|Monarch butterfly, probably male|
|side-cluster milkweed w/egg|
Monarchs have a peculiar life history. The first 3-4 generations of the year live approximately 4 weeks and grow and reproduce like a standard butterfly. They follow the fresh milkweed and flowers north as the season progresses. However, the last butterflies of the year to hatch live 6-9 months and migrate thousands of miles south from the Upper Midwest to Mexico. These butterflies are in reproductive diapause- that is, they don’t breed- and they focus their energy on gliding south in September, October, and November. Once they hit Texas (generally in October), their migration slows. Instead they feed, intent on gathering enough fuel to support themselves during the 6 months they spend overwintering in the oyamel fir forests in the mountain highlands west of Mexico City.
|Monarch ovipositing on milkweed|
|Fresh monarch egg|
|2nd instar monarch caterpillar|
Photo credits: Figures 2 & 4: Philip Barbour, CNTSC; Figure 1 & 3: Anne Stine; Figure 5: Rosanna Brown, CNTSC.