Hey! Nice one
Really like the detail - (those floating dust particles really add to the realism!) I feel that the background could have a touch more depth to it if it's total realism you are going for as it's a little too out of focus right now.
On the animation side of things it's wonderful! I like that little clean of the eyes as he gets to the middle of the leaf (nice opacity on that leaf btw) There is something about the motion of the legs just before he (or she... it is a ladybird after all (oh... we call 'em Ladybirds in the UK)) falls that doesn't look quite right.
I think the drop rate is spot on, but the leg motion is too quick. I'll try to explain why... It looks like the Ladybird(bug) is desperately clinging on for dear life, the quick leg motion has allowed us (the audience) to make a 'human' connection to the ladybird (or to anthropomorphise if you want to get clever

) which doesn't happen to things like ladybugs and has in some way detracted from the realism of the scene. Hmm hope that made sense and helped.
When I think or observe ladybugs or any beetles, I generally see them as very slow creatures (apart from when they suddenly remember that they can fly hehe) and I feel that it wouldn't really realise, or care, that it was about to fall as they all have that very hard exterior. Maybe it would make a half hearted attempt to continue along it's path...
Btw, I realise the irony of anthropomorphising the ladybug to explain my point hehe
Anyhoo - that's just me being too picky as usual just to keep you on your toes! It is a fantastic anim
*Global goes out to conduct gravitaional experiments on unsuspecting ladybugs*