Fig. 7

Alimentary tracts dissected from P. stali fed with colored water containing 0.05% Brilliant Blue FCF. a–c Fourth instar nymphs. d–f Adult insects. a, d Whole alimentary tract. b, e Around the symbiotic M4 region with crypts. Note that the main tract in the M4 region is not colored in the fourth instar nymph but deeply colored in the adult insect. c, f Around the M3–M4b junction. Red arrowheads indicate the constricted region that functionally separates the anterior and posterior regions of the midgut as a symbiont sorting organ that blocks food flow to the posterior midgut [44]. Abbreviations: M1, midgut first section; M2, midgut second section; M3, midgut third section; M4b, bulb-like region aboral to M4; M4, midgut fourth section with crypts; H, hindgut