The nest architecture of the ant, Pheidole oxyops Forel, 1908 （Hymenoptera： Formicidae）

Pheidole oxyops builds subterranean nests, with an external architecture that is distinctive and easily recognizable by its wide and specific entrance hole, measuring up to 12.2 cm in diameter, denoting a pitfall-trap. In order to study the nests＇ internal architecture, seven nests were excavated; four were identified with neutral talc, while the others were cast in cement and then excavated. Measurements were made in order to gain a better understand- ing of their structures, and a photographic documentation was obtained as well. The excavations revealed that the nests are perpendicular relative to the ground, beginning with a cylindrical channel with a mean length of 13.5 cm, containing irregular formations, and whose diameter becomes progressively narrower until the first chamber is formed. As the channel continues, dish-like chambers appear, interconnected by channels that become progressively narrower and longer, while the chambers are arranged at greater distances from each other as nest depth increases. Both channels and chambers are located on the vertical projection of the entrance hole. Nests may reach a depth of up to 5.09 m, with a number of chambers ranging between 4 and 14.

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.