The present paper describes the sensory structures on the apical segment of the labium in fifteen fulgoromorphan families (Hemiptera: Fulgoromorpha), using the scanning electron microscope. Thirteen morphologically distinct types of sensilla are identified: five types of multiporous sensilla, four types of uniporous sensilla and four types of nonporous sensilla. Three subapical sensory organ types are also recognized, formed from one to several sensilla, each characteristic of a family group. Sensilla chaetica (mechanoreceptive sensilla) fall into three categories dependent on length and are numerous and evenly distributed on the surface of the labium except where they occur on specialized sensory fields. The planthopper morphological ground plan is represented by two apical pair of sensory fields (dorsal and ventral) on which 11 dorsal pairs of sensilla (10 peg-like pairs + 1 specialized pair dome or cupola-like) and 2 ventral pairs of sensilla basiconica occur. Two main patterns (cixiid and issid) together with more specialized ones (derbid, lophopid, flatid and fulgorid) are reported. Disparity and diversity of the sensory structures are analyzed from a taxonomic and functional perspective. A gustatory function is provided for several chemoreceptive labial sensilla, as in the antennal flagellum sensilla in some other Hemiptera. This represents a more recently evolved function for the planthopper labium. Finally, further lines of study are suggested for future work on the phylogeny of the group based on the studied characters.

The Nepoidea superfamily belongs to the water bugs' infraorder (Nepomorpha) and consists of two families-Belostomatidae and Nepidae. Species from those families are the largest of all nepomorphans and are considered to be top predators in aquatic ecosystems. A characteristic feature of the group is the existence of short antennae concealed in grooves behind the eyes, which is an adaptation to the water habitat. The antennae bear many types of sensillar structures, which receive signals from the environment. Among such structures, mechanosensilla were of the greatest diversity. The antennal sensilla of species from both families were examined under the scanning electron microscope. 11 essential morphological types of sensilla were distinguished, including 5 new mechanosensilla types (sensilla paddle-like, cone-like, squamiformia, brush-like and club-like). Basal types of mechanosensilla such as trichodea, chaetica, basiconica (subtype 1) and campaniformia occur in Nepoidea and other Heteroptera. In some representatives of both families, sensilla paddle-like and sensilla basiconica type 1 were observed. Moreover, sensilla chaetica and cone-like were found in some species of Belostomatidae, whereas in Nepidae sensilla squamiformia, brush-like and club-like were observed. Apart from mechanosensilla, one type of thermohygrosensilla (ampullacea) and two different shaped olfactory sensilla basiconica (subtypes 2, 3) and coeloconica (subtypes 1, 2, 3) were found. It could indicate sensilla use in the identification of the water reservoirs and locating prey.

The external morphology and distribution of the antennal sensilla of 21 species from five families of semiaquatic bugs (Gerromorpha) were examined using scanning electron microscopy. Nine main types were distinguished based on their morphological structure: sensilla trichoidea, sensilla chaetica, sensilla leaflike, sensilla campaniformia, sensilla coeloconica, sensilla ampullacea, sensilla basiconica, sensilla placoidea and sensilla bell-mouthed. The specific morphological structure of one type of sensilla (bell-mouthed sensilla) was observed only in Aquarius paludum. Several subtypes of sensilla are described, differentiated by number, location and type of sensillum characteristic for each examined taxon. The present study provides new data about the morphology and distribution of the antennal sensilla in Gerromorpha.

The present paper describes sensory structures on the apical segment of the labium in representatives of the subfamily Peiratinae (Heteroptera: Reduviidae), using the scanning electron microscope. The study is based on dry material representing 19 species and 16 genera. Within Peiratinae thirteen morphologically distinct types of sensilla were identified. Among them were four new types of sensilla (porous placodea sensillum [PPLS], multilobate sensillum [MS], domeelongated sensillum [UDES], and pit peg sensillum type 2 [NPPS2]) were found. Mechanosensilla are evenly distributed on the surface of the labium and form a characteristic pattern in various species. The main characters of the third visible (apical) segment of the labium are: presence of different sized sensilla of the chaetica type 1, 2, and 3; trichodea sensilla (TS); campaniform sensilla (CS); and various types of nonporous pit peg sensilla (NPPS1, NPPS2, and NPPS3). Distally on the apical segment of the labium dome-elongated sensilla (UDES) there are a characteristic arrangements, described as (3+3) and (1+2). Chemical sensilla are grouped on the tip of the labium. The position, number, and types of chemical sensilla on this area are very similar in all studied species.

The first comparative morphology study on antennal sensilla of Ochteridae, Gelastocoridae and Aphelocheiridae, carried out with the use of a scanning electron microscope, is provided. Our research hypothesis was: the antennal sensilla of the studied families reflect their different adaptations for use in aquatic habitats, while maintaining a common set of sensilla similar to other water bugs (Nepomorpha). Therefore, the number and placement of antennal sensilla of several species in the mentioned families were studied using scanning electron microscopy. Nine main types of mechano- chemo- and thermo-hygroreceptive sensilla were confirmed on their surface, including sensilla trichodea, chaetica, club-like, campaniformia, basiconica, coeloconica, plate-like, ampullacea and sensilla placodea multilobated. While seven of these were already documented in other species, two of them (sensilla plate-like and placodea multilobated) were yet to be documented on the antennae of Nepomorpha. All families display differences in the shape and length of antennae as well as among sensilla types. These findings support our hypothesis regarding differences in sensillar structures among families adapted differently to suitable niches. Differences between these families and previously studied nepomorphan taxa (Nepoidea) were also documented. However, the general set of sensilla observed on the antennae of the studied species is very similar to the one documented in Nepoidea. Therefore, we confirmed our assumptions regarding similarities in antennal sensilla between the studied families and other nepomorphan insects.