the vegetable crisper, where lettuce is intended to be stored. Simply open the box about twice a month. No, don’t worry about them needing more oxygen. They aren’t breathing enough to worry about. They are in diapause – almost like suspended animation.

Keeping chrysalises in diapause indoors:

To keep chrysalises in diapause keep them in dark periods (their perceived nights) for 14 hours or longer. Keep them in constantly cooler temperatures, preferably below 70. When they perceive a shorter night and warmer temperatures, they are triggered to come out of diapause.

If chrysalises are stored in the refrigerator and the box is removed and left out for an extended period of time, they may break diapause. It doesn’t take long for them to be triggered to emerge.