Wednesday, April 27, 2016

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.

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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.

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