American Snout Butterfly

This is the American Snout (Libytheana carinenta) butterfly. Hundreds of them flew over the ranch throughout the day. I spent quite a bit of time trying to get a photo. This is the only one I saw land!

While he may not be the most beautiful, this little butterfly has an interesting story. Its population explosion and subsequent migration is a direct result of the drought-ending rains we have been experiencing.

Drought conditions reduce the predators, parasites, and pathogenic organisms that normally prey upon the American Snout butterflies. When the drought breaks, it takes longer for the predators of these butterflies to bounce back than the butterflies themselves. Most of the caterpillers - for a couple of generations - survive and become butterflies. As a result, they must migrate to find enough food. (The primary host for the American Snout is the hackberry tree.)

On Sept 9-10, 1921 the most severe rainstorm ever recorded in the continental US occurred in Thrall, Texas (about 40 miles NE of Austin). They had a total of 36.4-inches of rainfall in an 18 hour period. This devastating storm covered a large area of Central Texas resulting in 215 deaths and $19 million in property damage. As a result of the storm (it is thought), in late September 1921, southeasterly-bound Snout butterflies passed over a 250 mile area (from San Marcos to the Rio Grande River) at an estimated rate of 25 MILLION PER MINUTE. The flight lasted 18 days and may have involved more than SIX BILLION butterflies!

Since then, there have been numerous reports of mass snout migrations, most notably in 1976-1978, 2004-2005, and 2008.