Department of Entomology and Plant Pathology, Auburn University, Auburn, AL.
J Insect Sci. 2019 Sep 1;19(5). doi: 10.1093/jisesa/iez087.
The Asian cockroach, Blattella asahinai Mizukubo, has expanded its range throughout the southeastern United States since its introduction into Florida. Unlike its closest relative, the German cockroach, Blattella germanica (L.), B. asahinai lives outdoors and can fly. There is little information on the biology and development of B. asahinai, including the number of instars during nymphal development. To estimate the number of instars of B. asahinai, nymphs were photographed, sexed, and the lengths and widths of their pronota were measured digitally. The number of instars of B. asahinai was estimated using Gaussian mixture models with the pronotal data. The most probable model and its clusters were selected to assign individuals to an instar. Instars were also determined by counting the number of cercal annuli of nymphs. Both clustering and cercal annuli indicated that B. asahinai most frequently had six instars when reared at 30°C. Growth did not strictly follow the Brooks-Dyar Rule, because nymphs had different numbers of instars and different growth patterns. Although Gaussian mixture models are not efficient for field sampling experiments, digital measurements may provide a way to estimate instars with live specimens in development studies without handling the animals in a way that may alter growth.
亚洲蟑螂（Blattella asahinai Mizukubo）自引入佛罗里达州以来，已扩展其在美国东南部的分布范围。与最接近的德国蟑螂（Blattella germanica（L.））不同，B. asahinai 生活在户外，可以飞行。关于 B. asahinai 的生物学和发育的信息很少，包括在若虫发育期间的龄期数量。为了估计 B. asahinai 的龄期数量，我们对若虫进行了拍照、性别鉴定，并对其前胸背板的长度和宽度进行了数字测量。使用带有前胸背板数据的高斯混合模型来估计 B. asahinai 的龄期数量。选择最可能的模型及其聚类来将个体分配到一个龄期。通过计数若虫的尾须环数也可以确定龄期。聚类和尾须环都表明，在 30°C 下饲养时，B. asahinai 最常具有六个龄期。生长并不严格遵循布鲁克斯-达耶尔法则，因为若虫的龄期数量不同，生长模式也不同。虽然高斯混合模型对于野外采样实验效率不高，但数字测量可能为在不处理动物的情况下通过活体标本进行发育研究来估计龄期提供一种方法，这种方法不会改变生长。
