California’s Butterflies

Laguna Mountain Skipper

At Right: An adult Laguna Mountain Skipper butterfly (Pyrgus ruralis lagunae).

The Laguna Mountain Skipper (Pyrgus ruralis lagunae) is one of the rarest southern California butterflies.  Originally it was thought only to occur in the Laguna Mountains, but it was found in the mid-1980s at Palomar Mountain.  This skipper was last seen in the Laguna Mountains by Dr. Gordon Pratt in the spring of 1999.  It has not been seen there since.  Dr. Pratt thinks that the extirpation from the Laguna Mountains was largely due to an extended period of overgrazing by cattle .  Also, camping on the meadows and on top of the food plants when the larvae were feeding could have contributed to their extirpation.

Life History

This small checkered skipper occurs in early spring.  The adult hatches from a diapausing chrysalis.  The Laguna Mountain Skipper flies around in open meadows and males often patrol drainages.  Females lay their small white-colored eggs singly on the underside of the larger leaves of their food plants.  These eggs hatch about 9 days later.  Immediately the larvae form single homes on their food plants by cutting part way through a leaf and folding it over.  The folded leaf is usually secured by silk at several locations.

 

The larvae go through 5 instars and each instar takes about 7 days each.  Each larva has a very dark head capsule and a characteristic narrow neck.  It is very similar to the MacNeil’s Sootywing.  This narrow neck is found in most skipper larvae.  The larvae then pupate and about 2 weeks later form the second brood for the species.  There are very few late May and June records in the Laguna Mountains so it is thought that these pupae entered an obligate diapause.  By comparison, the pupae at Palomar Mountain in Mendenhall Valley form the second generation.

Diapause

This checkered skipper species diapauses as a chrysalis.  The larva forms a silken shelter, probably within dried leaves in the leaf litter, and pupates.  This chrysalis remains in diapause through the remaining summer and through the cold winter.  Diapause in the chrysalis is broken by warming conditions in spring and perhaps by an increase of day length.  It is thought that the chrysalis can diapause multiple years based on studies of other subspecies.

Mating

No in-depth mating studies have yet been done on this species.  Ken Osborne is attempting to mate the Laguna Mountain Skipper so that it can be put into a captive breeding program.

Feeding

These skippers appear to favor yellow flowers, particularly yellow composites.  Yellow buttercups are also used as nectar sources.  During the second brood the Horkelia food plant is used as a nectar source.

 

 

 

Above, At Left: A Laguna Mountain Skipper egg on a leaf of Horkelia.

Above, At Right: A Laguna Mountain Skipper larva.