FINE-STRUCTURE AND POSSIBLE FUNCTIONS OF ANTENNAL SENSILLA IN POLYXENUS-LAGURUS (DIPLOPODA, PENICILLATA, POLYAENIDAE)

The following types of sensilla occur on the antenna of both sexes of P. lagurus: apical cones, sensilla basiconica, sensilla coeloconica, s etiform sensilla and cupuliform sensilla. Four apical cones occur on t he distal (eighth) article, these being contact chemoreceptors. The se nsilla basiconica form a row on the distal part of the 6th and 7th art icles, each sensillum containing 1-3 sensory cells with a presumed olf actory function. Two sensilla coeloconica, each of which is located at the posterior end of the two rows of sensilla basiconica, have five s ensory cells each and are probably thermo-and hygroreceptors. Twenty-t hree setiform sensilla are distributed on the distal edge of the anten nal articles, except the 4th and 8th, and are each innervated by one b iciliate mechanosensitive neuron; on the 6th article another setiform sensillum has three sensory cells and might have thermo-and hygrorecep tive functions. Four cupuliform sensilla, occurring on the apical join t-membrane of the 1st, 3rd and 5th articles, have an unknown function. The ultrastructural differences of these sensilla from those of Insec ta are discussed.