Vespidae is an important insect family that is among the largest predators of other insects in natural environments. This study in mangrove swamps was carried out in order to know if social wasp, Mischocyttarus (Mischocyttarus) rotundicollis could be attracted by fish (sardine) in decomposition. The insects were collected in mangrove swamps in Itaborai, every two weeks, totaling 72 samples from August 2008 to July 2011. Over a 36 months period 69 individuals were caught. The abiotic factors (season and tidal variations) that could influence the occurrence of these wasps in mangrove swamps were recorded. The abundance of wasps was only affected by the spring season and the highest tides (spring-tides). The presence of the M. rotundicollis, in the mangrove swamps caught with fish in decomposition, may indicate that the studied forest area still represents a natural preserved refuge and reveals the importance of understanding of ecology these wasps and provides much information that will contribute greatly to environmental sciences.