SEASONAL ABUNDANCE AND SPATIAL PATTERNS OF THE PREDATOR LYCTOCORIS-CAMPESTRIS IN STORED CORN

A two-year sampling study (1992-93) in a flat storage of shelled corn showed that the larger pirate bug, Lyctocoris campestris (F.) (Heterop tera: Anthocoridae), can be detected by relative sampling techniques a s early as the second week of May. The perceived seasonal pattern of L . campestris varied with trapping method. Of the three relative sampli ng methods used, probe traps consistently captured more bugs of both s exes than cardboard traps in the grain and sticky flight traps. Probe traps showed a third degree polynomial trend through the season. On th e other hand, flight traps were effective for monitoring L. campestris population during early and mid-summer when temperatures were high, b ut the effectiveness declined during late summer and early fall. Cardb oard traps showed the opposite trend to those of flight traps, with in creasing L. campestris abundance during the fall when bugs sought refu ge as temperature decreased. Sampling date and environmental factors, including grain moisture content, air and grain temperatures were corr elated with trap capture. Earlier work reported that L. campestris sho wed 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 est imate 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 populatio ns. Absolute sampling using a 1140 mi cup sampler also showed no devia tion from a 1:1 sex ratio in the field population. The data suggested that relative sampling methods may be inappropriate for sex ratio esti mation 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. campes tris exhibit an aggregated spatial distribution in the grain.