Insects as Food
Sure, they are high in protein, and people eat them all over Mexico, and nightly on 'Fear Factor' I see mealworms, earth worms, blood worms, madagascar hissing cockroaches, cave spiders and scorpions being consumed en-mass by greedy 20 somethings with more stomach lining than sense. (I know, I know - scorpions and spiders are not really insects... quit being so technical). Anyone consider these a real part of their diet, or are they more of a novelty ?
Insects as Pests
Some insects such as locusts have a history of being a pest.
Insects as garden helpers
"There are no bad bugs in my garden, just Predator Bug Food." The concept of using insects as pest management is part of Integrated Pest Management, or IPM.
Ants and Aphids
Ants and aphids have a symbiotic relationship and are often found together on plants. Ants protect aphid eggs during the winter and then take them to a food source when they are born. As aphids eat, they secrete "honeydew," a sugary substance which the ants then suck out of them.
When they become a pest problem, some management techniques include the use of diatomaceous earth and adding predators, like chickens.
ants and aphids on my apple tree at richsoil.com Aphids - Ants and Aphids at science.jrank.org forum on ants and aphids at permies.com