Introduction

The Brazilian Atlantic Forest is of great relevance to biological conservation, and is among the areas in South America with the highest levels of diversity and endemism. The aim of this study was to survey the social wasp species in the subfamily Polistinae in Ubatuba, São Paulo state, in southwestern Brazil. Collecting work was conducted from May 2007 to May 2008 using attractive PET bottle traps and active searching. Twenty-one species belonging to eight genera were found, among which some may be considered rare in southeastern Brazil such as Mischocyttarus parallelogrammus and Polybia catillifex. The most abundant species were Agelaia angulata (64.31%), Agelaia nr. centralis (10.08%) and Angiopolybia pallens (8.49%). A correlation between species richness and relative humidity (r = 0.6435; p = 0.0176) was observed. Values of species richness were a little higher in the super humid (Sm = 11) than in the less humid (Sm = 9) season. This suggests that this season may have more favorable environmental conditions for a greater richness of species to found colonies. Despite not having a very high species richness compared with other surveys, the collected species in this study can be considered rare in southeastern Brazil, emphasizing the complexity of the Atlantic Forest biome and its relation to the diversity of wasps.

The colony defense behavior of the wasp Mischocyttarus cerberus Richards (Hymenoptera, Vespidae) was studied to verify whether there were different reactions of wasps of different ages and hierarchical positions during attacks of ants. Detailed nest mapping was first performed, then the wasps were marked and were divided in four distinct categories: queens, older workers, younger workers and males. Tests were made simulating attacks of ants in the nests. The main results showed that the M. cerberus behaviors against ant attacks is more related to the age of the wasps than to their hierarchical position. The oldest wasps (queens and older workers) defend the nest more than the younger workers and males, representing a form of temporal polyethism.

The primitive eusocial wasp Mischocyttarus cerberus forms colonies of independent foundation, without morphological differentiation among castes. Ants are natural enemies of the social wasps and defending the wasps' nests involves chemical and active defense strategies. The aims of this work were to verify the kind of defense the wasps use most frequently in post-emergent colonies of M. cerberus. We also observed whether the nest was abandoned during the ant attack and whether any relationship existed between the forms that colony defense took and the number of adults, the number of cells, and the number of immature wasps. The study was carried out on the campus of Universidade Estadual Paulista of Rio Claro, São Paulo, Brazil. The 23 nests under study were mapped weekly, and 68 bioassays were performed by simulating ant attacks against the nests. The results showed that wasps used both active and chemical strategies for nest defense, and the PCA analysis showed that the aggressive behaviors of biting the ant, wings vibrating, gaster hitting, and abdomen pumping were the dominant terms; the PCA correlation values were 2.70, 2.54, 1.64, and 1.63, respectively. The colonies in pre-and post-male substages with few immature wasps and the nests in post-male substage with one adult were more correlated with the nonaggressive behaviors of hiding, staying immobile, and flying; their PCA correlation values were 3.12, 2.56, and 1.77, respectively. These results show that the number of immature wasps is an important factor in the kind and in the intensity of the defense behavior against ant attacks.

The aim of this study was to analyze the distribution pattern of the food collected among groups of individuals in Mischocyttarus drewseni colonies. This behavior is one of the first actions exhibited by the foragers when they arrive in the colonies. Regarding nectar and prey collection, 95.90% of the collected nectar was given to larvae, whereas 3.57% to dominant individuals and 95.94% of the collected prey were given to the larvae, 2.54% to the dominant members, while the remainder of both was given to the workers. Despite not being significant, it was possible to observe a difference in food distribution among larvae, with larger larvae receiving more food than others. When the forager returns to the nest with pulp, it adds this material to cells in 64.29% of the times. Males showed agitated behavior with the arrival of the foragers, and sometimes took the foraged material from them.