Humidity and Tactile Responses of Sitophilus zeamais (Coleoptera: Curculionidae)

In laboratory choice tests, maize weevils, Sitophilus zeamais Motschulsky, initially preferred lower humidities when given a choice of two humidities. The absolute difference in humidities and position on the RH scale had little influence on the response. After 24 h, weevils generally were hygropositive, which suggests that starvation or desiccation or both moderated humidity preference. The same temporal response pattern was observed when weevils were given a choice of five humidities ranging from 0 to 100%. Weevils showed a pronounced preference for contact with tactile stimuli (glass beads) and apparently preferred contact with smaller beads (4 mm diameter) over larger beads (6 mm diameter). Superimposing humidity and tactile stimulus choices revealed that tactile preferences took-precedence over humidity preferences. The nature of the humidity response suggests that poor feedback exists between humidity perception and atmospheric water needs.