Lipids Mass of Monarch Butterflies* (in milligrams) Month Butterflies in Clusters Butterflies at Flowers Nov 138   Dec 128 53 Jan 101 23 Feb 73 21 Mar 58 21 Apr 26   * 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. Search Journey North Copyright 1997-2012 Journey North. All Rights Reserved. Questions or comments? Contact us.