Movement of Adult ferrugineus (Coleoptera: ) in Wheat: Response to Temperature Gradients and Gravity Author(s): Fuji Jian, Digvir S. Jayas, and Noel D. G. White Source: Environmental Entomology, 33(4):1003-1013. Published By: Entomological Society of America DOI: http://dx.doi.org/10.1603/0046-225X-33.4.1003 URL: http://www.bioone.org/doi/full/10.1603/0046-225X-33.4.1003

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BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research. BEHAVIOR Movement of Adult (Coleoptera: Laemophloeidae) in Wheat: Response to Temperature Gradients and Gravity

1 FUJI JIAN, DIGVIR S. JAYAS, AND NOEL D. G. WHITE

Department of Biosystems Engineering, University of Manitoba, Winnipeg, Mannitoba, R3T 5V6, Canada

Environ. Entomol. 33(4): 1003Ð1013 (2004) ABSTRACT Cryptolestes ferrugineus (Stephens) (Coleoptera: Laemophloeidae) is the most prev- alent species in granaries in western Canada. Their movement and distribution at different environmental conditions provide important information for insect detection and control and for models of their distribution in grain bins. The distribution and wandering movement of C. ferrugineus adults were studied in a 100 by 500 by 500-mm wheat (14.5 Ϯ 0.2% moisture content) chamber with or without a 5ЊC/m temperature gradient. In the grain chamber at a uniform temperature, adults dispersed homogeneously in each horizontal layer and heterogeneously in the vertical direction when the temperature was 22.5Ð30ЊC. Adults moved toward a warmer temperature and in the direction of gravity at the same time in the grain chamber with temperature gradients in the horizontal or/and vertical directions. Adult movement and distribution in the two-dimensional chamber could be represented by published data obtained in one-dimensional columns. The movement and distribution of females (mixed ages) were not signiÞcantly different from those of males (mixed ages) in response to temperature gradients and gravity. Wandering movement of adults was restricted by temperature gradients.

KEY WORDS Cryptolestes ferrugineus, stored grain, wandering, movement, distribution, tempera- ture gradient

BULK-STORED GRAIN IS A ARTIFICIAL ecosystem where Mate Þnding is another factor inßuencing dispersal of living organisms and their nonliving environment in- stored-product . White and Bell (1993) found that teract. This ecosystem is inßuenced by outside con- males of the C. ferreugineus are strongly stimulated to ditions such as seasonal weather variation. The exter- compete for sexual partners. Hagstrum et al. (1998) nal temperature changes cause temperature gradients found Tribolium castaneum (Herbst) males tended to within the grain mass, which may inßuence distribu- disperse more readily than females, but both sexes pre- tion of stored grain pests within the bulk. ferred temperatures Ͼ30ЊC. It is unknown whether male The rusty grain , Cryptolestes ferrugineus (Ste- and female C. ferrugineus respond similarly to tempera- phens) (Coleoptera: Laemophloeidae), is the most ture or other environmental stimuli. prevalent insect species in granaries in western Can- The distribution of C. ferrugineus adults was deter- ada (Smallman 1944, Loschiavo 1974, Madrid et al. mined in one-dimensional (1-D) grain columns (Flinn 1990) and is often found in abundance in association and Hagstrum 1998; Jian et al. 2002, 2003) under a with heating grain (Sinha and Wallace 1966). Under single physical factor condition because of the difÞ- uniform temperature conditions, both male and fe- culties in determining insect movement and distribu- male adults move, apparently randomly, in grain at 30ЊC and 14% moisture content (MC) (Surtees 1963). tion in two- (2-D) or three (3-D)-dimensional grain When temperature gradients exist within a grain mass, chambers with multifactors. The important question however, movement is no longer random (Flinn and arising from these experiments is whether the same Hagstrum 1998); adults move preferentially to warmer responses of individuals and the same patterns of pop- temperatures at 30Ð36.5ЊC (Jian et al. 2002, 2003). For ulation movement will be found in 2-D or 3-D cham- predicting beetle movement and distribution in stored bers. grain bins, the net displacement of the beetlesÕ random The aim of this research was to 1) characterize movement must be determined. movement of C. ferrugineus adults in 2-D grain cham- bers with or without a 5ЊC/m temperature gradient; 2) infer wandering movement of the adults in the grain 1 Agriculture and Agri-Food Canada, Cereal Research Centre, 195 chamber; 3) determine whether female and male C. Dafoe Rd., Winnipeg, MB. R3T 2M9. Canada. ferrugineus disperse similarly in the grain chamber;

0046-225X/04/1003Ð1013$04.00/0 ᭧ 2004 Entomological Society of America 1004 ENVIRONMENTAL ENTOMOLOGY Vol. 33, no. 4

Fig. 1. Two-dimensional grain chamber Þlled with wheat to test the movement of C. ferrugineus adults under a temperature gradient (right). and 4) document the difference in distribution of the base, whereas the female lacks this projection adults in 1-D versus 2-D grain chambers. (Rilett 1949). The adults were boiled in 10% sodium chloride for Ϸ10 min. After boiling, the mandibles were easily identiÞed under a microscope. Materials and Methods Insect Trap. The probe-pitfall traps (unbaited) Wheat. Hard red spring wheat (grade no.1, ÔAC were similar to those used by Loschiavo and Atkinson BarrieÕ certiÞed) was moistened in a rotating drum to (1973). The trap was a brass tube (25 mm in diameter, obtain the desired moisture content (Bruce and Giner 190 mm in length) with 2-mm-diameter holes in the 1993). The moisture content of the moistened wheat top 90-mm section. The lower section held a small was determined using a standard oven-drying method funnel and a collecting vial, which was removable by drying triplicate 10-g samples at 130ЊC for 19 h through a brass cap at the bottom of the trap. (ASAE 2002). Grain Chamber. The inside dimension of the grain and Sex Determination. C. ferrugineus was chamber was 500 by 500 by 100 mm (Fig. 1). One wall reared at 30 Ϯ 1ЊC and 75 Ϯ 5% RH on cracked wheat of the chamber was a copper box (500 by 100 by 80 plus wheat germ [95:5 (wt:wt)] and was held in the mm, referred to as a water box), and the other walls dark during rearing and in the experiments. The cul- were acrylic boards (30 mm in thickness). On the tures of C. ferrugineus had been reared in the labora- inside surfaces of the two opposite walls (500 mm in tory for Ͼ3 yr. The adults (mixed sex) were1dto2 mo old at the start of each experiment. The sex of the C. ferrugineus was determined by identifying the shape of the beetlesÕ mandibles. The male mandible has a lateral tooth-like projection near

Fig. 3. Locations of the traps in the two-dimensional grain chamber. In the graph, 1, 2, 3, and 4 indicate the locations of the traps. Dashed lines indicate the slots on the side walls of the grain chamber. The dashed lines separated Fig. 2. Copper-rod-frame. the grain chamber into 25 equal sections. August 2004 JIAN ET AL.: MOVEMENT OF C. ferrugineus ADULTS 1005

Fig. 4. Method of transferring the data. (a) Data determined in a 10-section column were transfer into a Þve-section column. The characters in each section (f1, •••, f10) were the numbers of the recovered adults in the 10 sections, respectively. (b) Two-dimensional data were transferred into 1-dimensional data. The characters in each section (a1, •••, and e5) were the numbers of the recovered adults in the 25 sections, respectively. X indicates the introduction location of the C. ferrugineus adults. width and 500 mm in length, referred to as side walls), conduction wall), four slots (each 106mm in length, eight slots per side (four in each of the vertical and 2 mm in width, and 30 mm in depth) separated the wall horizontal directions; each slot was 500 mm in length, into Þve equal pieces. Each slot on the conduction wall 2 mm in width, and 3 mm in depth) were made. The was at the same height with two slots on the inside distance between two parallel slots was 98 mm. On one surfaces of the side walls (one slot per side). There was end wall opposite to the copper box (referred to as the one insect introduction hole (35 mm in diameter) on 1006E NVIRONMENTAL ENTOMOLOGY Vol. 33, no. 4

Table 1. Statistical result of the movement (Wilcoxon and Median options) and distribution (KS option) of C. ferrugineus adults (comparison between in 2-D grain chambers and 1-D grain columns)

b b b Experimental temperature Wilcoxon Median KS a (ЊC) Z P Ͼ ZZP Ͼ Z Ksa P Ͼ KSa Without temperature gradients in the horizontal direction 22.5 22.5 Ϫ0.17 0.4342 Ϫ0.61 0.2725 1.21 0.1066 25.0 22.5 Ϫ0.17 0.4325 Ϫ0.44 0.3284 0.70 0.7092 30.0 27.5 Ϫ0.57 0.2859 Ϫ1.15 0.1242 0.90 0.3918 37.5 37.5 Ϫ1.43 0.076 Ϫ0.68 0.2485 1.41 0.0877 Without temperature gradients in the vertical direction 22.5 22.5 1.54 0.0561.44 0.074 1.01 0.2548 25.0 22.5 1.16 0.0561 1.20 0.0613 1.90 0.0714 30.0 27.5 1.12 0.0571 1.02 0.0219 1.13 0.1542 37.5 37.5 2.560.0052 * 2.88 0.0020* 2.40 Ͻ0.0001* With temperature gradients in the horizontal direction 22.5Ð25.0 22.5Ð27.5 Ϫ1.50 0.0663 Ϫ1.39 0.0625 1.08 0.1972 25.0Ð27.5 22.5Ð27.5 Ϫ0.04 0.4823 Ϫ0.15 0.4423 0.93 0.3563 30.0Ð32.5 27.5Ð32.5 Ϫ0.460.323 Ϫ0.47 0.3205 1.160.1384 35.0Ð37.5 32.5Ð37.5 Ϫ1.49 0.0554 Ϫ0.70 0.2408 0.97 0.3005 With temperature gradients in the vertical direction 22.5Ð25.0 22.5Ð27.5 1.43 0.0759 1.39 0.0814 0.62 0.8396 25.0Ð27.5 22.5Ð27.5 0.13 0.2663 1.09 0.1373 0.52 0.9512 30.0Ð32.5 27.5Ð32.5 1.42 0.0773 1.60 0.0547 0.99 0.2784 35.0Ð37.5 32.5Ð37.5 3.59 0.0002* 2.61 0.0046* 2.95 Ͻ0.0001* With temperature gradients in both the vertical and horizontal directions 30.0Ð32.5c 27.5Ð32.5c 1.22 0.1118 Ϫ1.03 0.1512 0.99 0.2742 30.0Ð32.5d 27.5Ð32.5d 1.01 0.15560.89 0.1858 0.58 0.8934

a Comparison between two experiments. When given as temperature range, the Þrst temperature was at the lower end of the 1-D grain column or 2-D chamber. b Means that are different between the two experiments at P Յ table-wise ␣* level by using Wilcoxon, Median, KS, and sequential Bonferroni tests. In the sequential Bonferroni test, comparisons with the same column direction and temperature gradient conditions were grouped, respectively. c Comparisons between two experiments in the horizontal direction. d Comparisons between two experiments in the vertical direction. the middle of one of the 500 by 100-mm walls (referred four shorter rods (300 mm in length) on the outside to as the cover) (Fig. 1). During testing, the hole was (Fig. 2). plugged by a rubber cork. To produce a temperature One acrylic box (500 by 500 by 100 mm) without a gradient in one direction (horizontal or vertical), the water box, Styrofoam boards, and copper-rod-frame conduction wall was exposed to ambient temperature was used to test insect movement at a constant grain and the other walls were insulated with Styrofoam temperature. boards (160 mm in thickness). To produce tempera- Temperature Control and Testing. Thermistors ture gradients in two directions (both vertical and (model 44007, OMEGA Engineering Inc., Stamford, horizontal), the conduction wall and the cover were CT) with an accuracy Ϯ0.2ЊC were used to measure exposed to ambient temperature, and the other walls the temperature. A data acquisition and control unit were insulated with Styrofoam boards (160 mm in (model HP 38524, HewlettÐPackard, Loveland, CO) thickness). was connected to the thermistors. Three thermistors To obtain an even and approximate-linear temper- were placed in the middle of the grain chamber with ature distribution through the grain mass in the grain the arrangement in the direction of the temperature chamber, a copper-rod-frame was Þxed into the grain gradient. The distance between two thermistors was chamber. The copper-rod-frame (Fig. 2) consisted of 100 mm. One thermistor was placed on the wall of the one copper plate (4 mm in thickness, 100 mm in width, water box, and one was placed near the conductive and 500 mm in length), six copper tubes (17 mm inner wall of the grain chamber. During testing, the data diameter and 25 mm in height), and six copper rods acquisition and the control unit were connected to a (16mm in diameter). The six copper tubes were computer. Temperatures in the grain chamber were welded onto the copper plate and were arranged with measured every 30 min and recorded throughout the two tubes in the middle and four tubes on the outside trials. (Fig. 2). There was a 70-mm gap between the two During an experiment, the water box was con- middle tubes and a 240-mm gap between a middle tube nected to a water bath (Fisher, Haahe, Berlin, Ger- and an outside tube. During testing, the copper rods many). The grain chamber and water bath were were inserted into the tubes with the arrangement of placed in a 2.7 by 2.7 by 2.2-m environmental room two longer rods (400 mm in length) in the middle and (model Conviron CMP3244, Controlled Environ- August 2004 JIAN ET AL.: MOVEMENT OF C. ferrugineus ADULTS 1007

Fig. 5. Number (mean) of recovered adult C. ferrugineus in each section of the two-dimensional grain chamber at a constant temperature by 24 h after introduction. In each replication, 250 adults were introduced in the middle of the chamber (n ϭ 3). Each dot represents one adult insect. ments Ltd., Winnipeg, MB, Canada) to provide con- temperature gradient (5ЊC/m) was established (4 d), stant ambient conditions. The temperature gradient in an acrylic tube (300 mm in length and 30 mm in the grain chamber was created and maintained by diameter) with a wood rod (350 mm in length and 30 controlling the temperature of the water bath and the mm outside diameter) inside the tube was inserted environmental room. into the middle of the grain chamber through the Testing Procedure and Replication. Before Þlling insect introduction hole. After the wood rod was re- the grain chamber, the four slots on the conduction moved, 250 adults of C. ferrugineus were introduced wall were sealed with tape (Fig. 1), and the copper- into the tube. After a further 3 min, the acrylic tube rod-frame was Þxed in the chamber with the copper was pull out of the chamber. After a further 24 h, the plate connected with the water box. The grain cham- cover and the tapes that were used to seal the slots on ber was Þlled with 14.5 Ϯ 0.2% MC (wet basis) wheat the conduction wall were removed. One galvanized and was kept in the environmental room (27.5 Ϯ steel plate (104 mm in wide, 600 mm in length) was 0.2ЊC) for at least 4 d. This procedure established an inserted into the grain chamber through the top slot even temperature distribution in the grain chamber. on the conduction wall and the top slots on the inside Temperature gradients in one direction (vertical or surfaces of the two side walls. Using this method, the horizontal) or in both the vertical and horizontal di- Þrst layer of the grain was segregated from the re- rections were established by maintaining the temper- maining gain in the chamber. Then four galvanized atures of the water box at 2.5ЊC higher than the en- steel slats (200 mm in height, 104 mm wide) were vironmental room temperature. After the desired inserted into the chamber through the slots on the 1008 ENVIRONMENTAL ENTOMOLOGY Vol. 33, no. 4

Fig. 6. Number (mean) of recovered adult C. ferrugineus in each section of the two-dimensional grain chamber with 5ЊC/m temperature gradients in the horizontal direction by 24 h after introduction. In each replication, 250 adults were introduced in the middle of the chamber (n ϭ 3). Each dot represents one adult insect. inside surfaces of the two side walls, the slats being opened and wheat was removed, and the number of perpendicular to the metal plate. This method divided insects in each trap was counted. The grain chamber the top layer into Þve equal sections (each section 100 was cleaned by a vacuum and then kept in the envi- by 100 by 100 mm) (Fig. 3). After removing the Þrst ronmental chamber (25ЊC and 75% RH) for Ͼ12 h piece of the conduction wall, the grain in each section between experiments. was removed with a brush. Then, the middle copper Each experiment was repeated three times with rods were pulled out of the grain chamber. The second new grain used for each replication. The recovered and other subsequent layers were divided similarly adults from two replications in the following experi- and grain was removed (Fig. 3). The shorter copper ments were further sexed to determine the distribu- rods were pulled out after the second layer of grain tion of the females and males: 1) movement in the 2-D was removed. The adults were separated from the chamber with temperature gradients in the horizontal wheat by using a sieve with 2-mm openings (Los- direction from 22.5 to 25ЊC; and 2) movement in the chiavo 1983). The beetles were placed in a porcelain 2-D chamber without temperature gradients at 22.5ЊC. tray and counted as they were aspirated into a vial. Data Collection. The net displacement of adults was To determine the number of adults caught in traps, measured in both the vertical and horizontal direc- four traps were buried in the grain chamber (Fig. 3) tions. The grain chamber was divided into Þve hori- as it was being Þlled with wheat (14.5 Ϯ 0.2% MC). zontal layers or Þve vertical columns (Fig. 3). One The methods of establishing a uniform temperature layer or column was further divided into Þve sections. and a temperature gradient, and introducing insects, In a layer or column, the net displacement of insects were the same as those described above. After 24 or was measured from the middle of the layer or column 72 h of the insect introduction, the chamber was to the middle of each section in which the adults were August 2004 JIAN ET AL.: MOVEMENT OF C. ferrugineus ADULTS 1009

Fig. 7. Number (mean) of recovered adult C. ferrugineus in each section of the two-dimensional grain chamber with temperature gradients in the vertical direction by 24 h after introduction. In each replication, 250 adults were introduced in the middle of the chamber (n ϭ 3). Each dot represents one adult insect. recovered. In a vertical column, “Ϫ” means that bee- at 5ЊC/m temperature gradients (30Ð32.5ЊC) in the tles moved down, and “ϩ” means that adults moved up. vertical or horizontal directions. A completely ran- In a layer, Ϫ means that insects moved to the left side, domized experiment was designed to conduct all of and ϩ means movement to the right side. the tests. For all tests, the recovery rate of the adults Experiment Design and Data Analysis. The follow- was 90.4 Ϯ 1.2% (n ϭ 27) because some adults were ing experiments were conducted: 1) movement of trapped in small gaps in the 2-D grain chamber or adults at 22.5, 25, 30, and 37.5ЊC; 2) movement of adults might remain in the sieved wheat. During the data at 5ЊC/m temperature gradients (22.5Ð25ЊC, analysis, the number of the recovered adults from each 25Ð27.5ЊC, 30Ð32.5ЊC, or 35Ð37.5ЊC) in the horizontal replication was adjusted to 250 (number of adults in or vertical direction; 3) movement of adults at 5ЊC/m the section equals the number of the recovered adults temperature gradients (30Ð32.5ЊC) in both the hori- in the section ϫ 250/number of the recovered adults zontal and vertical directions; 4) distribution of fe- in the chamber) for comparison. The number of adults males and males at 25ЊC; 5) distribution of females and in traps in the 2-D grain chambers without tempera- males at 5ЊC/m temperature gradients (22.5Ð25ЊC) in ture gradients was compared with those in traps at the the horizontal direction; 6) number of adults caught in same location in the chambers with temperature gra- traps at 30ЊC; and 7) number of adults caught in traps dients by conducting t-tests (Steel et al. 1997). Num- 1010 ENVIRONMENTAL ENTOMOLOGY Vol. 33, no. 4

Þed), data obtained from the 2-D grain chamber were compared with 1-D data published by Jian et al. (2002, 2003). The published data determined in a 10-section column were transferred into a Þve-section column by calculating the percentage of adults in every two sec-

tions (P1,P2,P3,P4, and P5) (Fig. 4). The data obtained in the 2-D chamber were transferred into 1-D data (vertical or horizontal column) by calculating the

percentage of adults in each layer or column (Pa,Pb, Pc,Pd,Pe,P1,P2,P3,P4, and P5) (Fig. 4). The calculated percentages were used to conduct the two-sample location test and the EDF statistics. The statistical result of the KolmogorovÐSmirov test was used to determine the difference of adult distribution be- tween the 2-D grain chamber and 1-D column. The Wilcoxon option tested for difference in location (at each section of the grain chamber or column), and the Fig. 8. Number (mean) of recovered adult C. ferrugineus Median option tested the movement direction in the in each section of the two-dimensional grain chamber with grain chamber and column. The comparison was made temperature gradients in both the vertical and horizontal only when the 2-D temperature range was in the 1-D directions by 24 h after introduction. In each replication, 250 temperature range. For example, when 1-D temper- adults were introduced in the middle of the chamber (n ϭ 3). ature range was 22.5Ð27.5ЊC, the 2-D chamber tem- Each dot represents one adult insect. perature range was 25.0Ð27.5ЊC (Table 1). To control the probability of incorrectly rejecting true null hypotheses and simultaneously maintain sub- ber of adults in traps at different location and at the stantial power in detecting false null hypotheses, sev- same environmental condition was compared by con- eral comparisons of t-test or two-sample location test ducting paired t-tests. Distribution of females in the and EDF statistics were grouped (Table 1). The table- 2-D grain chamber was compared with the distribu- wise signiÞcance levels (␣, type I error) were calcu- tion of males by conducting the two-sample location lated and the sequential Bonferroni test was con- test (Median and Wilcoxon options) and the empirical ducted in each group (Rice 1989). distribution function (EDF) statistics (KolmogorovÐ Smirov [KS] option) (SAS Institute 1998). The sta- tistical result of the KolmogorovÐSmirov option was Results and Discussion used to determine the difference of adult beetle dis- tribution in the 2-D grain chamber. The Wilcoxon Insect Movement and Distribution in 2-D Grain option tested for difference in location (at each sec- Chambers with or without Temperature Gradients. In tion of the grain chamber), and the Median option the absence of temperature gradients, Ͼ40% of adults tested whether adults moved to different sides of the were recovered in the bottom layer of the grain cham- grain chamber. bers (Fig. 5). In each layer, adults were homoge- To test whether the same responses of individuals neously distributed except at 37.5ЊC. This showed that and the same patterns of population distribution adults exhibited mainly positive geotaxis when tem- would be found in both the 2-D chamber and 1-D perature was uniform. The number of adults in the top column (a column was in one dimension and a cham- two layers increased with the increasing of tempera- ber was in two dimensions, unless otherwise speci- ture from 22.5 to 37.5ЊC (Fig. 5). This might be caused

Table 2. Statistical result of the movement (Wilcoxon and Median options) and distribution (KS option) of C. ferrugineus adults (comparison between the percentages of recovered females and males in the 2-D grain chambers)

Wilcoxonb Medianb KSb a Comparison P Ͼ Z P Ͼ ZZP Ͼ Z Ksa KSa No temperature gradient in both the vertical and horizontal directions (at 22.5ЊC) Vertical Ϫ2.97 0.0015* Ϫ2.94 0.0017* 1.35 0.0522 Horizontal 0.42 0.8314 Ϫ0.20 0.4199 0.15 1 Temperature gradient only in the horizontal direction from 22.5 to 25ЊC Vertical 0.49 0.9868 0.77 0.2206 0.76 0.6147 Horizontal 0.59 0.27560.85 0.1978 0.40 0.9972

a Comparison between the movement and distribution of the females and males in the 2-D grain chamber at the vertical or horizontal direction. b Means that are different between the two experiments at P Յ table-wise ␣* level by using Wilcoxon, Median, KS, and sequential Bonferroni tests. In the sequential Bonferroni test, comparisons with the same temperature gradient conditions were grouped, respectively. August 2004 JIAN ET AL.: MOVEMENT OF C. ferrugineus ADULTS 1011

Table 3. Number of C. ferrugineus adults caught in traps in the two dimensional grain chambers with or without temperature gradients by 24 and 72 h

C1b by 24 h C2c by 24 h C1b by 72 h C2c by 72 h Trap locationa (mean Ϯ SE) (mean Ϯ SE) (mean Ϯ SE) (mean Ϯ SE) Trap 1 1.0 Ϯ 1.0 0.0 Ϯ 0.0 12.5 Ϯ 2.5 2.3 Ϯ 0.9 Trap 2 0.7 Ϯ 0.3 1.7 Ϯ 0.3 4.7 Ϯ 0.3 9.7 Ϯ 1.5 Trap 3 0.3 Ϯ 0.3 0.0 Ϯ 0.0 8.7 Ϯ 2.0 1.7 Ϯ 0.3 Trap 4 13.0 Ϯ 1.5 21.0 Ϯ 7.4 38.7 Ϯ 5.0 46.0 Ϯ 10.8

a Refer to Fig. 3 for the trap location in the grain chamber. b C1 stands for grain chambers without temperature gradients at 30ЊC. c C2 stands for grain chambers with temperature gradients (both vertical and horizontal directions) at 30 to 32.5ЊC (the temperature at the top of the chamber was 30ЊC). by the gradual decrease in responsiveness to gravity direction. These results suggested that insect move- and the high locomotion of the adults at a high tem- ment and distribution in 2-D can be represented by perature (Jian et al. 2004). 1-D data. In grain chambers with temperature gradients in the The distribution patterns obtained in these exper- horizontal or/and vertical directions, adult C. ferrug- iments were spatial expressions of individual and ineus responded to both the temperature gradients group response to physical stimuli within the limits of and gravity (Figs. 6, 7, and 8). When the temperature the experimental setup, and were indicative of the was Ͼ35ЊC, adults did not aggregate in 1) the warmer type of behavior to be expected in the presence of bottom corner of the chamber with a temperature temperature gradients and localized grain conditions. gradient in the horizontal direction (Fig. 6); and 2) the The important question arising from these small-scale bottom layer of the chamber with a temperature gra- experiments is whether the same responses of indi- dient in the vertical direction (Fig. 7). This shows that viduals and the same distribution patterns of popula- 37.5ЊC is above the preference temperature of the tions will be found in large bulks of stored grain. beetles (Jian et al. 2003). When the temperature in the Because interpretation of population distribution de- chamber was Ͻ32.5ЊC, adults ended up 1) in the pends on the rate of movement relative to the entire warmer bottom corner when the temperature gradi- bin, and relative to the size of the unit chosen to ent was in the horizontal direction (Fig. 6); 2) along subdivide that total bulk, we must be concerned about the bottom warmer wall when the temperature gra- the extent to which population distribution is also dient was in the vertical direction (Fig. 7); and 3) in subjective. The most important property of large bulks the warmer bottom corner when the temperature gra- of grain is that adults will take longer to move and to dients were in both the vertical and horizontal direc- encounter various physical gradients to which they tions. These results indicated that adults moved to- respond. Their response could be the same as that in ward a warmer temperature and in the direction of a small-scale experiment at the same environmental gravity at the same time. condition. Therefore, the movement (or at least its There was no signiÞcant difference in insect move- resultant displacement) of an insect in 3-D space such ment (Wilcoxon and Median tests) and distribution as a grain bulk can be represented by a vector, which (KS test) between the 1-D column and the 2-D cham- can be resolved into three mutually perpendicular ber in either the vertical or horizontal direction except components. Because the vector representing dis- Њ Њ at 35Ð37.5 C (with temperature gradients) and 37.5 C placement can be replaced by these components, dis- (without temperature gradients) (Table 1). Figures 6 placement (movement and distribution) in response and 7 also show that the adult distributions in each to 3-D gradients can be predicted using essentially 1-D vertical column or layer were similar when the tem- data. This method will be veriÞed in the future when perature gradient was in the horizontal or vertical a predictive model of adult movement is developed and veriÞed in an entire bin. Table 4. Statistical result compared between the numbers of C. Female and Male Movement and Distribution. In ferrugineus adults caught in traps in the grain chamber at a constant total, 904 beetles (sex determination was conducted in temperature and those in the chamber with temperature gradients four replications, the number of the recovered adults In 24 h In 72 h was 227, 223, 220, and 234 respectively) were sexed, Trap locationa and 71.5 Ϯ 2.7% adults were females. The sex ratios t Value Pb t Value Pb agreed well with previous research Þndings (Rilett Trap 1 Ϫ1.00 0.3739 Ϫ3.71 0.0266 1949). Trap 2 Ϫ1.00 0.3739 3.35 0.0285 Trap 3 2.12 0.1012 Ϫ3.41 0.0271 In the grain chamber without temperature gradi- Trap 4 1.07 0.3478 0.61 0.5722 ents, beetles were distributed in proportion to their numbers. The signiÞcant difference of movement a Refer to Fig. 3 for the trap locations in the grain chamber. (Wilcoxon and Median test) in the vertical direction b Յ Means that are different between the two experiments at P between females and males was due to 1) the random table-wise ␣* level by using t and sequential Bonferroni tests. In the sequential Bonferroni test, the comparisons for the four traps were distribution of the males and females in the top four grouped. layers; and 2) a few adults were recovered in the top 1012 ENVIRONMENTAL ENTOMOLOGY Vol. 33, no. 4 four layers (Fig. 5). In the grain chamber with tem- Acknowledgments perature gradients, there was no signiÞcant difference We thank the Natural Sciences and Engineering Research of movement and distribution between females and Council of Canada and Canada Research Chairs Program for males (Table 2). This indicates that the male response partial funding of this study and Matthew McDonald, Dale to gravity and temperature gradients is no different Bourns, and Colin Demianyk for technical assistance. Ap- than that of the female. preciation is extended to James Throne (USDAÐARS Grain Adults Caught in Traps. In the grain chamber at Marketing and Production Research Center, Manhattan, KS) 30ЊC, 13.0 Ϯ 1.5 and 38.7 Ϯ 5.0 adults (from a total of for useful comments. 250 adults) were caught by trap four in 24 and 72 h, respectively (Table 3). The number of adults recov- ered in this section was 15 Ϯ 2.9 in 24 h (Fig. 5). In the References Cited grain chamber with temperature gradients at Њ Ϯ Ϯ [ASAE] American Society of Agricultural Engineers. 2002. 30Ð32.5 C, 21.0 7.4 and 46.0 10.8 adults were ASAE Standards 2002. American Society of Agricultural caught by trap four in 24 and 72 h, respectively (Table Engineers, St. Joseph, MI. 3), and the number of adults recovered in this section Bruce, D. M., and S. A. Giner. 1993. Mathematical model- was 7.0 Ϯ 5.8 (from a total of 250 adults in the cham- ling of grain drying in control-ßow beds; investigation of ber) in 24 h (Fig. 6). These results indicate that adults crossover of air and grain temperature. J. Agric. Eng. Res. wander in the grain chambers with or without tem- 55: 143Ð161. perature gradients. Flinn, P. W., and D. W. Hagstrum. 1998. Distribution of In 72 h, more adults were caught in trap one and trap Cryptolestes ferrugineus (Coleoptera: ) in re- three in the grain chamber without temperature gra- sponse to temperature gradients in stored wheat. J. Stored Products Res. 34: 107Ð112. dients than in the chamber with temperature gradi- Hagstrum, D. W., P. W. Flinn, and J. J. Gaffney. 1998. Tem- ents. There was no signiÞcant difference in the num- perature gradient on Tribolium castaneum (Coleoptera: bers of the adults caught in traps between the grain Tenebrionidae) adult dispersal in stored wheat. Physiol. chamber with and without temperature gradients (Ta- Chem. Ecol. 27: 123Ð129. ble 4). There was a signiÞcant difference in the num- Jian, F., D. S. Jayas, and N.D.G. White. 2002. Temperature bers of adults caught in the chamber with temperature and geotaxis preference by Cryptolestes ferrugineus (Co- gradients between trap two and trap three (t ϭϪ4.61, leoptera: Laemophloeidae) adults in response to 5ЊC/m P ϭ 0.0438). There was no signiÞcant difference in temperature gradients at optimum and hot temperatures numbers of adults caught in the chamber without in stored wheat and their mortality at high temperatures. Environ. Entomol. 31: 816Ð826. temperature gradients between trap two and trap ϭ ϭ Jian, F., D. S. Jayas, N.D.G. White, and W. E. Muir. 2003. three (t 1.92, P 0.1946). This difference showed Movement of adult rusty grain beetles, Cryptolestes fer- that adults respond to temperature gradients and the rugineus (Coleoptera: Cucujidae), in wheat in response wandering movement of the adults was restricted by to 5ЊC/m temperature gradients at cool temperatures. J. temperature gradients. Stored Products Res. 39: 87Ð101. All individuals are part of the population in a grain Jian, F., D. S. Jayas, and N.D.G. White. 2004. Movement and bin and the individuals must survive and multiply. distribution of adult Cryptolestes ferrugineus (Coleoptera: Almost continuous random movement is a character- Cucujidae) in stored wheat in response to temperature istic feature of individual behavior (Surtees 1964, Hag- gradients, dockage, and moisture differences. J. Stored Products Res. (in press). strum et al. 1998). Random movement causes distur- Loschiavo, S. R. 1974. Laboratory studies of a device to bance within the population and leads to dispersal. detect insects in grain, and of the distribution of adults of Insect distribution patterns result from the interaction the rusty grain beetle, Cryptolestes ferrugineus (Co- between the insectÕs selected environment and the leoptera: Cucujidae), in wheat-Þlled containers. Can. En- behavior that has evolved for survival in it. Therefore, tomol. 106: 1309Ð1318. modiÞcation and restriction of individual random Loschiavo, S. R. 1983. Distribution of the rusty grain beetle movement by environmental factors are fundamental (Coleoptera: Cucujidae) in columns of wheat stored dry processes in population dispersion (Surtees 1964). or with localized high moisture content. J. Econ. Entomol. These results were consistent with previous reports 76: 881Ð884. Loschiavo, S. R., and J. M. Atkinson. 1973. An improved trap (Surtees 1964) and also showed that the wandering to detect beetles (Coleoptera) in stored grain. Can. En- movement of adult C. ferrugineus would be limited to tomol. 105: 437Ð440. a short distance by temperature gradients. This ob- Madrid, F. J., N.D.G. White, and S. R. Loschiavo. 1990. In- servation proved that environmental stimuli were the sect in stored cereals, and their association with farming main factor(s) inßuencing insect movement and dis- practices in southern Manitoba. Can. Entomol. 122: 515Ð tribution in grain bins. 523. In conclusion, 1) adult C. ferrugineus moved toward Rice, W. R. 1989. Analyzing tables of statistical tests. Evo- a warmer temperature and in the direction of gravity lution 43: 223Ð225. at the same time; 2) insect movement and distribution Rilett, R. O. 1949. The biology of ferrugineus (Steph.). Can. J. Res. (D). 27: 112Ð148. in 2-D chambers could be represented by published SAS Institute. 1998. SAS userÕs guide, release 8.2. SAS In- data obtained in 1-D columns; 3) there was no differ- stitute, Cary, NC. ence between the distribution of adult males and fe- Sinha, R. N., and H.A.H. Wallace. 1966. Ecology of insect- males; and 4) wandering movement of adults was induced hot spots in stored grain in western Canada. Res. restricted by temperature gradients. Popul. Ecol. 8: 107Ð132. August 2004 JIAN ET AL.: MOVEMENT OF C. ferrugineus ADULTS 1013

Smallman, B. N. 1944. Entomological investigations. Report Surtees, G. 1964. Laboratory studies on dispersion behav- of Grain Res. Laboratory Canada 18: 39Ð40. iour of adult beetles in grain. V. Technique for three- Steel, R.G.D., J. H. Torrse, and D. A. Dickie. 1997. Princi- dimensional analysis of dispersion patterns within small ples and procedures of statistics: a biometric approach. bulks. Bull. Entomol. Res. 54: 723Ð725. McGraw-Hill Publishing Company, Toronto. White, N.D.G., and R. J. Bell. 1993. Effects of mating status, Surtees, G. 1963. Laboratory studies on dispersion behav- sex ratio, and population density on longevity and off- iour of adult beetles in grain. III. Tribolium castaneum spring production of Cryptolestes ferrugineus (Stephens) (Hbst.) (Coleoptera: Tenebrionidae) and Cryptolestes (Coleoptera: Cucujidae). Exp. Gerontol. 28: 617Ð631. ferrugineus (Steph.) (Coleoptera: Cucujidae). Bull. En- tomol. Res. 54: 297Ð306. Received 15 July 2003; accepted 17 March 2004.