SEASONAL ABUNDANCE AND SPATIAL PATTERNS OF THE PREDATOR LYCTOCORIS-CAMPESTRIS IN STORED CORN
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abstract
A twoyear sampling study (199293) in a flat storage of shelled corn showed that the larger pirate bug, Lyctocoris campestris (F.) (Heteroptera: Anthocoridae), can be detected by relative sampling techniques as early as the second week of May. The perceived seasonal pattern of L. campestris varied with trapping method. Of the three relative sampling methods used, probe traps consistently captured more bugs of both sexes than cardboard traps in the grain and sticky flight traps. Probe traps showed a third degree polynomial trend through the season. On the other hand, flight traps were effective for monitoring L. campestris population during early and midsummer when temperatures were high, but the effectiveness declined during late summer and early fall. Cardboard traps showed the opposite trend to those of flight traps, with increasing L. campestris abundance during the fall when bugs sought refuge as temperature decreased. Sampling date and environmental factors, including grain moisture content, air and grain temperatures were correlated with trap capture. Earlier work reported that L. campestris showed a highly female biased sex ratio in the field as opposed to a 1:1 sex ratio in laboratory colonies. The present study found that the estimate of sex ratios in the field can differ with trapping methods. Of the three relative sampling methods used, flight and cardboard traps, in most cases, showed no deviation from a 1:1 sex ratio. Probe traps, however, indicated a highly female biased sex ratio in field populations. Absolute sampling using a 1140 ml cup sampler also showed no deviation from a 1:1 sex ratio in the field population. The data suggested that relative sampling methods may be inappropriate for sex ratio estimation in the field. Thus, an absolute sampling method is required for determination of the true field sex ratio of L. campestris. Analyses of dispersion patterns showed that both males and females of L. campestris exhibit an aggregated spatial distribution in the grain. 1995 The Netherlands Entomological Society
