Wood ants produce a potent antimicrobial agent by applying formic acid on tree-collected resin.

Wood ants fight pathogens by incorporating tree resin with antimicrobial properties into their nests. They also produce large quantities of formic acid in their venom gland, which they readily spray to defend or disinfect their nest. Mixing chemicals to produce powerful antibiotics is common practice in human medicine, yet evidence for the use of such "defensive cocktails" by animals remains scant. Here, we test the hypothesis that wood ants enhance the antifungal activity of tree resin by treating it with formic acid. In a series of experiments, we document that (i) tree resin had much higher inhibitory activity against the common entomopathogenic fungus Metarhizium brunneum after having been in contact with ants, while no such effect was detected for other nest materials; (ii) wood ants applied significant amounts of endogenous formic and succinic acid on resin and other nest materials; and (iii) the application of synthetic formic acid greatly increased the antifungal activity of resin, but had no such effect when applied to inert glass material. Together, these results demonstrate that wood ants obtain an effective protection against a detrimental microorganism by mixing endogenous and plant-acquired chemical defenses. In conclusion, the ability to synergistically combine antimicrobial substances of diverse origins is not restricted to humans and may play an important role in insect societies

Ultra-high pressure liquid chromatography-mass spectrometry for plant metabolomics: a systematic comparison of high-resolution quadrupole-time-of-flight and single stage Orbitrap mass spectrometers.

The response of Arabidopsis to stress caused by mechanical wounding was chosen as a model to compare the performances of high resolution quadrupole-time-of-flight (Q-TOF) and single stage Orbitrap (Exactive Plus) mass spectrometers in untargeted metabolomics. Both instruments were coupled to ultra-high pressure liquid chromatography (UHPLC) systems set under identical conditions. The experiment was divided in two steps: the first analyses involved sixteen unwounded plants, half of which were spiked with pure standards that are not present in Arabidopsis. The second analyses compared the metabolomes of mechanically wounded plants to unwounded plants. Data from both systems were extracted using the same feature detection software and submitted to unsupervised and supervised multivariate analysis methods. Both mass spectrometers were compared in terms of number and identity of detected features, capacity to discriminate between samples, repeatability and sensitivity. Although analytical variability was lower for the UHPLC-Q-TOF, generally the results for the two detectors were quite similar, both of them proving to be highly efficient at detecting even subtle differences between plant groups. Overall, sensitivity was found to be comparable, although the Exactive Plus Orbitrap provided slightly lower detection limits for specific compounds. Finally, to evaluate the potential of the two mass spectrometers for the identification of unknown markers, mass and spectral accuracies were calculated on selected identified compounds. While both instruments showed excellent mass accuracy (<2.5ppm for all measured compounds), better spectral accuracy was recorded on the Q-TOF. Taken together, our results demonstrate that comparable performances can be obtained at acquisition frequencies compatible with UHPLC on Q-TOF and Exactive Plus MS, which may thus be equivalently used for plant metabolomics

Alien interference: Disruption of infochemical networks by invasive insect herbivores

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The third trophic level of plant defence: neotropical social wasps\u27 use of odours of freshly damaged leaves when hunting

An important aspect of the hunting strategy of neotropical social wasps (Hymenoptera: Vespidae) is where they hunt. Three species used two behavioural components in their selection of a place to search for prey. The wasps uti lizcd the odour of freshly damaged leaves as cues (which could be synomones) to select which leaves to inspect and also they remembered a place to which they were strongly attracted to hunt recently and returned there. Polybia ignobilis (Haliday, 1836) and Polistes satan Bequaert, 1940 hunted on a lawn of Digitaria diversinervis Stapf immediately after it was mown in significantly larger numbers than at other times. P. ignobilis and Polistes versicolor (Olivier, 1791) hunted in significantly greater numbers on freshly cut leaves of passion vine (Passiflora edulis Sims) than on uncut leaves. Sometimes wasps inspected cards rubbed with freshly crushed leaves of P. edulis, but not control cards. Preliminary data suggest that several other species of social wasps around Brasilia hunt in a similar manner on native and exotic plants. Apparently the production of ephemeral odours by freshly cut leaves attract generalist insectivorous predators which perceive these scents and the social wasps investigated are members of the third trophic level of the plants' defence against attacks by herbivores. Available information suggests a difference between the behaviour of generalists and that of specialist arthropod predators which arc attracted to the odour emitted after their particular prey have damaged the leaves