Structure and sensilla of the mouthparts of Alobaldia tobae, Maiestas dorsalis and Stirellus indrus (Hemiptera: Cicadellidae: Deltocephalinae)

Abstract

The morphology of adult mouthparts of the leafhoppers Alobaldia tobae, Maiestas dorsalis and Stirellus indrus was studied using a scanning electron microscope. The mouthparts are of the typical piercing–sucking type, similar to mouthparts found in other hemipteran insects, and comprise a three-segmented labium with a deep groove in the anterior side, a stylet fascicle consisting of two mandibular and two maxillary stylets, and a small cone-shaped labrum. The mandibular stylets, located laterad of the maxillary stylets, have sculpturing on their tips. The maxillary stylets are interlocked to form a larger food canal and a smaller salivary canal. Sensilla detected on the three leafhopper species were at different locations on the labium. Three kinds of sensilla were found on the Alobaldia tobae and Maiestas dorsalis labium, including two types of sensilla trichodea (I and II), two types of sensilla basiconica (I and II), and one type of sensilla coeloconica (Sco I). Three kinds of sensilla were found on the Stirellus indrus labium, including three types of sensilla trichodea (I, II and III), two types of sensilla basiconica (I and II), and one type of sensilla coeloconica (Sco I). Among them, sensilla trichodea I are the most abundant on all of three species. This is the first report of sensilla coeloconica (Sco I) and sensilla trichodea III on the mouthparts of Deltocephalinae. Sensilla trichodea I (St I) were also found on the surface of the Stirellus indrus labrum, which is also a first report in the Deltocephalinae. These sensilla may be involved in host recognition and are likely chemo- or mechanosensory, or both. The potential functions of the sensilla are discussed. The morphology of mouthparts and the distribution of sensilla on the labium in Alobaldia tobae, Maiestas dorsalis and Stirellus indrus are discussed with respect to their possible functional significance.