Comparative Morphology Of The Antennal Sensilla In Tachinidae (Insect:Diptera)

The Tachinidae is one of the most diverse Diptera clades,and is known parasitize a wide range of insects including Lepidoptera,Hymenoptera and Coleoptera.The co-evolution between the tachinid species and their hosts in ecology and behavior is ubiquity.Antennal sensilla play an important role in fly's sensory system,and their morphology and different types are closely related to ecological habits of flies.The comparative morphological research could provide valid information for the morphological definition and adaptive evolution of the antennal sensilla in the Tachinidae.Thirteen species from four subfamilies within the Tachinidae were selected for ultrastructure observation using light microscopy and scanning electron microscopy.A total of nine types of antennal sensilla were found.By comparing with other species in the Oestroidea,the morphological definition of antennal sensilla of the tachinid species involved in this research were summarized:(1)The plaque on antennal pedicel is a seta,which occurs directly on the pedicellar surface or on the smooth elevated socket.(2)Trichoid sensilla,basiconic sensilla and clavate sensilla,which located on the antennal funiculus,are easily confused.Some key morphological characteristics,such as shape and length,could be used to classify and define these sensilla.Several adaptive morphological characteristics related to the host orientation of the Tachinidae were discussed:(1)The elongated pedicel or funiculus and the branched or porous funicular sensilla could extending the attachment area or surface area of the sensilla,which is conducive to improving the sensitivity of the antennae to odour molecules.(2)The abundant sensory concavities and the centrally distributed sensilla on the funiculus are helpful for antennae to capture odour molecules.(3)The presence of pores on pedicellar button and its sexual dimorphism,the existence of the plaque-like sensilla on the pedicel and the distribution of the mechaoreceptor on the funiculus and arista all reflect the richness and morphological diversity of antennal sensilla in the Tachinidae.