The structure of the male sternal glands of the western flower thrips, Frankliniella occidentalis (Pergande)

Adult males of the western flower thrips, Frankliniella occidentalis (Thysanoptera: Thripidae), produce an aggregation pheromone that attracts both male and female adults. This pheromone is assumed to be produced by the sternal glands that are externally evident from distinctive regions known as pore plates or areae porosae on abdominal sternites III–VII of adult males. In this paper, we investigate the structure of these glands by light microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The structure of the glands is similar to that already found in other Thrips and Frankliniella species, with a dome of secretory cells near internal cuticular ridges. Many secretory ductules, about 100 nm in diameter, pass through the cuticle to pores on the outside surface of the cuticle. Despite their small size, these pores can be seen by light microscopy. Feltwork structures are present at the inner end of the ductules. The gland structure is consistent with pheromone production