Growing Up Monarch – 1

In 2014, monarch butterfly populations reached an all-time low—having declined approximately 90% in the last twenty two years. This sparked a Nation-wide effort to help preserve and protect the once common insect and its incredible 2000 mile migration. Now, studies have shown a potential rise in numbers, ending with the 2015-2016 annual overwintering count which reported the highest population since 2009. This increase in population was predicted by experts due to ideal weather conditions during the breeding months, as populations are widely effected by changing weather. For example, in 2002, a single storm killed an estimated 500 million monarchs. Statistics like this solidify the fact that monarchs need a very large population size in order to be resilient to threats. In other words, there must be a surplus of individuals in order for the species to endure.

monarch-population-figure-monarchwatch-2016

In addition to weather, monarch butterflies face numerous threats to their overall survival, many of which involve humans. The true difficulty in protecting this species also lies with the fact that it spans across three countries and two distinct “sites”. Monarch butterflies require a breeding and feeding site as well as an overwintering site. In search of these sites, a monarch butterfly may travel from Canada through the United States to Mexico. This large expanse of land covered makes it difficult to protect the entire range. These two specific sites also present their own unique threats; for example, loss of milkweed due to new agricultural practices. Monarch butterflies go through a 3-5 generation cycle during the breeding season, and the caterpillars feed exclusively on milkweed. It has been shown that nearly half of the migrating monarchs are produced in the U.S. “corn belt”, and yet with new agricultural practices, the milkweed found in this region is being eradicated, particularly due to modified crops that are herbicide-tolerant, allowing for wide-spread use of chemicals that eliminate all other vegetation.

Even after surviving through the summer months, monarchs face a whole new set of challenges, including the actual act of migrating up to 2,000 miles (a daunting task, even when you’re not an insect that weights half a gram). Once at the wintering grounds, the butterflies rely entirely on the microclimate provided by the forests of central Mexico. Due to this unique need, monarch butterflies are at special risk throughout the winter. One of the largest threats is deforestation (both legal and illegal logging practices) which removes roosts, as well as threatens the delicate microclimate. However, the nature of how the monarchs overwinter is a risk in and of itself. The butterflies are concentrated into one small region which makes the entire population vulnerable to a single storm or any other disaster such as fire and disease. Ecotourism also poses a threat to the integrity of the winter refuge, along with many other pressures. In short, people compete with monarch butterflies, not only for space, but also for food and water, and the needs of the people who live in this region must be balanced with the needs of the butterflies. And while many of these difficulties may seem far away and difficult to manage, especially for those living in the Midwest, there are many ways that anyone can make a difference in protecting monarch butterflies. The first and potentially most impactful way you can make a difference is through education. Many people are still unaware of the plight of the monarch butterfly, and even more don’t fully understand the effects of their actions, such as removing milkweed or spraying herbicides/insecticides. For this reason, it is important to not only remain up to date on developing research, but also to educate others as well. This can be as simple as planting a native plant garden in your yard, participating in citizen science, or attending one of many monarch butterfly events throughout the nation. River Bend Nature Center will be hosting one such event on June 10th—a program offering community members a chance to become certified citizen scientists for the Monarch Larva Monitoring Program. During the course of the program, participants will learn details on monarch life history, including their migration, before heading outside to get hands-on experience in searching for monarchs and collecting data.

River Bend will also be playing host to several monarchs in the Interpretive Building as we watch them go through their incredible life cycle. Stop in to see them transform from egg, to larva, to pupa, to adult, and finally, if you’re lucky, help us release them back into the wild!

Our current monarchs were laid on Tuesday, May 23rd. Adult female monarchs in Minnesota in late spring are most often “2nd generation” butterflies, meaning that they are the children of those individuals who overwintered in Mexico. They were hatched in the southern states and flew the remainder of the migration to the northern states and Canada where they breed, lay eggs, and die. This would make the eggs we have “3rd generation”, or the grandchildren of the butterflies in Mexico.

1 egg layingWhen laying their eggs, a female will cling to a leaf and bend her abdomen underneath so that the egg will be on the bottom side. This placement would potentially help moderate heat and moisture, and also reduce predation rates. The female will generally only lay one egg per plant in order to decrease competition between larva, but multiple eggs per plant are not unheard of if multiple females visit the same plant.
Photo credit: Stephanie Rathsack

2 egg
Monarch egg on the underside of a milkweed leaf. When the eggs are first laid, they’re often a creamy white, and will become more yellow in appearance as they age.
Photo credit: Stephanie Rathsack

The eggs are minuscule in size, and it takes a trained eye in order to spot them. However, they can be easily identified as monarchs by their pointed top and the distinct ridges that run vertically all around the egg.

It will take about four days for the eggs to be ready to hatch, though the process may be sped up or slowed down by temperatures. Colder temperatures will slow down the hatch rate, while warmer temperatures will speed it up.

3 egg
This photo, taken several days after the egg was laid, clearly shows the ridges that run up and down the outside of the shell, distinguishing it from other insect eggs as well as milkweed sap.
Photo credit: Stephanie Rathsack

Three of our four eggs hatched on Friday, May 26th and the fourth is scheduled to hatch some time today.

4 eggs
These two eggs side by side allow a clear distinction in age to be seen. The egg on the right is several days old, but is not yet ready to hatch, while the egg on the left has become translucent and allows the viewer to see the black head capsule of the caterpillar inside. This change in appearance indicates that the caterpillar could be emerging anywhere between hours and minutes.
Photo credit: Stephanie Rathsack

5 egg
Another view of the egg preparing to hatch.
Photo credit: Stephanie Rathsack
River Bend’s last monarch egg shows signs of being ready to hatch today, and we are eagerly waiting for it to emerge. Meanwhile, the other three caterpillars have already completed their first meal (their own eggshells) and have moved on to feeding on the provided milkweed leaves. As a species, monarch larva feed EXCLUSIVELY on plants in the milkweed family. Pictured here is the plant “common milkweed” which can often be found growing along roadsides and in prairies.

6 larva
When monarchs first hatch, they are roughly the size of the egg they were in, and their coloration is vastly different than their older counterparts. While older larva will have the distinct black, yellow, and white banding, these younger caterpillars are light gray with minimal banding, and have a large, black head.
Photo credit: Stephanie Rathsack

After feeding on its eggshell, monarch caterpillars will immediately begin to feed on the milkweed plant they were laid on. These youngest larva are known as “1st instars”, indicating that they have not yet molted their skin. After feeding almost nonstop, they’ll be ready to molt in several days. River Bend’s caterpillars are all currently 1st instars.

7 circleFirst instar caterpillars will feed in a circle around themselves until they’re large enough to not be at risk of drowning in milkweed sap.
Photo credit: Stephanie Rathsack

As our caterpillars start eating for the first time, they feed in a very distinctive circular pattern. Many scientists believe that this is to decrease sap flow in the leaf. While the sap is toxic to almost every other animal species except the monarch, these tiny caterpillars could easily drown if sap were to start flowing out of the cuts they make as they feed. To prevent this, the caterpillars feed shallowly, and create a safe “island” for themselves.

Want to learn more?

Stop by our interpretive center any day during the week to talk to a naturalist and see the monarchs for yourself! The building hours are as follows:
Mon-Fri 8:00-4:30
Sat 9:00-4:30
Sun 9:00-2:00

Interested in getting more involved?

River Bend will be offering MLMP trainings to teach interested members of the community to become certified MLMP volunteers! Monitor at home or at River Bend, and help save this amazing insect from extinction.
Register online to attend the training scheduled for June 10th from 1:00-4:00pm.

For more information, see our website at: http://www.rbnc.org/

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