Fig. 2

Semithin sagittal sections through the heads of male Philanthinae. a Single NQ-class 3 gland cells, i.e. complexes of a secretory cell and a canal cell, the latter forming a conspicuous end apparatus (white arrow heads) and canal that connects the secretory cell to the lumen of the MG (Philanthus multimaculatus, ID 24); b Acini of NQ-class 3 gland cells with end apparatuses (white arrow heads) connected to the MG reservoir by bundles of conducting canals (Philanthus T. diadema, ID 17); c Single gland cells possessing end apparatus (white arrow heads), thus resembling NQ-class 3 cells, but directly associated with the wall of the MG reservoir without canals (Clypeadon laticinctus, ID 3); d Aggregations of mononuclear secretory cells surrounding the fine branches of the PPG reservoir, interspersed with small rounded cells (white arrows) (Philanthus venustus, ID 8); e Multinuclear syncytia of secretory cells, containing many vesicles (black arrow heads), and in close contact to the fine branches of the PPG reservoir (thick black arrow; inset: detail of a PPG branch terminating in syncytium) (Philanthus histrio, ID 12); f Multinuclear syncytia of secretory cells surrounding the fine branches of the PPG reservoir and interspersed with small cells (white arrows) (Philanthus crotoniphilus, ID 21). Abbreviations: ac, acini of NQ-class 3 cells; br, brain; cc, conducting canal; cs. cuticular spines; ep, epithelium of the MG; gc. secretory cells not resembling NQ-class cells; gcA, aggregations of mononuclear secretory cells; gc3, NQ-class 3 gland cells; mg, lumen of the mandibular gland; nu, nucleus with nucleoli; ppg, fine branches of the postpharyngeal gland; se, secretion within the MG; sy, multinuclear syncytia; tr, tracheole. Scale bars [except inset in (E)] = 50 μm