A flaming torch would have been an excellent idea, but unfortunately, Jack didn't think of it, so he's left with standing back to back with Spike trying to pick off a swarm of giant, laughing wasps in the dark. This really isn't going to go well. On his own, he too probably would have made a run for it, but not with Spike there. Spike has always got his testosterone pumping anyway so he doesn't want to lose face, and now - now they finally seem to be getting along - he doesn't want to leave Spike to get hurt.
Two more shots (and one dead wasp) and he has to pause and look down to reload, but there's no time because the wasps are on them. He hefts his knife, feeling that perhaps a baseball bat might be more appropriate in this instance, and hears Spike curse behind him.
"You all right?" he asks sharply, swinging the knife as if it is indeed a bat and actually managing to slash a couple of wasps, who limp away, injured.