Bumblebees

by Carl Strang

Bumblebees are fascinating insects, and I have much to learn about them. So far I slowly am getting a handle on some of the local species. It happens that they are generally easy to distinguish through their different arrangements of yellow and black fur. I call it fur; it certainly holds in heat generated by their flight muscles, allowing them to range through temperate climates into the Arctic. I remember seeing bumblebees on my study area in western Alaska. In our area the most common species may be Bombus impatiens. Here is a queen of that species.

Bombus impatiens queen 2b

Bombus impatiens is marked by the thorax being almost entirely yellow, especially on the sides, and by the black abdomen with only the first segment yellow. The queens are all you see early in the season. Only they survived the winter. By June their much smaller daughters are visiting flowers. I suspect this may be why Solomon’s seal (mentioned yesterday) waits to bloom until now. The tiny faces of bumblebee workers just fit in the suspended flowers of that species. I doubt that a queen could manage it.

Ecological studies of bumblebees emphasize tongue length, with different species subdividing the range of flower sizes accordingly. B. impatiens, being a generalist, has an intermediate tongue length. As I get a handle on the species I will want to learn about this difference and see which bumblebees visit which local flowers. Here is Bombus vagans, which I photographed visiting wingstem at Fullersburg a couple years ago.

Bombus vagans 1b

Note that it has two yellow abdominal segments. It also is larger than impatiens. The next shot illustrates the significance of tongue length.

Bombus vagans 2b

A third species is Bombus fervidus. This one I haven’t caught in action. The photo is of a dead one I found on the trail at Tri-County State Park.

Bombus fervidus 3b

Note the large black area on the thorax and the mostly yellow abdomen. I have seen it at Mayslake, as well. In recent days the picture has become a little clouded as I have found another species at Mayslake that is very close to impatiens, and so needs close study to distinguish it.

Bombus bimaculatus 2b

Bombus bimaculatus has the first abdominal segment yellow plus the central part of the second segment. The feet are yellow, as is a tuft of hairs on the top of the head, barely visible in the next photo.

Bombus bimaculatus 3b

Those last minute features help distinguish it from another species, B. griseocollis, which I have yet to find.

Here is a website with a key to bumblebees of Wisconsin, which I have found helpful in making identifications.

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