Mechanisms of evolution of sterile defensive cast in aphids.

在鹿儿岛县竹群林和名古屋大学育苗室研究了具有不育防御等级（士兵）的Pseudoregma bambucicola和P. koshunensis的社会生物学。获得的结果如下:1)的比例增加士兵在p . bambucicola殖民地成为秋天,当主机的新茎增长,和多个相关分析表明,主要因素增加的士兵比殖民地大小和竹茎的长度,这与殖民地发展的新时期。2)放生实验和野外观察结果表明，bambuicola士兵能有效杀灭掠食性舌蚜（Eupeodes conator）一龄幼虫。在兵比高的蚜虫群落附近，成虫避免产卵，可能是由于兵在受到干扰时主动摇晃腿所致。3)科顺氏疏翅虫胎生幼虫先产正常幼虫，其次产战士幼虫，在其生命的最后阶段再产正常幼虫。首先是正常生殖阶层，其次是不育阶层，这与所有其他真社会性昆虫的顺序完全相反。这一发现可能为进一步研究昆虫防御等级的进化提供线索。

Social biology of Pseudoregma bambucicola and P. koshunensis, both of which have sterile defensive caste (soldier), was studied in Bambusa multiples stands in Kagoshima Pref., and in a rearing room of Nagoya University. The results obtained are as follows: 1) Ratio of soldiers in P. bambucicola colonies became increase in Autumn, when new stems of the host grew, and multiple correlation analysis showed that major factor concerning increase of soldier ratio were colony size and length of bamboo stems, which related to period of colony development. 2) Release experiments and field observations suggested that P. bambucicola soldiers could effectively kill first instar larvae of a predatory syrphid, Eupeodes confrator. Adult females of E. confrator avoided to oviposit near aphid colonies with high soldier ratio, possibly due to active shaking of legs by soldiers when disturbed. 3) Apterous viviparae of P. koshunensis laid some normal larvae first, some soldiers secondly, and in the final stage of their life, laid normal larvae again. Laying normal reproductive caste first and sterile caste secondly is the very reverse of order of laying these castes in all other eusocial insects. It was considered that this discovery may shed a light for further consideration of evolution of defensive castes in insects.