Aerial dispersal using silk ('ballooning') has evolved in spiders (Araneae), spider mites (Acari) and in the larvae of moths (Lepidoptera). Since the 17th century, over 500 observations of ballooning behaviours have been published, yet there is an absence of any evolutionary synthesis of these data. In this paper the literature is reviewed, extensively documenting the known world fauna that balloon and the principal behaviours involved. This knowledge is then incorporated into the current evolutionary phylogenies to examine how ballooning might have arisen. Whilst it is possible that ballooning co-evolved with silk and emerged as early as the Devonian (410-355 mya), it is arguably more likely that ballooning evolved in parallel with deciduous trees, herbaceous annuals and grasses in the Cretaceous (135-65 mya). During this period, temporal (e.g. bud burst, chlorophyll thresholds) and spatial (e.g. herbivory, trampling) heterogeneities in habitat structuring predominated and intensified into the Cenozoic (65 mya to the present). It is hypothesized that from the ancestral launch mechanism known as 'suspended ballooning', widely used by individuals in plant canopies, 'tip-toe' and 'rearing' take-off behaviours were strongly selected for as habitats changed. It is contended that ballooning behaviour in all three orders can be described as a mixed Evolutionary Stable Strategy. This comprises individual bet-hedging due to habitat unpredictability, giving an underlying randomness to individual ballooning, with adjustments to the individual ballooning probability being conferred by more predictable habitat changes or colonization strategies. Finally, current methods used to study ballooning, including modelling and genetic research, are illustrated and an indication of future prospects given.

Salinity (NaCl) stress impairs plant growth and inflicts severe crop losses. In roots, increasing extracellular NaCl causes Ca2+ influx to elevate cytosolic free Ca2+ ([Ca2+]cyt) as a second messenger for adaptive signaling. Amplification of the signal involves plasma membrane reduced nicotinamide adenine dinucleotide phosphate oxidase activation, with the resultant reactive oxygen species triggering Ca2+ influx. The genetic identities of the Ca2+-permeable channels involved in generating the [Ca2+]cyt signal are unknown. Potential candidates in the model plant Arabidopsis (Arabidopsis thaliana) include annexin1 (AtANN1). Here, luminescent detection of [Ca2+]cyt showed that AtANN1 responds to high extracellular NaCl by mediating reactive oxygen species-activated Ca2+ influx across the plasma membrane of root epidermal protoplasts. Electrophysiological analysis revealed that root epidermal plasma membrane Ca2+ influx currents activated by NaCl are absent from the Atann1 loss-of-function mutant. Both adaptive signaling and salt-responsive production of secondary roots are impaired in the loss-of-function mutant, thus identifying AtANN1 as a key component of root cell adaptation to salinity.

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Humans commonly apply chemicals to manage agroecosystems. If those chemicals influence the behaviour or survival of non-target arthropods, the food web could be altered in unintended ways. Glyphosate-based herbicides are among the most ubiquitous pesticides used around the world, yet little is known about if and how they might affect the success of terrestrial predatory arthropods in agroecosystems. In this study, we quantified the effects of a commercial formulation of a glyphosate-based herbicide on the activity of three predatory arthropod species that inhabit agricultural fields in the eastern United States. We also measured the survival of the most common species. We tested the reactions of the wolf spider, Pardosa milvina, to either direct application (topical) or contact with a treated substrate (residual). We quantified the reactions of a larger wolf spider, Hogna helluo, and a ground beetle, Scarites quadriceps, to a compound (topical plus residual) exposure. Pardosa milvina reduced locomotion time and distance under topical herbicide exposure, but increased speed and non-locomotory activity time on exposed substrate. Both H. helluo and S. quadriceps increased non-locomotory activity time under compound herbicide exposure. Over a period of 60 days post-exposure, residually exposed P. milvina exhibited lower survivorship compared to topically exposed and control groups. Thus, exposure of terrestrial arthropods to glyphosate-based herbicides affects their behaviour and long-term survival. These results suggest that herbicides can affect arthropod community dynamics separate from their impact on the plant community and may influence biological control in agroecosystems.

Pesticides can modify invertebrate movement and feeding behaviour which could reduce predation in agroecosystems. Previous assays have exposed the spider Pardosa amentata (Clerck) to the synthetic pyrethroid cypermethrin and monitored prey items consumed in small containers (requiring very little movement to capture prey). The current study used larger arenas containing artificial 'vegetation' (a plastic analogue) to encourage spiders to hunt and capture prey. The period 24 h after exposure produced greatest variability in prey item consumption between treatments and was used to examine treatment effects. At this time, cypermethrin reduced prey consumption rates but these effects did not persist. Findings did not suggest that the presence of artificial vegetation in arenas modified prey consumption rates, which was consistent for individuals treated with cypermethrin and a control group. This is despite the majority of pesticide-treated individuals exhibiting both ataxia and paralysis of the hind legs (these effects persisting for a maximum of 3 and 6 days respectively). These findings were consistent for both sexes. Spider longevity under starvation conditions was not significantly reduced by cypermethrin exposure but overall females survived longer than males. The findings are discussed in the context of the arenas used and the ecology of this common predator.