# Effect of Near Ultraviolet Radiation on Varroa Destructor Using Digital Holographic Interferometry
## 4 Results and Discussion  
In Figure 3a-d, the amplitude of four holograms reconstructed through digital processing is depicted. In Figure 3a, it is observed that the mite reflects less intensity than its surroundings, suggesting the significant absorption of UVA radiation by the mite. To improve measurement results, attempts were made to reduce the reflection from the surroundings by adding a dark background and optimizing the exposure time (10 ms). The results are shown in Figure 3a-c.  
Figure 4 displays the first nine phase difference maps extracted from a series of holograms. Each of the images represents the phase difference between two consecutive holograms whose registration differs by a time corresponding to one dose of UVA irradiation (1.6 min). In Figure 4b, it is possible to observe a subtle but meaningful deformation around the mite's genital shield (GS).  
Figure 5a depicts the displacement map with the highest amplitude (approximately 0.5 \(\upmu\)m). Areas enclosed by a red circle (referred to as anal shield (AS) and genital shield (GS) as designated in [18]) indicate regions of the Varroa specimen undergoing more pronounced swelling. Figure 5b displays the displacement maps extracted from the phase maps of Figure 4. These displacement maps show the progression of alterations in the mite over time. The difference in amplitude among the maps in Figure 5b suggests a deceleration of alterations after the third dose of irradiation.  
Figure 6 shows a graph of the average displacement value over time for each specimen. In this plot, it can be observed that all specimens exhibit the same behavior; however, the time at which they reach maximum displacement varies across experiments. This suggests that each specimen may absorb a different amount of UVA radiation.  
Figure 3: Amplitude reconstruction of four Varroa destructor specimens. Holograms were recorded with a UVA laser at \(\lambda=355\) nm.  
The curves in the graph of Figure 6 were generated using the equation  
\[\Delta u(t)=\frac{a}{1+be^{-kt}} \tag{2}\]  
Figure 4: Difference phase maps extracted from a series of holograms recorded with a UVA laser at \(\lambda=355\) nm. Each map of phase difference was extracted between two consecutive holograms. (**a**) Phase difference at 1.6 min. (**b**) Phase difference at 3.2 min. (**c**) Phase difference at 4.8 min. (**d**) Phase difference at 6.4 min. (**e**) Phase difference at 8.0 min. (**f**) Phase difference at 9.6 min. (**g**) Phase difference at 11.2 min. (**h**) Phase difference at 12.8 min. (**i**) Phase difference at 14.4 min.  
Figure 5: (**a**) Displacement map extracted from Figure 4b, (**b**) displacement maps extracted from Figure 4.  
where \(a,b,\) and \(k\) are constants selected in such a way that the curves best fit the experimental data. The values of these constants are shown in Table 1.  
The current study shows, through the use of DHI, the effects of UVA irradiation on Varroa mites. These effects were observed by measuring the changes in phase maps derived from a series of holograms. The experimental methodology presented in the study demonstrates a novel approach for measuring alterations in the Varroa mite. The measured changes occur on a small scale and are captured in real time. The research also highlights positive aspects in the fight against the Varroa mite by introducing new methods that reduce reliance on chemical products and minimize the risk of resistance development in mites. The changes on the surface of the mite specimens indicate that the applied irradiation has adverse effects that directly impact the mite's integrity. Building on the aforementioned, this research is expected to contribute to the lines of knowledge applied to bee conservation, as well as to topics related to the applications of digital holographic interferometric techniques.