Varroa does have a heart
The heart of Varroa destructor has been discovered by Alexandros Papachristoforou and Evgenia Koutouvela in a project part-funded by Vita Bee Health.
The heart is tiny — measuring just 165 μm by 60 μm — and it beats with an average duration of just over 7.39 seconds at an average frequency of 0.13 Hz.
Surprisingly, until now there has been no mention in the literature as to whether varroa had a heart or not! Because of its size, physiological study of varroa has been difficult. (Ticks, which are slightly bigger, are easier to study.)
The heart was eventually found quite near to the brain and is quite like that of ticks. But unlike other mites, varroa has two ventricula (chambers) and six rather than four ostia (openings).
The discovery of the heart is expected to help in developing a new bioassay to measure the effect of varroa control treatments.
For the full paper, see: https://www.biotaxa.org/saa/article/view/saa.24.4.9