Experimental Scheme for Observation of Lepidopteran Larval Morphology Utilizing Anaesthetization in Water

Abstract

Experimental methods to observe the morphology of lepidopteran larvae anaesthetized in water were developed. Lepidopteran larvae are stabilized by an immersion in water which induces hypoxia. Sixth-instar larvae of the rice armyworm, Pseudaletia separata, were anaesthetized in water in order to facilitate observation of their external

morphology. Larval external morphology was then easily observed in detail with a stereomicroscope while anaesthetization in water. Anaesthetization up to 1 hour at 20°C resulted in no noticeable ill effect on the larvae. Larvae treated this way have developed into adult moth by a continuous rearing following the anaesthetization. By using water cooled at 4°C, the duration of anaesthetization without any ill effect on the larvae was prolonged at least to 6 hours. Anaesthetizing treatment in water is suggested as a means of the observation of lepidopteran larval external morphology in science education.