Abstract:

Antennal morphology and sensilla of the fire ants, Solenopsis invicta Buren (Hymenoptera: Formicidae) collected from Wuchuan, Guangdong and Nanning, Guangxi were observed by scanning electronmicroscopy. The antennae are sexually dimorphic: the female antenna is geniculate, and the male antenna wirelike. The worker antenna has 10 antennomers， with most sensilla distributed on the two distal segments (the antennal club). The queen antenna has 11 antennomers, with sensilla distributed on the three distal segments (the antennal club); whereas the clubless male antenna has 12 antennomers, with sensilla distributed on all segments. Seven types of sensilla were found on antennae of the female. They are sensillum trichodea, sensillum trichodea curvata, sensillum basiconica, sensillum coeloconica, sensillum ampullaceal, sensillum chaetica, and Böhm bristles. Most of these sensilla are on the female antennal club, except Böhm bristles which are located on the scape and pedicel. The male also have seven types of sensilla, while their distribution is different with that on the female. Böhm bristles are in the same distribution as on the female, but sensillum basiconica is distributed on the two distal segments, and sensillum ampullaceal is distributed on the three distal segments, and the rest four types of sensilla are distributed on each flagellum. An ultra-short sensillum trichodea was first found on males, which is absent on females and different from other known sensilla trichodea. The morphology and distribution of these sensilla were described, and their difference between castes and sexes was discussed.
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Key words: Solenopsis invicta Buren, antenna, morphology, sensilla, ultrastructure, electronmicroscopy