Comparative antennal morphometry and sensilla distribution pattern of three species of Siagoninae (Coleoptera, Carabidae)

Antennal sensilla typology, number and distribution pattern were studied in three myrmecophagous species: S. jenissoni Dejean 1826, S. dejeani Rambur 1837 and S. europaea Dejean 1826 using scanning electron microscopy. Morphometric analyses show that the antennae of male and female beetles are similar in their general structure for each of the three species and vary only in size. Five different sensillar types were distinguished: sensilla chaetica, sensilla basiconica, sensillum coelocapitolum, sensillum styloconicum and sensillum. "sicula-sickle"-shaped. Sensilla chaetica form four subtypes while sensilla basiconica - three subtypes. So, ten different sensilla were recognised on the antennae of each species of Siagona. The possible function of the sensilla was discussed and two types of sensilla (sensilla chaetica types 3 and 4) were considered as mechanoreceptors; sensilla basiconica type 3 - as proprioceptor; sensilla chaetica types 1 and 2, sensilla basiconica types 1 and 2, sensilla styloconica and possibly sensilla sicula-sickle-shaped - as chemoreceptors; sensilla coelocapitula - as thermoreceptors. No differences occur about sensillar typologies while their distribution is susceptible of increasing or diminution in number in all three species.