While out in a floodplain forest in southern Michigan, I came across a lot of spotted ladysthumb (Polygonum persicaria, Polygonaceae). Introduced from Europe, this invasive plant is very common in this area. While photographing the foliage, I noticed several leaves that were curled up in a peculiar fashion:
Intrigued by these dome shapes, I turned over a few of the leaves in search of a cause. It turned out that members of a certain species of comb-footed spider (family Theridiidae) were using them as homes:
It seemed that they had used their webs to pull the sides of the leaves together to create their domiciles. I imagine that once insect prey were snared in their webs, they brought them back to these dark, quiet locations to feed in peace. The dark spots on the spotted ladysthumb leaves may have offered some additional shade.
I can’t tell what the spider in the first photo is eating, but the second spider seems to have a common midge (family Chironomidae) on its dinner table.