Hi all
In discussing resistance, whether of weeds to herbicides, mites to acaricides, or bees to varroa, it is well to bear in mind that there is no single mode of adaptation. Even within species there are many changes that may occur that render the species resistant; some of these changes are heritable. Almost all discussions on the topic list many changes that can take place:

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it is an oversimplification to attribute a particular genetic change to a specific mechanism (e.g., point mutation to target-site resistance or gene amplification to metabolic resistance), as resistance in insects has shown a remarkable diversity of mechanisms that are only now emerging. 

All living organisms are regularly exposed to potentially harmful compounds. They can survive exposure only if these compounds are detoxified rapidly or if specific adaptations confer tolerance or resistance. For arthropods, this challenge is compounded by the variety of habitats and food sources upon which they rely. 

Resistance to toxic substances can evolve by modifying the target site of a chemical, either by mutations altering the protein sequence or by mechanisms altering the expression of the target site.

Horizontal gene transfer (HGT), or lateral gene transfer, can be defined as the movement of genetic material across species boundaries and is widely accepted as a strong evolutionary adaptive force in prokaryotes. The acquisition of genes by horizontal gene transfer provide snew routes to handle toxins, for example, the β-cyanoalanine synthase enzyme that metabolizes cyanide.

Approaches that use forward and reverse genetics to link genotype to phenotype are fundamental to many biological disciplines. ... protocols for reverse genetics by RNAi exist for several mite species, including Varroa destructor ... dsRNA ingested by honey bees was transferred to Varroa mites and resulted in a 60% decrease in mite populations, offering an exciting prospect for alternative control tools ...

Van Leeuwen, T., & Dermauw, W. (2016). The molecular evolution of xenobiotic metabolism and resistance in chelicerate mites. Annual review of entomology, 61, 475-498.

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