QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by SCHIMIDT, J. M. Articles by SMITH, J.J. B. Search for Related Content PubMed Articles by SCHIMIDT, J. M. Articles by SMITH, J.J. B.

Journal of Experimental Biology 129,151-164 (1987)
Published by Company of Biologists 1987

Measurement of Host Curvature by The Parasitoid Wasp Trichogramma Minutum, and Its Effect on Host Examination and Progeny Allocation

J. M. SCHIMIDT ¹ and J.J. B. SMITH ¹

¹ Department of Zoology, University of Toronto, Toronto, Ontario, Canada M5S IAI

The parasitoid wasp Trichogramma minutum Riley (Hymenoptera: Chalcidoidea: Trichogrammatidae) adjusts its progeny allocation and host examining behaviour to the exposed volume of its host -- an insect egg. The female wasp examines a potential host by walking over its surface while drumming its antennae against it, spending a longer time examining larger hosts. If wasps of different sizes are presented with glass beads of the same diameter, examining time increases significantly the larger the bead is relative to the wasp. Since the wasps' velocities do not differ with wasp size, the total distance travelled during host examination also increases with relative host diameter.

When large and small wasps are placed on large and small hosts such that the relative curvature is constant, examining time and total path length are the same. Smaller wasps take more steps to travel the same distance, therefore the duration of the examination walk, rather than step number or relative distance, is adjusted to host curvature. This adjustment of examination time may ensure that the surface of hosts of different sizes are examined adequately, despite differences in total area.

Progeny allocation, usually dependent only on exposed host surface area, can be affected by the wasps' measure of curvature. When hosts are mounted on the tips of thin wires rather than on the substrate, no finite cues dependent on surface area are available to the wasps. Such hosts receive only 25% more progeny, either in the light or in total darkness, than hosts which are resting on the substrate, demonstrating that an upper limit to clutch size is set by cues dependent on curvature. The structure of the compound eyes suggests that the visual acuity of Trichogramma is insufficient to account for their ability to discriminate between small differences in host curvature. By placing large and small wasps on point-mounted hosts of fixed diameter, we show that the clutch size limit is set according to the relative size of the host.

These observations are discussed in terms of a mechanosensory mechanism of curvature measurement.

Key words: Trichogramma, parasitoid, oviposition, host examination, host measurement, compound eye

Accepted on December 15, 1986

This article has been cited by other articles:

				J. M. SCHMIDT and J. J. B. SMITH Short Interval Time Measurement by a Parasitoid Wasp Science, August 21, 1987; 237(4817): 903 - 905. [Abstract] [PDF]