THE PHYLOGENY, UNIQUE MOUTHPARTS, FEEDING BIOLOGY AND LIFE HABITS OF A MOSQUITO-LIKE, LONG-PROBOSCID SCORPIONFLY FROM THE MID CRETACEOUS OF MYANMAR

Long-proboscid scorpionflies (Mecoptera) have an extensive history whose first appearance is the late Permian of Russia and last occurrence the mid Cretaceous of Myanmar. During this interval, five major lineages interacted as pollinators of gymnosperms and angiosperm based on evidence of mouthpart structure, features of ovulate organs and pollen associations. The long-proboscid condition probably originated three times within Mecoptera, supported by a phylogenetic analysis of major extinct and extant clades of Mecoptera, basal Diptera (true flies) and Siphonaptera (fleas), as well as lineage-specific features of proboscides that relate to their pollinated host plants. A recently described lineage, Dualulidae, is among the smallest of scorpionflies and superficially resemble mosquitoes (Diptera), including reduction of their hind wings to haltere-like nubbins and the prolongation of mouthpart elements into gracile, penetrative proboscides. The Dualulidae proboscis structure is unique compared with other mecopteran, long-proboscid lineages or other known extinct or extant insects. A central feature of the dualulid proboscis is an elongate siphon that accesses incoming fluid food whose suction is powered by a contractile cibarial pump mounted under the clypeus. Suspended within the food tube is a tubular hypopharyngeal duct of much smaller diameter that secreted outgoing salivary fluids and powered by a small pharyngeal pump with a regulating dentate valve. This double pump system with a food tube of inflowing fluid and a salivary duct of outflowing secretions likely was used to access gymnosperm pollination drops and possibly angiosperm nectar, consistent with food tube and hypopharyngeal duct termini that are blunt and straw-like. Examination of closely related, probably confamilial Parapolycentropus and Dualula indicate that haltere-like hind wings can be explained by an Ultrabithorax homeotic gene system similar to modern Drosophila. Discovery of a pair in copulo indicates that male and female genitalia are highly conserved, as is associated swarming behavior involved in mating. Features of the phylogenetic context, feeding mechanism, wing function, genitalia and mating of Dualulidae portray a life history pattern rarely found in fossil insects.