Nuptial Flight in two Ponerine Ants,Pachycondyla Impressa and P. Fauveli,Overlooking Machu Picchu,Peru

We report on a simultaneous nuptial flight of ants of two sympatric ponerine species, Pachycondyla impressa and P. fauveli, on the top of Huayna Picchu (2700 m), Peru. After flying in and landing on the flat, hare rocks of the summit, the conspecific sexuals approached, antennated and mated without any previous female calling behaviour. During one hour of observation, the number of approximately 30 ♂ ♂ and ♀ ♀ Pachycondyla impressa and 70–86 of P. fauveli on the site remained constant because of individuals continuously arriving and leaving. Although nuptial flight seems to be the most common type of mating system in ants, this is one of the very few reports on the occurrence of this behaviour in ponerine species.     

Dynamics and Consequences of Hierarchy Formation in the Ant Leptothorax sp. A

In the Nearctic ant Leptothorax sp. A, aggressive interactions among wingless intermorphic queens and primarily winged gynomorphic queens lead to the formation of dominance hierarchies, in which the highest-ranking individual is the only egg-layer in a colony. Fighting occurs during two periods of the annual cycle: in late summer, newly adopted young queens are integrated into the colony's hierarchy; after hibernation, fighting resumes and the high aggressiveness of α-queens may now lead to the emigration of β and other middle-ranking queens. The α-position appears to be very stable over successive fighting periods, though an estimate of nestmate relatedness by allozyme electrophoresis (Polyacrylamide gels and cellulose acetate plates) suggests that queen replacement occasionally occurs. The mean relatedness determined for adult workers in a functionally monogynous population of Leptothorax sp. A was 0.54 and their effective number of mothers therefore 1.5. This is lower than expected and found for monogynous colonies. Dominance rank is apparently not correlated with queen morph, weight, and size, but an influence of insemination, age, or previous reproductive experience is likely.