Structure of Antennal Pseudoplacoid Sensilla in the Caddisfly Philopotamus montanus Donovan (Trichoptera, Philopotamidae)

Abstract

The structure of pseudoplacoid sensilla characteristic of Amphiesmenoptera was studied by SEM and TEM methods by the example of the mushroom-like sensilla in Philopotamus montanus Don., a member of the primitive family Philopotamidae. These sensilla were found to be different from the externally similar placoid sensilla in the presence of a socket-like depression and a sensillar stem arising from it. The expanded terminal part filled with the dendrites of the sensory neurons has numerous pores on its upper and lower surfaces. The sensillar dendrites have subterminal expansions filled with electron-transparent fluid, while their thin terminal parts have electron-dense central elements. The pseudoplacoid sensillum of Ph. montanus comprises three sensory neurons. The mushroom-like pseudoplacoid sensilla of Ph. montanus are compared with chemoreceptive sensilla of other insects.