Fernbank Science Center - Just For Teachers Newsletter

Migratory Butterflies

By Trecia Neal
Fernbank Science Center/Monarch Watch Conservation Specialist

Declining Populations: The monarch butterfly has been in the headlines for the past two years because of its dramatic decline in numbers. The population has declined by almost 80% from a high of over one billion monarchs in 1996, to 56.6 million in 2014. There are a number of reasons the population has declined including habitat loss, early-year storms that have devastated the wintering population, and the adoption of glyphosate corn and soy across North America to the exclusion of non-GMO corn. The result of this adoption of GMO corn has wiped out the primary food source for monarch caterpillars – milkweed. Luckily, this dramatic decline in numbers has galvanized our government and citizens to provide much-needed habitat for the monarch: habitat which benefits other pollinators as well.

There are many interesting migratory butterflies in the world. Butterflies migrate for several reasons, but the primary reasons are due to seasonal weather changes and/or food availability. Butterflies belong to the class Insecta which means they are ectotherms. For ectotherms internal physiological sources of heat are of relatively small importance in controlling body temperature. Instead, they rely on the temperature of the local environment or behaviors to regulate body temperature. For butterflies, optimum temperature for flying is between 82° and 102°F. Below 60°F butterflies cannot fly. This means in marginally cool weather, butterflies must warm their body in order to fly. They can do this two different ways: 1) with behavioral tactics by shivering their thorax, or 2) by basking in the sun on a warm rock. In fact, a nice flat rock in a sunny spot can be very beneficial for butterflies on a cool, cloudy day.

Because they are ectotherms, winter poses a significant challenge to butterflies. Some butterflies overwinter as eggs, some as caterpillars, some as chrysalids, and some even as adults. However, some butterflies use a different strategy and will migrate to warmer temperatures where their nectar food sources are still available and/or to breed. Tropical butterflies, that don’t have to battle cold temperatures will "disperse", although for a different reason. These butterflies move to establish new colonies. If they stay in one place for too long, the caterpillars will consume all of their host plants. This will leave no place for the adults to lay eggs and the local colony will die out. Thus, dispersing a short distance is an excellent evolutionary behavioral strategy for survival of the species. Technically these dispersals are not true migrations since it is not a true two-way migration like true migratory butterflies do, like the monarch.

It is important to understand the difference between dispersal and migration. Dispersal is an ecological process that plays an adaptive role in the life history of the organism involved. In other words, the fitness of the organism is increased in some way through the process of dispersal. For butterflies, dispersal is the movement away from the site where a butterfly emerges or where the local population currently is to find food or to reduce competition. However, dispersing butterflies are easily diverted from their course by ecological factors such as weather, food availability or obstacles. The term migration refers to movements of all or most of the individuals in a population between spatially separated breeding and non-breeding home ranges occurring on predictable cyclical time scales. Migrating butterflies have a strong purposeful flight and are undeterred by obstacles or hostile weather. Migrations begin across a wide area, but once in the air the butterflies all head towards a common destination. Migration is a 2-way process, meaning butterflies migrate to and from specific places seasonally. In some cases an individual butterfly will take part in both legs of the journey, but in many species, such as the monarch, the 'parent' generation flies in one direction and while they may begin the return trip, it is the offspring that often finishes the return journey, having been born along the way.

Migratory butterflies need our help! There are many ways to help, but one of the easiest ways is to add plants that are beneficial to butterflies to your garden. Butterflies only lay their eggs on specific plants called "host" plants. Please see below for a list of migratory butterflies and the host plants that they need in order to survive.

Migratory Butterflies		Host Plants
Common Name	Scientific Name	Common Name and Scientific Name
Little Yellow	Pyrisitia lisa	Partridge Pea (Chamaecrista fasciculate), Wild Senna (Senna macrilandico), Coffee Senna (Senna occidentalis), Powderpuff (Mimosa strigillosa), Texas Bluebonnet (Lupinus texensis) Deer Pea Vetch (Vicia ludoviciana).
Gulf Fritillary	Agraulis vanilla	Maypop (Passiflora incarnata), Yellow Passionvine (P. lutea), and the more uncommon Bird Wing Passionvine (P. tenuiloba), as well as the imported passionvines – Blue Passionvine (P. caerulea), and to varying degrees Purple Passionvine (P. incarnata x “incense”), Red Passionvine (P. foetida) and many others.
American Lady	Vanessa virginiensis	ASTERACEAE: Pearly Everlasting (Anaphalis margaritacea), Pussy-Toes (Antennaria parlinii), Mexican Sagebrush (Artemisia ludoviciana), Purple Cudweed (Gamochaeta purpurea), Scotch-Thistle (Onopordum acanththium), Cudweed (Pseudognaphalium spp.), Ragwort (Senecio spp.), Milk-Thistle (Silybum marianum), BORAGINACEAE: Blueweed (Echium vulgare) Forget-Me-Not (Myosotis spp.) MALVACEAE: Hollyhock (Alcea rosea).
Painted Lady	Vanessa cardui	An incredibly wide range of host plants from many different families. ASTERACEAE: Yarrow (Achillea millefolium), Pearly Everlasting (Anaphalis margaritacea), Western Sagewort (Artemisia campestris), Mexican Sagebrush (A. ludoviciana), Musk-Thistle (Carduus nutans), Basket-Flower (Centaureaa spp.), Tall Thistle (Cirsium altissimum), Texas Thistle (C. texanum), Wavy-Leaf Thistle (C. undulatum), Bull Thistle (C. vulgare), Common Sunflower (Helianthus annuus), Milk-Thistle (Silybum marianum). BORAGINACEAE: Borage (Borago officinalis), Blueweed (Echium vulgare). CHENOPODIACEAE: Beet (Beta vulgaris), Lamb’s Quarters (Chenopodium album). FABACEAE: Soy Bean (Glycine max). MALVACEAE: Hollyhock (Alcea rosea), Common Mallow (Malva neglecta), Little Mallow (M. parviflora), Running Mallow (M. rotundifolia, High Mallow (M. sylvestris), Globe Mallow (Sphaeralcea spp). PLANTAGINACEAE: English Plantain (Plantago lanceolata), Dooryard Plantain (P. major). URTICACEAE: Nettle (Urtica spp).
Red Admiral	Vanessa atalanta	False Nettle (Boehmeria cylindrical), Pellitory (Parietaria pensylvanica), Stinging Nettle (Urtica chamaedryoides), Hops (Humulus lupulus).
Common Buckeye	Junonia coenia	ACANTHACEAE: Snake-herb (Dyschoriste linearis), Violet Ruellia (Ruellia nudiflora), PLANTAGINACEAE: English Plantain (Plantago lanceolata), Pale-Seed Plantain (P. virginica), Buck-Horn Plantain (P. coronopus), Dooryard Plantain (P. major), Common Plantain (P. rugelii), Cedar Plantain (P. helleri), Tallow-Weed (P. hookeriana); SCROPHULARIACEAE: Beach Gerardia (Agalinis fasciculate), Flat-Flower Gerardia (Agalinis homalantha), Slender Gerardia (A. tenuifolia), False Foxglove (Aureolaria grandifloria), American Bluehearts (Buchnera americana), Texas Paintbrush (Castilleja indivisa), Prairie Indian Paintbrush (C. purpurea), Butter and Eggs (Linaria vulgaris); Snapdragon Vine (Maurandya antirrhiniflora), Toad-Flax (Nuttallanthus canadensis); VERBENACEAE: Common Frogfruit (Lippia nodiflora), Lance-Leaf Frogfruit (L. lanceolata), Brazilian Verbena (Verbena bonariensis).
Monarch	Danaus plexippus	Milkweed – Asclepias spp. 21 native species in Georgia. http://www.eealliance.org/assets/Documents/MAG/field_guide.pdf
Long-Tailed Skipper	Urbanus proteus	Atlantic Pigeon-Wings (Clitoria mariana), Velvet-Leaf Tick-Clover (Desmodium viridiflorum), Hoary Tick-Clover (D. canescens), Southern Hog-Peanut (Amphicarpaea bracteata), Soy-Bean (Glycine max), Bean (Phaseolus vulgaris), Lima Bean (Phaseolus limensis), and Wisteria (Wisteria fructescens).
Clouded Skipper	Lerema accius	St. Augustine (Stenotaphrum secundatum), Corn (Zea mays), Thin Paspalum (Paspalum setaceum var. ciliatifolium), Buffel Grass (Pennisetum ciliare), Witch Grass (Panicum capillare), and Johnson Grass (Sorghum halepense).
Fiery Skipper	Hylephila phyleus	Bermuda Grass (Cynodon dactylon), St. Augustine Grass (Stenotaphrum secundatum), Bent Grass (Agrostis spp.), Teal Love Grass (Eragrostis hypnoides), Kentucky Blue Grass (Poa pratensis), Hairy Crab Grass (Digitaria sanguinalis), Southern Crab Grass (D. ciliaris), and Sugar Cane (Saccharum officinarum).
Sachem	Atalopedes campestris huron	Bermuda Grass (Cynodon dactylon), St. Augustine (Stenotaphrum secundatum), Hairy Crab Grass (Digitaria sanguinalis), Goose Grass (Eleusine indica).
Ocola Skipper	Panoquina ocola	Rice (Oryza sativa), Sugar Cane (saccharum officinarum), and Rice Cut Grass (Leersia oryzoides ), and no doubt others.