HCA: Hermit Crab Association

I have had two surprising bug findings in my crab tank.
One happened many months ago when the weather was warmer and I was battling humidity levels. I found a small draginfly in the tank. I had the glass lid open a crack so I think it just flew in that way and was trapped.
But the second has me thrown through a loop as to how, why and what. A few weeks ago(yes I'm late in asking but it's been on my mind) I found a black caterpillar looking thing with a red head. About one inch long. I've had my humidity stable for a good while now so the lid has been shut except for maintenance for near two months. Maybe more. What is it and how did it get in there? Did it somehow come in with their food? I order most of it dried from online stores, with weekly fresh food as treats.
Any ideas? Nothing resembling this is on the crab bug list.

Your caterpillar sounds like a Galium Sphinx. I am unsure how it may have made it into your tank, but it's not likely to be in their food. Try checking your tank for openings, especially along the seams of glass and corners.

Thank you for the reply.

I googled it. Looks similar but the one I found didn't have spots. I'm clueless.

I think its fine, the tanks less then a year old, but I'll do a double check on the tank seams.