Comparative Morphology Of The Antenna In Cicadomorpha

Insect antennae are segmented appendages that are well-equipped with a wide variety of antennal sensilla and function primarily in chemoreception,thermoreception and hygroreception.Antennae play crucial roles in ecological behaviors,including host location and recognition,as well as mating behavior.The morphology of antennae changes greatly due to its precise function and the significant difference of sensilla,which has potential value in classification and phylogeny.Members of the infraorder Cicadomorpha(Hemiptera)are distributed worldwidely and consist of three superfamilies(Cercopoidea,Cicadoidea and Membracoidea).Many of these species are economically significant pests.Therefore,in the study of these groups,it is very important to know the sensory systems of their antennae,which are used for the recognition of host plants.To provide background information for chemical ecology and phylogenetic studies,the fine morphology of antennae and the types and distribution of the sensilla in 25 species of five families belonging to 3 superfamilies were investigated by means of scanning electron microscopy.The cicadomorphan antennae are inserted in antennal foveae on the head capsule at the side of the postclypeus and below the antennal ledges.The gross morphology of antennae is similar in the other Hemipterans,consisting of three segments: a basal scape,a cylindrical pedicel and a long,filiform flagellum.The scape,which connects to the antennal socket where it functions as the fulcrum to the antennae.The pedicel,connected proximal to the concaved distal end of the scape and distal to the flagellum.Flagellum consists of several subsegments.In Cercopoidea,the scape,which connects to the antennal socket,is irregular in shape and prominently constricted around the base.The outer margin of the scape is conspicuously concaved at apical half and concaved,with scattered small imbricate papillae and sparsely covered with sensilla.The pedicel,connected proximal to the concaved distal end of the scape and distal to the bulb-shaped portion of flagellum,is a short and generally cylindrical segment,wrinkled with numerous transverse small imbricate papillae.The flagellum is divided into two distinct portions,an expanded basal bulb-shaped portion and a threadlike apical arista and the thread like arista is not segmented.In Cercopidae,There are four types sensilla including sensilla trichodea,sensilla basiconca,sensilla campaniformium and sensilla coeloconica.In Aphrophoridae,there are five types sensilla,including sensilla trichodea,sensilla basiconca,sensilla campaniformium,sensilla coeloconica and sensilla placodea.In Membracoidea,the scape,which connects to the antennal socket,is irregular in shape and prominently constricted around the base.The pedicel,connected proximal to the concaved distal end of the scape and distal to the bulb-shaped portion of flagellum,is a short and generally cylindrical segment.The length of flagellum is much longer than the scape and pedicel and consists of multiple flagellomeres,several basal flagellomeres are slightly inflated,and then gradually taper to apex.In Cicadellidae,there are four types with sensilla trichodea,sensilla basiconca,sensilla campaniformium and sensilla coeloconica.In Membracidae,there are sensilla trichodea and sensilla coeloconica.The scape and pedicel of the antennae in Cicadoidea are nearly cylindrical.The flagellum is composed of 5 flagellomeres and is tapered to apex.In Cicadidae,there are four types sensilla including sensilla trichodea,sensilla basiconca,sensilla campaniformium and sensilla coeloconica.The antenna sensillum types in different species of Cicadomorpha exhibit considerable structural similarity.Based on these morphological observations,we found that the fine morphology of antennae of 25 species in 5 families are very similar to each other.However,there were significant differences in the level of different families and species,including shape of flagellum,distribution and number and type of sensory organs.These data provide an important starting point and are complementary to further physiological and behavioural studies on cicadomorphan species,and may be useful for future study of taxonomic and phylogenetic analysis of Cicadomorpha.