Sticks, and stones, and broken bones, that’s what my nest plug is made of…
The plug type that we are focusing on for this week’s “Plugs & Bugs” is Loose Debris. In all of our other P&B posts we have talked about plugs that are very sturdy in their construction – plugs fit for fortresses. This week’s plug seems less secure. Loose Debris is easily moved or re-moved. Still, it seems to work in many cases, at least as long as necessary for the young inside to mature.
What is Loose Debris? It’s little bits of organic and inorganic matter that the wasps or bees collect one piece at a time. It’s not just stick and stones, but seeds, withered anthers, mud clods, bark bits, and even the occasional broken piece of a dead insects.
We have two very different kinds of insects that make loose debris plugs – a wasp (Solierella) and a bee (Anthidium). Both these genera can have multiple generations per summer here in Colorado. It is very difficult to tell if a loos debris nest plug has emerged (or has a “hole” in it). If a lot of the material disappears, record it as having a hole in the plug.
Solierella sp. are small, slightly stocky, charcoal grey to black wasps. There are about a dozen species in Colorado and at least two different species that nest in our blocks. One of these species nests in the smaller diameter tunnels and provisions their nests with hatchling grasshoppers. Another species nests in the medium size tunnels and provisions with true bugs (order Hemiptera). They use loose debris not only for nest plugs, but also for walls that separate the reproductive cells.
Anthidium sp. are the wool-carder bees. These are the species that line their cells, and often plug their nests with white, cottony, plant fuzz. Thanks to our volunteers, we’ve learned that some Anthidium plug their nests with sticks and stones after they have completed their pillowy cells. (Other Anthidium plug with just plant fuzz.) These nests are built in the tunnels with the largest diameters. Sometimes the males spend the night in the bee blocks. Zzzzz Zzzzz. During the day, the territorial males can be seen “patrolling” flower patches.