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A 2016 study also attributed the last decade 's ten-fold decline in overwintering numbers of the eastern monarch population to the loss of breeding habitat , namely the many species of milkweed ( " Asclepias " species ) that developing larvae require for food ; however , scientists believe there are other factors as well .
 Asclepias
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Asclepias