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.     

Brain GABA and glutamate levels in workers of two ant species （Hymenoptera： Formicidae）： Interspecific differences and effects of queen presence/absence

Presence of amino acid neurotransmitters gamma-aminobutyric acid （GABA） and glutamate （Glu） in ant brains was reported in very few studies. To learn more about factors influencing GABA and Glu levels in ant brains, we applied high-performance liquid chromatography to measure levels of these compounds in single brains of workers of 2 ant species, Myrmica ruginodis （subfamily Myrmicinae） and Formica polyctena （subfamily Formicinae） taken from queenright/queenless colony fragments and tested in dyadic aggression tests consisting of an encounter with a nestrnate, an alien conspecific or a small cricket. Brain glutamate levels were higher than those of GABA in both tested species. Brain GABA levels （in μmol/brain） and GABA ： Glu ratio were higher in M. ruginodis （a submissive species） than in E polyctena （a dominant, aggressive species） in spite of smaller brain weight of M. ruginodis. Brain glutamate levels （in μmol/brain） did not differ between the tested species, which implies that glutamate concentration （in μmol/mg of brain tissue） was higher in M. ruginodis. Queen absence was associated with increased worker brain GABA levels in E polyctena, but not in M. ruginodis. No significant effects of opponent type were discovered. As GABA agonists enhance friendly social behavior in rodents, we hypothesize that elevated brain GABA levels of orphaned workers of F.polyctena facilitate the adoption of a new queen. This is the first report providing information on GABA and glutamate levels in single ant brains and documenting the effects of queen presence/absence on brain levels of amino acid neurotransmitters in workers of social Hymenoptera.