WHO tube bioassays are used to verify the susceptibility of adult mosquitoes to a standard dose of a given insecticide.
The WHO tube bioassay is a direct response to exposure test that is used to monitor resistance in mosquito populations exposed to a discriminating (or diagnostic) dose of insecticide.
Mosquitoes introduced to the WHO tube are exposed to an insecticide-impregnated test paper, supplied by the WHO, for a set amount of time. Mosquito mortality is measured immediately post-exposure and 24 hours post-exposure. The results can be used to determine if the mosquitoes are resistant or susceptible to the known insecticide at the discriminating dose. This same WHO tube bioassay procedure can be used to expose mosquitoes to a variety of concentrations of insecticides to answer different experimental questions.
Further details about this assay can be provided on request and the WHO guidelines can be found here.