Sunday, April 06, 2014

Garden Drama 2014: Jumping Spider vs. Blue Orchard Mason Bee

Yesterday I noticed that my blue orchard mason bees were active already - a few were flying around the bee nest that I have in my garden.  This morning, I decided to try to get some pictures...and I was lucky enough to witness my first "garden drama" of 2014!

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.

The bee seemed oblivious to the spider.  It came out of one tube and flew to the tube immediately adjacent to the spider's tube, going deep into the tube as soon as it landed.  The spider and I both waited until the bee came backing out.

Instead of sensing danger and flying away, the bee hung around the entrance to the tube for precious seconds, seeming just to look around.

The spider moved in closer...

and closer...

...and suddenly pounced!  The bee had waited too long.

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.

Meanwhile, the spider was patient and just held on.  After a while, it pulled the bee up to the upper edge of the tube where the bee had been exploring.

Eventually the spider pulled the bee into the crevice between the tubes and the outer edge of the bee nest.

When the only thing still visible was the face of the doomed bee, another orchard bee flew in to the area just on the other side of the spider's tube. 

Shortly after the new bee moved out of sight, the doomed bee seemed to finally quit all struggle.  It quickly disappeared totally from sight, pulled to the back of the nest box.

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.

As fascinating as it was to witness this fatal encounter, I feel guilty.  I meant to replace the old orchard bee nest box with a fresh one last year, but I never got around to ordering a new box.  I've read that parasites build up in the old nest boxes, so they should be replaced every 2 years.  Not only was the spider living in the nest box and able to harvest at least one orchard bee, but as I looked at the photos closely, I noticed small round dots on the bee's thorax that I'm afraid are mites of some sort - parasites.

So this evening I ordered TWO new nest boxes, so I can put one up as soon as it arrives and have a second one in reserve.  I'm hoping I'm not too late.  Blue orchard mason bees have a single generation each year.  They emerge early in the growing season, nectaring at apple, plum, cherry, and other early blossoms.

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!


Marilyn Kircus said...

Great post on a very important species. I hope this encourages more people to put bee houses in their gardens. They don't sting and fertilize your fruit trees, and other species fertilize other plants.

Susan K. said...

Great photos! I don't think new nests would help with the spider problem. We just put up a bunch of new nesting blocks this year and the jumping spiders were there pretty much immediately. We have really fat spiders now and not too many bees. : (

Casa Mariposa said...

We're having work done on our exterior and haven't put up our bee house yet. But we should have them up this weekend. Now I just need to get the cocoons ready and buy new tubes. I would have scared away the spider and let it eat something else. I would have had a hard time watching it eat a mason bee. I haven't had a spider problem in my house and I hope they don't decide to suddenly show up!