Flight behavior of Listronotus bonariensis (Coleoptera: Curculionidae) in the Waikato, New Zealand

The flight behavior of Listronotus bonariensis (Kuschel) in Waikato (New Zealand) pastures was studied by recording catches on aerial sticky traps and sampling ground populations; this was supported by dissection studies and laboratory experimentation. All flight activity in the field occurred between 25 August and 5 May. Flight phenology and intensity varied greatly between localities and years. Intensity was generally low, although occasional mass flights were observed. Sampled ground populations indicated that only a proportion of the weevils exhibited development of flight musculature and hence flight capability: the proportion of these "flight capable" weevils varied greatly from generation to generation. Field sampling and laboratory experimentation indicated partitioning of reproductive and dispersive effort among individuals in the population. Following emergence, some weevils became reproductive and others developed flight musculature before ovarian development and dispersal. The proportion of weevils in the latter category was highest in the field following peak emergence and was shown by laboratory experimentation to be increased by weevil crowding, particularly on unfavorable host plants. The laboratory experiments also indicated that alleviation of crowding resulted in degeneration of flight musculature and resumption of reproductive activity. Field sampling indicated overwintering in the pastures (summer breeding grounds) and no migration to adjacent potential hibernation sites. These results are discussed in relation to the climate of the Waikato and the dynamics of the populations.