Highlights

In late/February/early March the first butterfly to be seen out and about on sunny days is the mourning cloak. Windy March is a harsh month in New England with plenty of wet snow, rain and nighttime temperatures often below freezing. Not the kind of weather one normally associates with butterflies. So, what are they doing out now and where did they come from?

Let’s first take a close look at one of these hardy butterflies. The mourning cloak is a large forest butterfly with a 3 to 4 inch wingspan. The wings are a dark purplish-brown to maroon with a pale to dark yellow, ragged, irregular edge. Iridescent blue spots line the inner edge of the yellow band. These colors are the colors of traditional cloaks people wore, in the past, when they were in mourning …hence the name of this butterfly. The underside of the wing is colored a camouflaging pattern of grey and brown and the wing edge has the same yellowish band pattern as the upper surface of the wing. Males and females look alike.

Mourning cloaks are out so early in the spring because they are mature mourning cloaks looking for mates and they all went into hibernation last fall in the very same areas where we are seeing them now. Where have they been hibernating? In hollow trees and hidden away under loose and shaggy bark of dead trees.

Mourning cloaks, like all other butterflies are “cold blooded” and their temperature is the same as that of their surroundings. When temperatures drop below freezing the moisture in their cells would freeze and kill them except that mourning cloaks produce an anti-freeze chemical that protects their body when temperatures begin to drop in the fall. By winter they have sufficient amounts deposited in their cells to prevent them from freezing. 

Once the overwintering mourning cloaks leave their hibernaculums they must warm-up before they can fly. They walk to a sunny spot on a tree trunk or position themselves on a branch high in a tree facing the sun. Dark colors absorb more heat from the sun than light colors. As the sun moves east to west they adjust their dark colored wings accordingly to absorb the highest amount of solar radiation possible. 

Once their wings are warmed males fly to a sunny clearing and display seeking to attract receptive females. The male will usually return to the same clearing each day and mate with the females drawn to that location. Males are territorial and fiercely defend their individual sunny locations from other males. A healthy, vigorous male may patrol and defend as much as 1200 square feet of territory.

Shortly after mating the females lay their light green eggs on twigs and leaves of willow, birch, aspen, hackberry, elm and hawthorn.  The eggs are densely packed together and are arranged spirally around the twig or massed together if on a leaf.

Twelve to fifteen days later tiny green-bodied black-headed caterpillars hatch from the eggs. Unlike the young of most of our local butterflies, the morning cloak caterpillars, when small, stay together and move about as one unit feeding together on tender spring leaves. If disturbed they will all act in unison twitching about and staying close together giving the appearance of a larger animal perhaps moving to attack.

Older caterpillars are black with red feet and red dots along their backs, covered in black spines. As they mature, getting ready to pupate, they wander about, individually, searching for the ideal location to attach. They secrete a small silk pad to a twig or other object which they cling to and transform into a tan and grey chrysalis. The adult butterfly emerges from its chrysalis after 12 to 15 days.

When adult mourning cloaks emerge from hibernation what do they eat? Especially when it is often way too early for flowers to be blooming. Although mourning cloaks will feed from flowers in the summer, in early spring they feed on tree sap often following around sapsuckers and other woodpeckers and feeding from the holes in the bark left by the woodpeckers. In fall, rotting fruit is a major food source.

The range of the mourning cloak is circumpolar. In North America they are found across the continent from the edge of the tundra to central Mexico.

The mourning cloak has many predators. Although their camouflaged underwings, when folded, resemble dried leaves, many mourning cloaks are eaten by large predaceous insects such as the praying mantis and small wasps that parasitize them. Voles, mice and shrews will eat chrysalises and most forest insect eating birds and bats will take adults.

Our common mourning cloak has some very uncommon behaviors. Watch for them on sunny days in late winter/early spring.

Directions to trailhead: 

We will meet on Blossom Road at Corduroy Trail approximately 400' north of Fall River Water Department's Watuppa Headquarters at 2929 Blossom Road, Fall River, MA. Park along the east side of the road.

Due to the extremely poor road conditions make sure you approach the meeting location from the Westport, south end, of Blossom Road.

ACTIVITY ALERT CHANGE OF DATE: Walking by the light of the moon will be Saturday, MARCH 4th however Groundhog Day is February 2nd, so don't forget to celebrate the furry, weather prognosticating critter's BIG DAY!

February's Walk -

Cancelled due to projected "bitterly cold temperatures and high wind chill factor."