By Chase Olsen, Naturalist Intern, Lime Creek Nature Center
A staple in the fields of prairie restoration, pollinator conservation, and entomology is the monarch butterfly. A jet-black body with white spots, brilliant orange and black wings, and a graceful flight pattern; this insect plays an important role in its ecosystem and in our own practices of conservation.
The monarch butterfly is a pollinator, responsible for the successful reproduction of many native flowers. In order to survive it must first rely on a single genus of plants, milkweed. A common sight in prairies and roadside ditches, this plant is toxic to humans and most animals, but it is the only plant monarch caterpillars will eat before they become butterflies. It is this specialized diet, and the species’ overall importance, that has led to Lime Creek Nature Center’s newest project, a monarch rearing station.
Located in the Pollinator Room, the rearing station consists of two mesh cages. The taller of the two is for the caterpillars, and the other is for the adult butterflies. Caterpillars start as eggs and hatch after about three days, then remain as caterpillars for two weeks. A chrysalis (pupa) is formed for another two weeks, and then most adult butterflies will live for an additional four weeks.
In the caterpillar cage, large caterpillars are able to eat milkweed until they climb up and hang from the cage ceiling. Soon after, they form a chrysalis. Once all of the caterpillars form a chrysalis, the lids are swapped on the two cages so new caterpillars can form their chrysalises and the old ones can emerge as butterflies. It is important to keep the old caterpillars separate from the new caterpillars, otherwise there is a risk of parasites being transferred.
After about two weeks in the chrysalis stage, the adult butterflies are ready to come out. When they first emerge, their wings are crumpled, and their bodies bloated. They have to spend the rest of the day pumping all of the fluid in their bodies into their wings so they can fly properly. The wings are also wet and need to dry off before the butterflies can fly properly. If all goes well, the butterflies can be released into the wild by the end of the day or the following morning.
Caterpillars await being moved to fresh milkweed cuttings.
The caterpillars are usually much smaller when they arrive at the nature center. Of the over fifty specimens that have been successfully raised thus far, most were collected at Lime Creek’s prairie just north of the parking lot. Nature center staff either find them as eggs or caterpillars on the many milkweed plants found on the prairie.
Eggs and small caterpillars are kept in small condiment containers by themselves until they are about an inch long. The lids have small holes poked in them to allow for air to get in, a milkweed leaf is provided for food or support, and a small moist piece of paper towel is put in as well to provide moisture.
Later they are put in a small plasticware container with a few other caterpillars until they are big enough to be put in the cage. Leaves and a larger moist paper towel are provided as well. Like the separate cages, the separate containers help prevent parasite transfer. Lime Creek tracks how many specimens are collected and how many make it to each life stage, ending in the release into the wild.
Currently, Lime Creek has seen over a hundred specimens come through its doors, but not all of the eggs and caterpillars have been successful. Parasites can threaten even captive caterpillars and monarchs. A microscopic parasite known as Ophryocystis elektroscirrha, OE for short, spreads quickly and prevents the adults’ wings from developing properly.
Another parasite, the larva of the tachinid fly, lives inside the caterpillar, slowly feeding off of it until it begins to form a chrysalis. From there, the larva bursts out in a move that is fatal to the caterpillar/chrysalis. To date, no caterpillars have been lost to OE, but a few have been victim to tachinid flies. When it comes to rearing monarchs, there are no guarantees. Sometimes things just go wrong, and a perfectly healthy caterpillar will not survive past the chrysalis stage.
Towards the end of the August, butterflies that are released from Lime Creek will also be fitted with a tag. Monarch butterflies make a massive migration to Mexico each winter, and the tags help scientists keep track of the butterflies’ general movements and how many actually survive the migration.
The butterflies that make it to Mexico will overwinter before they begin back north. The migration back occurs in generations. The first generation will arrive in Texas and raise the next generation which goes further north to do the same thing. Roughly two generations pass by the time the butterflies arrive in Iowa. This magnificent phenomenon, combined with the service of pollination that they provide for us, is why Lime Creek has dedicated this summer (and future summers) to helping keep the monarch population healthy.
Lime Creek encourages visitors to come out and see the monarch rearing station for themselves. For those who would like more information on monarchs as well as ways to get involved, www.monarchwatch.org is the site of Monarch Watch, a program based at the University of Kansas. Information can also be found at www.monarchmania.com, the site for Monarch Mania, a program within Cerro Gordo County. These websites also provide information for individuals interested in tagging monarchs themselves. Lime Creek appreciates the support in this new program and looks forward to the start of the migration!
Keep up the good work Chase.