The true flies include house flies, horse flies, fruit flies, and mosquitoes. You can tell they are the scientifically official flies because their common names have "flies" as a separate word (unlike dragonflies, stoneflies, butterflies, etc.). The back pair of wings have become halteres, which are small appendages with knobs that provide balance during flight. There are about 150,000 described species with potentially 240,000 in existence.
There are 550 species of scorpionflies and hangingflies. The scorpion stinger is actually the end of the male abdomen curved upward with an enlarged genital.
The 2,000 species of fleas are external parasites of mammals and birds that feed on blood. They no longer have wings, but they can jump impressive heights and distances.
Caddisflies are aquatic insects resembling moths. Their larvae make nets, tubes, and casings of sand, pebbles, leaves, twigs, and other debris glued together, which they use as housing. There are about 12,000 described species, with possibly 50,000 total.
Butterflies and moths are much loved for their very large, wide, often highly colorful wings. 160,000 species have been described so far.
Bees, wasps, sawflies, and ants weigh in at 130,000 species. Many species are highly social and form colonies.