An Introduction to the Dytiscidae: Their Diversity, Historical Importance, Cultural Significance, and Other Musings

Abstract

Predaceous diving beetles (Family Dytiscidae) are one of the most fearsome predators in freshwater environments, however most of their biology and ecology remains to be measured. The Dytiscidae exhibit a complex life cycle with both adults and larvae using a variety of aquatic habitats for feeding, reproduction, and intra- and interspecific interactions. Adults are vagile and capable of dispersal across great distances, making them an important component of the terrestrial environment and potentially important for linking various habitats via the movement of energy and materials. Both larvae and adults are predaceous, and the former often possess large curved hollow mandibles that are capable of dispatching large prey, including vertebrates. As predators, they exhibit different hunting behaviors and a full repertoire of chemicals used for defense and communication. Adult dytiscids also display one of the most complex and fascinating examples of sexual selection, with both pre- and post-copulatory mating choice dispersed among different phylogenetic branches of the family. Although the systematics of dytiscids has been of interest for decades, phylogenies are now becoming clearer, allowing us to better understand their dynamic and interesting evolutionary history. These beetles also can instruct us on bigger concepts, like the current focus on conservation both of species and of the habitats that harbor them; to this dytiscids make a good case study. Although often overlooked in the scientific literature compared to other aquatic insect groups, their importance in human culture, both past and present, is compelling and worthy of note. With all this, perhaps the most intriguing thing about dytiscids is that we know so little about them.

I am surprised what an indelible impression many of the beetles which I caught at Cambridge have left on my mind.

(Charles Darwin 1887)