By Beth Taylor
The Monarch butterfly is the poster child for the health of our Northeastern ecosystem. The striking red and black of the adults, the gold-spotted green chrysalis and the yellow, black and white striped caterpillar draw our interest and our sympathy. Combine these physical characteristics with this insect’s amazing migration to Mexico each Fall, and its return to the Northeast through successive, leap-frogging generations, and we are hooked.
The Monarch belongs to the order Lepidoptera (scaled wings): butterflies and moths. Over the past 350 years, 73 butterfly species and 1685 moth species have been described in Barnstable County.1,2 The number of species in Chatham is lower due to the area’s plant diversity and loss of habitat. All Lepidopterans share the characteristics of two antennae, six legs, three body parts, and four scaled wings. In general, butterflies are diurnal, have slender bodies and clubbed antennae, pupate as a chrysalis and hold their wings upright while resting. Conversely, moths are nocturnal, have thick bodies and either feathery or hair-like antennae, pupate in cocoons or underground, and rest with their wings horizontal.
Both groups share a life cycle pattern known as complete metamorphosis: egg, larva (caterpillar), pupa and adult. This type of life cycle triples the challenges that an organism faces, as each stage must be adapted to different niches in an ecosystem. Adults must avoid predation (butterflies: birds; moths: bats), find sources of nectar, mate and locate host plants for egg laying. The eggs are also preyed on, most often by other insects. The caterpillars depend on a plentiful supply of leaves to develop and suffer predation from birds, rodents and insects. The pupa must avoid predation, usually by rodents, hiding underground or in leaf litter to rest.
In short, predation is a major factor determining the success of becoming a moth or butterfly. Research has determined that it takes over 5,000 caterpillars to raise a nest-full of chickadees.3 The majority of native songbirds all require a steady supply of caterpillars to raise their young. Those caterpillars don’t include Monarch caterpillars which gain protection from a milkweed chemical. Adult birds are searching out caterpillars without the adaptive protection of plant toxins, spines and camouflage. These larvae are primary consumers in the “energy pyramid” and support the next levels of secondary, tertiary (including humans) and quaternary consumers in an ecosystem.
Multiple recent research studies have shown a precipitous decline in insect populations, among them a 75% loss in flying insect biomass and a 45% reduction in two thirds of the taxa.4 In Chatham sightings of the large silk moths at night and multiple butterflies during the day, common 50 years ago, are now rare. Fortunately, any native plant that is saved or planted will feed at least one species of caterpillar. Doug Tallamy, professor at the University of Delaware, has determined that there are “keystone” plant species that support the majority of Lepidopteran species: trees (oak, cherry, maple, poplar, pine); shrubs (willow, blueberry, bayberry, dogwood, serviceberry), flowering perennials (goldenrod, asters, sunflowers, black-eyed Susans).5 Promoting these plant species in our landscapes, public and private, will contribute to a healthier ecosystem.
1. Mello, Mark J. and Hansen, Tor. Butterflies across Cape Cod. A guide to finding, attracting and observing butterflies on the Cape. 2004.
3. Tallamy, Doug. Bringing Nature Home. 2019. 256 pages.
4. van der Sluijs, Jeroen P. Insect decline, an emerging global environmental risk. Current Opinion in Environmental Sustainability. Volume 46, 2020, Pages 39-42. ISSN 1877-3435. https://www.sciencedirect.com/science/article/pii/S1877343520300671
5. National Wildlife Federation. Keystone Native Plants. NWF GFW Plant List Ecoregion8.indd