Diverticula in Male Lycorea halia Butterflies (Lepidoptera: Nymphalidae: Danaini: Itunina)—Support Organs for Everted Hairpencils with Unique Ultrastructure

The involvement of the diverticula, a synapomorphy for Itunina, in protrusion and expansion of hairpencils by male Lycorea halia (Hübner, 1816) is demonstrated for the first time. They facilitate maintaining the haemolymph pressure necessary to keep the hairpencils everted. The diverticula are curved hook-like lobes, open to the body cavity and densely filled with tracheae and threads made by units of two staggered cells surrounding a central extracellular fibril bundle. Such complex structures, apparently metabolically active, have not been reported for insects previously and might indicate additional functions, but their functional role(s) remains a puzzle. When a male emerges from pupa, the diverticula are not yet formed; this happens only during the first protrusion of the hairpencils.