加拿大麦克马斯特大学(McMaster University)生物学家大卫·罗洛(David Rollo)在研究蟑螂上午社会行为时发现了这种奇怪现象。他发现，蟑螂在找到处所的时候（比如像厨房的碗橱），会散发出一种化学信号，来吸引它的同类。为了查明这种化学物质的具体成份，罗洛和他的团队就将死亡的蟑螂身体捣碎，然后把它们的体液撒播在一些事先找好的地方。

罗洛表示：“我们惊奇的发现，蟑螂在爬行的时候，会避开这些撒播了死蟑螂提取物的地方。于是，我们就想查出，到底是什么物质让它们要避开这些地方。”

不过，要想最终查明这种物质，必须查证其它虫子是否会在死亡后散发出驱赶同类的味道。大卫·罗洛和其同事经过试验发现，不仅仅是蟑螂，在蚂蚁、毛虫、树虱以及潮虫身上，都存在此类现象。尽管，从分类上来说，这些动物都属于甲壳类动物，而不是昆虫，但是从功能上来讲，他们散发出酸性脂肪类混合物是一样的。

虽然早在4亿年前，昆虫和甲壳类动物就开始分属于不同物种，但是研究人员认为，它们死后散发出酸性脂肪类混合物这种现象是普遍存在，而且从功能上来讲是一样，主要表示一种警告信号。罗洛在公布研究报告的时候就表示：“确认同类死亡后，并且避免和它们靠近，能够减少感染疾病的几率。而且，这种方法也能让动物激活自身免疫能力。”

科学家希望能够将死亡后昆虫的这种气味混合物提炼出来，并且通过这种方法来保护农作物免受害虫侵害。比如说，在原木上涂上酸性脂肪类混合物，能够让其在一个月内不会受到木蠹蛾的侵害。

不过，幸运的是，人类的鼻子还无法辨别出这种酸性脂肪类提取物。罗洛在一份电子邮件当中称：“腐烂的尸体散发出的气味在远处是无法闻到的。我试着将这种气味的提取物涂到纸上，但我并没有闻到有刺激性的味道，并且我也不排斥这种气味。”

研究人员已经把这项科学成果发表在今年9月刊的Evolutionary Biology上。

原始出处：

Evolutionary Biology DOI:10.1007/s11692-009-9069-4

The Ancient Chemistry of Avoiding Risks of Predation and Disease

M. Yao1, J. Rosenfeld2, S. Attridge1, S. Sidhu1, V. Aksenov1 and C. D. Rollo1

(1) Department of Biology, McMaster University, 1280 Main St. W, Hamilton, Ontario, L8S 4K1, Canada
(2) Department of Pathology and Molecular Medicine, McMaster University, 1280 Main St. W, Hamilton, Ontario, L8S 4K1, Canada

Abstract  Illness, death, and costs of immunity and injury strongly select for avoidance of predators or contagion. Ants, cockroaches, and collembola recognize their dead using unsaturated fatty acids (e.g., oleic or linoleic acid) as “necromone” cues. Ants, bees, and termites remove dead from their nests (necrophoric behavior) whereas semi-social species seal off corpses or simply avoid their dead or injured (necrophobic behavior). Alarm and avoidance responses to exudates from injured conspecifics are widespread. This involves diverse pheromones, complex chemistry and learning. We hypothesized that necromones are a phylogenetically ancient class of related signals and predicted that terrestrial Isopoda (that strongly aggregate and lack known dispersants) would avoid body fluids and corpses using fatty acid “necromones.” Isopods were repelled by crushed conspecifics (blood), intact corpses, and alcohol extracts of bodies. As predicted, the repellent fraction contained oleic and linoleic acids and authentic standards repelled several isopod species. We further predicted a priori that social caterpillars (lacking known dispersants) would be repelled by their own body fluids and unsaturated fatty acids. Both tent caterpillars and fall webworms avoided branches treated with conspecific body fluid. Oleic and linoleic acids were also strongly avoided by both species. Necromone signaling appears widespread and likely traces to aquatic ancestors pre-dating the divergence of the Crustacea and Hexapoda at least 420 million years ago.