Title

Microscopic structure and significance of male Japanese Rhinoceros Beetle horns

Presenter Information

Paul Weingarden

Presentation Type

Poster

Abstract

Male Japanese Rhinoceros Beetles (Allomyrina dichotoma) possess remarkable horns on their head and thorax used for prying rival males off females and for more direct male-male competition. While they play a critical role in the life history of these insects, the micro-topography of these horns has remained largely unexplored. Understanding horn structure on a microscopic scale may lead to insights into combat behavior among males. I performed scanning electron microscopy (SEM) on the horns of A. dichotoma in order to understand how the topography changes on different regions of the horn surface. In addition, I analyzed videos of male combat to discover which areas of the horns made contact more frequently during use. These areas were then specifically targeted for SEM. Video analysis showed the importance of the prothorax horn tines in stabilization as a beetle lifts a rival male with the head horn. In addition, it was found that the middle tine valley of the head horn is used to disable movement of the rival’s horn. SEM images revealed particular areas of the horn with greater hair density, as well as three unique types of micro-topography: smooth, stepped & smooth, and stepped & rough. Certain areas of the horns are likely to create more friction than others due to their microscopic structure. Thus, better understanding of these horns on a microscopic scale may provide new insight into why males fight in the matter they do.

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Apr 13th, 11:00 AM Apr 13th, 12:00 PM

Microscopic structure and significance of male Japanese Rhinoceros Beetle horns

UC Ballroom

Male Japanese Rhinoceros Beetles (Allomyrina dichotoma) possess remarkable horns on their head and thorax used for prying rival males off females and for more direct male-male competition. While they play a critical role in the life history of these insects, the micro-topography of these horns has remained largely unexplored. Understanding horn structure on a microscopic scale may lead to insights into combat behavior among males. I performed scanning electron microscopy (SEM) on the horns of A. dichotoma in order to understand how the topography changes on different regions of the horn surface. In addition, I analyzed videos of male combat to discover which areas of the horns made contact more frequently during use. These areas were then specifically targeted for SEM. Video analysis showed the importance of the prothorax horn tines in stabilization as a beetle lifts a rival male with the head horn. In addition, it was found that the middle tine valley of the head horn is used to disable movement of the rival’s horn. SEM images revealed particular areas of the horn with greater hair density, as well as three unique types of micro-topography: smooth, stepped & smooth, and stepped & rough. Certain areas of the horns are likely to create more friction than others due to their microscopic structure. Thus, better understanding of these horns on a microscopic scale may provide new insight into why males fight in the matter they do.