Plant Fuzz Plugs & Anthidium

White Plant Fuzz nest plugs made by Anthidium sp.

White Plant Fuzz nest plugs made by Anthidium sp.

What’s white, furry, sits in a bee block, and looks like a joke? An Anthidium nest plug made from Plant Fuzz! Seriously, it looks like someone stuffed a cotton ball into the nesting tunnel(s). Well, someone – or something – did, and she was a wool-carder bee.

These uncommon nest plugs tend to be found in groups, so if your block has one, it is likely to have many. These plugs tend to be in the larger diameter tunnels, since the bees that make these plugs are fairly good sized.


Anthidium oblongatum

Anthidium sp. visiting a flower. (Photo by D. Wilson)

The bees superficially resemble yellowjackets in that they are robust black bees with yellow marking and not terribly hairy. The bees are a rounder, shinier and nest in the blocks, which the yellowjackets don’t do (although next year’s queens may spend the winter in your block). Two of our more common species are introduced, but we do have native species that nest in our blocks.

Unlike most our other bees, the males of a given Anthidium species tend to be larger than their female counterparts, and are often reared from the innermost (first constructed) cells in a nest. The males can be territorial over a patch of their favorite flowers and may be seen, rather aggressively, chasing away anyone who dares enters “his” turf.  Fear not, he doesn’t have a stinger (though he does have formidable mandibles and can dispatch smaller insects, including honey bees).

Where do the females get the fuzz for their nests? Not from the end of a Q-tipTM, that’s for sure.  They are very adept at finding hairy plants (sagebrush, lamb’s ear…), scraping the hairs into a ball and carrying them back to their nests. They are, after all, in the family Megachilidae, with the rest of the Leaf-cutting bees. They could be called the leaf-scraper bees, but they are known as with wool carders, since they card the “wool” of plants. They not only make nest plugs from plant fuzz, but they line their cells with it as well. These larvae have it made, lying in a bed of fluff, eating pollen all day long!

A female Anthidium scrapes fuzz of plant leaves as wads it up into a ball in preparation for carrying back to her nest.

A female Anthidium scrapes fuzz of leaves and wads it up into a ball in preparation for carrying it back to her nest.

Balded leaves indicate Anthidium have been here.

Bee pattern baldness on leaves indicates Anthidium have been here.

This entry was posted in 2015, Nest Plugs, Plugs and Bugs. Bookmark the permalink.

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