Ladybugs are amazing insects and wonderful aphid predators. However, there are a ton of reasons why you should never buy them and why they shouldn't even be legal to sell. 

I was fortunate to get an expert who has been studying ladybugs and their ecology for decades.

Dr. J.P. Michaud is an insect ecologist specializing in biological control and other aspects of crop protection entomology.  He has a background in evolutionary ecology and many of his research endeavors are guided by the implications of evolutionary theory.  His interests include cultural and conservation approaches to biological control of aphids in field crops, ecology of the Coccinellidae, and the interface between host plant resistance and biological control. Dr. Michaud completed his B.Sc. at McGill University and his masters and Ph.D. at Simon Fraser University.  After seven years at the University of Florida studying biological control of disease vectors in citrus, he moved to Kansas State University where he has been developing integrated management strategies for pests of field crops and approaches to conserving their natural enemies since 2003.

https://www.kisorganics.com/pages/cannabis-cultivation-and-science-podcast-episode-62