Comparative Morphology Study Of The Antennae And Mouthparts In The Deltocephalinae

Deltocephalinae is the largest subfamily in the Cicadellidae,including 39 tribes,926 genera,and around 6700 valid species that are widely distributed around the world.Many deltocephaline species are important agricultural pests.At present,relatively few studies have been conducted on the morphology of antennae and mouthparts of Deltocephalinae.Therefore,the morphology of antennae and mouthparts in 14 deltocephaline species including Chiasmini: Aconurella prolixa,Aconurella montana,Aconurella sibirica,Exitianus nanus,Nephotettix cincticeps,Deltocephalini: Alobaldia tobae,Graminella nigrinota,Maiestas dorsalis,Maiestas latifrons,Maiestas maculata,Goniagnathini: Goniagnathus punctifer,Platymetopiini:Phlogotettix cyclops,Stenometopiini: Stirellus indrus and Stirellus yeongnamensis were compared and observed using scanning electron microscopy.The morphological differences were compared and analyzed for the purpose of providing reference for the systematic research of Deltocephalinae.The results are as follows:The antenna of Deltocephalinae is bristle-like,and consists of scape,pedicel and flagellum.The female antenna is slightly longer than that of males.The scape and pedicel are short and wide,the type and number of sensilla distributed on the scape are the smallest.Two pairs of sensilla trichodea(St I)are distributed at the base of the antennal scape.Also there are numerous squamiformia denticles and brochosomes on the surface,the squamiformia denticles of Nephotettix cincticeps is more triangular than other species,and a pore is found on the surface.There are several wrinkles on the surface of joint between the pedicel and the end of scape,squamiformia denticles and brochosomes are similar to the surface of the scape,there are more types and number of sensilla distributed on it than on the scape,a single sensilla trichodea(St I)is distributed at the base of antennal pedicel,and a pore was found on the surface of Alobaldia tobae and Maiestas latifrons.The flagellum is relatively slender and consists of many subnodes,squamiformia denticles and brochosomes are attached to the base,the largest number and type of sensilla distributed in the first few subnodes of the flagellum,and there are no sensilla on remaining subnodes.In addition,the sensilla distributed on Goniagnathus punctifer were initially inferred as a variation of sensilla basiconica(Sb II)based on their positions,it is the first time that it has been discovered in the antennal research of Deltocephalinae.Five types of sensilla were recorded on leafhoppers antennae,including sensilla trichodea,sensilla chaetica,sensilla basiconica,sensilla coelocomica and sensilla campaniformia,and each sensilla type has multiple subtypes.The mouthparts of Deltocephalinae resemble those of other piercing-sucking insect pests,having labrum,labium and a stylet fascicle.The labrum is triangular and is located above the deep groove on the ventral surface of labium.The labium is long and cylindrical,divided into three sections,and different types of sensilla are distributed on the surface,partly distributed symmetrically on both sides of the deep groove,and partly born on the end of labium.The stylet fascicle is needle-like,the most obvious feature of the mandibular stylets is that the ends are sculptured,the inner edge has two rows of tooth-like projections and there are serrate ridges on the outside.The maxillary stylets outer surfaces are smooth and unmarked,and the tips are sharp and curved,the two maxillary stylets are tightly interlocked to form a hollow food canal and a salivary canal,the diameter of food canal is greater than the diameter of salivary canal.The labrum length varies between different species,the length of females is slightly longer than that of males.Among them,Goniagnathus punctifer is significantly longer than other species.There are different shapes of cuticular processes on the labrum surface.Among them,Aconurella prolixa,Aconurella montana,Aconurella sibirica,and Goniagnathus punctifer have smoother surfaces and only a few irregular cuticular processes.Nephotettix cincticeps has a smooth surface without cuticular processes,with a few triangular cuticular processes distributed on the end sections.Alobaldia tobae,Maiestas dorsalis,Maiestas latifrons,Maiestas maculata,Phlogotettix cyclops and Stirellus indrus have sharper triangular cuticles processes on the surface.The cuticular processes distributed on the surface of Exitianus nanus,Graminella nigrinota and Stirellus yeongnamensis are similar to squamiformia denticles and relatively flat.In addition,sensilla trichodea(St I)are also distributed on the labrum surface of Stirellus indrus,which is the first research discovery in the mouthparts of Deltocephalinae.The labium length varies between different species,the length of females is slightly longer than that of males.And the labium length of Goniagnathus punctifer is significantly longer than that of other species.Moreover,there is a certain interspecies difference in length of the three labium segments.A large number of different types of sensilla are distributed on both sides of the deep labial groove on the ventral surface of the labium,while fewer sensilla are present on the dorsal surface and sides.The sensilla is distributed on the three labial segments with the third segment being the most,the second segment being the second average,and the first segment being the least.There are three types of sensilla located on the surface of labium,including sensilla trichodea and sensilla basiconica.Also there are multiple subtypes of sensilla trichodea and sensilla basiconica.Among them,the number of sensilla trichodea(St I)is the most.Sensilla trichodea(St III)are only scattered on the dorsal surface of the labium of Stirellus indrus,this is the first discovery in study of the mouthparts of Deltocephalinae.Sensilla basiconica(Sb II)was not found on the labium surface of Goniagnathus punctifer,and sensilla coelocomica was not present on the labium surface of Exitianus nanus and Goniagnathus punctifer.The stylet fascicle is wrapped in the labium and is composed of two mandibular stylets and two maxillary stylets.The mandibular stylets are located on both sides of the maxillary stylets and shorter in length than the maxillary stylets.The length of stylet fascicle varies between different species,the stylet fascicle length in females is slightly longer than that of males,and the length stylet fascicle in Goniagnathus punctifer is significantly longer than other species.A comparative study of the antenna and mouthpart morphology of 14 leafhopper species revealed that there was no significant difference between males and females.The sensilla types,numbers,and distribution positions vary between different species.Among them,the variation between different genera is small,and the great variation exists between different tribes.This study provides morphological data for the study of behavioral biology,chemical ecology,and electrophysiology of the subfamily Deltocephalinae,and provides a reference for the morphological and systematic studies of the family Cicadellidae,and provides services for pest control of this group.