California’s Butterflies

Roosting Sites

There has been very little reported on nocturnal roosting sites for butterflies.  These same roosting sites may be important for roosting through stormy periods as well.  Part of the reason for this is that most butterfly naturalists stop observing butterflies once butterflies stop flying for the day.

 

Dr. Pratt believes that some butterflies have become adapted to specific plants for roosting since there are advantages to these plants.  It has been noted for many years with populations of such butterflies as Satyrium fuliginosum and Icaricia icarioides that they are not only associated with a specific lupine as a food plant, but also to great basin sage.  Dr. Pratt has observed some butterflies late in the day, or when it looks like it is about to rain, spending a few minutes searching for and eventually landing on specific plants.

 

As an example, Dr. Pratt has watched Euphilotes intermedia (battoides) comstocki fly around old flower stalks of the great basin sage, Artemisia tridentata.  Eventually the butterflies land facing up towards the sky, then turn around and face downward.  After a few minutes these butterflies seem to become secure in their roosting site choice and are no longer easily disturbed.

 

The reason the great basin sage may be chosen is that this plant is rarely fed upon by insects.  The great basin sage is probably filled with toxic chemicals, making it an unpopular plant to feed upon, and most herbivorous insects would avoid it.  This makes great basin sage rather sterile for insect predators and parasites.  Since there are very few predators searching these plants, it would make an excellent place to hide.

 

Late in the evening Dr. Pratt has watched zerene fritillaries searching pines for roosting sites.  Pines may be important for habitat restoration for some of the zerene fritillary habitats.  Without these trees, these fritillaries may not have places to hide.  Unfortunately in some areas where there are endangered fritillaries, pines are being burned off to improve coastal views.

 

 

 

 

At Right: Two adult Lupine Blue butterflies find a roosting site for the evening.