Although the defecation behavior (ejection of waste products of animals) is indispensable for survival, it has not been paid attention. However, a small number of studies suggest that defecation behavior affect fitness in several aspects. One representative example is the behavior that flies excrements far away.

We studied the flying direction of kicked frass in the grasshopper (Atractomorpha lata), which is known to kick its frass to the distance more than 10 times of its body length. To test whether the direction of kicked frass and the direction of the body of the grasshopper change in response to the light condition of the surrounding of the grasshopper, we observed the grasshoppers in the experimental apparatus which has a dark part and bright part in the side wall.

Both the direction of kicked frass and the direction of the body of the grasshopper were not uniformly distributed but clustered around the direction opposite to the direction of the dark part.

This result can be the consequence of two possibilities. One is that the grasshopper selects the direction of kicking its frass based on the visual condition. The other is that the direction of grasshopper is determined by the factor other than the frass kicking behavior, and the direction of frass kicking behavior is clustered as the by-product of other factor.