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Abstract

The parasitoid tachinid Xy Homotrixa alleni
detects its hosts by their acoustic signals. The tympanal
organ of the Xy is located at the prothorax and contains
scolopidial sensory units of diVerent size and orientation.
The tympanal membrane vibrates in the frequency
range of approximately 4–35 kHz, which is also
reXected in the hearing threshold measured at the neck
connective. The auditory organ is not tuned to the
peak frequency (5 kHz) of the main host, the bush
cricket Sciarasaga quadrata. Auditory aVerents project
in the three thoracic neuromeres. Most of the ascending
interneurons branch in all thoracic neuromeres and
terminate in the deutocerebrum of the brain. The
interneurons do not diVer considerably in frequency
tuning, but in their sensitivity with lowest thresholds
around 30 dB SPL. Suprathreshold responses of most
neurons depend on frequency and intensity, indicating
inhibitory inXuence at higher intensities. Some neurons
respond particularly well at low frequency sounds
(around 5 kHz) and high intensities (80–90 dB SPL),
and thus may be involved in detection of the primary
host, S. quadrata. The auditory system of H. alleni contains
auditory interneurons reacting in a wide range of
temporal patterns from strictly phasic to tonic and with
clear diVerences in frequency responses.

Item Type:	Article
Authors/Creators:	Stumpner, A and Allen, GR and Lakes-Harlan, R
Keywords:	Auditory system · Host detection · Interneurons · Temporal pattern · Sensory adaptation
Journal or Publication Title:	Journal of Comparative Physiology A
Publisher:	Springer-Verlag
ISSN:	0340-7594
DOI / ID Number:	https://doi.org/10.1007/s00359-006-0174-x
Additional Information:	The original publication is available at www.springerlink.com
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