Thursday, March 05, 2015

Climate Change Impacts on Valley Carpenter Bees

While our unseasonably warm January/February weather was enjoyable for us humans, it challenges normal life cycles for some of our native California insects. 

mourning cloak butterfly
The warm weather convinced many butterfly and bee species that spring had arrived. Then, just as suddenly, winter returned with cold damp days challenging their survival. Typically insects overwinter in one developmental stage. Some butterflies like the monarch and the mourning cloak overwinter as adults, while others overwinter as a chrysalis waiting for spring to metamorphose into an adult. Preying mantises overwinter as eggs.

The female Valley carpenter bee (Xylocopa varipuncta) overwinters as an adult, her male counterpart does not survive the winter. When the female emerges from a winter torpor in the spring, she starts laying eggs to start a new generation. It takes 40-45 days for the young bees to mature from egg, to larva and then emerge as adults. 

In early January I was surprised to see a female Valley carpenter bee active and stashing supplies in a carved-out wooden den. Now in the last few days, these young Valley carpenter bees have begun to emerge. Unfortunately, instead of the warm spring weather they were expecting to find they have emerged into crisp winter days with cold nights. 

Tuesday evening walking home from voting, I found this newly emerged female Valley carpenter bee listless on the sidewalk. She was cold and appeared thin.

She was just able to cling to a stick that I used to pick her up. I found some native ceanothus flowers and other blooms that I have seen Valley carpenter bees frequent. I put the flowers with the bee in a bug box. We kept her in the house over night.

female Valley carpenter bee with a dusting of pollen

In the morning I was afraid she had not survived the night, but she showed a bit of movement. We opened the box and put her out in the sun in the yard adjacent to flowering plants. By mid-morning she had warmed up and flown off.

The weather is warming again. I hope she survives to pollinate the spring flowers and raise a family of her own. When thousands of years of evolution have timed your entrance into the world to coincide with specific weather and blooming plants, small changes in that series of events can challenge your survival. These are the small impacts of climate change that many of us do not notice, but which will eventually add up to large change.

Hummingbirds challenged by weather changes.
Climate changes to native plants and the animals that depend on them.
Alaskan glacier melting

Video of busy Valley carpenter bees on The Earth Minute.
 Compare them to European honey bees.

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