Diptera is also a large group with many forms. Mosquito larvae are familiar enough and are often illustrated in pictures so no description of them will be given here.
The house fly larva (maggot) is often pictured too, but you may not be able to separate it from close relatives such as face fly, root maggots, flesh flies and blow flies just by looking at the picture. They are all peg-shaped, white and without a developed head. Many of them occur in the same places.
They all can be called muscoid fly larvae to be on the safe side. Cattle grubs are grub-like and are identified as the grubs that occur in the swellings on the backs of cattle. The grubs can be squeezed out of the warble (swelling on the animal's back) in winter.
Rat-tail maggots are soft-bodied larvae with a long thin tail at the end of the body. They occur in farm lagoons or other shallow water high in organic matter. The adult is a drone fly that resembles a drone honey bee in appearance.
You will probably find many kinds of fly larvae that you can't identify without rearing them.