Monday, May 14, 2012

A Monarch Spring

Male Monarch nectaring on Calotropis procera
Monarch butterflies ruled the skies in the Phoenix area this Spring and they continue to steal the show as temperatures soar. While monarchs are more common in the Fall and in mild Winters, Spring sightings are more unusual. But our extremely mild temps in January and February created perfect breeding conditions this year for monarch butterflies to flourish.

Monarch pupae 4/19/12
One generation eclosed in late February and early March, another in late April and early May.  A few of the monarchs lingered rather than heading north on their spring migration. I marked some and noted a few were still in my yard three weeks later. When I noticed wasps harvesting the monarch caterpillars to feed to their young, I collected 96 fourth and fifth instars into a large cage to help their odds of survival. This is one of the corners of the cage when they formed their chrysalids.

Monarch pupae
When our first 100 degree day in Phoenix arrived in April and forecasters predicted 104 the next day, I decided to bring the pupae inside. At a conference a few years ago, I talked to Dr. Karen Oberhauser of the Monarch Larva Monitoring Project about the effect of high temperatures on monarch larvae. In her studies she found that high temperatures of 104 and above were often fatal to caterpillars. While the temperatures were held constant in her study, unlike our cooler dry desert nights even when reach 100+ temps during the day, I didn't want to take any chances.
We found pupae around the yard in some pretty funny places wherever we looked, like this one on a piece of wood....

...or on an irrigation valve...

...or on the propane tank when we went to light the grill. We found them on the back of chairs, hanging from the patio cover, hanging even from a tablecloth!

We were very fortunate that of  96 pupae, 94 new monarchs eclosed well over several days in May.


This morning I stepped out to water the milkweed in pots under a tree. With temps climbing to over 100 degrees again, I thought I'd look once again for larvae. I found five fourth and fifth instars....

...then a female monarch flew in and laid more eggs, oblivious to my presence. So, the cycle begins again. Never before have I seen monarch egg-laying so late in the year here in the desert. Most may not survive with our sizzling temps the next few days. But since the beginning of this year just over 300 new monarchs did. It is definitely a monarch butterfly Spring!