Once again, we are experiencing an erruption in the population of the butterfly, the California Tortoise Shell (Nymphalis californica) along El Portal Road between Windy Point, to down past Yosemite View Lodge. This beautiful orange and brown butterfly is being killed by vehicles in the thousands in this area. While complete avoidance of hitting butterflies is not possible, the carnage can be substantially reduced if drivers reduce their speed. At around 25 mph, the butterflies tend to be swept over the vehicle unharmed. At faster speeds, the butterflies are struck in large numbers by the grills and windshield of vehicle. So during this period, which may last through June, please slow down and enjoy this spectacle. In most years California Tortoise Shells are a relative uncommon species. But in certain years, they emerge in overwhelming numbers. This species could be responsible for our county’s name, Mariposa, which is Spanish for butterfly.

The larvae of the species feed mostly on ceanothus shrubs. Several generations of egg-larvae-pupa-adult metamorphosis may occur in spring-summer, but the butterflies tend to move progressively higher in elevation as the year advances. Some scientists believe this is because plants at these elevations have new, tender growth, and lower levels of tannins later in the season, making them more nutritious for larvae.