Which insects, besides ladybugs eat aphids, and how do they look?
There are several insects that eat aphids.
Parasitic Wasps that look like a tiny fly, lay their eggs inside an aphid and the baby eats if from the inside out.
Praying Mantis will kill aphids and various other bugs
Lacewing larva kill aphis. See Picture
There is an insects called the assassin bug but it is not recommended in the garden because it bites.