A few weeks ago I first noticed a large black and yellow bug spending time at my “Victoria Blue” Salvia flowers. It would fly from the plant at one end of my garden bed to the plant at other end before flying over the fence to the neighbour’s yard. A few minutes later it would fly back over the fence into my yard, visit both plants, and then disappear again. It was so quick I wasn’t able to photograph it, but it had a habit of hovering in place, so I thought it was a large hover fly of some sort.
Then, last weekend, I noticed several of these large bugs, all following the same route over the neighbour’s fence into mine. For some reason I have thistles blooming in my backyard, and they were visiting both the thistles and the Salvia. It was an overcast day, so they weren’t moving as fast as they usually do. I grabbed my camera and went out to photograph them. To my surprise they weren’t hover flies, they were bees – European Wool Carder Bees – a new species for the yard!
As its name suggests, this member of family Megachilidae is not native to North America. It arrived on the east coast in 1963 and has slowly spread across the continent, reaching the west coast only about a decade ago. The term “wool carder” comes from the female’s habit of scraping plant hairs off of fuzzy plants such as Lamb’s Ear or other members of the mint family, which she gathers in a ball and carries back to her nest. Unlike honey bees and some wasps, the European Wool Carder bee is solitary, meaning it does not live in a hive or colony with others of its species. European Wool Carder Bees nest in existing cavities found in old wood, including trees, masonry, soil, wood piles, or even plant stems, and use the plant hairs to line the cavity. Each cavity usually contains several cells where the female deposits her eggs together with pollen and nectar collected exclusively from plants in the mint family; once she has finished laying the eggs she seals the entrance with a plug made of pieces of organic and inorganic material. The new generation emerges either later that summer, or overwinters in the pupal stage until the following spring.
Up close, these bees are really fuzzy which gives them quite a cute appearance. They have yellow legs and yellow faces, and the females have yellow markings at the edge of the thorax. They differ from hover flies in the shape of the eyes as well as the lack of a scutellum between the thorax and abdomen.
Females are smaller than males and have a stinger. They can be identified by the longer yellow abdominal stripes.
The male has smaller yellow markings on the abdomen and therefore appears darker. It also has five spikes or projections at the tip of its abdomen used for battling other insects. European Wool Carder Bees are quite territorial, and aggressively defend their favourite flower patch from other insects. They are particularly known for battling against honey bees, sometimes even killing them, which has caused concern amongst those worried about the decline in the honey bee population. However, there is no evidence to suggest that the aggressive European Wool Carder Bee is a direct threat to the honey bee’s survival whether in Europe, where both species are native, or elsewhere in the world where they are both considered foreign invaders.
I watched the males for almost an hour over the course of the weekend and found their behaviour fascinating. Often they would nectar on the flowers briefly before landing on a sunny leaf to watch for intruders. There weren’t that many; the bumble bees seem to prefer the colourful Million Bells I have planted in containers, and I only saw the Wool Carder Bees chase a bumble bee off once, and a shiny green Blow Fly off once. It’s sometimes easy to forget that insects aren’t just pretty creatures mindlessly visiting flowers, but are just as territorial as any member of the animal kingdom, and behave accordingly.
The males were also quite interested in the females that came to visit – at once point I saw three females and two males at the Salvia, and on three separate occasions I saw the male land on top of a female while she was visiting the flowers, hold her down, and attempt to mate with her!
The females were otherwise occupied by their constant search for nectar and pollen. I didn’t see any carrying any plant fibres, suggesting they have already built their nests and are now busy collecting enough food to provision their young. It will be exciting to see the new generation of European Wool Carder Bees in the spring; I will be sure to plant more “Victoria Blue” Salvia for them!