Acadian hairstreak

These butterflies have a very large range and have been known to occupy areas as far as British Columbia to Nova Scotia. However, in the U.S. we can expect to find this species in the northern U.S. and can extend into southern Canada. There is a low distribution of Acadian hairstreaks in the southeastern part of the U.S. Within New Jersey, it is local and uncommon, currently found only in the northern portion of the state.

Like many hairstreaks, these butterflies are most commonly found in willow-lined streams, marshes, and moist wetlands. More specifically they are found most easily in milkweed and dogbane flowers.

The Acadian hairstreak is almost always associated with willowed-bordered wetlands, such as wet meadows and streamsides. However, they can be found at drier sites, such as rocky hilltops.

The caterpillars of this species are known to feed on the leaves of willows. Once the caterpillar forms into an adult it will begin to drink nectar from a variety of different flowers. Some of the flower species that we can find these butterflies feeding on are milkweeds, dogbane, butterflyweed, meadowsweet, New Jersey tea, and thistles.

The males of this species perch on low standing vegetation during the day waiting for any interested females. The males may even go out in search for a female in some cases. During reproduction the female lays white eggs with a greenish or pink tint. The eggs are laid on top of twigs of willows until they hatch the following spring.

Once the eggs hatch the following spring, caterpillar larvae emerge. The larvae have brown heads with a green body and pale yellowish greenish striped. Once these caterpillars are done growing and have reached a full length and weight, they form into a pupa. This is also known as chrysalis. During this stage the pupa is yellowish brown on the top with many brown spots, the bottom site is brown and contains various dark bands. During this stage the caterpillar’s tissues, limbs, and organs are rapidly changing through metamorphosis. When the butterfly emerges it is very weak, and it can take several hours to get the blood pumping and muscles working properly.

The adult butterflies make one flight. The flight occurs from June-August. This species overwinters in the form of eggs.

The current conservation status for the Acadian hairstreak is G5. The status of G5 means that populations are widespread, abundant, and secure. Although this status represents the species as a whole, there are still many problems that have led to a decline in particular meta-populations of this species. For generations, it has been thought that the southern boundary of this population stopped in New Jersey and in Pennsylvania. However, the only currently know location to look for the species in New Jersey is located along the Appalachian Trail in Sussex County. The last Acadian hairstreak was seen here in 2012. There have also been reports of populations disappearing in parts of New York and Massachusetts.

Climate warming appears to be the primary threat to the species, but there are a number of addition factors that could be causing these declines. Factors such as urbanization, forestry practices, agricultural pesticides, and habitat loss are also contributing factors. Many of the current populations do not occur on protected lands and therefore, are susceptible to all of these factors. If climate change continues we can see the current range for the species decrease more than it already has. We could see their range contract from the north and west. This will lead to dense populations and resource competition which may further decrease populations. This contraction may also cause the species to move to higher elevations and less ideal habitat.

There should be an increase in the effort of identifying current populations. This is necessary in order to know what areas to protect and how to go about conserving the populations. These areas should be protected from development and should be monitored often in order to keep track of population trends. Conservation efforts should be aimed at limiting habitat loss as well as preservation of host plants for reproduction. Additional searches should also be conducted in order to discover previously unknown populations.

In 2015, the New Jersey Endangered and Nongame Advisory Committee recommended an Endangered status for this species within the state, but no formal rule proposal has been filed to date.

Text written by Michael Colella in 2015.