I have been meaning to write this earlier but oh well, better late than never. Thanks for your help!
1. Location (on a map) of collection: Prospect Hill (park/trail/hilly area), Waltham, MA.
2. Date of collection: 7.5.17
3. Habitat of collection: In a forest, right off a hiking trail underneath dried leaves and next to a wall of rocks.
4. Length (from head to gaster): 5 – 6 mm.
5. Color, hue, pattern and texture: Entirely red from head to petiole. The gaster is black.
6. Distinguishing characteristics: It has 1 spikey petiole. The thorax has about 2 bumps, with 1 more prominent (closest to the head).
7. Distinguishing behavior: Aggressive and fast. Also it seems to either have parasitized a colony of black Formica sp ants or enslaved them (hence both are in the tubes tending to pupae).
8. Nest description: I uncovered these ants with pupae under a pile of dried leaves on the forest floor off a hiking trail. I didn’t see a nest entrance and I think they were just warming/moving their brood or it could have been a satellite. Could have been a raid but I didn’t see ants attacking each other on collection.