One of our favorite end of summer activities is raising and releasing monarch butterflies. Several times a year, we hike down the road picking up trash and recycling. We explore all the roadside weeds and wildflowers and look for butterfly eggs, and caterpillars. Along our road there are several large patches of milkweed. We check them periodically for monarch eggs and cats before the county mowers come by and mow them down.
We began rescuing and raising monarchs several years ago, and it is really rewarding and fun for the whole family. The kids still get excited watching the caterpillars grow and change, and then getting to release them.
On our latest hike, we were thrilled to spot 4 tiny little caterpillars. Three of the four were newly hatched, and extremely tiny. Around 4mm long. If we didn't know what we were looking for, we probably would not have known they were monarch cats. The fourth caterpillar was slightly bigger, around 10mm. Caterpillars skin does not grow, and so they molt (shed their skin) several times. The intervals between molts are called instars. Our tiny caterpillars were in the 1st instar, and had not yet shed their skin. We believe our bigger caterpillar was in it's second instar and had shed it skin one time.
Once monarchs hatch from their eggs they spend about 10-14 days munching and crunching on milkweed. They shed their skin 5 times, before their final molt when they form their chrysalis.
We found our caterpillars on August 7th. and they were at least a day or two old. So our caterpillars are probably about a week old, and will be forming their chrysalis in just few days. Our largest cat has tripled in size over the last couple days. He is measuring about 41mm, while the others are around 17 mm long.
In a few days we'll hike back down the road and look for more eggs and cats, before the county mowers get to them. The survival rate for monarch caterpillars in the wild is less than 10%, but when rearing them at home we have a survival rate of about 90%. We do occasionally lose a couple to disease or parasites, which is a really good learning experience for the kids.
We have observed parasitic infection which resulted in Tachinid fly larva emerging from the chrysalis instead of a butterfly...yuck! We also had a couple cases of OE last year, which i'm guessing came from contaminated milkweed.
Overall the monarchs chances are much better when we rear them inside, and it's such an amazing process to experience and their are so many opportunities for learning.