Assertion: monarch's migration | /r/RelatedTo | three principle factors
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Source sentences:
text: Mr. Urquhart states that migration is related to three principle factors: (1) monarch larvae feed exclusively on species of milkweed; (2) the migratory pattern is from northeast to southwest; and (3) there is a long history, extending over eons of time, of the distribution of the milkweed species of the genus Asclepias (p.119).