Mn. Parajulee et Tw. Phillips, SEASONAL ABUNDANCE AND SPATIAL PATTERNS OF THE PREDATOR LYCTOCORIS-CAMPESTRIS IN STORED CORN, Entomologia experimentalis et applicata, 75(1), 1995, pp. 33-42
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.