Problem in the heart area

I have a 2 year old bumblebee. Last night i noticed the scales around his heart(especially the belly scales) were being pushed out quite a way,really quite prominent with the heart beat i have never noticed this with him before. I had just taken him out of his tank.Had him out for about 10 minutes, it didn't happen all the time, do you think it was just the excitement of coming out that got his heart pumping, or Is it be something more serious. Can they get muscle cramps like we can?

any advice, many thanks

scott