May 9, 2005 | David F. Coppedge

The Monarch Butterflies in the Flight Simulator, II

How much software can fit in a butterfly brain?  Scientists are again amazed at the navigating ability of Monarch butterflies.  In the 07/09/2002 entry, we reported about how Canadian researchers used a clever flight simulator to test Monarch butterfly navigation with reference to sun angle.  Now, using an enhanced version of the earlier “butterfly flight simulator,” with controls for wavelength and polarization of light, an international team reporting in Neuron1 found that the ultraviolet component of sunlight is critical for their navigation (see summary on EurekAlert).  The small amount of UV light that makes it through Earth’s shielding atmosphere was also found to connect the butterfly’s circadian clock to its ability to orient itself.  This provides the Monarch with a “time-compensated sun compass.”  With this high-tech navigation gear, a Monarch butterfly can stay on course throughout the day, as the sun angle continuously changes.  Another brain network detected by the team might regulate the insect’s hormonal system, “to induce the longevity that enables the butterfly to extend its survival in its overwintering grounds in Mexico.”  That’s quite a bit of fancy software for a bug brain.


1Sauman et al., ”Connecting the Navigational Clock to Sun Compass Input in Monarch Butterfly Brain,” Neuron, Vol 46, 457-467, 5 May 2005,

Most software has bugs, but who would have thought that bugs have software?  The authors did a short phylogenetic analysis of light-sensing genes among butterflies, but otherwise never mentioned evolution.  They made no attempt to explain how a time-compensated sun compass, circadian clock, hormonal system and flight navigation hardware and software arose by a Darwinian process.  Intelligent human designers of guidance and control systems should stand meekly and humbly before the Monarch butterfly, and – much more than they did as kids – wonder.

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Categories: Terrestrial Zoology

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