3. Hover Flies, aka flower flies or syrphid flies
Adults look like small bees with striped abdomens; the grayish or greenish slug- like larvae have pointed heads. Flower flies are attracted to flowers to feed on nectar and pollen. The larvae feed on aphids in tight places where other good bugs can't go, and are especially helpful in early spring, before other beneficial insects are active. Flower flies also pollinate strawberries and raspberries, producing larger fruits and higher yields.
Adult: Whitney Cranshaw, Colorado State University, Bugwood.org
Larva: R.J. Reynolds Tobacco Company Slide Set, R.J. Reynolds Tobacco Company, Bugwood.org