Project Noah Moth of the Month: Tau Emperor (Aglia tau)

The Project Noah Moth of the Month for October is the Tau Emperor (Aglia tau), spotted by Project Noah member Daniele Pralong in Switzerland!

A male Tau Emperor (Aglia tau) spotted by Daniele Pralong.

A male Tau Emperor (Aglia tau) spotted by Daniele Pralong.

The Tau Emperor (Aglia tau) has a very interesting adult behavior. The males, with larger feathery antennae as pictured above, fly diurnally, while the females only fly at night. Although this may seem counterintuitive for the purposes of mating, mating actually occurs in the late morning. Females hide during the day, and the males “smell” the pheromone-releasing females with the chemoreceptors located in their antennae. This is ironically very efficient, keeping the females concealed from predators while ensuring the successful males are the most physically fit, chemically receptive individuals of the species.


  • Aglia tau.”
  • Pronin, Georg. “The Mating Time of Lepidoptera.” Journal of the Lepidopterists’ Society. 1964. Volume 18. Number 1.
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4 thoughts on “Project Noah Moth of the Month: Tau Emperor (Aglia tau)”

  1. Scott S Mcmahon says:

    Is the Tau Emperor moth common in North America?

    1. Hi Scott, this species is not found in North America and is native to Europe. There are a few species similar in appearance – especially from the angle this individual was photographed at. The Polyphemus moth (Antheraea polyphemus) is probably the most similar and is widespread and common in much of North America.

  2. Jim Wright says:

    Very cool. Where was it photographed?

    1. Hi Jim!

      This moth was photographed in Switzerland. I’ve updated the post to reflect this information. You can see the “spotting information” here:

      Happy mothing!

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