Predator-prey encounters:deciphering the robbery relationship between highwayman flies and their ant victims

Examples of predator–prey interactions in which flies rob ants are uncommon.To date,this behavior has only been recorded in the genus Bengalia Robineau-Desvoidy(Bengaliinae,Diptera,Calliphoridae).These predatory flies ambush ants,and rob them of the food or offspring that they are carrying.However,because of the rarity of this behavior,the reasons and consequences(evolutionary advantages)are unknown,and indeed,the behavior has been sometimes considered anecdotal.In this study,we employed field investigations and behavioral analyses to investigate whether the sex of the fly Bengalia varicolor,or the weight and quality of the food carried by Pheidole nodus ants influenced fly–ant interactions in their natural habitats.We show that food weight and quality influenced the behavior of B.varicolor independent of the fly’s sex.Robbing behavior by the flies was more successful when the food robbed was of high-quality and light in weight.Furthermore,the weight of the food robbed modulated the escape distance the flies could carry it.This then may affect the food quality and weight transported by the ants.This is a novel example of deciphering the relationship between highwayman flies and their ant victims.Given the widespread distribution of Bengalia flies,we suggest that such interspecific predator–prey encounters may shape the robbery interactions and the carrying behavior of further ant species in nature.

The flip side of the coin:ecological function of the bee-hawking Asian hornet

Biological invasions around the world have experienced an unprecedented increase over the past few decades as a result of global change,worldwide trade and human mobility(Mack et al.2000).Invasive species have serious ecological and economic impacts across the globe.Among the areas with high levels of invasion,Europe faces the greatest biological invasion(van Kleunen et al.2015).The European Union commissioned a report on invasive alien species to assess their ecological and economic impacts.Nowadays,the Asian bee-hawking hornet Vespa velutina Lepeletier,1836 is in the line of fire in Europe(Rome&Villemant 2016).This hornet species is known as a serious predator of pollinators(such as honeybees),thus severely affecting insect pollination as well as apiculture in various European countries(Villemant et al.2011).