Structure and Sensilla of the Mouthparts of the Spotted Lanternfly Lycorma delicatula (Hemiptera: Fulgoromorpha: Fulgoridae), a Polyphagous Invasive Planthopper.

Yanan Hao,Christopher H Dietrich,Wu Dai,Alex Córdoba-Aguilar

doi:10.1371/journal.pone.0156640

Abstract

Mouthparts are among the most important sensory and feeding structures in insects and comparative morphological study may help explain differences in feeding behavior and diet breadth among species. The spotted lanternfly Lycorma delicatula (White) (Hemiptera: Fulgoromorpha: Fulgoridae) is a polyphagous agricultural pest originating in China, recently established and becoming widespread in Korea, and more recently introduced into eastern North America. It causes severe economic damage by sucking phloem sap and the sugary excrement produced by nymphs and adults serves as a medium for sooty mold. To facilitate future study of feeding mechanisms in this insect, the fine-structural morphology of mouthparts focusing on the distribution of sensilla located on the labium in adult L. delicatula was observed using a scanning electron microscope. The mouthparts consist of a small cone-shaped labrum, a tubular labium and a stylet fascicle consisting of two inner interlocked maxillary stylets partially surrounded by two shorter mandibular stylets similar to those found in other hemipteran insects. The five-segmented labium is unusual (most other Fulgoromorpha have four segments) and is provided with several types of sensilla and cuticular processes situated on the apex of its distal labial segment. In general, nine types of sensilla were found on the mouthparts. Six types of sensilla and four types of cuticular processes are present on sensory fields of the labial apex. The proposed taxonomic and functional significance of the sensilla are discussed. Morphological similarities in the interlocking mechanism of the stylets suggest a relationship between Fulgoromorpha and Heteroptera.

Highlights

Hemiptera, a very large and diverse insect order, are united by their specialized piercing-sucking mouthparts that are highly modified for piercing host tissues and extracting their fluid contents
Previous studies on mouthparts in Fulgoromorpha, which were conducted by scanning electron microscope (SEM) and transmission electron microscope (TEM), have mostly focused upon one aspect such as labial sensilla [1,2,21,22,23,24,25], the interlocking mechanism of maxillae and mandibles [16,17], or gross morphology [10,26], except for a recent study of the delphacid, Sogatella furcifera which provided a comprehensive description of the morphology of mouthparts [27]
As in other members of Auchenorrhyncha, the mouthparts of Lycorma delicatula arise from the posteroventral part of the head capsule (Hc) (Figs 1 and 2A) and consist of a small coneshaped labrum (Lm) (Fig 2D) and a tubular labium (Lb) (Fig 2B) with a deep longitudinal labial groove (Lg) on the dorsal surface that houses the stylet fascicle (Sf) (Fig 2B)

Summary

Introduction

A very large and diverse insect order, are united by their specialized piercing-sucking mouthparts that are highly modified for piercing host tissues and extracting their fluid contents. Abundant data are available on some aspects of mouthpart morphology of Hemiptera based on light and scanning electron microscopy but detailed studies including scanning electron micrographs have been published only for a few species [3,4,5,6,7,8,9,10,11,12,13,14,15]. Available data indicate that details of mouthpart morphology, including shape, segmentation and fine structure, vary considerably among hemipteran species and higher taxa and that such differences may be used to distinguish taxa [15,16,17,18,19], provide insight into feeding mechanisms and contribute to assessment of phylogenetic relationships [20]. More detailed and comparative studies of other economically important planthopper species are needed to support research on feeding mechanisms

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