Sensillia twig basiconica
Similar to the labial palps, sensilla twig basiconica (STB) also occur only at the apical end of adult mandibular palps and can also be divided into four subtypes (STB I, STB II, STB III, and STB IV). The shape of these sensors varies markedly between subtypes (Fig. 6).
The terminal tapered inductor of the mandibular palpus showed little overall difference in external morphological features, but females likewise differed significantly from males in the length of STB IV (t = 4.54, P < 0.01). In terms of number, STB I (t = -5.62, P < 0.01) were more numerous in males than females, while females had significantly more STB IV (t = 2.63, P < 0.05) than males.