North Campus Monarchs

Yesterday afternoon myself and number of other staff members braved the heat to continue our survey of North Campus insects. On the heels of last week's Gulf Fritillary discovery, I found the site's first Monarch butterfly caterpillar, Danaus plexippus!

Monarch butterfly caterpillar

As soon as I saw the caterpillar I knew it was a Monarch: There isn't another caterpillar in our area with such yellow, black, and white banding. Also, the caterpillar was found on a narrow-leaved milkweed plant, Asclepias fascicularis, which is one of the food plants of this well-known species.

Based on its size, this caterpillar is in the second to last caterpillar stage (4th instar). Over the coming weeks it will molt to the last and final stage (5th instar), and then turn into a chrysalis.  In time for its fall migration, the adult Monarch will emerge and make its way to an overwintering site somewhere along the coast.

In the coming years I hope to tag and track the adult Monarchs that emerge in the North Campus, so we can determine the exact location(s) of our Monarchs' overwintering site(s). Tagging Monarchs is an easy process that in no way hurts the butterflies. The adults are collected with a net and then carefully held while a small sticker (approximately 2% of the butterflies weight) is attached to the hind wing of the butterfly. The butterfly is then released and flies onto its overwintering site. When the Monarchs dies the following spring (after mating) the tags are hopefully retrieved and we can answer the question, where do our North Campus Monarchs overwinter?

Demonstrating how to handle a Monarch for tagging