A new type of ant-decapitation in the Phoridae (Insecta: Diptera)

The genus Dohrniphora is a hyperdiverse group of phorid flies, a family whose species are commonly characterized as generalized scavengers. The lifestyle of most species of Dohrniphora is unknown, although one cosmopolitan, synanthropic species, D. cornuta (Bigot) fits the general scavenger mold. Here we show that flies of the D. longirostrata species group exhibit highly specific “headhunting” behavior in which injured Odontomachus ants are decapitated, the heads dragged away, and females either feed on their contents or lay an egg nearby. Since most females studied lacked eggs in their ovaries, we conclude that this bizarrely specialized feeding is necessary to provide nutrients for reproduction in these flies. Our study provides further evidence that injured ants are a common, stable resource in tropical ecosystems that support a wide array of phorid flies. Such narrowly constrained lifestyles, as exemplified by exclusively feeding on and breeding in the head contents of certain ponerine worker ants, could allow the co-existence of a huge community of saprophagous flies.