Quality Control
Samples from all boxes of each shipment of pupae are processed through the Mediterranean Fruit Fly Exclusion Program Quality Control (QC) Section. Employees in QC test each shipment of pupae for flight ability and emergence. Mating propensity tests are conducted weekly for each laboratory of origin.
For the flight ability test, the inside of five black tubes are dusted with talcum powder. A black plastic cover is then taped over one of the ends and a small piece of folded cardboard is dropped into each tube. 100 pupae are placed in the tubes, which are then placed into a clear plexiglass cage. This plexiglass cage is taken to an environmentally controlled room where the temperature is maintained at 78 degrees Fahrenheit, 70 percent humidity and a day/night cycle of 14/10 hours. The emerging flies are vacuumed from the cages every morning and evening. On the morning of the fourth day, the contents of the five tubes are counted for unemerged pupae, partially emerged pupae, deformed flies and normal-appearing flies that were unable to fly out of the tubes. From the original sample of 500 pupae form each shipment, the staff is able to determine percentages of emergence and flight ability.
A grid emergence test is conducted to provide an early indicator of any problems with emergence. This test involves setting up two grids of 100 compartments with one pupae per grid and plexiglass is used to close off the cells. A wire screen provides air circulation on the opposite side of the grid. The grids are counted for emergence twice a day.
The QC staff also conducts mating propensity tests on pupae shipments from each of the three labs once a week. On the second day of incubation, six separate containers of 30 males and 30 females are prepared and provided with water and a diet mixture of sugar and yeast for seven days. After holding for seven days, five cages are prepared and 25 males are released into each container. Twenty five (25) females are then added to the cages of males and the light level is raised to 1500 lux. Every ten minutes for the next hour, mating couples are counted and removed with an aspirator. The rapidity with which mating initiates is a factor in determining the mating index. After one hour, the remaining flies are counted by sex and the lesser number is factored in as a failure rate.
On occasion, a stress test is performed to determine the nutrient reserves of the Medflies. Shortly after emergence, 100 flies - 50 males and 50 females - are placed into a cage without food or water. After 48 hours the dead flies are counted. A survival rate of 50 percent is considered acceptable.
