Midgut ultrastructure of queens and foraging workers of Melipona quadrifasciata anthidioides (Hymenoptera, Apidae, Meliponini)

Stingless bees, the most important pollinators of several native plant species are widespread in Brazil. Many studies have described the morphological aspects of the insects' midgut, the main site of chemical digestion and nutrient absorption. In this work, we used scanning electron microscopy to describe and compare the ultrastructure of the midgut in individuals from different castes of Melipona quadrifasciata anthidioides. The midgut of these bees has two layers of muscular fibers: a circular one, involved in the formation offolds, and an external, longitudinal layer. The peritrophic membrane was thicker and homogeneous in the presence of food. Microvilli were evident on the surface of the main cells. We have not found morphological differences in the midgut among individuals from the castes analysed. Our analyses corroborate previous descriptions made with light microscopy and transmission electron microscopy (TEM).5031117112