雌性昆虫在繁殖结束后通常会死去，而日本研究人员日前却发现了繁殖结束后依然生存的雌性蚜虫。这种长寿蚜虫分泌黏液击退天敌，帮助子孙生存下去。
东京大学教授岛田正和与研究生植松圭吾发现的这种长寿蚜虫是一种日本特有的蚜虫品种中的雌性，它们生活在常绿的蚁母树上。这种蚜虫出生半年后就开始不断繁殖，在丧失繁殖能力以后，它们仍继续分泌黏液，攻击瓢虫等天敌，帮助子孙实现自立。
大部分灵长类到了不能妊娠、生育的年龄就要准备迎接死亡，而人类的女性却能够活到当奶奶的岁数。有一种“老奶奶假说”认为，女性长寿是为了更好地照顾子孙，帮助他们繁殖。
这是人们首次在昆虫世界里发现这一现象。研究人员认为，这有可能是这种蚜虫为了切实留下后代的一种进化策略。
这一成果已刊登在最新一期美国科学杂志《当代生物学》上。(生物谷Bioon.net)
生物谷推荐原文出处：
Current Biology doi:10.1016/j.cub.2010.04.057
Altruistic Colony Defense by Menopausal Female Insects
Keigo Uematsu, Mayako Kutsukake, Takema Fukatsu, Masakazu Shimada, Harunobu Shibao
Recent studies have suggested that an extended postreproductive life span, such as life after menopause in human females, will evolve when the indirect (kin-selected) fitness benefits from altruistic behavior are greater than the direct fitness benefits from continuing reproduction [1,2,3,4]. Under some conditions in which postreproductive altruism is more beneficial and/or continuing reproduction is more costly, the postreproductive life span can be shaped by natural selection [5, 6,5, 6]. However, indirect fitness benefits during postreproductive survival have been documented mainly in intelligent mammals such as humans and cetaceans, in which elder females possess enhanced social knowledge through learning [7,8,9,10]. Here we show that postreproductive females of the gall-forming aphid Quadrartus yoshinomiyai (Nipponaphidini) can gain indirect fitness benefits through their altruistic colony defense. These females cease reproduction around the time of gall opening and defend the colony by sticking themselves to intruding predators with a waxy secretion that is accumulated in their body with aging. Our results suggest that the presence of an age-related trait for altruistic behavior promotes the evolution of postreproductive altruism in this social insect via kin selection under natural selection imposed by predators.
