Morphological characteristics of the antennal flagellum and its sensilla chaetica with character displacement in the sandfly Phlebotomus argentipes Annandale and Brunetti sensu lato (Diptera : Psychodidae)

Using light microscope and scanning electron microscope, the external morph ological characteristics of the antennal flagellum and its sensilla are des cribed in the sandfly, Phlebotomus argentipes Annandale and Brunetti sensu late, a well known vector of visceral leishmaniasis in India. A revised ter minology is given for the antennal segments to bring phlebotomine more in l ine with other subfamilies and families while a description of antennal sen silla is provided for the first time in phlebotomine sandflies. Each flagel lum consists of scape, pedicel, flagellomeres I to XIII and apiculus. The a ntennal segments contain scales and sensilla and the latter consist of sens illa trichodea, s. basiconica, s. auricillica, s. coeloconica and s. chaeti ca and their putative functions are discussed. The sensilla chaeticum hitherto known as antennal ascoid in the phlebotomin e sandflies was used to differentiate within and between species. Differenc es in its relative size to the flagellomere between the populations of P. a rgentipes collected from the endemic and non-endemic areas in Tamil Nadu st ate, southern India were established. These differences are considered to b e a character displacement as means of premating reproductive isolating mec hanism among the populations/members of species complex.