In honour of World Bee Day, May 20, 2024

Last fall, a friend asked me how to distinguish male bees from female bees.  I thought this could be a good topic to help celebrate World Bee Day on May 20.

The answer is complicated and also depends on the type of bee. To make it as simple as possible, let’s look at a common  Squamish bee, the Yellow-faced bumblebee (Bombus vosnesenskii). It’s easily recognized: relatively big, mostly black, with a yellow face and shoulders and at least one yellow stripe on the tip of its back.

Season: The first individuals emerge from winter hibernation in mid to late March. They’re the queens, very large females (up to 2.5 cm) who will spend the spring and summer laying eggs. The first eggs, fertilized by semen the queen has carried in her body since mating the previous fall, hatch as workers. The workers are smaller females who will spend the summer gathering pollen to provision for new broods as well as nectar to feed the queen in the nest. Later in the season, unfertilized eggs will become drones (males) and at least some fertilized eggs will become the new generation of queens. In fall you might see males as well as both types of females.

Size: The largest bees usually are queens, but we’ve seen some very large males recently. The worker females are always smaller than the queens but like males they can vary in size. This variation is often attributed to the amount of food available for the larvae.

Hind legs: Worker females carry pollen in sacs in their hind legs: this is a sure-fire distinguishing feature. The “sac” is formed by a concave tibia with hairs on both sides to form a basket of sorts. Male bumblebees have different-shaped hind tibia – convex and narrower – and they do not collect and carry pollen for the young. The male leg shape is hard to recognize in the field.

Sleeping site: In spring we often see queens sleeping more or less in the open if they haven’t found a nest site yet.  The worker females return to the nest to sleep, but the males usually leave as soon as they become adult as they don’t take part in feeding the colony. You might see males sleeping under flowers when it’s rainy or snoozing on leaves when it’s dry.

Colouration: Colour patterns vary between bumblebee species and are not necessarily different between males and females. Our males have either the same colour pattern as the females OR they have an extra yellow stripe (interrupted in the middle) on the tip of their backs. Females never have that second stripe.

To sum up:

• The really large bumblebees we see in spring are females (queens).
• All bumblebees that carry lumps of pollen on their hind legs are female. (But not all females carry lumps of pollen …)
• All Yellow-faced bumblebees that have two yellow stripes on the tip of their backs are male. (But not all males have two yellow stripes …)

These photos highlight some of the factors to consider.

Information and photos shared by an interested amateur ….

Banner photo: On March 19, this early queen was moving around on the ground in a garden as if searching for a nest site.