在秘鲁雨林的深处，一种蜣螂将自己的身份从清道夫变成了杀手。与成千上万的同胞兄弟不一样，这种小虫子竟然不爱吃臭烘烘的粪便，而是会将千足虫撕成两段，并以它们的内脏为食。在动物王国中，这种食性上的戏剧性变化极为罕见，从而使其成为生物进化的一个完美例证。
当蜣螂对动物的粪便大快朵颐时，它们实际上是在寻找构成这些排泄物的大量细菌。不管你相不相信，这是一种竞争激烈的生活方式，在某些地方，80种蜣螂会为了同样的粪便而大打出手。美国普林斯顿大学的生态学家Trond Larsen认为，这或许就是迫使某一种蜣螂（Deltochilum valgum）与过去的最爱说再见的真正原因。
出于对生活在秘鲁雨林中的许多种蜣螂的食性的兴趣，Larsen和他的同事用粪便、腐肉、水果和菌类做诱饵。研究人员同时还用活的千足虫吸引蜣螂，这是因为Larsen之前曾经看到过一些蜣螂以千足虫的尸体为食。经过11个月，研究小组记录了132种蜣螂以及超过10万只个体的食性。他们发现，Deltochilum valgum是唯一以千足虫为食的蜣螂。研究人员在最近的《生物学快报》网络版上报告了这一研究成果。
更让研究人员吃惊的是Deltochilum valgum攻击千足虫的方式。利用红外摄像机，Larsen观察到一只8毫米长的Deltochilum valgum会将自己生有锯齿的头部楔入千足虫的体节中，直至最终将猎物的身体撕裂为两段。随后，这种蜣螂便会肢解千足虫的剩余部分并分而食之。Larsen解释说，Deltochilum valgum之所以能够杀死体长是自身13倍的千足虫，完全是因为体型微妙变化的结果，包括其楔形的头部以及适于抓住千足虫并将其撕碎的后腿。
Larsen指出，这些改变为捕食性蜣螂新种的迅速暴发创造了可能性。事实上，在他的发现公布之后，Larsen又观察到几个以千足虫为食的Deltochilum亚种。
美国布卢明顿市印第安纳大学的生物学家Armin Moczek认为，这真是一个“相当引人入胜的发现”。但是Moczek指出，千足虫体内具有很高比例的粪便，这是因为它们以腐烂的植物为食。因此他推测，如果这种蜣螂以千足虫的内脏为食，那么它们实际上还是在吃粪便。（生物谷Bioon.com）
生物谷推荐原始出处：
Biology Letters DOI：10.1098/rsbl.2008.0654
From coprophagy to predation: a dung beetle that kills millipedes
Trond H. Larsen1, Alejandro Lopera2, Adrian Forsyth3, Fran?ois Génier4
1Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA
2Department of Biology, University of New Orleans, New Orleans, LA 70148, USA
3 Blue Moon Fund, Charlottesville, VA 22902, USA
4 401-60 Rue du Minervois, Gatineau, Québec, Canada J9H 7M1
The dung beetle subfamily Scarabaeinae is a cosmopolitan group of insects that feed primarily on dung. We describe the first case of an obligate predatory dung beetle and contrast its behaviour and morphology with those of its coprophagous sympatric congeners. Deltochilum valgum Burmeister killed and consumed millipedes in lowland rainforest in Peru. Ancestral ball-rolling behaviour shared by other canthonine species is abandoned, and the head, hind tibiae and pygidium of D. valgum are modified for novel functions during millipede predation. Millipedes were killed by disarticulation, often through decapitation, using the clypeus as a lever. Beetles killed millipedes much larger than themselves. In pitfall traps, D. valgum was attracted exclusively to millipedes, and preferred injured over uninjured millipedes. Morphological similarities placing D. valgum in the same subgenus with non-predatory dung-feeding species suggest a major and potentially rapid behavioural shift from coprophagy to predation. Ecological transitions enabling the exploitation of dramatically atypical niches, which may be more likely to occur when competition is intense, may help explain the evolution of novel ecological guilds and the diversification of exceptionally species-rich groups such as insects.
