Edwards' Hairstreak Butterfly Census 2018

Since I don’t actually count the butterflies or produce any type of tally, my annual observations of the Edwards’ Hairstreak Butterfly can’t really be called a census.  What I do is search appropriate habitat at Blue Jay Barrens to get an idea of current size and distribution of this uncommon butterfly.

Each year, I find butterflies in new locations and in concentrations larger than the year before.

Edwards’ Hairstreak Butterflies were quite rare when I first surveyed this property 33 years ago.  It took years before I found my first specimen.  Subsequent annual searches resulted in sightings of just a few individuals or, in some years, no sightings at all.  Now I can find that many or more sharing a single flower cluster.

One of my first management projects was to make the property more suitable to Edwards’ Hairstreaks.  I cleared Eastern Red Cedar from the fields to promote prairie like habitat, and encouraged the growth of Blackjack Oak, the Edwards’ Hairstreak preferred larval food. 

As habitat improved, the number of butterflies increased.  Nectar plants also responded to the management efforts and increased in number.  Butterfly Weed, a favorite of the hairstreaks, is now common in most areas containing butterfly colonies.

A few years ago it was uncommon to see more than a single Edwards’ Hairstreak on a clump of Butterfly Weed flowers.  Now the butterflies visit the blooms in masses.  There are 10 butterflies clearly visible nectaring on Butterfly Weed in the above photo.  There are still suitable areas not yet being utilized by the butterflies, so butterfly numbers have the potential to increase for many years yet.

The above video shows some Edwards’ Hairstreak nectaring action.  A few Honeybees are also trying grab some of the nectar.  Near the end of the video, one butterfly appears to headbutt another away from his flower cluster.  This video can be viewed on YouTube by clicking HERE.

Edwards' Hairstsreak Larvae - Night Feeding

Within the Blue Jay Barrens prairie openings are a scattering of medium to small sized Blackjack Oaks.  Some of these trees are decades old, but various environmental factors keep them from getting very large.  Dry site conditions limit water available to the tree, White-tail Deer find them to be the perfect choice for rubbing antlers, Periodical Cicadas cause a dramatic die-back every 17 years and a wide variety of insects find the leaves extremely palatable.  I make several close examinations of these trees each spring as I follow the development of the Edwards’ Hairstreak butterfly larvae, one of those species with a dietary preference for Blackjack Oak.

Edwards’ Hairstreak eggs hatch just as the oak buds begin to swell in early spring.  The larvae feed on the buds and newly developing leaves.  On May 8, temperatures dropped to 29°F causing frost and freeze damage to many plants.  Damage to Blackjack Oaks varied between individual trees, but all suffered the loss of some new growth.  This was a setback for both the trees and the Edwards’ Hairstreak larvae.  Fortunately, buds were not affected and regrowth was rapid.

When I checked the Blackjack Oaks three days ago, the leaves were showing signs of heavy predation by the Edwards’ Hairstreak larvae.  When this magnitude of damage occurs to the leaves it is a good indicator that the larvae have reached their final instar stage and will soon be pupating.  At this point it does no good to search the tree for larvae, because they do not spend the day in the open.

Young Edwards’ Hairstreak larvae remain in the open feeding through the day.  When they become older, they feed only at night and spend the day at the base of the oaks, hidden in cavities constructed by Allegheny Mound Ants. 

Near sundown, the larvae leave their shelter and begin climbing the tree.

Each larva is accompanied by its own cadre of ants. From the time they hatch until emergence as adults, the Edwards’ Hairstreaks are accompanied by ants.  The larvae achieve a degree of protection from the ants and the ants receive a sugary Honeydew solution excreted by the larvae.

The larvae on the first tree went too high to be easily observed, so I switched my attention to a smaller tree that displayed feeding activity.  This tree was less than three feet high and struggling to regrow leaves killed by the freeze.

The larva’s head is located near the top of this photo.  As the larva eats, an ant visits honeydew producing glands near the larva’s tail.

It’s fortunate that pupation is near.  This tree was loaded with larvae.  At the rate they’re eating, the tree may soon be stripped bare of leaves.

The above video is a compilation of several shots of moving and feeding Edwards' Hairstreak Larvae.  Make sure your sound is on, so you can enjoy the call of the Chuck-will's-widow while you watch.  This video, in a possibly clearer form, may also be viewed on YouTube by clicking HERE.

Edwards' Hairstreak Hatchlings

The eggs laid last summer by the Edwards’ Hairstreak butterflies have recently hatched and the buds of the Blackjack Oaks on the barrens are now full of Edwards’ Hairstreak larvae and their attendant Allegheny Mound Ants.

Most of the action takes place on these small Blackjack Oaks. The Edwards’ Hairstreak butterflies sometimes lay their eggs on the larger Oaks, but it’s much more likely that they will use an oak that is less than 6 feet tall.

In order to consume the sweet secretions, called honeydew, produced by Edwards' Hairstreak larvae, Allegheny Mound Ants stand guard and protect the larvae from predators.  The ants protect the larvae from hatching until emergence of the adult butterfly, even though the larvae only produce honeydew during the final few instars prior to pupation.  This type of behavior, where two different species interact to each species benefit, is called mutualism.  In the photo above, two larvae are located just to the left of the ant's head.

The larvae tend to begin feeding at the base of the bud. Leaves that unfurl in a couple of weeks will be laced with holes made by the larvae munching their way through the bud.

Blue Jay barrens has four different Prairie openings that contain quantities of young Blackjack Oaks. I found Edwards’ Hairstreak larvae on trees in all four areas. Some of the buds were really loaded down with larvae. There may not be anything left of these buds to produce leaves later on.

The key to finding the larvae is in finding the ants. If there are no ants on the tree, there are no larvae.  In a couple of cases, ants congregated to protect tree hopper larvae, which also form a type of honeydew. Even in these instances there were butterfly larvae feeding at the same location.

On occasion I would get a bit too close with the camera, causing an ant to take action against me. In each instance, I would direct the ant back onto its bud so it could continue with its duties.

I have been nurturing small Blackjack Oaks at Blue Jay Barrens in hopes of expanding the population size of the uncommon Edwards’ Hairstreak butterfly. I’ve been seeing signs of success during the past couple of years, but this year, the quantity of young larvae far exceeds anything I have seen in the past. The ants have always been present, and now the addition of more trees means more butterflies. The numbers of adult butterflies should be truly amazing this summer.

I’ve included a couple of short videos showing Allegheny mound ants interacting with the Edwards’ Hairstreak larvae. You can watch the above video on YouTube by clicking HERE, or the below video by clicking HERE.

Edwards' Hairstreak Census

The Edwards’ Hairstreak butterfly is one of the Blue Jay Barrens rarities that has been the target of many of my management activities.  Each year, in late June, I take a day to search the property for this small butterfly.  Things have changed considerably since I first found the species here more than 25 years ago.

Edwards’ Hairstreaks are strongly attracted to the orange flowers of the Butterflyweed.  Fortunately, the blooming season for this plant coincides exactly with the flight period of the butterfly.  As part of my search, I check every Butterflyweed I can find.  Last year I was impressed to find many flowers with two Hairstreaks visiting at once.  This year there were frequently three butterflies per flower head. 

Not every Butterflyweed had an attending Edwards’ Hairstreak.  The butterflies stay in close proximity to their larva food plant, Blackjack Oak.  I have been doing what I can to encourage the growth of Blackjack Oak in the fields and now have these oaks growing in several places that they had not been before.  In each of these areas, I’m now finding the Edwards’ Hairstreak butterflies.

This is the original site of the Edwards’ Hairstreak at Blue Jay Barrens.  Even here, the population size has increased through the years.  The caterpillars are generally found on the small, three to six feet tall trees.  Fortunately for the butterflies, the harsh growing conditions in this shallow soil causes the trees to die back during dry years, so the trees tend to stay perpetually short.

The butterflies are also found on and around the oaks.  Females will lay their eggs in the rough bark of the older branches of the tree.  So far, my efforts to photograph the egg laying process have been unrewarded.

Eggs hatch early in the spring and the caterpillars begin feeding on the tender, newly emerging leaves.  Later on, they feed on the larger leaves.  The evidence of their feeding remains through the summer. 

Male Edwards’ Hairstreaks select a courtship territory that they defend against other males.  Typically the territory centers around an oak that is suitable for receiving eggs.  Females entering the territory are pursued by the male in an effort to mate.  Butterfly numbers are trending upward and the territory they occupy continues to increase.  I like to think of these increases are indicators of the success of my management efforts.

I’ve included a short video of a male taking off from an oak leaf to chase away an intruder.  There were so many males in close proximity that a chase by one caused an encroachment on another’s territory, so there were often several individuals involved in the chase.  This video can also be viewed on YouTube by clicking HERE.

Edwards' Hairstreaks 2014

The first week of July seems to be the peak flight period for Edwards’ Hairstreak Butterflies at Blue Jay Barrens.  Because of this, it has become a Fourth of July Holiday tradition for me to take a little time to survey the Edwards’ Hairstreak population.  Of course, I also look at many other things, but for this one outing my priority is to find the hairstreaks.

I had plenty to look at.  There were dozens of Edwards’ Hairstreaks nectaring on the Butterfly Weed.  I’ve never before found so many occurrences of multiple hairstreaks on the same flower clusters.

In order to have Edwards’ Hairstreak butterflies, a site must have young oak trees to provide food for the larvae and it must have Allegheny Mound Ants, an ant species that acts as guardians for the butterflies during their early developmental stages.  Click here for more details on Edwards’ Hairstreaks at Blue Jay Barrens.

When I first discovered Edwards’ Hairstreaks at Blue Jay Barrens twenty years ago, they were located in only one small area near the center of the property.  Since that time, I’ve been encouraging oaks to colonize areas near the large ant mounds.  Young Black Jack Oaks seem to be the preferred host species, so these trees are given priority in all management activities.

I was particularly impressed by the butterfly numbers at this site.  It was nearly ten years ago when I discovered a single Edwards’ Hairstreak in this small opening.  Now there is a thriving population.  Oaks and anthills indicate that the hairstreaks are a possibility.  Add in a clump of Butterfly Weed and you have the perfect opportunity to observe this butterfly.

I’m not sure how to sex these butterflies, but I would think eggs each time I saw an individual with such a robust abdomen.  I felt like shooing her off the flower and sending her over to the tree to deposit those eggs before one of the many flower lurking predators made a meal of her.  I always have to remind myself that wild animals probably know more than I do about what they should be doing to insure future generations of their species.

A few of the hairstreaks looked like they were freshly emerged, but most had lost some of their luster and were looking slightly worn.  Damaged wings suggested probable encounters with predators.

A couple just looked downright battered.  It looks like this one has had quite a time, but it proved to be a strong flier despite the wing damage.

It’s always encouraging to see positive results from your management efforts.  I’m hoping that the Edwards’ Hairstreak population at Blue Jay Barrens continues its expansion.

Edwards' Hairstreak Larva at Night

I went out Memorial Day evening to witness the Edwards’ Hairstreak butterfly larvae exiting their daytime underground shelter and climbing the tree for a night of oak leaf consumption.  This is a behavior exhibited by only the more developed larvae and it is an event that I have always managed to miss.  I think I nearly missed it again this year.  I did see some larvae, but several trees that showed signs of heavy feeding were free of larvae.  Adult butterflies begin emerging in early June, so it’s likely that many of the larvae have already pupated.

I arrived at my target tree at 8:45, just as a Whip-poor-will began its song.  After checking the tree and finding no larva movement, I set up my lawn chair and got ready for a wait.  Despite a temperature of 84 degrees, I put on my jacket and hood to keep off the swarm of mosquitoes.  At 8:48 I again checked the base of the tree and witnessed the emergence of the first larva.  I guess I did a pretty good job of guessing when activity would start.  At 9:03 a Chuck-will’s-widow began calling in the valley below the ant ridge.

A four battery Mag-Lite was my source of light, but the camera flash illuminated all of my photos.  The flash light beam caused the larva to stop its progress and seek cover, so I used it as sparingly as possible.  As the larva began its journey up the tree, there was still enough natural light to find my subject through the view finder.  The larva had to endure only random flashes which I thought wouldn’t be too much different from what would be experienced as a result of an electrical storm.  For serious behavioral observations I’ll have to have a light that doesn’t change the larva’s behavior.

The larva spent about six minutes traveling three feet up to its feeding position.  While the larva was traveling, the Chuck-will’s-widow moved into a cluster of small trees about 50 feet from my position.  After about a minute of making its typical call, it began producing a low rhythmic call that sounded like a soft Bong-Bong-Bong note produced through a Didgeridoo accompanied by the sound of clapping wings.  Chucks have just become common in this area during the last few years and I thoroughly enjoyed this opportunity to experience this aspect of its courtship display.

There was always one ant with the larva.  This one is receiving its motivation for attending the larva, a taste of honeydew.  I’ve read several accounts that describe the ants herding or driving the larvae as they journey up and down the tree.  I never witnessed any indication that the ants had any control over the actions of the larvae. The ants remained in the company of the larvae, but the larvae seemed to control their own actions.  The ant behavior reminded me more of children following after the ice cream truck.

Once on the leaf, the larva ate continuously.  The mouth was never visible from above and except for subtle shifts in position, no movement could be observed.  I headed back to the house after a couple hours of observation.  I was really happy to finally see this phase of the Edwards’ Hairstreak life cycle.  If I can manage to witness adults depositing eggs on the oak, I’ll have captured the entire life cycle.  Maybe I can manage that next month.

Edwards' Hairstreak Larva

At a certain stage in the development of an Edwards’ Hairstreak Butterfly larva, it will begin feeding at night and hiding at the base of the tree during daylight hours.  I’m trying hard to witness this daily migration of the larvae up and down the tree.  On a recent early morning visit to a small oak hosting a family of caterpillars, I was lucky enough to find a larva that was still actively feeding.

Allegheny Mound Ants normally keep close company to the larvae.  The larva receives protection from the ant and the ant is rewarded with a bit of sweet honeydew secreted by the larva.

The ant may patrol the near vicinity, but it is seldom more than an ant length from the larva.  When the early morning sunlight illuminated the larva, it left the leaf and began its journey down the tree.

From the reading I have done, I thought the larva would move at a slow pace.  I was surprised at the rapid pace at which the larva actually traveled.  It wasn’t nearly as quick as an ant, but it made a respectable retreat down the stem.

I also thought that the ant would give more direction to the larva.  The behavior of the ant suggested that it was just following along in an attempt to keep with its source of food.  There’s got to be more to the association than just a bit of food, because the larva only produces honeydew during the final stages of its development, but the ant protects it from the time the larva hatches from the egg until the winged adult butterfly emerges from the pupa.

The larva didn’t slow upon reaching the trunk.  The downward trek continued at a constant pace.

When it emerged into a band of sunlight, it stopped.  Its reaction was like that of a typical movie vampire.  At the first touch of sunlight, it quickly reversed course.

It finally tucked itself into a protected area of the tree bark and stopped.  It appeared to be settling in for a long stay, so I didn’t stick around to see if it resumed its journey when the shade finally covered the rest of the tree trunk.

There’s evidence of feeding on many of the oaks.  I hope this year to witness the night time feeding and the mass migration of larvae heading down the tree towards daytime shelter. 

Note: Piece together the whole story by clicking on Edwards’ Hairstreak in the list of labels.