In 2013, it took until May 15 for the pond in the woods out back to thaw enough to go netting for aquatic insects. One kind that is easy to find early in the season, is these caddisfly larvae. These three were in a single scoop of the net. The bottom of that pond must be absolutely crawling with them.
These were all photographed in a dish of water so that they would behave naturally. Only one of them showed much inclination to poke its head out, though.
The cases were made from aquatic grass debris, cemented together by silk on the inside. They probably aren’t much actual protection from a determined predator, but they are excellent camouflage.
From the ID key here, these all look like they are in the family Limnephilidae, the “Northern Caddisflies”. There are evidently at least 44 species of Limnephilidae in Michigan, and according to the Caddisfly page at Aquatic Insects of Michigan, “Many species still do not have their larval or pupal stages associated with adults, making species-level identifications of immatures difficult or simply not possible.”
Which means that the next thing we should try, is to catch some more of these this spring, get some really good photographs, and try our best to rear them to adulthood. Since these particular ones apparently eat decaying vegetation in stagnant ponds, they should be not too difficult to rear in a bowl in the house. Although, if they are the ones that come out as adults in November, we might need to do some sort of chilling to get them to emerge.
Anyway, I think that one of the reasons that Michigan has such a huge number of caddisfly species, is that their aquatic lifestyle helps them get through the winter. Since streams and ponds generally don’t freeze all the way to the bottom around here, they don’t have to have any particular adaptations to allow them to make it through to the spring. And they may actually be able to continue eating and growing all winter, not just surviving.