Stephanie Mason did some digging, as it were, and turned up this identification for the mystery animal that made the burrows armored with pine needles and beech scales: one of the wolf spiders. Participant Sheryl has posted an image of one of the hidey-holes. Stephanie writes:
After some investigating, I believe the amazing burrows we admired and photographed were constructed by scrub burrowing wolf spiders (Geolycosa sp.). There are 18 species found in the US, with the greatest diversity in the scrub areas of Florida. I don’t know what species is/are found in the mid-Atlantic, but here’s an excerpt from an article on these neat arachnids.
The six species of scrub burrowing wolf spider that occur in scrub habitat are never found all together on a single ridge…. Instead, each of the several high ridge systems in Florida is home to only two species. And although both species of scrub burrowing wolf spiders live in scrub, they occupy different microhabitats. One of the species lives in open, bare patches of sand with no overhanging shrubs, while the other species lives in areas covered with leaf litter, closer to shrubs and trees. You rarely find bare-sand-loving burrowing wolf spiders and leaf-litter-loving burrowing wolf spiders in the same place! Both species are extremely sensitive to an obvious difference in microhabitat: the presence or absence of leaf litter on the sand.
The well-camouflaged, bare-sand-loving burrowing wolf spider mixes sand with silk to reinforce its burrow entrance. If conditions have been windy, the silk and sand will sometimes form a slight raised edge, giving the burrow an ant hill appearance. Bare-sand-loving burrowing wolf spiders are picky about their space! If leaf litter suddenly covers an area where a bare-sand-loving spider lives, the spider will abandon its burrow!
The leaf-litter-loving burrowing wolf spider, which tends to be darker in color than the bare-sand-loving burrowing wolf spider, uses its silk to weave a turret (raised collar) of leaves and pine needles around the mouth of its burrow. The turret helps camouflage the burrow entrance and also helps to reinforce it. Leaf-litter-loving burrowing wolf spiders can be found in open lawns as well as in scrub.
Burrows of both scrub burrowing wolf spiders are usually found near their own kind in an aggregation, or cluster. The bare-sand-loving wolf spiders are very particular and have a tough time finding suitable sites. So when a site is good, lots of spiders will live there. Also, breeding is easier for both species if they don’t have to travel far to find a mate!