Intra-abdominal injection of amitraz (0.25 nmol per honeybee, i.e., approx 2.3 nmol/g) to emerging worker bees, in vivo, led to a significant hypertrehalosemia (300-400%) followed by a hyperglucosemia (approximately equal to 600%). Maxima were reached at 0.5 and 2 h, respectively. A strong negative correlation between glucosemia and trehalosemia appeared after injection of pure phentolamine (1 nmol per bee), suggesting stimulation of trehalase activities. Simultaneous administration of the alpha-blocker at greater than or equal to 0.25 nmol per individual suppressed the hyperglycemic response of amitraz. The formamidine pesticide thus likely acts on the honeybee alpha-aminergic system.