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United States Department of Agriculture

Agricultural Research Service


item Schaefer, Paul
item Taylor, Philip

Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/2006
Publication Date: 7/20/2006
Citation: Schaefer, P.W., Taylor, P.B. 2006. Ultrastructure of female external translucent pits useful in sexing gypsy moth (Lepidoptera: Lymantriidae) caterpillars. Journal of Entomological Science. p.266-270.

Interpretive Summary: When rearing any insect, there are various occasions when one wishes to know the sex of an individual. In our work with the gypsy moth (GM), the question of sex determination in immature individuals has been important to know at various times. Generally, rearing to pupae, where genital pores are easily distinguishable, has been the method for identification. In the past, procedures for sexing larvae of moths and butterflies have been somewhat invasive through tissue sample, staining, or identifiable spots or characters on caterpillars under close examination. Guided by some of these previous descriptions, we have developed a method for handling active larvae, identified and described external distinguishing characters of GM larvae, tested the accuracy of such criteria to sex larvae, and provided electron microscopy images to enhance the detail of these structures. Researchers, when studying population dynamics in the field, as it relates to sex ratios, can use this method without killing or altering immature specimens

Technical Abstract: Distinguishing the presence of “translucent pits” on the ventral sternites of the 8th and 9th abdominal segments in gypsy moth, Lymantria dispar, caterpillars identified female from male caterpillars when viewed under a dissecting microscope. Ultrastructural details of the translucent pits were revealed by scanning electron microscopy and suggest a canal or opening. The most difficult aspect of the technique was holding the squirming caterpillar ventral surface uppermost between two standard microscope slides in the form of a “viewing sandwich”. Our trials showed greater than 99% accuracy in sexing 3rd instar or later gypsy moth caterpillars.

Last Modified: 06/24/2017
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