Final answer:
The type of transmission described where a fly deposits microbes on food that is then consumed by a host is referred to as mechanical vector transmission.
Step-by-step explanation:
The scenario described involves the transmission of microbes from the surface of food to a host by an arthropod vector in this case, a fly. The type of transmission represented here is termed vector transmission, specifically mechanical transmission.
In this instance, the fly does not infect the host through a bite (as would be the case in biological transmission) but instead, it deposits the pathogen on the food, which is then consumed by the host. Mechanical transmission occurs when the arthropod carries the viral pathogen on the outside of its body and transmits it to a new host through physical contact with items such as food, which then becomes the medium for the pathogen to enter the host's system.