Ladybeetles can be invited into a garden by providing plants that adults use as nectar/pollen sources, sustaining levels of aphids or other prey, and using insecticides with care.
The larvae of ladybeetles that feed on aphids found in dense colonies of curled leaves, and those that feed on mealybugs,often are covered with waxy strands and appear similar to mealybugs.
Ladybeetles require food for themselves and their young and an important way to encourage ladybeetles is to have a source of aphids or other preferred prey for them to feed on.
Ladybeetles are readily available commercially in North America and I'm sure throughout the world as well.
LadyBeetles are commercially available BUT the species commonly sold (Hippodamia convergens) is not the preferred ladybeetle for effective bio-control of pests.
The one sold is the convergentladybeetle that is captured while overwintering in migratory hordes, many in California.