California’s Butterflies

Palos Verdes Blue

At Right: An adult Palos Verdes Blue butterfly (Glaucopsyche lygdamus palosverdesensis).

The Palos Verdes Blue (Glaucopsyche lygdamus palosverdesensis) is exclusively found on the Palos Verdes Peninsula in southern California.  Much of the habitat of this butterfly has disappeared due to development.  In the 1980s the last location for the Palos Verdes Blue was set aside as a park.  It was then extirpated from the park when bulldozers removed all of the remaining butterflies’ food plants, and thought to have gone extinct.  In the early 1990s the Palos Verdes Blue was discovered by Rudi Mattoni to be present at the Military Installation at San Pedro.  Originally the larvae of this butterfly were described to feed only on the leaves, flowers, and seeds of the rattlebox (Astragalus trichopodus).  This butterfly has been recently found to also feed on Deer weed (Lotus scoparius).

Life History

In late winter and/or early spring Palos Verdes Blues emerge from diapausing pupae and fly about the habitat at San Pedro.  Males generally emerge before females, but there is overlap in emergence times.  Once sexually mature, the males search for females to mate with.  Mated females then search for oviposition sites.  Females generally prefer young deer weed plants (Lotus scoparius) and oviposit upon flower and leaf buds.  They often bury their eggs deep within the buds.

 

Three to five days later (depending on temperature) the young larvae eclose and begin to feed upon the flower and leaf buds.  The larvae go through 4 instars while feeding upon flower and leaf buds.  As the larvae get larger, carpenter ants (Camponotus species) will tend Palos Verdes Blue larvae in a symbiotic or mutualistic relationship.  The ants protect the larvae against predators and parasites.  Butterfly larval parasites generally kill the larvae so this protection helps the larvae survive.

 

The Palos Verdes Blue larvae in return provide the carpenter ants nutritive rewards, which consist of amino acids and sugars.  The butterfly larvae also use the ants’ pheromone communication system to their advantage.  The larvae have eversible tubes which produce semiochemicals that mimic ant alarm pheromones, while body lenticles of the larvae have semiochemicals that mimic brood pheromone.  The butterfly’s brood pheromone mimic makes the ants think that the Palos Verdes Blue larvae are ant larvae.  There are probably other semiochemicals that are mimicking other pheromones.

 

After about three to four weeks the larvae mature and go through a wandering stage in search of a pupation site.  It is believed that the ants follow the larvae in this wandering stage and continue to protect the larvae into pupation.  (Gordon Pratt found ants with a pupating larva of another subspecies of Glaucopsyche lygdamus beneath a very large rock.)  The preferred pupation sites for the Palos Verdes Blue are still not known.

Below, At Left: An early instar Palos Verdes  larva with a carpenter ant.

Below, At Right: A green Palos Verdes larva is tended by carpenter ants.

Diapause

A diapausing chrysalis can be thought of as a bag of fluid with floating imaginal disks.  Many other butterflies that diapause in the chrysalis stage will enter diapause as nearly-formed adults within the chrysalis.  Diapause in the Palos Verdes Blue is obligate, meaning that all larvae that pupate will enter diapause.

 

Through previous studies of other butterflies that diapause in the pupal stage, it has been found that the chrysalis must be exposed to at least 4 months of cold conditions in order to break diapause.  Once the chrysalises are removed from the refrigerator the adults generally eclose 14 to 20 days later.  The development time depends on the temperatures at which the chrysalises are exposed to upon removal from the refrigerator.

Mating

Captive mating with this species is presently being conducted by cage pairing.  The Palos Verdes Blue butterfly is probably too small to hand pair.  Cage pairing involves putting males from a single female lineage into a cage together.  (This means that all of the males in the cage are brothers.)  Meanwhile females are fed and stored in the fridge until they are ready for mating.

 

The males are set up in cages on sunny days generally after 9 AM.  They are all fed a honey/water (3:1) mixture.  When the males have become active and start chasing each other females from a different parental lineage are introduced into the cage.  (This means that the males and females are not closely related.)  Once mated, the pairs are removed and stored in containers until the matings are completed.  The pairs should remain together for at least 20 minutes to help ensure a successful mating.

Feeding

These Blues are fed a honey/water mixture in the lab.  In the field Palos Verdes Blues have been observed nectaring on flowers of the larval food plant deer weed (Lotus scoparius) and rattlebox (Astragalus trichopodus).  Other nectar sources are probably used but how important these other nectar sources are has not been determined.

At Left: A Palos Verdes pupa.

At Left: The underside of a Palos Verdes Blue butterfly’s wings.