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External sexual characters of larvae of Spodoptera littorails (Boisduval) and S. exempta (Walker) (Lepidoptera: Noctuidae) and their use for sexing live larvae

Published online by Cambridge University Press:  10 July 2009

Linda C. Haines
Linda C. Haines
Affiliation:
Centre for Overseas Pest Research, College House, Wrights Lane, London W8 5SJ, UK
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Abstract

External sexual characters are described for the larvae of Spodoptera littoralis (Boisd) and S. exempta (Wlk.). The characters on the female consist of two pairs of pits on the ventral surface of the eighth and ninth abdominal segments. These pits are visible under a light microscope and can therefore be used for the accurate sexing of live larvae from the third instar onwards. The first- and second-instar larvae of both species could not be sexed using external characters because of their small size. In the males of both species, there are no obvious external sexual characters until the last instar, and therefore the sexes are most easily separated by the presence or absence of the female characters. Third- to sixth-instar larvae of both species were examined for the presence or absence of the female pits and were then sexed by dissection. The accuracy of sexing using the external characters was 90–98% for S. littoralis and 100% in all cases for S. exempta. The histology of the female pits and their appearance under the scanning electron microscope is described. These pits in the female larvae give rise to the external openings of the adult reproductive system.

Type
Original Articles
Information
Bulletin of Entomological Research , Volume 72 , Issue 3 , September 1982 , pp. 403 - 408
Copyright
Copyright © Cambridge University Press 1982

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