Temporary stay at various environmental humidities affects attachment ability of Colorado potato beetles Leptinotarsa decemlineata (Coleoptera, Chrysomelidae)

Abstract

In a natural environment, insects live in different microhabitats varying in their humidity. Because insect adhesive mechanism at least partly relies on the capillary force, it is natural to assume that environmental humidity may considerably influence insect attachment. However, this aspect has been neglected in the literature so far. We present the first experimental study demonstrating the influence of the exposure to moist surfaces on the attachment of Colorado potato beetles Leptinotarsa decemlineata. Male beetles were kept at either a dry or moist condition with varying duration of stay for a period up to 160 min. Using centrifugal force tester, their friction forces were then measured on a plexiglas surface. The results show significant differences in force depending on the kind of pre-conditioning. A temporary stay in dry environment had no significant impact on the generated friction forces within the tested time scale. After walking on moist filter paper, forces increased significantly up to 171% of the initial forces measured after 1 min of preconditioning. These results show that insects of the same species may be strongly influenced in their attachment by environmental conditions. The second important conclusion is that results of different experimental studies on insect attachment can hardly be compared if they were performed under different environmental conditions.

The influence of humidity on the attachment ability of the spiderPhilodromus dispar(Araneae, Philodromidae)

“…This argument was recently used as an explanation for humidity-enhanced adhesion of gecko setae [19]. In insects it has been reported that resting in a humid environment positively influences attachment forces [29]. This could be owing to the hydration of setae.…”

Adhesion and running speed of a tropical arboreal ant (Cephalotes atratus) on wet substrates

“…The results of this study clearly indicate that ants, and probably other insects with smooth tarsal pads, are unable to do this, as there are only fine wrinkles on the tarsal pads (see [49] and [50] for images of cockroach and stick insect smooth pads, respectively). Physical limitations of the smooth pad are probably heightened on flooded surfaces, similar to the fibrillar pads of beetles and spiders [51][52][53], where adhesion-enhancing capillary effects are eliminated due to thick water layers that build up in high humidity, or when ant tarsi encounter standing water from rain. Resolving the physical mechanisms for these patterns was beyond the scope of this study but is a potentially fruitful direction for further research.…”

Influence of ambient humidity on the attachment ability of ladybird beetles (Coccinella septempunctata)

“…Voigt et al [48] observed significantly higher forces generated by beetles ( Leptinotarsa decemlineata ) on a dry surface, which were kept prior the experiment under humid conditions if compared to beetles kept prior the experiment under dry conditions. In the present study we observed a distinct difference between both types of experiments (Experiment 1 and 2).…”