Sexually selected signals are common in many animals, though little reported in social insects. We investigated the occurrence of male visual signals mediating the dominance relationships among males and female choice of sexual partner in the paper wasp Polistes simillimus. Males have three conspicuous, variable and sexually dimorphic traits: black pigmentation on the head, a pair of yellow abdominal spots and body size differences. By conducting behavioral assays, we found that none of the three visual traits are associated with male-male dominance relationship. However, males with higher proportion of black facial pigmentation and bigger yellow abdominal spots are more likely chosen as sexual partners. Also, after experimentally manipulating the proportion of black pigment on males' face, we found that females may evaluate male facial coloration during the choice of a sexual partner. Thus, the black pigmentation on P. simillimus male's head appears to play a role as a sexually selected visual signal. We suggest that sexual selection is a common force in Polistes and we highlight the importance of this group as a model for the study of visual communication in insects.

Leks are characterized by strong male competition and female mate choice. While there is convincing evidence that female choice on leks may be based on male ornaments, little is known about the possibility that the same traits can also mediate conflicts among rivals. Males of Polistes dominula paper wasps have variable yellow abdominal spots. In an earlier experiment in a glass arena, these spots functioned as sexually selected signals: males with elliptical spots were dominant over rivals and preferred by females compared to males with irregularly shaped spots. Whether male spots are sexually selected signals under field conditions is an open question. By conducting a decoy challenge in a natural lek, we observed that lures with manipulated spot shape received more aggression by territorial males when they had regular than irregular spots; these results suggest that males with regular spots were perceived as potentially dangerous rivals. Lekking males could use these condition-dependent ornaments to quickly assess the fighting ability of rivals and to mediate aggressive interactions.

Nesting substrata, colony success and productivity of the wasp Mischocyttarus cassununga. Colonies of the wasp Mischocyttarus cassununga (von Ihering, 1903) are easily found in urban areas. However, in spite of the massive presence of this species in cities, little is known about its nesting habits, colony success and productivity. The present study aimed at answering the following questions: What are the substrates used for nesting by M. cassununga? What is the main foundation strategy adopted by M. cassununga in urban areas: a solitary female or associative foundation? Is there a relationship between foundation strategies and colony success? Is the total number of cells per nest related to the number of adults produced? The study was conducted in Juiz de Fora, southeastern Brazil, from December 2006 to November 2007. Nesting in man-made substrata seems to be a common strategy in M. cassununga (90.9%), with preference for nest building with a horizontal comb facing north. The colonies were established mainly by groups of foundresses (67.6%), with a success of 84%. The number of brood cells produced per nest was 71.74 ± 45.25 (18-203), and it was positively correlated with the number of adults produced. Hence, we can say that the nests founded by M. cassununga are located mainly in man-made substrata and mostly founded by a group of females. The cell reuse behavior increases the number of adults produced, as it optimizes foraging. These characteristics together with its behavior and nesting habits promote the success of this species in thriving in urban environments.