眉斑并脊天牛幼虫龄数及各龄特征

测定头壳宽度室内观察结果表明,眉斑并脊天牛Glenea cantor(Fabricius)幼虫有4龄。1~4龄幼虫的头壳宽度分别为(0.66±0.20),(1.45±0.20),(2.22±0.23),(3.26±0.29)mm。其龄数(Y)与幼虫头壳宽(X)度符合关系式Y=0.2975+1.1606X。在25℃条件下,1~4龄幼虫的平均龄期分别为(5.25±0.60),(4.94±0.58),(5.98±0.63)d和(22.92±1.28)d,整个幼虫期为(39.09±2.14)d。还对眉斑并脊天牛各龄幼虫的形态特征作了描述。     

Divergent nutrition-related adaptations in two cockroach populations inhabiting different environments

Developmental, reproductive and size‐related variables were compared between two ecologically different strains of Periplaneta americana (L.). One strain was a laboratory‐reared culture, and the other a feral strain inhabiting an urban environment. The feral population was originally founded by escapees from the culture, but may also include immigrants from other urban populations. Both final‐instar nymphs and adults of the feral insects were heavier than their equivalents from the cultured population, this weight difference being due to a higher capacity for the storage of water and heavier fat‐free carcasses. Feral cockroaches also had heavier oothecae, which contained heavier offspring than those from cultured females. Feral animals had one or two more larval stadia and higher growth rates. Size‐related differences persisted in first and second filial generations reared under laboratory conditions on a nutritionally balanced diet, but were not apparent in first filial insects reared on a vegetable diet. Greater resistance to starvation was found in feral animals, and this was attributed primarily to their larger water stores. Feral animals were found to harbour a higher density of endosymbiotic bacteria in the fat body, which are known to enhance the efficiency of protein utilization. The data suggest that the characteristics of feral animals have been selected in the nutritionally harsh feral environment compared with the more benign culture conditions, with water availability playing a role.     

人工饲养背摇蚊幼虫龄数和龄期的测定

本文采用了人工饲养定期取样的方法,测定了背摇蚊Chironomus dorsalis(Anderson)幼虫的龄数以及各龄的龄期。分别测量不同发育阶段幼虫的头壳长、颏中齿顶端至冠突前缘间距离、头壳宽、颏宽、颏中齿宽、触角长、触角基节长、触角比(触角基节与其余各节的长度之比)等8项指标,以期得到区分和判定幼虫虫龄的最佳形态特征及指标。运用频次分布、均差分析和回归分析对8项指标测量数据进行统计分析,结果表明,背摇蚊幼虫可分4龄,触角长可作为理想的分龄特征和分龄指标,其次是颏中齿顶端至冠突前缘间距离和颏宽。利用种群众数龄期法计算1-4龄幼虫的平均龄期分别为1.32 d、2.00 d、7.51 d和8.39 d,幼虫期共为19.22 d。