A common experience with home worm farms is lifting the lid to discover a writhing mass of maggots, usually white in colour with a segmented body. Whilst your initial reaction may be one of horror and disgust it is nowhere near as bad as it looks!!
These larvae (see picture) are the progeny of a benign insect called the soldier fly. The scientific name for these interesting insects is Hermetia illucens and they are a common inhabitant of compost heaps, manure piles as well as worm farms. They perform much the same role as tiger and red worms in that they eat dead organic materials and recycle the nutrients from them. They are not generally harmful to humans but their presence in a worm farm is not ideal as the conditions that suit them are not optimal for your worms. They tend to exude acidic substances that are detrimental to earthworms and they prefer very moist conditions.
It is my experience that soldier fly maggots appear when the contents of your worm farm become too wet (often when too many moist kitchen scraps are added in one go) or too acidic (or both). To tip the balance back in favour of your earthworms, mix in a coarse fibrous material such as shredded newspaper or lucerne hay with moist materials. Also, a sprinkle of Tumbleweed Worm Farm and Compost Conditioner to neutralise any build up of organic acids. Cheers Angus Stewart