Monarch butterflies suffer declineBy JEFF NORTH,
The food plot Ford and I were walking in has been untouched since last fall. I suppose I should qualify that by stating untouched by man. The local whitetail population has been wreaking havoc on the clover, chicory, and numerous other tender morsels that have been offered to them all summer. The incessant grazing has diminished the desired plant species and a multitude of “undesirables” have taken their place.
Our agenda was to discuss how to rid the food plot of the abundant Carolina horse nettle that had been released by the lack of competition from the good plants. Phenoxy herbicides were discussed as an option. Another option was just plain ole good cold steel from the disk that has been sitting in the weeds all summer which I am sure are harboring wasp and black widow spiders. It was then that we spied numerous caterpillars with distinct white, yellow, and black bands, dangling from another weed species present in the food plot. The plants, green antelope milkweed, were covered in Monarch butterfly larvae. Voila, the idea for another article was born.
The Monarch butterfly, or simply monarch, is a milkweed butterfly in the family Nymphalidae. It is easily recognizable by its black, orange, and white wing pattern and is only mistaken at times by the much smaller Viceroy butterfly that has an extra black stripe across each hindwing. The eastern North American monarch, (Danaus plexippus), is notable for its annual southward migration in late summer. In fact, this iconic pollinator is probably packing its bags for the long journey to Mexico at this very moment. Hopefully, TSA won’t intervene with their travels.
The name “monarch” is in honor of King William III of England. Linnaeus originally described this notable insect in his Systema Naturae of 1758 and placed it in the genus Papillio. However, in 1780 Jan Krzysztof Kluk placed the monarch in a new genus Danaus.
As mentioned, this butterfly has a similar wing pattern and coloration to the Viceroy. This similarity is the basis for a natural defense mechanism known as insect mimicry. The larvae of the monarch feed on the poisonous milkweed. Over time, these toxins known as cardenolide aglycones or more specifically cardenolides, accumulate in the larvae as they ingest the milkweed substrate. These steroids leave a very foul taste in the mouths of predators like birds and through learned behavior predators tend to shy away from this insect as a food source. Additionally, these steroids are transferred to the wings and abdomen when they emerge as an adult from the chrysalis. The viceroy is confused with the monarch by predators by the color similarities thus the perfect example of defense through mimicry. What an interesting phenomenon this truly is for the entomologist.
Sadly, this noble insect faces many threats. A 20-year comparison of overwintering numbers is quite alarming. Statistics show there is a 50 percent reduction in numbers for those species west of the Rocky Mountains and more than a 90 percent reduction in numbers east of the Rockies. In February 2015, the U.S. Fish and Wildlife Service released a report showing that nearly a billion monarchs vanished from overwintering sites since 1990. Though speculative, it is believed by some that habitat loss due to herbicides plays a significant role in the monarch’s population decline. We can all be assured that if the population of native milkweed is reduced, it only makes sense that this insect’s population will follow. We must note however that just because there is a correlation between herbicide use and milkweed decline, this does not by any way prove causation. There are notable other causes of milkweed decline other than herbicides and also other probable causes of overwintering populations declines. Regardless, there are numerous conservation efforts for this unique insect species that can assuredly help to protect and perpetuate the species.
In 2015, the Pollinator Task force issued a “National Strategy to Promote the Health of Honey Bees and Other Pollinators.” This strategy lays out a plan to achieve goals for the benefit of not only honey bees and monarchs but all pollinators. Many hours of scientific study has the best interest of the monarch at heart. Additionally, there are lobbyist groups working diligently to help ensure the future of this unique insect. Of course we at home can do our part also. Everyone could set up a small flower garden for all pollinators. Of course to help out the monarch, milkweed species need to be a part of this. There is much information on how and what to plant to benefit the monarch and other desirable species. I’m sure you all know how to “google.” I think Ford and I will do our part by holding off on spraying and disking until at least the fall migration is in sunny Florida or in the tropics of Mexico. Of course our delay in fall food plot planting may also save us from the armyworms that are just waiting for the tender shoots of rye, oats, and triticale to emerge. This could be a topic of symbiosis between hunter and monarch but alas, for another day. I encourage you to keep your eyes to the sky for migrating monarchs and to the ground for the caterpillars feeding on succulent milkweed. I hope you observe both. Until next time enjoy our woods and waters and remember, let’s leave it better than we found it.