Elements composition analysis in mandibles of Neotropical social wasps (Vespidae, Polistinae)
Juan José Lagos-Oviedo, Juan José Lagos Oviedo , Carlos Eduardo Sarmiento M
Instituto de Ciencias Naturales, Universidad Nacional de Colombia, Colombia; Instituto de Ciencias Naturales, Universidad Nacional de Colombia, Colombia ; Instituto de Ciencias Naturales, Universidad Nacional de Colombia, Colombia
In many insects, ovipositors, claws, and mandibles are reinforced with metals that increase the hardness and elasticity of the structure to avoid fracture or wear. Social wasps use their mandibles in nest construction incorporating materials with different characteristics; these materials can be composed of hard or soft woods, plant hairs or mud, and very little is known on the effect of such materials on mandible wear. This work aims to characterize the presence of metals in mandibles of social wasps and to relate them to the material used to build the nest. Mandibles of 13 Polistinae species and one Eumeninae were dissected and studied. Identification of metallic elements was done through energy dispersive analysis by X-ray (EDAX) in a FEI Quanta200 SEM. Quantitative measurement of elements included Phi-Rho-Zeta correction. One to seven measurements at different regions per mandible were taken (3.85, SD=1.77). The mandible region selected for measurement considered areas prone to wear such as teeth and denticles. Following previous studies, recordings were categorized into three groups: trace (<0.5% mass weight), minor (0.5-5% mass weight) or major (>5%). Metal elements are reported in mandibles of Vespidae, including Zn, Si, Al, Mg, Mn, Fe, Ca, K, Cl, and Na. SEM images did not show clusters of metal elements in a specific mandible region. Na and Mg were recorded at high concentrations in eight and six species each, while the other elements were found as trace or in smaller quantities. No relationship between presence and abundance of metals and the type of material for nest construction was found, which suggests that the incorporation of these metal elements into the mandibles of social wasps is not responding to the costs of using a certain type of material to build the nest.