Movement and Distribution of Cryptolestes ferrugineus (Coleoptera: Laemophloeidae) Adults Under Different Temperature Differences in Different Lengths of Horizontal Grain Columns

Abstract

Understanding insect movement and distribution is critical for developing an effective insect pest management protocol. Movement and distribution of adult Cryptolestes ferrugineus (Stephens) in response to nominal temperature differences of 5, 10, 15, and 20°C in 1- and 2-m horizontal columns filled with 12.5% moisture content wheat were studied in 24, 48, and 72 h of movement times. In the wheat columns without temperature differences, adults had a diffusion distribution pattern caused by their random movement. Adults showed bias movement to the warmer grain in wheat columns with temperature differences and preferred the warmer grain regardless of the magnitude of temperature differences in less than 24 h. Their distribution did not have significant differences among different movement times in 1- or 2-m columns. About 40% of adults moved to the warmer wheat located at 0.4 to 0.5 m in the 1 m column but did not move to the warmer wheat located at 0.9 to 1 m in the 2-m column. Therefore, length of grain column influenced detection of warmer grain by insects. Adults under different temperatures had a similar response as that under linear temperature gradients.

Response of Cryptolestes ferrugineus (Coleoptera: Laemophloeidae) adults to small temperature (0–6 °C) and moisture (1%) differences in wheat

“…The cultures of the C. ferrugineus had been reared in the laboratory for more than 3 yr before the start of the experiments. The procedure for rearing insects was the same as that used in our earlier manuscript (Anukiruthika et al 2022). One hundred reared adults were aspirated into a glass vial (0.8 cm diameter and 2.5 cm in length) filled with about 10 g of the moisture-conditioned wheat.…”

“…The dimensions of each grain column were 0.1 × 0.1 × 1 m. The structure and insulation of the columns were similar to the columns used by Jian et al (2002) with the elimination of the copper rod assembly. The design and other specifications of the grain column were detailed in our previous manuscript (Anukiruthika et al 2022). The acclimated 100 adults were introduced through the upright plastic tube attached to the middle of the wooden lid of the grain column.…”

“…A wooden stick of approximately the same diameter as the plastic tube was used to seal the tube during the experiment to prevent insects from escaping. At the end of the insect movement period, the top wooden lid was removed, and the grain column was partitioned with thin metal steel slats (101 × 110 mm) to form 10 grain sections (each 0.1 × 0.1 × 0.1 m) along the entire length of the column (Anukiruthika et al 2022).…”

“…The experimental procedure was similar to that described in our previous manuscript (Anukiruthika et al 2022). The 3-grain columns, external water circulation pump, and a water bath were placed inside the environmental chamber set at 20 °C and 75% r.h. (25 °C and 75% r.h. for moisture difference experiments).…”

“…Therefore, the study of insect movement under nonlinear temperature and moisture differences is needed for understanding insect movement in stored-grain bins. Addressing this research need, a study was conducted to determine the movement and distribution of adults of Cryptolestus ferrugineus , (Stephens) (Coleoptera: Laemophloeidae) under different temperature differences (5, 10, 15, and 20 °C) for different movement periods (24, 48, and 72 h) in stored wheat of 12.5% moisture content (Anukiruthika et al 2022). The lowest temperature difference in this study was 5 °C.…”