A friend (who's reasonably bug-savvy in the first place) has some bugs
in the basement of a house he's caretaking.

They look somewhat like crickets, although the shells aren't as thick
and defined. They also don't have any sort of wings. They have very
long thin whip-like antennae. They congregate in large groups in cool
dark places. They also seem to like to jump. The boddies are mottled
brown (different shades of brown). They don't chirp or make any other
'noise'.

They're found in central NJ on a family farm.

Any clues what they might be?