Morphology of egg and larva of the lawn cutworm Spodoptera depravata (Butler) (Lepidoptera: Noctuidae)

Abstract

Spodoptera depravata (Butler) is an important lawn pest in northeastern Asian countries, and its larvae mainly target the leaves of Gramineae crops. However, the morphological traits of egg and larva of this species have not been well elucidated. In this study, we examined the external morphology and ultrastructure of egg and larva of S. depravata using light and scanning electron microscopy. The egg is subspherical and covered with abundant female hair silk (modified scales). The upper exochorion sculpture consists of a dense network of irregular contiguous polygonal cells, with 2–3 micropyles at the top. Three types of sensilla were observed on larval antenna and maxilla: sensilla chaetica, sensilla basiconica and sensilla styloconica. The larva, eruciform, bears three pairs of thoracic legs, and five pairs of prolegs on abdominal segment III to VI and X (anal prolegs), respectively. The crochets of prolegs are arranged in uniordinal mesal penellipse, and protected by membranous stripes. Besides, the head and body chaetotaxy of S. depravata were illustrated and described in detail. This study also briefly discussed the application of morphological traits of eggs and larvae to classification and systematic studies on Spodoptera species.