Warming temperatures and rain during the second week of January contributed to significant snow melt. Winter tracking can be a challenge when only intermittent patches of snow remain in the woods. There was just enough at Quabbin Gate 40 on 1/11 and at Barre Falls Dam on 1/14 to present tracking students with identification challenges.
Remember: don't just look at the tracks themselves, but also study the patterns and learn about the different types of animal movements--trotting, walking, loping, bounding, etc.
The Common Porcupine (Erethizon dorsatum) was nowhere in sight, but clearly it had been feeding on the bark of a nearby tree. The freshly-gnawed bark wasn't an unusual sight, but the exposed, sappy area was covered with raisin-like specks that deserved a closer look. The specks turned out to be flies known as Sapromyza brachysoma. Although the "sapro" part of the fly's name sounds like it refers to the sap the flies were apparently enjoying, "sapro" actually refers to decay or rot, which gives you an idea of other means of sustenance for these insects. "Myza" refers to feeding by suction.
Thank you to Tom Murray, a local insect expert, for ID help. Both Charley Eisenmen (https://bugtracks.wordpress.com/) and Tom note that these flies can be seen at relatively cool times of the year. Below is Tom's far better photograph of S. brachysoma, which he posted on bugguide http://bugguide.net/node/view/475548/bgimage