Resin bees come home to roost

Each spring since 2013 I’ve been lucky enough to watch the roosting habits of male resin bees, Megachile ferox, near our home. These bees regularly congregated on one particular plant along the walking path in East Albury. But in spring 2017, the bees didn’t show up. Uh-oh! That seems pretty disappointing?

Instead, M. ferox bees roosted on a Dianella flax lily by our letterbox! We have had other native bees, and other insects, use this spot for overnight stays in the past. But we’d not had the spring series of visits by M. ferox here before.

Photo: The bees are each only about 10 mm long, so it's not hard to miss them! Plus they only congregate late in the day, and disappear again most mornings. 

You may recall my excitement at the first of these bees I saw in October 2013 (see here or jump straight to the video). Well, that’s pretty much what they do each night during their season! Even after watching them over these years, their antics (and simply their presence!) never fail to amaze me.

Here’s a video of some of their typical antics, from this spring:

Video: some of the resin bee antics. 

The bees usually begin to fly around the site an hour or so before sunset. Some land near, or on, their preferred stems. Yes, they not only have a preferred plant to roost on, they seem to favour certain stems over others! As other bees approach, they will grip the stem with their mouthparts (mandibles), put all six of their legs in the air, and wave them like crazy. Presumably it’s to signal ‘this is my spot, buzz off’. (The same response is triggered by camera lenses getting too close and human hands trying to point the bees out to others).

Once they are no longer defending their spot (and sometimes between contentions), they will often groom. They use their legs to clean their antennae and body; perhaps gleaning pollen grains acquired on flowers?  Or maybe it’s dirt. Anyway, this grooming seems a consistent part of their routine – maybe like us brushing our teeth before bed?

You also often see their abdominal segments move in and out. I understand this to be a sort of bee ‘cool down’, in readiness for rest. As the evening light fades and the temperature drops, the bees cease their actions, and become motionless on the stems, where they spend the night. Once this stage is achieved (and it varies with the weather and light), they generally don’t respond to anything, even if quite close to their bodies. Although they can’t close their eyes (no eyelids!), and there is some contention as to whether they sleep or not, they are certainly resting and less easily roused than during the day.

Photo: Roosting Megachile ferox males ... gripping the stem by their mouth parts all night!

In the morning, their evening routine is repeated in reverse: a bit of a warm-up, then grooming, maybe some movement, and finally, departure. It can be hours between the first signs of activity and all the bees leaving, to spend the day chasing females and foraging on flowers.

It looks somewhat amusing when one bee stretching or grooming seemingly kicks another bee, triggering yet another round of leg waving! If the weather is poor (wet or cool), they will conserve energy and stay put on their roost, sometimes all day.

The bees by the letterbox this spring included the most individuals (of this species) that I’ve seen on a single night – 17! The M. ferox bees I’ve watched in previous years have typically been only up to half a dozen or so bees, over a period of six to ten weeks. This year there were 42 nights with one or more M. ferox roosting (and six nights with none – including after they were rudely knocked off their stems by hail!).  Granted, it’s a far cry from the tens or hundreds that some species of native bees have been seen to aggregate in. Mind you, it wouldn’t be hard to be oblivious to their presence, either.

Here’s a snapshot of my observations each spring:

# Note that as 2013 was the first time I saw them, it’s likely they were present before my first sighting that season.

I’m just as excited about watching these bees as I was the very first time I saw them.  You can be sure I’ll be watching out again next spring. I hope they will return!