Comparison of two sampling methods for chironomid midges in rice fields

Author of the article:HE JiaChun1LI ZhiYu1,2YANG Hong2HU Yang1

Author's Workplace：1. State Key Laboratory of Rice Biology,China National Rice Research Institute, Hangzhou 310006, China；

Key Words：ampling methods, emergence trap method, motorsucking method, chironomids, biocommunity. population, rice

Abstract：     The nature, operation and operator time requirements for emergence traps as a method for studying rice fielddwelling, non-biting midges are introduced. The bio-community structure and major aspects of population dynamics of non-biting midges determined using emergence traps are compared with those determined using the classical sampling method, a motorised suction trap. We found that both methods collected four species, namely Chironomus sinicus Kiknadze, Wang, Istomina & Gunderina; Tanytarsus formosanus Kieffer；Polypedilum nubifer Skuse and Tanypus punctipennis Meigen. In addition, Limnophyes minimus Meigen was collected by the motorized suction method only. Both methods demonstrated C. sinicus and T. formosanus to be the dominant species in rice fields, but the emergence trap collected significantly more midges than the motorised suction trap. For example, the estimated density of T. formosanus collected by the emergence trap was 22 times as high as that for the motorized suction method at the rice elongation stage. The comparison of variation coefficients shows that neither method has a marked advantage over the other. We suspect that both methods require the taking of more samples to increase accuracy. In comparison with the emergence trap, the motorized suction trap requires is much more labor intensive and time consuming in the field and laboratory. Therefore, sampling frequency can be more readily increased by use of the emergence trap providing much better information on population dynamics. We consider that the emergence trap is also a suitable method for studying mosquitoes in rice fields as mosquitoes have similar biological characteristics to non-biting midges.