Wednesday, October 26, 2011

Monarch Butterflies in the Phoenix Area

Laura's monarch 10-25-11
Laura called me yesterday excited to see a female monarch butterfly laying eggs in her yard in Scottsdale. She was sitting on the ground looking at her milkweed searching for caterpillars, when a female appeared and eagerly looked for the perfect spot to lay her eggs. Monarch butterflies usually lay their eggs on the under side of a milkweed leaf, often on the newest and freshest growth. Funny thing, I was watching the same thing in my yard.
On Sunday morning this ragged-winged lady visited my yard laying eggs on every available milkweed. It seems like the same monarch was laying more eggs yesterday on Arizona Milkweed, Asclepias angustifolia, near my house. She flew in early and nectared on lantana and zinnias, then began choosing her milkweeds for a  future generation. The only problem is this is really late in the season for this kind of behavior. The usual life cycle of egg-larva-pupa-adult is about 30 days and it is all temperature controlled. With our cooler weather finally arriving today it can take longer. By now most monarchs are arriving or near their overwintering homes near Mexico City or the coast of California.

Reports of monarchs in the Phoenix area are the highest we have heard in recent years. But they are later than usual. Everyone seems to have hungry monarch caterpillars in their yards. If you have milkweed, check your plants for small areas of skeletonizing on your leaves or small holes - often there is a tiny caterpillar chewing there.

Laura's third instar monarch caterpillar
 Earlier in the day Laura found this third instar monarch larva in her yard. By the different sizes we know more than one female likely visited her yard. I know I have seen at least six female monarchs laying eggs in my yard since the beginning of September. While usually I have around 20 monarch caterpillars in a good year, this year I am now over 125 caterpillars! Just amazing. And Tatsuyo on South Mountain is over 100 already. These numbers are extraordinary in the Sonoran Desert.

Asclepias angustifolia
Monarch larvae are vulnerable to many predators. While a female monarch may lay up to 400 eggs in her lifetime, only about 10% will complete the full life-cycle to an adult butterfly. Ants can eat eggs, parasitic wasps can lay their eggs in the caterpillar itself, wasps can harvest the larvae to feed their young. I always try to protect a few caterpillars on one-gallon potted plants in a simple mesh laundry basket on my back patio to increase their chances of survival.

To transfer tiny caterpillars easily, either cut the leaf and move it to the new plant or use a soft, firm brush to easily move them.

Keep your eyes out for monarch pupa in odd places around the yard. Sometimes you can find them where you least expect them. Often caterpillars will wander up to 30 feet away to pupate.

Monarch sightings are higher than usual in Scottsdale, along the Salt River channel, and South Mountain. Monarchs are already reported in Yuma and Tucson, too. Of course you can also see monarch butterflies at the exhibit at the Desert Botanical Garden until mid-November.
Keep your eyes open for blue-tagged monarchs. Many have been tagged by the Southwest Monarch Study around town to monitor their migration movements throughout the state.  We are all citizen-scientists and by our keen eyes we can help better understand the monarch migration through Arizona.

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