Mealworms.

I feed these to the wild birds.  They are alive and easy to keep. When they arrived this morning they were hungry and thirsty. You can see they're thirsty because they have attached themselves to the banana skin. They keep for weeks in a garage in an open container.  They cannot climb or escape from a smooth sided container.  Their favourite food is porridge oats or bran. They don't smell and are clean to handle.  The birds love them. 
See here https://www.blipfoto.com/entry/3107976638801907140
And here  https://www.blipfoto.com/entry/2854393021749790161
Blue tit here  https://www.blipfoto.com/entry/2849393878564342033