Before observation, adult V. destructor and T. mercedesae mites were submerged in 30% peroxide for 5 days to make the cuticle transparent. Nymphal mites were only rinsed with 70% ethanol to remove biostains that may be attached to their exterior, because their cuticles were sufficiently transparent without treatment. Then, pictures were taken with a Leica M205 FCA fluorescent stereomicroscope equipped with a Leica DFC7000T digital color camera (Leica Microsystems, Germany). The fluorescent signal of Nile red was acquired through an RFP filter set (541–551 nm excitation, LP 590 nm emission), and the Uranine signal was acquired through a GFP filter set (450–490 nm excitation, LP 500 nm emission).
Additionally, the distribution of fat bodies in the abdomen of developing worker pupae and adults were investigated. In vitro reared honey bee larvae were fluorescently stained as described above. Subsets of resulting biostained pupae were sampled every other day from the start of pupation until adult emergence. The abdominal sternite was cut out and briefly washed with PBS. Then, the inner surface of the abdominal sternite was photographed using a Leica M205 FCA fluorescent stereomicroscope equipped with a Leica DFC7000T digital color camera. Photos were captured and processed using LASX software (v2.02.15022).
Additionally, the distribution of fat bodies in the abdomen of developing worker pupae and adults were investigated. In vitro reared honey bee larvae were fluorescently stained as described above. Subsets of resulting biostained pupae were sampled every other day from the start of pupation until adult emergence. The abdominal sternite was cut out and briefly washed with PBS. Then, the inner surface of the abdominal sternite was photographed using a Leica M205 FCA fluorescent stereomicroscope equipped with a Leica DFC7000T digital color camera. Photos were captured and processed using LASX software (v2.02.15022).