Introduction

The jewel beetle Julodimorpha bakewelli is category challenged (Gwynne and Rentz 1983; Gwynne 2003). For the male of the species, spotting instances of the category “desirable female” is a pursuit of enduring interest and, to this end, he scours his environment for telltale signs of a female's shiny, dimpled, yellow-brown elytra (wing cases). Unfortunately for him, many males of the species Homo sapiens, who sojourn in his habitats within the Dongara area of Western Australia, are attracted by instances of the category “full beer bottle” but not by instances of the category “empty beer bottle,” and are therefore prone to toss their emptied bottles (stubbies) unceremoniously from their cars. As it happens, stubbies are shiny, dimpled, and just the right shade of brown to trigger, in the poor beetle, a category error. Male beetles find stubbies irresistible. Forsaking all normal females, they swarm the stubbies, genitalia everted, and doggedly try to copulate despite repeated glassy rebuffs. Compounding misfortune, ants of the species Iridomyrmex discors capitalize on the beetles' category errors; the ants sequester themselves near stubbies, wait for befuddled beetles, and consume them, genitalia first, as they persist in their amorous advances.

Categories have consequences. Conflating beetle and bottle led male J. bakewelli into mating mistakes that nudged their species to the brink of extinction.