* Based on butterflies collected at the Mexican overwintering sites by many researchers over serveral years at different times during the overwintering months. Exception: April data, in red above, were butterflies collected in the southern United States after successfully migrating from Mexico. From: Alonso-Mejia, A., E Rendon-Salinas, Brower, L.P. 1997. Use of lipid reserves by monarch butterflies overwintering in Mexico: Implications for conservation. Ecological Applications, 7(3), 1997, pp 934-947.
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