What's That Bug? does not endorse extermination

Subject: large moth, approx. 2 inch wing span
Location: Northeast Pennsylvania
June 25, 2016 7:00 pm
found this on our slider, my husband knocked it off and it revealed inside wings..very pretty. We live in Effort, PA, Monroe County and it is summer time..June 25, 2016. Thinking it might be an Imperial moth, would appreciate further identification. After it was still, not moving, on the deck for a while, it moved to the bottom of the slider, then it’s wings started fluttering and then it took off.
Signature: Christine

Male Io Moth

Male Io Moth

Dear Christine,
This is a male Io Moth and your images nicely illustrate its protective mimicry.  Many Giant Silkmoths in the family Saturniidae, including your Io Moth, and some Sphinx Moths in the family Sphingidae have evolved an excellent survival strategy.  Markings on the underwings resemble eyespots and are known as ocelli.  When the moth is resting, the upper wings cover the underwings.  When disturbed, the moth reveals its underwings, flashing its eyes, potentially startling a predator like a bird into thinking it has awakened a sleeping giant.  Io Moths have also evolved to exhibit sexual dimorphism, meaning the two sexes have obvious visible differences.  Female Io Moths have brown upper wings.

Male Io Moth

Male Io Moth

Thank you very much for the information Daniel!

What's That Bug? does not endorse extermination
Location: Effort, Pennsylvania

2 Responses to Male Io Moth Illustrates protective Mimicry

  1. Austin says:

    ‘Eyespot’ can either refer to the primitive invertebrate eyes found on many insects, or to the eye-like markings used for mimicry. ‘Ocelli’ (sing. ocellus) on the other hand, refers specifically to the primitive insect eye, not to the eyes used for mimicry on some insects. It is an easy mistake to make.

    • bugman says:

      We are going to disagree with your take on the etymology. We are basing our use of the term Ocellus from the BugGuide definition where it states, as an alternate to the simple eye you mention: “An eye-like spot of color, consisting of annuli of different colors, enclosing a central spot or pupil, as present on the wings of some lepidoptera. Photos of the eye-spot type of ocelli.” The term Eyespot, on the other hand, does NOT refer to the simple eyes. According to our understanding, Ocellus can be either but Eyespot refers only to the marking that does not have vision.

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