Sexing Bess Beetles (Odontotaenius disjunctus)

[Bill Myers]

I have two Bess Beetles. One, I've had for over a year and a half. The other one, I found in June of this year (2013). They seem to enjoy each others company.

The newer Bess Beetle is a lot smaller than the older beetle. So, at first, I was thinking they might be of opposite sexes. However, I haven't observed any mating or eggs being laid. Therefore, I am assuming they are of the same gender.

That being said, I was just curious as to if anyone could clue me in to how I can accurately determine the sex of my Bess Beetles without having to dissect them or put them under any undue stress?

 

[Lucanus]

I'm not 100% positive about this but the horn shape might be a key to sexing this species.

When you look at the cephalic horn on the bess beetle, you'll see ones with large horns and ones with small horns.

My speculation is that the ones with big horns are the males and the ones with small horns are females.

 

[Bill Myers]

I'm not 100% positive about this but the horn shape might be a key to sexing this species.

When you look at the cephalic horn on the bess beetle, you'll see ones with large horns and ones with small horns.

My speculation is that the ones with big horns are the males and the ones with small horns are females.

Okay, that's a major clue!

So, I started searching the net for those key words about the horns and found this!:

http://www.insectscience.org/13.107/i1536-2442-13-107.pdf

According to their research, it is the FEMALE that has the larger horn. Also, the females have a wider pronotum. The difference between the males and females isn't much, but if I pull out my digital calipers, that should help me out, a lot!

Thanks for pointing me in the right direction!

Cheers