Encore - Spicebush Swallowtail and Pipevine Swallowtail Butterflies

December 26, 2015

EPOD_Encore PipevineButterfly

Today, and every Saturday Earth Science Picture of the Day invites you to rediscover favorites from the past. Saturday posts feature an EPOD that was chosen by viewers like you in our monthly Viewers' Choice polls. Join us as we look back at these intriguing and captivating images.

: Don G. Lambert
Summary Author
: Don G. Lambert

The photo pair above shows a Spicebush Swallowtail at left and a Pipevine Swallowtail butterfly (Battus philenor) at right. Note that the orange dots on the undersides of the hind wings are very different in these two species. Spicebush Swallowtails mimic Pipevines.The underside of the Pipevine is mostly brownish-black with an inverted "C" in orange spots. When the wings are at a certain angle with the Sun a brilliant iridescent blue appears, apparently caused by cell structures which act as a diffraction grating. The function of this iridescence has been thought to be to attract a mate, or to warn predators of the Pipevine's poisonous nature. The larvae feed on the pipevine bush, which contains poisonous compounds such as aristolochic acid. Like the Monarch butterfly whose larvae ingest poisons from milkweed, the adults retain the poisons. In additon to the Spicebush Swallowtail, Pipevine Swallowtails are mimicked by other nonpoisonous species such as the Eastern Tiger Swallowtail. Photo taken on August 8. 2010.

Photo Details: Both images taken with a Canon EOS Rebel T1 camera with an 18-200 mm Canon lens in a field near my home. Left photo taken 8/7/2010 at 8:41 a.m -- f 7.1; 1/250 seconds; ISO 100; 200 mm. Right photo taken 8/8/2010 at 11:39 a.m. -- f 5.7; 1/1600 second; ISO 640; 200 mm. Thanks to Monika Landy-Gyebnar, Jeff Pippen and Bill Hilton for their help.