…these would be the beetles of choice.
showing size and horn variation among males.
Dung beetles in the widespread genus Onthophagus sport a bewildering array of horns. Not only do the horns of different species vary in shape, size, and the body part from which they grow, many species show a marked dimorphism within the males.
Consider these two male morphs of O. nigriventris, an African species:
The big guy on the right is a major male, and he does pretty much what you’d expect. He bullies his way around with shows of bravado, guarding his burrows with impressive weaponry and beating up on lesser males in hope of monopolizing the females. The lesser-endowed guy on the left is a minor male, and as you might guess he’s not much of a fighter. He is small, agile, and sneaky, gaining access to females on the sly. Indeed, he even looks a lot like a female, perhaps enough to fool the brutes.
As it turns out, the two morphs are developmental variants. Large male larvae have the resources to grow the massive horn and metamorphose into effective fighters. Small male larvae don’t gain anything by growing the horn, as they’re destined to lose out in any confrontations with other males. So at a particular point in development they shunt their limited resources into testes instead of horns.
And the female herself? Here she is!
The fantastic variation within and among Onthophagus species have made the genus a biologist’s playground. These dung beetles are an exemplary system where behavior, ecology, development, and phylogeny can be integrated to form a comprehensive picture of the evolution of novel traits. I can’t cover all the research here, but instead I’ll point you in the direction of dung beetle gurus Doug Emlen and Armin Moczek(*).
Another shot of the O. nigriventris major male:
Here’s O. gazella, an African beetle that’s been introduced worldwide to help manage cattle dung:
Finally, another O. taurus male. Go Longhorns!
(*)my thanks to secret sources deep within the Moczek lab who arranged the O. nigriventris and O. taurus for a photo shoot last weekend.
The images with the plain backdrop were done in a white box.
What’s a white box? Exactly what it sounds like: a large cardboard box colored white on the inside. It’s a mini-studio for insects. When I fire a strobe inside the box, the box flashes with a lovely diffuse white. It gives enough light for a good fast exposure but without the glare of a point-source. Perfect for capturing the intricate sculpture of a beetle’s integument.