Ultrastructural changes of rectal pads induced by low humidity in indoor psocid, Lepinotus patruelis Pearman (Psocoptera: Trogidae)

Abstract

Reduced atmospheric humidity caused variable progressive deterioration of the fine structure of the pad cell organelles in L. patruelis. The effects started by mitochondrial swelling and vacuolation at 60% RH. ended with disappearance of mitochondrial cristae and endoplasmic reticulum at 30% RH. Low humidity caused a decrease in relative volume of both mitochondrial cristae and endoplasmic reticulum. As a result, the surface to volume ratio increased indicating a massive destruction of rectal pad function as a mean of water resorption. The results suggest that keeping atmospheric relative humidity lower than 70%, in kitchens and other grain stores can control the insect by making an unsuitable dry condition beyond the ability of the insect to re-absorb water from rectal contents.