Orange slice is a good idea, or a small piece of banana. The banana will attract other flying insects in your house as well which your pygmy will like.
If you can establish some microfauna in your vivarium that will reproduce beneath the leaf litter, then the chameleon will have a consistent supply of food when some venture out beyond the cover of the leaves.
A really good one to use are tropical woodlice Trichorhina tomentosa, they are very high in calcium as well.
I'd suggest starting a culture in a margarine tub, and a colony within the viv.