• Monarchs passing through the Eastern migratory area tend to have the lowest level on infection. (less than 8% are heavily infected with OE)

• Monarchs passing through the Western migratory area has moderate levels of infection ranging from about 30% being heavily infected

• The non-migratory population of South Florida has the largest population of heavily infected monarchs with over 70% being heavily infected

-Authors: Andrew K. Davis, and Jacobus C. de Roode

• Testing wing surface area, color hue, and wing density of uninfected and infected monarchs

• New comparative research compiling information across a

wide variety of animals that migrate indicates the costs of

these parasites to their host are often small, but they can

include lower body stores, reduced movement capacity,

delayed migration phenology and lower rates of survival

during migration

• 147 monarchs were tested, 66 infected and 81 uninfected

• This experiment examines how infections impact the size (surface area), color (orange pigmentation) and density (mass per unit area) of monarch forewings

• The experiment was conducted using a combination of computer-assisted image analysis techniques as well as a novel device designed for measuring tear-resistance of butterfly wings.

• There was a slight trend for infected monarchs to have larger wings, there was no effect of sex on wing area but there was a large effect of hostplant

• Orange hue did not differ between uninfected and infected monarchs, but again the hostplant effects were significant, driven by a single plan species, A currasavica.

• Infections with OE affected the density significantly. The magnitude being approximately 6%, including a difference between males and females - females having higher density values than males

• Continued studies on wing tear resistance showed a clear effect of OE on monarch wings, infected monarchs were more easily torn.

.Infection with the protozoan parasite, OE is one of the few known factors that can reduce migratory success

Through the past it was always thought to do so by reducing flight capacity but through this experiment it is uncovered that new evidence points to an additional mechanism by which OE could reduce migratory ability, reductions in wing strength. Monarchs with OE have lower wing mass, as well as their wings tear more easily