Big Weapons Have Little Downside

Rhinoceros beetle

    The male rhinoceros beetles are the beetles of this species that have the huge horns.  These horns are used to gain mates and were believed by biologists to be costly by making them vulnerable in other ways.  Erin McCullough and Douglas Emlen put together an experiment to try to quantify the probably costs in laboratory and wild beetles.  When this experiment was performed, no costs were found.  The beetle's ability to fly, survival, immune response, or growth of other body parts were not affected, if at all, by the horn size. 

    The explanation that the researchers came to was "weapons may evolve along with traits that let males make best use of them, offsetting survival costs".  The only way, therefore, that the beetles' horns became so diverse and elaborate can be explained is by low cost.  I'm not a big fan of bugs but I thought this was a very interesting article that elaborates how certain structures evolve with animals, just like with humans and our tail bones.  If the horn size or the horn in general was a high cost, I'm guessing that the species wouldn't have been able to survive. 

http://doi.org/n34
http://onlinelibrary.wiley.com/doi/10.1111/j.1523-1739.1998.97207.x/abstract;jsessionid=BFC4CDFFA6AB4B4CD002C88CA0BF34E9.f01t01?deniedAccessCustomisedMessage=&userIsAuthenticated=false