Larvae tunnels

Occasionally, we will come across one of these leaves, patterned by larvae tunnels. This one was seen at Strathcona Park Ravine yesterday morning.

"Black, continuous string within long, silvery tunnel right under epidermis of leaf:....Phyllocnistis populiella (Lepidoptera: Gracillariidae". From www.helsinki.fi/science. Not sure if this explanation fits my specimen - it sounded right : )

"The larva of an aspen leaf-miner moth, Phyllocnistis populiella, feeds between the two epidermal layers of a leaf. This larva his eaten his way over much of the leaf and has left a well defined trail which ends where he exits as a moth. Damage is caused when eggs that have been deposited between the leaf layers hatch and larvae begin to feed on the nutritive tissue between the dermal leaf layers creating a small pocket as they meander back and forth. The bugs attacking the aspens are tiny whitish moths as thin as pencil lead, so small that four of them could ride on the back of a mosquito. These moths overwinter on the forest floor, emerge after the snow melts, and lay eggs on aspen buds when they pop from stems. When the aspen leaves develop, so do the little yellow caterpillars that scar them. The caterpillars feed on leaves until they emerge as an adult moth in about three weeks. Typically, the damage does not affect the health of the tree."