This is because Grasshopper ( the incentive)provide little motivation .
Based on the Reward Motivation Theory;Motivationis marjorly drive by external rewards or incentive.
An inncentive is any mateials in the environment that prompted an induvidual to perform an action withoit any physiological demand or drive.
Therefore Grasshopper, the incentive,provided low value of motivation for a drive to consume it ,because the rewards may not be favourable or maybe delayed.
Like transpiration in plants mammal's hypothalamus makes sweat glands functional and mammal's body secretes sweat which on evaporation decreases the body temperature