For sure! Usually the first sign of larvae for me is 'heaving' wheat bran. Kinda creepy.
And I have a pan of frass with trails running thru it.
I will be sure to look for those signs, as well. I have heaving-wheat-bran PTSD - the last time I saw it heaving, it was grain mites making the heaves. I obsessively look for those, too, but so far, so good.