Studies on the distribution, behaviour, ecology, habitats, and nesting of species of the family Vespidae, especially those of Polistinae in the Neotropical region are important due to reduced information on this subfamily (Clemente et al., 2020). The distribution of Polistinae species in Brazil was studied in the Amazon (Somavilla et al., 2014) and Atlantic Forest (Clemente et al., 2020) biomes, but information on these insects in the Cerrado (Clemente et al., 2020) and Caatinga (Somavilla et al., 2017) are scarce. Polybia occidentalis (Oliver) (Hymenoptera: Vespidae) has been reported in phytophysiognomies of the Atlantic Forest (Locher et al., 2014), Amazon (Somavilla et al., 2012), Cerrado (Clemente et al., 2020; Lima et al., 2024), Pantanal (Auko et al., 2017), and Caatinga (Steppe) (Santos et al., 2007) biomes in Brazil.
The successful establishment of social wasps depends on factors such as the choice of nesting site, number of founders, temperature, plant characteristics, including thorns and height increasing protection against predators, besides water and prey availability (López et al., 2012; Pérez-Bote et al., 2020). In addition, foliage density, distribution, and abundance of arthropods affect Vespidae nesting, and these insects prefer plants with similar colors to that of their nests (Pérez-Bote et al., 2020; Silva et al., 2023), increasing defense by camouflage (Milani et al., 2021). In Colombia urban areas, Polybia occidentalis Olivier (Hymenoptera: Vespidae) builds nests on plants taller than two meters to reduce predation (López et al., 2012). However, this wasp nested on Astrocarium sp. (Arecales: Arecaceae), Carapa guianensis Aublet (Sapindales: Meliaceae), and Eugenia malaccensis L. (Myrtales: Myrtaceae) plants at approximately one meter and seventy, two meters and four meters high, respectively (Somavilla et al., 2012).
Polybia occidentalis nested on Cereus jamacaru DC. and Pilosocereus catingicola (Gurke) Byles & Rowley (Caryophyllales: Cactaceae) plants, increasing the protection of their nests due to the thorns, reducing attacks by predators and foraged on flowers of these plants in the Caatinga (Santos et al., 2007). The number of flower buds of Turnera ulmifolia L. (Malpighiales: Turneraceae) was greater on plants with P. occidentalis nests. Extrafloral nectaries, in leaves or in plant reproductive structures, attract ants and wasps, in addition to bees, beetles, flies, mites, and spiders (Cuautle & Rico-Gray, 2003) due to sugary substances. This shows important relationships with P. occidentalis and the places it nests; however, the mechanisms of nesting site choice by this wasp are poorly understood, highlighting the need for more studies on the relationships between wasps and plants (Souza et al., 2014).
The ecological importance of P. occidentalis is high and therefore, the community structure (Cabral et al., 2024), prey and nectar stock (Karsai & Runciman, 2012), and plant associations (Cuautle & Rico-Gray, 2003) should be studied for this wasp. Studies on the preference of social wasps for plant substrate and the mechanisms for this choice in a semi-arid region is important for the conservation of these natural enemies (Souza et al., 2014). Social insects are also found in the Southeast USA where the identification of their nesting choice for plants will help to preserve them for the biological control of pests (Smith-Pardo et al., 2020). The objective is to report the first occurrence of P. occidentalis nesting on a Lafoensia glyptocarpa Koehne (Lythraceae) plant in the Cerrado region.