Ultrastructure of antennal sensilla of Anastatus orientalis (Hymenoptera: Eupelmidae), an egg parasitoid of the invasive spotted lanternfly, Lycorma delicatula (Hemiptera: Fulgoridae)

Abstract

Anastatus orientalis (Hymenoptera: Eupelmidae) is an egg parasitoid of the internationally quarantined pest Lycorma delicatula, and can be used as a potential biological control agent in practice. Antennae are the important olfactory organs that play a key role in host-parasitoid chemical communication. Therefore, recognition of morphological features is crucial for investigating the olfactory behavior mechanism of parasitic wasps. Here, we observed the ultrastructure of sensilla on the antennae in male and female wasps of A. orientalis using scanning electron microscope. Our results revealed that the antennae of A. orientalis are geniculate, with 13 segments in female wasps and 10 segments in males. The average length of female antennae (1761.17 ± 60.77) μm was shorter than that of males (1883.06 ± 95.68) μm. Ten morphological types of antennal sensilla were found on A. orientalis antennae, including sensilla trichodea (ST), sensilla chaetica (SC), sensilla basiconica (SB), i-type sensilla (IS), corneous sensilla (CS), sensilla campaniformia (Ca), sensilla placodea (Pl), lance sensilla (LS), sensilla coeloconica (Co), and böhm bristles (BBs). Among these, ST had two subtypes (ST I and ST II). SC and Pl were the most abundant sensilla on the antennae of A. orientalis, with wide distribution and large number. Sexual dimorphism was observed in the length, width, abundance, and distribution of sensilla on the antennae. IS were unique to female wasps, suggesting their important role in the recognition and acceptance of host eggs.