Monday, April 11, 2016

Dusky Skippers Puddliing

Puddling party in the valley - REK
Juvenal's Duskywing - REK
We are seeing lots of Duskwing Skippers the last week, clustered in groups of 50-100 plus gathered on dry sand in our gravel drives.  These are the Rodney Dangerfields of the butterfly world and some would even go so far as to separate them from butterflies altogether.  The duskywing skippers are notoriously hard to identify by species and only the fact that I was seeing such large numbers at scattered sites made me curious enough to the trouble to ID them.

 These are all Juvenal's Duskywings, Erynnis juvenalisThey  are nearly identical to
 Horace's Duskywings and both were named for Roman poets for unknown reasons.  The marking details separating the two species are very minute, one requiring pulling the forewing forward to expose two tiny white apical spots, cumbersome for me and I suspect embarrassing for the butterfly.  From now on I will confidently call them Dusky Skippers and skip on to the next species.

Juvenal's Duskywings fly earlier in the year than Horace's.    Juvenal's was one of the first North American butterflies to be described.  They were initially associated with dry, sandy regions with shrub oak but are found anywhere in the eastern US where their caterpillar host plant oaks occur.  Oaks occur all over our land so they have a lot to choose from.

E. juvenalis caterpillar -  Bob Barber CC
Males will cling to branches along the edge of woodlands and patrol for females.  Eggs are laid on early oak leaaf buds or seedlings where their caterpillars will  feed on leaves and rest in nests of rolled or tied leaves.


  Tom Murray
 Puddling or mud-puddling behavior is observed in lepidoptera and a few other insect species.  It is a way for them to collect minerals such as salt similar to what sweat bees do landing on our skin in summer.  Some species will do this on animal dung, presumably collecting ammonium.  These gatherings are predominately male as they collect sodium and amino acids which they then transfer to the female as a "nuptial gift" delivered with their spermatophore during mating.  It is common to see several species puddling together in the summer.


When I began writing this I suddenly noticed something else about the puddling photograph.   While the Duskywings wingspan measured less that 1.5" there was something even smaller on the sand.  See if you can spot them in the picture at the top.

There are two tiny black moths with multiple white spots on their wings.  These are Mournful Thyris, Thyris sepulchralis with a wingspan of less than an inchWhile most moths are out at night, these are day flying moths that feed on flower nectar and are noted for collecting fluid on moist sand.  Our sand appeared dry to sight and touch but many species shoot fluid out their rectum to moisten the area and dissolve the salts for absorption.  (Note to self - wash hands after testing sand).

One photographic trick is to pour a little salt water on the ground and wait for butterflies to puddle for the camera.  Some photographers suggest placing a decoy of a dead butterfly or even a piece of colored paper to attract species in the neighborhood.  A naturalist, most likely but not necessarily male, may chose to supply ammonium in the form of urea from a convenient resource. 

Find the moths?  Click on this picture.

1 comment:

  1. Great post and lovely photos. Thank you so much for sharing.

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