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EFFECTS OF MOISTURE, GRAVITY, AND LIGHT ON THE BEHAVIOR OF LARVAE OF THE WHEAT STEM SAWFLY, CEPHUS CINCTUS (HYMENOPTERA: CEPHIDAE)

Published online by Cambridge University Press:  31 May 2012

N. D. Holmes
N. D. Holmes
Affiliation:
Research Station, Canada Department of Agriculture, Lethbridge, Alberta
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Abstract

Until mid- or late July, most larvae of the wheat stem sawfly generally move into the upper internodes of the host stems. Then, as the stems mature, the larvae migrate down to the basal internodes and cut the stems at about ground level.

The migration is initiated in response to the visible and infrared light transmitted through the ripening stems. The direction of the migration, toward the basal internodes, results from the orientation of the larvae to the vertical axis of the stems reinforced by a positive larval response to gravity.

The larvae cut the stems at ground level because they are shielded there by the soil from visible and infrared radiation. The location of cutting is also influenced by the preference of the larvae for drier sites in which to cut.

The date of cutting is directly related to the loss of moisture from the stems, but not to a precise level of stem moisture. The larvae may form their cocoons in response to desiccation.

Type
Articles
Information
The Canadian Entomologist , Volume 107 , Issue 4 , April 1975 , pp. 391 - 401
Copyright
Copyright © Entomological Society of Canada 1975

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References

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