Journal of Comparative Physiology A

, Volume 174, Issue 5, pp 575–579 | Cite as

Optical releasers of the innate proboscis extension in the hoverfly Eristalis tenax L. (Syrphidae, Diptera)

  • K. Lunau
  • S. Wacht


Freshly emerged, inexperienced imagos of the hoverfly Eristalis tenax L. extend their proboscis towards small, yellow colour stimuli, such as anther parts and artificial floral guides. The releasing of this behaviour, which is adapted to pollen feeding, was investigated in behavioural tests using white, UV-reflecting artificial flowers with four small screens illuminated with test stimuli serving as artificial floral guides. The releasing of the innate proboscis extension was tested using monochromatic test lights. Within an intensity range from approx. 5·1011 to approx. 1014 quanta · cm-2· s-1, the flies extended their proboscis only towards green and yellow test lights (approx. 520–600 nm). The inhibition of the innate proboscis extension was tested using mixed light stimuli composed of a yellow monochromatic reference light (560 nm, 1013 quanta·cm-2-1) and of a monochromatic test light. When the reference light was mixed with ultraviolet or blue test lights, the releasing of the innate proboscis extension was strongly inhibited, whereas admixing green/yellow light slightly promoted it; admixing red light had no effect. The results indicate that the releasing of the innate proboscis extension is mediated by the photoreceptor type R8y. Other receptor types which could cause the inhibition of the proboscis reaction are discussed.

Key words

Proboscis extension Eristalis Wavelength specific behaviour Colour preference Pollen feeding 


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Copyright information

© Springer-Verlag 1994

Authors and Affiliations

  • K. Lunau
    • 1
  • S. Wacht
    • 1
  1. 1.Institut für Zoologie, Universität RegensburgRegensburgGermany

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