Euthanizing dying, diseased, crippled (unable to fly and feed), and other butterflies and moths, from egg through adult, is not fun. But at times it is the kindest thing to do.
The beauty of raising caterpillars indoors is that nature no longer has as much control over their fate. Outdoors, nature only allows about 1 or 2 percent of eggs to become adult butterflies. But on the flip side, there are times hard decisions must be made.
There comes a super sad time for most butterfly enthusiasts. They have a crippled butterfly, too many caterpillars and not enough food (even in the wild), they have diseased caterpillars, or one of the many other nasty things nature brings into a butterfly’s life. Eventually most of us reach a point that we know we should euthanize (kill) it to be kind to it. Letting it live is less kind.
A crippled butterfly that cannot fly can normally be fed with sugar water, juice, Gatorade, or other substitute food. Sometimes people simply are not able to take the time to feed the butterfly or they have pets that make it dangerous for the butterfly.
Perhaps a butterfly has laid hundreds of eggs and the person does not have enough plants to feed the caterpillars, even outdoors in nature. Or perhaps hundreds of caterpillars have hatched and the enthusiast cannot find the proper plants to feed the caterpillars. Knowing that nature would kill 98% before they become adults (if they were outdoors) makes the unhappy task of euthanizing the eggs or caterpillars a bit easier. At least humans can euthanize them quickly. Nature often brings about a slow death.
Chrysalises are sometimes deformed and the adult butterfly will not be able to emerge or, if it does emerge, it cannot fly or cannot live.
Some Monarch and Queen butterflies are so coated with spores of the parasite OE, some of us prefer to euthanize the adult butterfly rather than let it loose in our gardens.
Sometimes we enthusiasts buy plants to feed caterpillars only to realize a day or two later that it had been treated with Bt. Bt is a slow acting totally organic bacteria. Plants are treated with it to kill caterpillars. Once the caterpillar eats a couple of bites of the leaf that is coated with Bt, it is living on borrowed time. It CANNOT be saved but it will take three days to die. It’s gut is dissolving as it crawls about, wanting to eat but unable to do so.
A quick and easy method to euthanize butterfly eggs, caterpillars, chrysalises, and adults is simply to place them in the freezer overnight. Within a couple of minutes, they are normally already dead. They can be placed in a paper or plastic bag, sealed shut, and laid in the freezer. It is recommended that the bag never be opened if disease or parasitoids are the reason for the decision to euthanize the insect. It can be thrown into the trash the following day. Within a couple of minutes, the insect is normally dead. In rare cases, depending upon the species and time of year, it can live for a longer time.
The quickest method to euthanize is simply to (gasp!) squish the egg, caterpillar, chrysalis, or adult. Most of us cannot do this. It is an instant kind death to the insect but it goes against everything inside us. Squishing takes a second. Freezing takes a few minutes.
Others choose to flush the insect down the drain. This is also a quick death but it means that the insect drowns, a slower death since they can often live for minutes underwater.
If you find yourself in the position of this necessity, we hurt with you. It is never fun. But it is often the kindest thing we can do.