The effects of the sphragis on male and female genitalia in Acraea (Nymphalidae) butterflies

Shannon Summers

Authors:  Shannon Summers, Akito Y. Kawahara, Ana P. S. Carvalho

Faculty Mentor: Akito Y. Kawahara

College:  Florida Museum of Natural History


Mating plugs have been used by males in many species to prevent female re-mating and sperm competition. One of the most extreme versions of mating plugs is the sphragis, which is a large, complex and externalized plug found only in butterflies. This trait is widespread within the genus Acraea (Nymphalidae) and provides an opportunity for investigation into the effects of the sphragis, on the morphology of the genitalia. Our investigation aims to document morphological differences in Acraea genitalia between species that produce or do not produce a sphragis after mating. Using specimens from museum collections, genitalia dissections were conducted on 19 species of Acraea, 9 sphragis bearing and 10 non-sphragis bearing species. Genitalia imaging was performed for easier comparison and analysis and measurements of genitalia structures was done using ImageJ software. We found that there are some distinguishing morphological characters in the females and the most obvious difference is the larger and more externalized copulatory opening. We believe that these differences are due to a sexually antagonistic coevolution between the males and females, where the females evolve externalized genitalia that are more difficult to plug, and the males attempt to prevent re-mating with larger mating plugs like the sphragis.

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12 Responses
  1. I recently got into collecting insects and I found this extremely interesting. Do you have any website or book suggestions on more of the basics of insect mating, because I am interested, this is wild.



  2. Marni Shabash

    This poster was super interesting, great job! What got you interested in studying sexual conflict? Why do you think you did not find any statistical significance in the measurements?

    1. Shannon Summers

      Hi Marni thanks for your questions!
      I got interested in sexual conflict because I’ve always been curious about how different sexes interact with one another and why some traits are more important in mating than others. I think one of the main reasons we didn’t get a statistical significance was my sample size as I only had 9 species for each group.

  3. Marni Shabash

    This poster is super interesting, great job! What got you interested in studying sexual conflict? Why do you think you did not find any statistically significant data with the measurements?

  4. Jordan Moumne


    This is really interesting and something I never would have thought about before today. How did you decide to study this topic?

    1. Shannon Summers

      Hi Jordan,
      Great question! This project started out as a just a volunteer position and somehow evolved into this large research project. I’ve always been interested in evolution and I jumped at the chance to study it at a place like the Florida Museum where there are lots of specimens we can use.

  5. Sara

    Hi Shannon, your research and findings are very interesting! You mention this research could be extended to other specimens, is this type of phenomenon typical in other butterfly or insect species?

    1. Shannon Summers

      Hi Sara,
      That’s a really great question, thank you for asking! Mating plugs in general are a fairly common strategy in butterflies and some other insect species. The sphragis, however, is a very particular type of mating plug that is partially external. These are only found in butterflies, but within butterflies they are found in approximately 270 species across the Papilionidae and Nymphalidae families. This paper talks about the diversity of the sphragis in butterflies if your interested: doi: 10.3897/zookeys.694.13097

  6. Yian Wu

    Hi Shannon! Your work looks so interesting!! So do you have some other specimens that you already have in mind that you want to expand your research?

    Great job!!

    1. Shannon Summers

      Hi Yian,
      I’m actually wrapping up my project and I just got finished writing a manuscript, but one of my mentors works on a very similar project and she will be looking at various other butterfly species in her PhD research.