Shortly after I started looking at the nest box closely, I noticed a little jumping spider hanging around the top of the box. I tried to get a couple photos, but I had the wrong lens, so I went inside and changed lenses, coming back to see what I could find to photograph.
I returned to my spot, about 3 feet in front of the bee nest, and almost immediately noticed an orchard bee checking out a couple tubes near the top. The spider noticed the bee, too, coming to the front of the tube it was currently hiding in.
Despite being held firmly in the spider's embrace, the bee struggled for an amazingly long time. I had thought that spider venom would be injected immediately and that the bee would die relatively rapidly, but the bee kept on moving for minute after minute after long minute.
I pretty sure the bees are blue orchard mason bees (Osmia lignaria), but I don't really know for sure. Some guides suggest ordering the blue orchard mason bees to release when you put up a new nest box, but I trusted that there would be native bees interested in utilizing the new nesting sites I was providing. I was correct, and the bee nest box began to be occupied during the first spring that I put it up. I've submitted the photos of my exciting drama to Bug Guide for verification of the species of bee. Hopefully they'll be able to help me with the identification of the little jumping spider as well.
In nature, female blue orchard mason bees make their nests in hollow stems or twigs. With mud, a female will build a wall across the hollow space and then she will pack in a mixture of pollen and nectar. When she judges that she has enough stored to raise one new bee to adulthood, she lays a single egg on the provisions, closes the cell off with another mud wall, and then begins to provision another cell. The females are able to determine the sex of the egg they lay by whether they fertilize the egg or not - female eggs (fertilized) are laid deep in the stem, with male eggs (unfertilized) closer to the entrances. That way, if the nests are discovered and a cell or two are broken into, it is males that are sacrificed. One male can fertilize more than one female. On the other hand, the females only lay about 2-3 dozen eggs each, so each female is important to the survival of the species.
With such an early start in the growth season each year, it would seem likely that the blue orchard mason bees would raise more than one brood annually, but that's not what happens. The females keep gathering provisions and laying eggs, cell by cell, until the day they die, which is generally in late spring to early summer. There is no retirement plan...and no backup plan either.
Meanwhile, deep in the well-provisioned, mud cells, the next generation begins. Like all bees and wasps, blue orchard mason bees undergo complete metamorphosis: egg to larva to pupa to adult. The egg hatches fairly soon after it is laid, and the tiny larva begins to eat the stores of pollen and nectar that its mother gathered for it. By late summer, the larva will have eaten all of its food and grown tremendously, going through multiple growth stages known as instars. When it reaches the proper stage of growth towards the end of summer, it will pupate. Then, by late fall, the adult will hatch from its pupal cocoon, still snug within its mud cell. It is the adult that hibernates over winter, safely hidden away, until the temperatures warm up enough in the spring to signal time for emergence.
It seems like a miracle to me that year after year, generation after generation, the blue orchard mason bees survive and reproduce. With only one generation each year, it would only take one really bad year, where survival was impossible, to wipe out the population of this gentle and hard-working little bee. Thank goodness that hasn't happened. I hope it never does.
Meanwhile, I'm very glad to have these gentle, busy little bees in my garden. May the (food) source be with them!