A comparative study of adult Tanyderidae mouthparts, with notes on Blephariceridae (Insecta: Diptera).

The Tanyderidae are a small, ancient, poorly studied nematoceran family with 10 extant genera. А previous study found in the adults of Eutanyderus and Peringueomyina a full set of mouthparts (including mandibles) - a rare case among Diptera. The new study examined the mouthparts of adult Tanyderus, Araucoderus and Nothoderus using light and scanning electron microscopy. A full set of mouthparts, with no significant differences between sexes, was again found in all three genera. Three structural types were identified, suggesting as many feeding strategies among recent Tanyderidae. The genera form a series according to the degree of reduction of mandibles and other piercing structures. The well-developed toothed mandibles, hypopharynx, and laciniae were found only in both sexes of Tanyderus. Such a pattern has not previously been observed in males of any recent Nematocera. In the absence of live observations, the structure of these mouthparts suggests active penetration or laceration during feeding. Similar mouthparts, with both mandibles and hypopharynx toothed, are described, for the first time, in a female of Jurassic Protanyderus. For comparison, piercing mouthparts of two recent predaceous genera of Blephariceridae, Blepharicera and Liponeura, were examined. They showed numerous differences from the mouthparts of Tanyderus. Moreover, the mandibles, well-developed in the females, were absent in the males, suggesting sexual dimorphism in the feeding of these blepharicerids. Correlations between the structure of the mandibulate mouthparts, their sexual dimorphism, and the diet in lower Diptera are reviewed from the evolutionary perspective.