LU Hui-ming, MENG Feng-xia, GAO Cong-fen, LIU Qi-yong, REN Dong-sheng
Chines Journal of Vector Biology and Control. 2013, 24(2): 125-127.
Objective To determine the nymphal instar of Blattella germanica by observing its ecdysis and acquire the physical characteristics of B. germanica in different nymphal instars, and to provide a basis for judging the nymphal instar of B. germanica in the field work and laboratory study and standardizing the experimental study of B. germanica. Methods Egg capsules were collected from female adults of B. germanica and then hatched to obtain nymphs. The nymphs were fed, and their ecdysis and instars were observed and recorded every day. The head width, body length, and body weight of the B. germanica in each nymphal instar were measured to statistically analyse the correlation between the nymphal instar and these physical characteristics. Results In the laboratory, the nymph of B. germanica went through six instars, with durations of (13.00±1.29), (11.17±1.17), (12.33± 2.07), (10.20± 1.10), (10.50± 1.05), and (9.50± 1.05) days, respectively, and there were no significant differences among the instars. From the first to the sixth instar, the head widths were (0.99±0.16), (1.03±0.15), (1.62±0.19), (1.83±0.22), (2.02±0.21), and (2.05±0.22) mm, respectively; the body lengths were (3.69±0.35), (5.27±0.57), (7.03±0.70), (9.48±0.67), (11.19±0.61), and (11.48±0.44) mm, respectively; the body weights were (2.39±0.11), (8.70±0.69), (17.64±5.27), (37.97± 5.04), (50.66±9.23), and (66.20±11.60) mg, respectively. There was a significant positive correlation of the nymphal instar of B. germanica with the head width, body length, and body weight (r＝0.9539, 0.9854, and 0.9879). Conclusion Under the relatively stable conditions, the B. germanica in different nymphal instars shows the most significant change in body weight, followed by body length, so the nymphal instar of B. germanica can be judged by its body weight, body length, and head width.
