The Palos Verdes Blue Butterfly was initially found on the Palos Verdes Hills on the Palos Verdes Peninsula in Los Angeles County. Historically the population of the butterfly was continuous on the coastal scrub habitat on the south half of the peninsula. In 1950, there was extensive industrial development in the area that threatened the habitat. Prior to this construction of housing on the butterfly’s habitat, entomologists talked to city officials about relocating some of the butterfly’s Astragalus plants to a different site on the peninsula. However, due to this continuing destruction, by 1970 the habitat was considered fragmented. This fragmentation greatly affected the population of butterflies in the peninsula, and the species struggled for survival.
In 1977, the butterfly was described as a new subspecies, Glaucopsyche lygdamus palosverdesensis. In 1980 the US Fish and Wildlife determined that the Palo Verdes Blue Butterfly was endangered, along with its sole larval food plant, Astragalus trichopodus, or the locoweed. As the Astragalus has declined in most remaining sites, the butterfly began to face localized extinctions based on the varied presence of its food source. The distances between the Astragalus sites also increased, making it harder for the Palos Verdes Butterfly to recolonize in previously occupied areas. With this extreme habitat fragmentation, there were only three areas that could support the insect with an estimated 300 adults remaining.
This chart reveals the correlation present between the conservation status of the Astragalus plant and the Palos Verdes Butterfly. As seen on the chart, there is a positive correlation between the plant and the butterfly, meaning that as the number of plants increases, so does the population of butterflies. The butterfly had faced near extinction many times before 1983, as in many different areas, there were less than 10 butterflies observed. Around 280 Astragalus plants were lost at these five locations and the last Palos Verdes Blue Butterfly observed was a single adult at colony 4 in 1982. Additionally, Astragalus plant numbers at seven different localities declined 89%. In 1983 and 1984, there were extremely harsh winters and it was thought that the butterfly had gone extinct. The extinction can be seen on the chart as in 1983, there were only 6 observed adults, in the Gulfcrest Heroic Drive area, and one adult in the Fields West of Palos Verdes Drive East, and there was no record of any other spottings in the years thereafter.
After 11 years, the butterfly was rediscovered in San Pedro, California. Since there were only a few hundred butterflies, and the population was in danger of extinction, there was a propagation effort initiated to restore the habitat for the butterfly. The program, that has been going on since 1995, fosters captive populations of the Palo Verdes Butterfly to breed new pupae. The results of this program fluctuate per year, as there are population increases and decreases due to weather.
Palos Verdes Blue Butterfly 