You've read that native bee numbers are declining, and that some of the 3,600 native bee species we have in the US and Canada have become extinct, or are perilously close to extinction. Habitat loss and pesticide use (homeowners use 10 times more pesticides per acre than do farmers) are the main culprits.
Nevertheless, one morning I was reminded that, just like all animals, bees have natural predators. I spied a bumblebee sleeping inside a white rugosa rose and upon closer inspection, I realized that the bee was dead, with her tongue hanging out. Poor bee! Then I saw a small movement next to it. Here's a picture of what I saw:
It's a crab spider, who lurks inside flowers to prey on bees and other pollinators. Over a period of days, the females can change to green or yellow to better match their surroundings. Too bad about the bumble bee, but these spiders also dine on mosquitoes, aphids, and flies. OK by me.
Folks are responding to the "Plight of the Bumble Bee" and our other native bees by learning about, and then creating, bee nesting habitat and floral richness in their gardens. As an outreach volunteer for the Xerces Society, an invertebrate conservation organization, I'm learning to examine these various responses and see what I can do to increase habitat in my own yard. As often happens, nothing has an easy answer, and creating habitat for bees requires some thought.
What I've learned so far: in nature, mason bee and leaf cutter bee mamas are solitary brood cell makers, with individual nests that are not necessarily close together. That increases the chances of their nests not being targeted by pests and diseases. A bee hotel with large amounts of bee larvae can be easy food for varroa mites, houdini flies, ants, earwigs, and wasps. Chalkbrood disease can spread to many individual larvae instead of staying contained in a solitary nest of perhaps 6 to 8 brood cells, each with a larva.
The other consideration has to do with the diversity of bees (and other animals!). Each bee population has adapted to life in a specific area. Mason bee species from our county may use different materials for their nests and different floral sources than a mason bee from a different part of Washington, let alone from a mason bee in Indiana. (This also applies to procuring butterfly eggs from a different part of the country).
Diseases and parasites can be brought in from another sector that don't exist here. Honey bee hives being moved all over the country for agricultural use can spread these things, too. Hives are often placed so closely together that a mass amount of larvae is available for the "Trojan horse" bees to carry diseases or parasites from another hive.
As with Transition Fidalgo's seed bank at the Anacortes Library, we want to foster genetic diversity in our bee population, to ensure the ability of living things to adapt to a changing habitat. Current USDA research of honey bees shows that those bees have very little genetic diversity, making them susceptible to disease, climate change, parasites, and malnutrition. More info is at: https://www.ars.usda.gov/news-events/news/research-news/2023/dna-research-finds-low-genetic-diversity-among-us-honey-bees
I don't want our native bees to end up with the same problems as the honey bees.
It's possible that if you put up empty nest boxes for bees such as masons and leaf cutters, your own yard's mama bee residents will find them convenient for housing. At least then you'll be fostering the local bee genetics! You'll still need to keep the housing sanitary, monitor for problems, store the cocoons over winter and inspect them for chalkbrood and mites. But there ya go, no easy answers!
Think again about creating habitat and floral resources (please, no pesticides) and letting the bees sort it out for themselves! Learn about stem nesting, tunnel nesting, ground nesting, and the ways bees have managed for eons quite successfully, without our deciding what they need. Sadly, we humans are not always the best managers of our natural world.