Figure 25Types and sizes of the sensilla of the Pleidae (Paraplea order inhibitor frontalis). (a) CH2 and CH3 are less numerous and spread unevenly over all segment; TRS1 (one) is placed dorsally near the apex; one pair of COS is situated on the II segment. (b) TRS1 (three) are …Figure 26Types and sizes of the sensilla of the Helotrephidae (Hydrotrephes visayasinensis). (a) Several CH3, one CH2, and one CH1 are spread dorsally (D) oil the IV segment. (b) TRS1 (one) and TRS2 (one) are situated dorsally (D) near the apex. (c) Several CH3 …Figure 27Types and sizes of the sensilla of the Notonectidae: Anisopinae (Buenoa uhleri). (a) Several CH3 and CH2 are present on the III segment (dorsal view). (b) Several CH3 and CH2 are present on the IV segment (dorsal view). (c) Several CH3 are scattered all …

Figure 28Types and sizes of the sensilla of the Notonectidae: Notonectinae (Notonecta glauca). (a) The arrangement of several CH2, CH3, and CH1 on the dorsal surface of the II segment; COS is situated near the edge of the I segment. (b) TRS1 (one pair) placed …Large (50�C100��m) (TRS1) and short (1.0�C49��m) (TRS2) trichoid sensilla are placed on the ventral side on the fourth segment of the labium (Figure 4(c)). These sensilla have been identified in the Nepidae (Figures 9(b), 10(b), and 10(c)), Belostomatidae (Figures 11(b), 12(e), 13(c), and 14(b)), Ochteridae (Figures 15(c) and 15(g)), Gelastocoridae (Figures 16(d) and 17(b)), Aphelocheiridae (Figure 18(b)), Naucoridae, Cheirochelinae (Figures 19(b) and 19(g)), Laccocorinae (Figure 20(f)), Limnocorinae (Figure 21(c)), Cryphocricinae (Figures 22(a) and 23(d)), Naucorinae (Figures 24(a), 24(b), 24(d), 24(e), and 24(g)), Pleidae (Figure 25(b)), Helotrephidae (Figure 26(e)), and Notonectidae (Figures 27(e) and 28(e)).

Large (50�C100��m) (TRS1) and short (1.0�C49��m) (TRS2) trichoid sensilla placed on the dorsal side on the third segment of the labium (Figures GSK-3 4(a) and 4(b)). These sensilla have been identified only in the Naucoridae, Cheirochelinae (Figures 19(a), 19(d), 19(f), and 19(h)), Laccocorinae (Figures 20(a), 20(b), 20(e), and 20(f)), Limnocorinae (Figure 21(e)), Cryphocricinae (Figure 23(c)), and Naucorinae (Figures 24(a), 24(b), 24(d), and 24(f)).3.5. Chemoreceptive Sensillum Sunken in an Inflexible SocketPapilla sensillum��gustative sensillum (PAS) (Figures 5(a) and 5(b)). This type of sensillum is wide and low. Two subtypes have been recognized as PAS1 (Figure 5(a)) with a flattened tip and PAS2 (Figure 5(b)) with a slightly rounded tip. They possess inflexible sockets and are placed in a depression of the cuticle.