Finding native bee nests with emergence traps

Nesting is a key feature of native bee biology. Bees are central-place foragers, returning from their foraging trips with pollen and nectar for their young. Yet despite it’s importance, nesting has been challenging to study. Not only do most bees nest in the ground, but their nests can be hard to find- they might be hidden under plant roots, or tucked in the side of a crack in the soil. Even the rounded holes bees create as their tunnel entrances often look like holes made by other insects. So what’s a melittologist to do?

I just published a paper in Basic and Applied Ecology on a novel adaptation of emergence traps (they look a lot like  REI model tents- see picture below) to examine native bee nesting. And I found some interesting things using them. For example, I found native bees mostly nested in areas where the ground had steeper slopes. I also found that bare ground was key for nesting. But surprisingly, I didn’t find any soil characteristics, like percent sand silt clay, or organic matter content, that influenced nesting. My study was conducted in a natural area, so it is important to test these findings to see if they hold true in agricultural areas. And that’s exactly what I’ll be looking at next.

For bee biologists out there- I also compared e-traps to 2 other known sampling methods, pan traps and aerial netting. I found that e-traps captured about 14% of the total community, adding 8 species that weren’t collected by other methods. In fact, I found that all three sampling techniques were highly dissimilar, and therefore potentially complimentary. I think e-traps have the potential to help us find more nests and sample landscapes for nesting bees.

Let me know if you have any more questions about my study.


Emergence traps in study landscape.

Sardiñas, H.S., and Kremen, C. 2014. Evaluating nesting microhabitat for ground-nesting bees using emergence traps. Basic and Applied Ecology 15: 161-168.

Southern Diversity

I’m a San Diego native, so I can’t resist writing about James Hung, who works on native bee inventorying in SD county. Hung is PhD student at UCSD who I met while on the Bee Course in Arizona. He has been cataloging bees visiting flowering in patches of habitat in what he calls “a sea of development.” He’s found over 350 species- that’s about 2x as many as I’ve seen in Yolo County in the Central Valley. He has even described new species previously unknown to science. All of these are being curated at the San Diego Museum of Natural History.

It is hoped that his work can help identify areas for conservation, and shed light on how drought affects bee communities.

In addition to this, he is also a wonderful photographer:


Check out the full article on his research at ucsd news. Or follow his new bee blog, which is sure to contain more beautiful pictures and neat insights into the bee fauna of Southern California.

Virus transfer among bees

As a colonial, social species honey bees are plagued by a variety of viruses. It is suspected that viruses may be behind colony collapse disorder. Bumble bees are also social, and related to honey bees. New work is showing that they are susceptible to many of the same diseases honey bees are, and that viruses can pass between species.
Particularly alarming is that the virus seems able to survive in pollen grains, moving from infected bees to uninfected bees and thereby spreading. A number of floral species were found to contain viruses– and the viruses were not just honey bee specific, but affected carpenter bees, mining bees and sweat bees, even some wasps. While the viruses may not be able to survive in pollen for very long, when flowers are in peak bloom, lots of pollinators may visit in bursts, leading to high rates of transfer.

Should we be concerned about this? In short, yes– spillover effects of disease from managed bumble bee colonies in greenhouses have been shown to harm nearby native, unmanaged bumble bee populations.  Of course, wild populations could also serve as disease reservoirs passing diseases back to honey bees. The authors of the article highlight the need to promote health in both managed and unmanaged populations, and recognize the overlap between the two. Healthy bee populations are important to our food supply.

This paper was written in 2010- I’ll try to look into newer findings soon!

Singh, R., Levitt, A. L., Rajotte, E. G., Holmes, E. C., Ostiguy, N., Lipkin, W. I., … & Cox-Foster, D. L. (2010). RNA viruses in hymenopteran pollinators: evidence of inter-taxa virus transmission via pollen and potential impact on non-Apis hymenopteran species. PLoS One, 5(12), e14357.