Monarch Rearing 2024
In the summer of 2024 I didn’t really have a plan to actively start rearing Monarch butterflies, but when I noticed that the caterpillars in our garden were disappearing I decided to make an effort to protect them from predators. Our milkweed patch seemed to have an overabundance of wasps and flies and I wanted to limit the damage they could inflict. So I bought a set of plastic insect-rearing containers which have air holes in the lids with fabric covering to keep out unwanted insects (like tiny flies). I started to gather any caterpillars and eggs that I could find each day in the garden and I collected milkweed leaves to feed them. I washed the leaves and wrapped the stems in a damp paper towel and stored them in a plastic bag in the fridge. Each caterpillar had its own container (to reduce the potential spread of disease) and each day I emptied the “frass” (caterpillar poop) and made sure they had fresh leaves to eat. I kept the containers outdoors to try to keep the light and temperature as natural as possible (going forward I would prefer not to use plastic containers). I kept the containers in laundry baskets to make it easier for me to carry them in and out of the house for maintenance.
It got to the point where I was spending a couple of hours each day taking care of caterpillars because the bigger they get, the more they eat and the more they poop. I hatched almost 40 butterflies over the span of about two months. A couple of those were caterpillars which pupated out in the garden because I ran out of housing units. The caterpillars in containers mostly pupated on the lids, but a couple attached themselves to milkweed pods that I had put in the containers. As each chrysalis got closer to emerging I removed it from the plastic lid and hung it from a dowel set in a milk crate. This milk crate nursery allowed multiple butterflies to emerge with room to move around. I put a towel in the bottom of the milk crate as a cushion in case a chrysalis fell, and I put some netting around the edge of the crate to give the butterflies something to grasp. The plastic crate itself is too smooth for them to hold onto. In the milk crate photo below there are six butterflies which recently emerged and four more chrysalids (one is very dark, it probably hatched the day after this photo was taken). When a butterfly first emerges, it needs to hang upside down for a few hours so that fluid in the abdomen can fill out the wings. Some dark fluid can drip to the floor, and can be seen as dark stains on the towel in the photo.
To move a chrysalis that is hanging, cut a piece of thread maybe six inches long and knot it around the stem at the top of the chrysalis (the cremaster) and gently pry the stem away from the surface to which it’s attached. It will have a small pad of sticky silk attached to it (unless it’s defective), which is what keeps it in place. Then use the thread to tie the chrysalis in a new location.
One day two butterflies were victimized (apparently eaten by birds?) while hanging out on the milk crate so we (that is, my husband) built an enclosure for the milk crate which allows the butterflies to safely emerge and then practice flight before being released.
This was a fascinating learning experience…I laughed, I cried, I became extraordinarily attached to a bunch of insects! And here are some of the things I learned…
Monarch butterflies lay their eggs on milkweed plants, usually on the underside of a leaf. The eggs are very, very tiny, round, and white.
In about 3 to 5 days when the caterpillar hatches, it too is extraordinarily tiny, difficult to spot without a magnifying glass. The hatchling will eat the eggshell before it starts to eat milkweed leaves.
Over the next 10 to 14 days the caterpillar will eat nothing but milkweed and will grow to be about an inch and a half to two inches long. It will shed its skin four times during this time, and it will often eat the skin that is shed. This photo provides an idea of how much it will grow.
When the caterpillar is ready to pupate, it climbs to a spot where it can hang freely in a “J” position. Sometimes a caterpillar will travel a good distance to find a spot it feels is well protected. Most of the caterpillars in these photos were raised in plastic containers so they did their J hang from the lid, as in this photo. I did collect some chrysalids that I found outdoors, only because I saw a few of them disappear, as they are at risk of predation by animals like rodents and raccoons.
During the J hanging process the caterpillar will shed its skin for the last time and expose a chrysalis. The chrysalis is very vulnerable for about a day while it develops and hardens to a delicate shell. If anything interrupts this development the butterfly can be damaged.
