Cactus Flower Pollination and Pollinator Week Events

Did you know that this week is Pollinator Week?

If you live in Arizona, you might want to check out the National Pollinator Week celebration at Tohono Chul in Tucson. It is going to be from 10 a.m. to 4 p.m. on Saturday June 22, 2013. The first 50 families attending the event will get to make their own native bee habitat to take home. There will be special showings of Wings of Life, a new film from Disneynature narrated by Academy Award winner Meryl Streep, and a talk by bee specialist Dr. Stephen Buchmann of Pollinator Partnership. Sounds like a great way to spend the day!

If you don’t live in Arizona, you can find your state on the clickable map at to locate events near you.

When talking about pollinators, we often hear that they are responsible for the viable production of about one third of our food supply. Although we think of grocery store staples like apples, squash and almonds as foodstuffs that require pollination, cactus fruit – or “tunas” as they are also called – are another source of food that requires pollinators.


It is almost impossible to look into a cactus flower and not find a bee. Most of them are covered with copious amounts of pollen.


The flowers of the cactus genus Opuntia even have a special mechanism that causes the stamens to move when they are touched. You can see it in action in this video.

The movement of the stamens is thought to add more pollen to any pollinators that enter the flower.


A layperson might say it’s almost like the bee is getting a “hug” from the flower.


The end result is that the flowers are pollinated and produce lovely red fruit that make delicious jelly and syrup.

Even if they aren’t consumed by humans, some 75% of flowering plants need an animal to carry pollen from flower to flower. Pollination is an incredibly important service that we need to be aware of and support.

What are you doing to celebrate pollinator week?
Wings of Life is also available on DVD/Bluray.

(Affiliate link to Amazon)

More About Leafcutter Bees

Because Rebecca had a question about the leafcutter bees in my last post, I thought I would expand a bit on their biology.

Leafcutter bees (genus Megachile) are solitary bees that are important pollinators. As with most solitary bees, each female constructs its own nest.

The leafcutter bees prefer to nest in pre-formed holes about the size of a pencil (roughly) in diameter. They often nest in wood or hollow stems, although they will also use sites like holes between bricks or even screw holes in patio furniture.

The female bees cut circular patches out of leaves with their mandibles.

They then carry the pieces back to the nest hole they chose and use the leaves to line the cavity and construct chambers to lay their eggs in.

Below is a completed nest that I found between two cement blocks:

Inside this bundle will be several chambers separated by neat walls of leaf. Within each chamber will be a ball of bee bread, a mixture of nectar and pollen (see sweat bee post for what this looks like). On the ball will be a single white egg, which will hatch into a larva and consume the bee bread. It will pupate within the chamber and later emerge as an adult.

Leafcutter bees harvest leaves from relatively few species of plants. In addition to the pomegranate, they will also use the bracts of bougainvillea, creating a lovely bright pink or red nest. The plants they seem to prefer most are roses, which gets them into trouble with rosarians.

As with many solitary bees, leafcutters are important pollinators. The females carry the pollen in the bristly hairs on the underside of their abdomen, which are called scopae.

It is the white area on the underside of the abdomen in this photograph.

Leafcutter bees are managed commercially for pollination of alfalfa for seed production. The idea is that honey bees avoid the elaborate tripping mechanism of the alfalfa flower, but the leafcutter will readily use and pollinate the flowers. The alfalfa leafcutter bee is an introduced species.

The farm were I worked once brought in leafcutters to pollinate an alfalfa crop. Although they are solitary, these leafcutters will nest in aggregations. The farmer brought in a smallish trailer piled high with leafcutter nests, each with an active female. During the day there was a cloud of bees flying to and from the trailer. It was actually very cool, and I wish I had taken a few pictures.

Have you ever seen leafcutters in action?

Places to find out more about solitary bees:

Distracted by Leafcutter Bees

With all the flowers in bloom, it is hard not to be distracted by bees.

Take this leafcutter bee.

How can you ignore a bee that can cut a leaf like this?

Within seconds the leaf is processed.

The last cut…

and off it goes.

In case you were wondering, the plant is a dwarf pomegranate.

I was actually looking for bees performing a different behavior, but I haven’t managed to get that on film yet.

Maybe later in the week.

Edit:  More information about leafcutter bees.