Hoverflies possess several antipredator adaptations that minimize predation risk during foraging. Some species of Syrphinae shows ‘hesitation behaviour’ after approaching flower. They moves backwards and forwards in front of a flower before landing. This behavior have been said as antipredator adaptations of hoverflies to avoid ambush by crab spiders. Such hesitation behavior may enable to elicit a crab spider on the flower to attack, resulting in the decrease of the predation risk. However, there may be few number of hoverflies that show the hesitation behavior in the habitat without crab spider. Field experiments were conducted to investigate whether the number of hesitation behavior of Sphaerophoria indiana changes after they were artificially attacked as if predators landed on flower. The number of hesitation behavior was counted in the grassland where Erigeron annus was dominant with a lot of flower, that was visited by hoverflies. The number of hesitation behavior of S. indiana was almost zero in habitat. During foraging on the flower, we picked strongly, but not killing, an abdomen of each individual up with tweezers once and counted the number of hesitation at following visit of the flower. Although the number of hesitation behavior did not change after they were attacked, the number of hoverflies that reject to the next flower increased. Hoverflies in the habitat where crab spider is absent did not show hesitation behavior, but they reject flower after they experienced artificially attack. Hoverflies could know the presence of ambush predator by attacker once, but they do not change the number of hesitation behavior immediately. Hesitation behavior of hoverflies could be used to evaluate information on the flower such as flower resources.