Thursday, May 24, 2012

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.


  1. Cool observation! I hope you're able to capture and post the mass migration.

  2. Wonderful documentation of one of nature's small, but fascinating stories.

  3. Hi Troy. I'll do everything I can and just hope the caterpillars cooperate.

    Thanks Pat.