Antennal sensilla and their nerve innervation in first-instar nymphs of Porphyrophora sophorae Arch. (Hemiptera: Coccomorpha: Margarodidae).

Porphyrophora (Hemiptera: Coccomorpha: Margarodidae) is a genus of soil-inhabiting scale insects. The antennal sensilla and their innervation in the first-instar nymphs of Porphyrophora sophorae were studied using light microscopy and scanning and transmission electron microscopy to understand the function of these sensilla and determine the sensillar innervation feature on these small antennae. The results show that the six-segmented antennae of these nymphs have 20-23 sensilla which can be morphologically classified into seven types, for example, one Böhm's bristle (Bb), one campaniform sensillum (Ca), one Johnston's organ (Jo), 13-16 aporous sensilla trichodea (St), two coeloconic sensilla (Co), one straight multiporous peg (Mp1), and one curvy multiporous peg (Mp2). According to their function, these sensilla can be categorized into three categories: mechanoreceptors, that is, Bb, Ca, Jo, and St; thermo/hygroreceptors, that is, Co only; and chemoreceptors, that is, Mp1 and Mp2. The dendrites that innervate the Mp1, Mp2, and Co sensilla combine to form a large nerve tract (NT1) in the antennal lumen. Because NT1 extends through and out of the antenna, the somata of these neurons are present in the lymph cavity of the insect's head. The dendrites that innervate the mechanoreceptors form another nerve tract (NT2). The somata of these neurons are located inside the scape and pedicel. J. Morphol. 277:1631-1647, 2016. © 2016 Wiley Periodicals, Inc.