6日刊登在《自然》期刊（Nature）的研究报告指出，角蝉头上引人注目的突起物，其实是翼状翅膀，经过2亿年演化淘汰后，又重新长回来。专家说，这项发现或许会震惊昆虫学家，也挑战昆虫学部分根基。

昆虫的身体分为头部、胸部（thorax）和腹部，地球上所有昆虫胸部分成3节，每节都有2只脚。大部分昆虫目有2对翅膀，一对在胸部中节，一对在后节。苍蝇和蚊子只有在后节有一对翅膀，少数昆虫，如大多数蚂蚁则完全没有翅膀。胸部第一节有翅膀的昆虫，如今已不存在，不过它们的先祖却有。

研究主笔人、法国马赛鲁米尼生物发展机构的普鲁道姆（Benjamin Prudhomme）说，「3亿5000万年前的原始昆虫身体每节都有翅膀。我们不晓得是不是用来飞行，不过我们确实知道，从化石纪录来看，这些翼状结构存在于身体每节上。」经过了1亿年，昆虫胸部第一节和腹部翅膀完全消失。

不过，5000多万年后，角蝉发生了异变，胸部第一节出现看起来像翅膀的东西。这些分岔的突起物，有些长得像角，有些像触角，有些像被触怒的蚂蚁，有些则像动物粪便，五花八门。专家长久以来认为这些所谓的「安全帽」，是昆虫外部甲壳构造的延伸。

仔细观察角蝉的生长后，普鲁道姆和同事发现，这些突起物一开始长得像一对芽，附着在两侧，之后再长成翼状物，期间还会合并。演化通常被认为是单方向进行，不过这些翅膀显示演化有可能绕了一圈重回起点。

原文出处：

Nature 473, 83–86 (05 May 2011) doi:10.1038/nature09977

Body plan innovation in treehoppers through the evolution of an extra wing-like appendage

Benjamin Prud’homme1, Caroline Minervino1, Mélanie Hocine1, Jessica D. Cande1, A?cha Aouane1, Hélo?se D. Dufour2, Victoria A. Kassner2 & Nicolas Gompel1

Body plans, which characterize the anatomical organization of animal groups of high taxonomic rank1, often evolve by the reduction or loss of appendages (limbs in vertebrates and legs and wings in insects, for example). In contrast, the addition of new features is extremely rare and is thought to be heavily constrained, although the nature of the constraints remains elusive2, 3, 4. Here we show that the treehopper (Membracidae) ‘helmet’ is actually an appendage, a wing serial homologue on the first thoracic segment. This innovation in the insect body plan is an unprecedented situation in 250?Myr of insect evolution. We provide evidence suggesting that the helmet arose by escaping the ancestral repression of wing formation imparted by a member of the Hox gene family, which sculpts the number and pattern of appendages along the body axis5, 6, 7, 8. Moreover, we propose that the exceptional morphological diversification of the helmet was possible because, in contrast to the wings, it escaped the stringent functional requirements imposed by flight. This example illustrates how complex morphological structures can arise by the expression of ancestral developmental potentials and fuel the morphological diversification of an evolutionary lineage.