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2015 Diel Patterns of brunnea and Colaspis crinicornis (Coleoptera: Chrysomelidae) in Southeastern Nebraska Kentaro Miwa University of Nebraska-Lincoln

Lance Meinke University of Nebraska--Lincoln, [email protected]

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Miwa, Kentaro and Meinke, Lance, "Diel Patterns of Colaspis brunnea and Colaspis crinicornis (Coleoptera: Chrysomelidae) in Southeastern Nebraska" (2015). Faculty Publications: Department of Entomology. 410. http://digitalcommons.unl.edu/entomologyfacpub/410

This Article is brought to you for free and open access by the Entomology, Department of at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Faculty Publications: Department of Entomology by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Published in Environmental Entomology 44(6): 1553–1561 (2015); doi: 10.1093/ee/nvv132 Copyright © 2015 Kentaro Miwa and Lance J. Meinke. Published by Oxford University Press on behalf of Entomological Society of America. Used by permission. Submitted December 22, 2014; accepted July 24, 2015. digitalcommons.unl.edudigitalcommons.unl.edu

Diel Patterns of Colaspis brunnea and Colaspis crinicornis (Coleoptera: Chrysomelidae) in Southeastern Nebraska

Kentaro Miwa and Lance J. Meinke

Department of Entomology, University of Nebraska–Lincoln, NE 68583.

Corresponding author — L. J. Meinke, email [email protected]

Abstract A field study was conducted to increase our understanding of diel activity patterns ofColaspis brunnea (F.) and Colaspis crinicornis Schaeffer (Coleoptera: Chrysomelidae) in key crop habitats. Within 24-h periods, C. brunnea was sampled in clover fields (primarily red clover, Trifolium pretense (L.), with some sweet clover, Melilotus officinalis (L.) Pallas, and downy brome, Bromus tectorum (L.)) and , Glycine max (L.) Merrill, fields, using a sweep-net, while whole-plant- count sampling was used to monitor C. crinicornis densities in field corn,Zea mays (L.). Sweep-net captures of C. brunnea were significantly greater at night than during the day, suggesting possible vertical movement within the canopy during a 24-h period. Colaspis crinicornis densities on corn plants were fairly constant throughout a 24-h period, but ac- tivity (e.g., walking, mating) was significantly greater at night than during the day. Results suggest that both Colaspis species may be exhibiting similar increases in activity at night that facilitates movement from more protected to more exposed areas within a habitat. It is unclear what mechanisms drive this diel pattern, but vegetation architecture and associated interactions with environmental conditions may play a role. Sweep-netting in clover or soybean fields and use of whole-plant-counts in cornfields were effective sampling methods for Colaspis adults. However, because activity and behaviors of Colaspis were influenced by time of day in this study, use of a consistent sampling time within a diel period would be recommended for future population studies or integrated pest management decision-making.

Keywords: Colaspis brunnea, Colaspis crinicornis, grape colaspis, diel activity

The genus Colaspis F. (Coleoptera: Chrysomelidae) in- some Great Plains states (Riley et al. 2003; K. Miwa, cludes a number of species known to be pests of agricul- personal observation). Although museum specimens in- tural crops in North and South America (Ostmark 1975, dicate that C. crinicornis has been present in Nebraska Balsbaugh 1982, Flynn and Reagan 1984, Oliver 1987, Lo- for at least a century, its presence in Nebraska or Iowa pez et al. 2002). In the United States, the grape colaspis, was not noticeable in crops until recently (Bradshaw et Colaspis brunnea (F.), has been the most intensively stud- al. 2011; L. J. Meinke, personal observation). The rea- ied pest species. Colaspis brunnea is an important pest of sons for this are unclear; however, the ability to reproduce rice, Oryza sativa (L.), in southeastern states (Rolston and on multiple hosts (Miwa and Meinke 2015) and shifts in Rouse 1965, Wilf et al. 2010) and is an occasional pest of agronomic practices may have facilitated establishment corn, Zea mays (L.), and soybean, Glycine max (L.) Mer- and increased survival in agroecosystems (Miwa 2014). In rill, east of the Rocky Mountains (Bigger and Farrar 1943, southeastern Nebraska, adults of C. crinicornis are gen- Lindsay 1943, Eaton 1978, Lambert 1994, Steffey 1999). erally present in crops from June through August (Miwa Adult C. brunnea can also be common in red clover, Tri- 2014), and population densities of C. crinicornis have been folium pretense (L.), and lespedeza, Lespedeza spp. (Big- increasing in corn and soybean fields during the past de- ger and Farrar 1943, Lindsay 1943). Colaspis brunnea lar- cade (L. J. Meinke, personal observation). This species vae are root feeders, whereas adults feed on aboveground often coexists in cornfields with Diabrotica virgifera vir- plant tissues (Lindsay 1943). Although both adults and gifera LeConte and Diabrotica barberi Smith and Law- larvae of this species attack crops, larvae are generally rence (Coleoptera: Chrysomelidae), which are two of the more destructive (Lindsay 1943). In addition, larval dam- major pests of corn in the U.S. Corn Belt (Krysan age to rice and corn is usually greater when legumes such 1986). However, little information is currently available as soybean, red clover, or lespedeza are planted during the on the biology and pest potential of C. crinicornis. preceding year (Lindsay 1943, Rolston and Rouse 1965). Many insect species exhibit peak activity patterns at A related species, Colaspis crinicornis Schaeffer, over- certain times of day, and their behaviors can change over laps in distribution with C. brunnea in Nebraska and time throughout a 24-h period (Taylor 1963, Lewis and

1553 1554 M i w a & M e i n k e i n E n v i r o n m e n t a l E n t o m o l o g y 44 (2015)

Taylor 1965). Currently, little information exists on C. 1943, Rolston and Rouse 1965, Rudd and Jensen 1977, brunnea diel activity patterns, whereas no such informa- Eaton 1978). A 38-cm-diameter sweep net with a 61-cm- tion is available on C. crinicornis. Eaton (1978) observed long handle (BioQuip Products Inc., Rancho Dominguez, highest densities of adult C. brunnea during the early CA) was used to sample in clover and soybean fields. Each morning and late evening when sweep-net samples were field was divided into four sections. A randomly selected taken in soybean fields between 0800 and 2000 h in North area in each section was sampled during each sampling Carolina, but night-time sampling was not included in the period. Four sets of 20 sweeps were taken during each study. Therefore, as part of a more comprehensive study sampling period on each sampling date. For each set, a to better understand the natural history of these two Co- sweep was made on each step for 20 consecutive steps laspis species in southeastern Nebraska, a field study was while walking in a line in clover fields and between rows conducted to increase our understanding of diel activity in the soybean field. The net was held with two hands by patterns of each species in various habitats. the sampler. One sweep consisted of the movement of the net from the shoulder height on one side of the sampler Materials and Methods to the same height on the other side, moving vigorously through the vegetation. Enough force was given so that Diel activity patterns of C. brunnea and C. crinicornis the net moved as deeply as possible without collecting soy- were characterized in key habitats where each species bean stems but one to three trifoliates per 20 sweeps. A was consistently observed and where densities were high different sweep-net was used for each set of 20 sweeps to enough to study. Colaspis brunnea was sampled in clover prevent the nets from being completely wet when dew was and soybean fields, whereas C. crinicornis was sampled present on plants at night. Because adult C. brunnea often in cornfields in southeastern Nebraska. On each sampling attempted to escape by quickly crawling or flying out of date, data were collected every three hours for a 24-h pe- the net, especially at night, whole contents inside the net, riod, with the first sampling period beginning at 1000 h including plant material, were directly placed in plastic on the first day and the last sampling period beginning bags and stored in a freezer. Samples were counted in the at 1000 h on the following day. Plant phenology was sim- laboratory, and sex was determined using a dissecting mi- ilar across sampling dates within each habitat type. Be- croscope based on the description given by Lindsay (1943). cause C. brunnea and C. crinicornis are univoltine (Miwa Cornfields: Whole-Plant-Count Sampling. Whole- 2014), diel activity data were only collected during a finite plant-count sampling, which has been commonly used to period when the majority of adults emerged and mating estimate adult population densities of D. v virgifera and occurred. Sampling was conducted on warm, sunny days D. barberi (Tollefson 1986), was conducted in cornfields to add consistency over sampling dates. This set of con- to study C. crinicornis diel activity patterns in Nemaha ditions was common during peak beetle emergence and County (8 June 2012) and at the ARDC (23 June 2012 appeared to facilitate Colaspis beetle activity (K. Miwa, and 25 June 2012). Corn was planted in these fields dur- personal observation). To avoid potential sampling vari- ing 2011, and notillage practices were followed in both ation caused by multiple samplers (Morris 1960, Powell 2011 and 2012. Corn was planted with 76-cm row spac- et al. 1996, Musser et al. 2007), all data were collected by ing. A corn hybrid expressing Bacillus thuringiensis (Bt) the same person. toxins (Cry1F and Cry34/35Ab1) was planted, and seeds Clover and Soybean Fields: Sweep-Net Sampling. were treated with the neonicotinoid clothianidin (250 mg Clover fields were sampled by sweep-net forC. brunnea on per seed). 16 July 2011 and 6 July 2012 adjacent to Nine-Mile Prai- Sampling was performed when most plants in the fields rie, a remnant tallgrass prairie site in Lancaster County, were between the V8 and V12 growth stages based on and on 16 July 2012 and 23 July 2012 at the University of Ritchie et al. (1993). Each field was divided into four sec- Nebraska Agricultural Research and Development Center tions, and 20 plants of similar height were randomly se- (ARDC) in Saunders County. The clover fields had high lected in each section at each sampling period. During population densities of red clover mixed with other plants whole-plant-count sampling, beetles on plants were vi- such as sweet clover, Melilotus officinalis(L.) Pallas, and sually counted, examining both sides of every leaf, the downy brome, Bromus tectorum (L.). Red clover plants whorl, and the stalk of each plant. Caution was taken were between 40 and 60cm in height. A soybean field was not to disturb the beetles, as adult Colaspis often exhib- sampled for C. brunnea on 8 July 2012, 12 July 2012, ited escape behaviors (i.e., dropping to the ground or fly- and 23 July 2012 at the ARDC. Corn was planted in this ing away) when they were disturbed (K. Miwa, personal field during 2011, and no-tillage practices were followed observation). In addition to counting beetles found on in both 2011 and 2012. Soybean was planted with 76-cm plants, the location at which each beetle was found on row spacing. Most soybean plants were between the R1 corn plants was recorded in one of three categories: in the and R2 stages (Fehr et al. 1977) and were between 50 and whorl (whorl), at the base of a leaf where the leaf joins 80 cm in height during data collection. the stalk (base), or on an exposed part of leaves or stalk Sweep-netting was selected as a sampling method dur- (open). The behavior of each beetle was also recorded in ing this study because several authors have reported suc- four categories: motionless, crawling, feeding, or mating. cessful utilization of a sweep net for adult C. brunnea Because beetles were not collected but visually counted in sampling in red clover, soybean, and lespedeza (Lindsay the field, sex was not determined. D i e l p a t t e r n s o f C. b r u n n e a & C. c r i n i c o r n i s i n SE N e b r a s k a 1555

Night-Time Sampling. A light-emitting diode (LED) ber of adult C. brunnea per 20 sweeps across periods was headlamp was worn by the sampler during the sampling 19.0361.49. The effect of time on sweep-net captures was periods between 1900 and 0700 h in all habitat types. In significant (Table 2), with captures between 2200 and cornfields, a hand-held LED flashlight was also used dur- 0700 h significantly greater than captures during other ing the same periods to allow the sampler to more clearly periods (Figure 1). When the potential effect of sex on observe beetles and their habitats. Preliminary data in- sweep-net captures in clover fields was added to the anal- dicated that LED lights when carefully lit on beetles did ysis model, neither the main effect sex nor the time by sex not disturb or elicit escape behaviors (K. Miwa, unpub- interaction was significant (Table 2). The mean numbers lished data). of male and female C. brunnea per 20 sweeps across peri- Statistical Analyses. Data were analyzed using ods were 8.7160.77 and 10.3260.80, respectively. PROC GLIMMIX in SAS software 9.2 (SAS Institute In the soybean field, the mean number of C. brunnea 2008). Repeated-measures analysis of variance (ANOVA) per 20 sweeps across periods was 23.9061.03. Period sig- was performed to evaluate the effect of time within a nificantly affected the number ofC. brunnea captured (Ta- diel period on the mean total number of adult C. brun- ble 2). The number of beetles was significantly greater be- nea in sweep-net captures and the mean total C. crinicor- tween 2200 and 0700 h sampling periods than any other nis found on corn plants. Analyses were conducted sepa- periods (Figure 2). However, no significant difference be- rately for the three habitat types. In clover and soybean, tween males and females or time by sex interaction was the additional effect of C. brunnea sex on mean sweep cap- found (Table 2). The mean number of males per 20 sweeps tures was analyzed as a split-plot design carried in ran- was 12.1960.53, while that of females was 11.5060.52. domized complete block. The whole-plot was the section Visual counts of C. brunnea adults were not made in of the field, while the split-plot was sex. In corn, the addi- either clover or soybean during this study. However, it tional factors, C. crinicornis location and behavior exhib- is interesting to note that during periods when sweep ited, were evaluated over time using a similar split-plot sampling was conducted in each crop, C. brunnea adults design. The whole-plot was the section of the field, while were consistently more visible at the top of the canopy the split-plot factor was the location of beetles found on at night than during daytime periods (K. Miwa, personal corn plants (whorl, base, or open) or the behavior of the observation). beetle (motionless, crawling, mating, or feeding). For all Cornfields: Whole-Plant-Count Sampling. The analyses in each habitat type, date was considered as a mean number of beetles observed per 20 corn plants was blocking factor and a random effect, and time was the re- 19.8760.46 for C. crinicornis and 0.0760.05 for C. brun- peated-measures factor. nea. Because few individuals of C. brunnea were found, Data were log (y+0.01) transformed before each anal- only C. crinicornis data were analyzed. Time of day did ysis to better meet the normality and variance assump- not significantly affect the total number of C. crinicornis tions of ANOVA. Non-transformed data are presented found on plants (Table 3). However, when the location of in the results. For each repeated-measures analysis, an C. crinicornis over time was analyzed, both the main ef- appropriate covariance structure was selected based on fect location and the time by location interaction were sig- Akaike’s information criterion (AIC), and the model with nificant (Table 3). The mean number of beetles found at the minimum AIC value was used for each analysis. Fish- the base of a leaf per 20 plants across periods (8.4460.53) er’s least significant difference test was performed to dif- was significantly greater than those found in the whorl ferentiate means. The 0.05 level of significance was used (6.1960.66) or on open areas of a plant (5.2560.28) (Table in all analyses. 3). The numbers of beetles found in the whorl and at the base of a leaf were significantly greater during sampling Results periods between 1000 and 1900 h than periods between 2200 and 0700 h (Figure 3). In contrast, the number of C. Environmental Conditions. Basic meteorological crinicornis observed on open areas of corn plants was sig- data were recorded at automated stations near field sites nificantly greater during sampling periods between 2200 (Table 1). High and low temperatures on sampling dates and 0700 h than during other sampling periods (Figure ranged from 32.5 to 38.8°C and 20.2 to 25.5°C, respec- 3). Only 5 to 11% of total beetles observed were found in tively (Table 1). It was sunny on all sampling dates, and open areas of plants between 1000 and 1900 h, whereas 53 no precipitation occurred during this study. Mean wind to 65% of total beetles were found in open areas between speed was between 1.5 and 2.9 m/s (Table 1). Sunset oc- 2200 and 0700 h (Figure 3). curred approximately at 2100 h, while sunrise was ap- The analysis of C. crinicornis behavior on corn plants proximately at 0600 h. over time resulted in significant differences among behav- Clover and Soybean Fields: Sweep-Net Sampling. ior categories and a significant time by behavior interac- Both C. brunnea and C. crinicornis were collected during tion (Table 3). The mean number of motionless beetles sweep-net sampling in clover and soybean fields. How- per 20 plants across periods (16.6760.51) was significantly ever, only C. brunnea data were analyzed because the greater than means of beetles observed to be crawling number of C. crinicornis captured was low (0.1660.04 (1.6860.23), mating (0.5860.11), and feeding (0.9460.13) and 0.0560.02 beetles per 20 sweeps in clover and soy- (Table 3). The number of motionless beetles was signifi- bean fields, respectively). In clover fields, the mean num- cantly greater during sampling periods between 1000 and 1556 M i w a & M e i n k e i n E n v i r o n m e n t a l E n t o m o l o g y 44 (2015)

Table 1. Meteorological data for each sampling date and site where diel data were collected Date Site High temp. Low temp. Mean wind Mean relative Accumulated solar (°C) (°C) speed (m/s) humidity (%) radiation (kJ/m2) Clover 16 July 2011 Nine-Mile Prairiea 34.9 24.5 2.7 71.1 26,045 6 July 2012 Nine-Mile Prairiea 38.8 25.5 2.9 44.3 28,343 16 July 2012 ARDCb 37.5 22.8 2.5 56.4 27,227 23 July 2012 ARDCb 36.8 20.2 2.2 54.7 26,163 Soybean 8 July 2012 ARDCb 38.7 21.8 2.5 55.1 27,421 12 July 2012 ARDCb 34.5 20.3 1.5 60.7 25,738 23 July 2012 ARDCb 36.8 20.2 2.2 54.7 26,163 Corn 8 June 2012 Nemaha Countyc 32.7 20.4 2.9 60.2 28,562 23 June 2012 ARDCb 36.8 20.2 2.2 54.7 26,163 25 June 2012 ARDCb 32.5 21.4 2.9 76.8 27,795 a. Weather station was approximately 5 km away from the study site. b. Weather station was approximately 1 km away from the study site. c. Weather station was approximately 10 km away from the study site.

Table 2. ANOVA results of sweep-net captures of C. brunnea during diel experiments in clover and soybean fields Analyses Effects F df P Total sweep-net captures in clover fields Time 5.52 8, 17.17 0.0015 Section 0.15 3, 13.25 0.9260 Time × section 1.40 24, 23.08 0.2116 Sweep-net captures in clover fields between sexes Time 18.22 8, 69.80 < 0.0001 Section 0.35 3, 36.53 0.7893 Sex 2.22 1, 36.53 0.1447 Time × section 1.53 24, 104.1 0.0745 Time × sex 0.78 8, 69.80 0.6232 Section × sex 0.03 3, 36.53 0.9923 Time × section_sex 1.09 24, 104.1 0.3654 Total sweep-net captures in soybean field Time 11.41 8, 56.67 < 0.0001 Section 0.49 3, 23.71 0.6948 Time × section 1.14 24, 54.22 0.3399 Sweep-net captures in soybean field between sexes Time 14.50 8, 44.33 <0.0001 Section 0.13 3, 6.507 0.9396 Sex 1.95 1, 45.35 0.1697 Time × section 1.59 24, 63.79 0.0718 Time × sex 1.46 8, 44.33 0.1979 Section × sex 0.30 3, 45.35 0.8283 Time × section × sex 1.02 24, 63.79 0.4533

1900 h than periods between 2200 and 0700 h (Figure 4). commonly during some periods at night than during the Only 1–5% of beetles were active during the day in com- day. The sweep-net captures of C. brunnea were also af- parison with 21 to 26% of beetles exhibiting active behav- fected by time of day in both clover and soybean fields, iors at night (Figure 4). Most of this difference could be with a significant increase in the number of beetles col- attributed to significantly greater numbers of crawling, lected at night compared with daytime periods in both feeding, and mating beetles during one or more sampling habitat types. Fewkes (1961) demonstrated that vertical periods between 2200 and 0700 h when compared with be- movement of nabid species (Hemiptera: Nabidae) within havioral activity between 1000 and 1900 h. vegetation varied over time throughout a day. This influ- enced the number of individuals captured by sweep-net Discussion sampling, as captures were greater when more individu- als were found in the upper portion of the plant canopy. A consistent diel pattern was observed for each Colas- The sweep-net sampling results from this study coupled pis species in this study. The whole-plant-count results with night-time observations of increased beetle visibil- clearly indicated that many adult C. crinicornis moved ity at the top of the canopy suggest that adult C. brunnea to and remained in protected areas of corn plants such as may also move vertically during a 24-h period, becoming inside whorls and at the leaf–stalk junction during the more common in the upper part of the canopy at night and day, whereas more beetles were found on open areas of moving to lower levels of the vegetation during the day in plants (e.g., on leaf blades) at night. Moreover, beetles both clover and soybean fields. This behavior could explain were observed to be crawling, mating, and feeding more the significant differences in sweep-net catch obtained at D i e l p a t t e r n s o f C. b r u n n e a & C. c r i n i c o r n i s i n SE N e b r a s k a 1557

Figure 1. Mean sweep-net captures per period of C. brunnea in clover fields during 2011 and 2012 in southeastern Nebraska. Means across four dates are shown (16 July 2011, 6 July 2012, 16 July 2012, and 23 July 2012). Means with the same letter within the all (males and fe- males combined), male, and female categories are not significantly different (P>0.05: Fisher’s LSD test). An error bar represents the stan- dard error of the mean.

Figure 2. Mean sweep-net captures per period of C. brunnea in a soybean field during 2012 in southeastern Nebraska. Means across three dates are shown (8 July, 12 July, and 23 July 2012). Means with the same letter within the all (males and females combined), male, and fe- male categories are not significantly different P( >0.05: Fisher’s LSD test). An error bar represents the standard error of the mean. 1558 M i w a & M e i n k e i n E n v i r o n m e n t a l E n t o m o l o g y 44 (2015)

Figure 3. Mean numbers of adult C. crinicornis observed by location (whorl = in the whorl, base = at the base of a leaf where the leaf joins the stalk, open = on an exposed part of leaves or stalk) and period on corn plants during 2012 whole-plant-count sampling in southeastern Nebraska. Means across three dates are shown (8 June, 23 June, and 25 June 2012). Means with the same letter within the whorl, base, and open categories are not significantly different P( >0.05: Fisher’s LSD test). An error bar represents the standard error of the mean.

Table 3. ANOVA results of whole-plant counts of C. crinicornis during diel experiments in cornfields Analyses Effects F df P Total number of beetles Time 0.48 8, 19.88 0.8591 Section 0.51 3, 28.10 0.6812 Time × section 1.49 24, 24.38 0.1657 Number of beetles among locations on plants Time 0.51 8, 68.96 0.8416 Section 0.61 3, 22.43 0.6164 Location 10.36 2, 22.43 0.0007 Time × section 1.45 24, 101.60 0.1026 Time × location 15.77 16, 90.51 < 0.0001 Section × location 1.29 6, 22.43 0.3036 Time × section × location 1.13 48, 111.40 0.2965 Number of beetles among behaviors Time 0.31 8, 97.22 0.9624 Section 0.10 3, 32.40 0.9605 Behavior 414.69 2, 32.40 < 0.0001 Time × section 1.36 24, 145.00 0.1349 Time × behavior 13.25 16, 145.00 < 0.0001 Section × behavior 0.14 6, 32.40 0.9982 Time × section × behavior 1.28 48, 163.20 0.1018 night versus during the day. The plant architecture of clo- that some individuals undoubtedly moved into or out of ver and soybean prevented direct observation and quan- the sampling areas over time. Adults were likely to be tification of C. brunnea diel behaviors, but the diel pat- present in and on the soil at various times because C. tern of C. brunnea sweep-net collections and C. crinicornis crinicornis oviposits in the soil (Miwa and Meinke 2015). whole-plant-counts both suggest that each species may be In addition, adult flight has been observed during day exhibiting similar increases in activity at night that facil- or night periods (K. Miwa, personal observation). There- itates movement from more protected to more exposed ar- fore, data from this study suggest that adult C. crinicornis eas within a habitat. were fairly mobile within local habitat patches, but trivial It is interesting to note that the relative density of C. movement did not result in a net increase or decrease in crinicornis observed in corn remained nearly constant the mean total number of C. crinicornis present on corn over a 24-h period (Table 3). This is in spite of the fact plants within a 24-h period. D i e l p a t t e r n s o f C. b r u n n e a & C. c r i n i c o r n i s i n SE N e b r a s k a 1559

Figure 4. Mean numbers of adult C. crinicornis observed on corn plants by behavior and period during 2012 whole-plant-count sampling in southeastern Nebraska. Means across three dates are shown (8 June, 23 June, and 25 June 2012). Means with the same letter within the motionless, crawling, mating, and feeding categories are not significantly different (P>0.05: Fisher’s LSD test). An error bar represents the standard error of the mean.

A common trend found in the whole-plant-count results potential interaction between plant structure and verti- was that a majority of adult C. crinicornis stayed motion- cal diel insect movement). less in shady sites during the day in cornfields. One of the During this study, sampling was performed under one possible explanations for this behavior may be that bee- set of environmental conditions (i.e., warm, sunny days) tles sought shelter to avoid direct exposure to sunlight to be consistent over multiple sampling dates. However, and associated adverse environmental conditions. Vari- adult Colaspis may exhibit greater activity during day- ous insect species are known to stay in shade during peri- time periods than observed in this study under cloudy ods of high temperatures to avoid overheating (May 1979, conditions and/or lower temperatures. Additional experi- Chappell 1983, Whitman 1987, Kreuger and Potter 2001). ments designed to measure the impacts of specific micro- The shade-seeking behavior may be one of the thermoreg- environmental factors on C. crinicornis activity and be- ulatory mechanisms Colaspis beetles use when the tem- haviors within cornfields would help explain diel patterns peratures are higher than optimal. An associated issue observed in this study. Moreover, quantifying activity and would be water regulation in adults. Resting during the behaviors of C. brunnea may also demonstrate whether or heat of the day at the base of leaves or in the whorl would not activity patterns observed in clover and soybean were maximize exposure to humidity that is present and poten- the result of similar general responses to environmental tially reduce water loss. Reductions in temperature that conditions among Colaspis species. occurred at night (Table 1) and changes in light intensity For successful development and implementation of in- may have been contributing factors that led to greater ac- tegrated pest management (IPM) programs, accurate es- tivity observed at night. timation of pest population densities is critical (Pedigo Although general diel patterns of C. brunnea sweepnet et al. 1986). Both sweep-netting in clover and soybean captures were similar between the clover and soybean fields and whole-plant-count sampling in cornfields were habitats during this study, a more dramatic decrease in effective Colaspis sampling techniques during this study. captures occurred during the day in the clover fields than Under the conditions of this experiment, the sweep- in the soybean field (Figs. 1 and 2). The reasons for this net captures were consistent over time during most of are unclear, but the vegetation structure of each crop (e.g., the daytime periods. This result and successful sweep- plant height and growth pattern, canopy size) may have net sampling reported by other authors (Lindsay 1943, differentially affected the type and location of beetle rest- Rolston and Rouse 1965, Rudd and Jensen 1977, Eaton ing sites within the canopy, daytime microclimates as- 1978) would support use of this sampling technique in clo- sociated with each crop, and the proportion of the beetle ver or soybean IPM programs. If C. crinicornis eventually population intercepted by the sweep net (i.e., function of becomes a pest species in corn, this study demonstrates 1560 M i w a & M e i n k e i n E n v i r o n m e n t a l E n t o m o l o g y 44 (2015) that the whole-plant-count sampling method would be a Fehr, W. R., and C. E. Caviness. 1977. Stages of soybean devel- viable option for this species in the future. A sweep net, opment, pp. 3–11. Iowa Agricultural and Home Economics Ex- which is a useful sampling tool in habitats with relatively periment Station Special Report, Ames, IA. low vegetation, cannot be used effectively to collect adult Fewkes, D. W. 1961. Diel vertical movements in some grassland Nabidae (Heteroptera). Entomol. Mon. Mag. 97: 128–130. Colaspis in corn (K. Miwa, unpublished data). In addition, the results of this study demonstrated that even though Flynn, J. L., and T. E. Reagan. 1984. Pollination interference in seed corn from silk feeding by Colaspis louisianae Blake (Cole- the total number of C. crinicornis beetles on plants did optera: Chrysomelidae). J. Econ. Entomol. 77: 1185–1188. not fluctuate over time throughout a 24-h period, the lo- Kreuger, B., and D. A. Potter. 2001. Diel feeding activity and cation of beetles on plants did. Therefore, visual sampling thermoregulation by Japanese beetles (Coleoptera: Scarabaei- of whole plants would be a better option for C. crinicornis dae) within host plant canopies. Environ. Entomol. 30: 172–180. than stratified sampling (e.g., counting beetles on small Krysan, J. L. 1986. Introduction: Biology, distribution, and iden- portions of corn plants such as the ear zone). tification of pest Diabrotica, pp. 1–23. In J. L. Krysan, and This study is the first to characterize diel activity pat- T. A. Miller (eds.), Methods for the study of pest Diabrotica. terns of a Colaspis species. Results suggest that both C. Springer-Verlag, New York, NY. brunnea and C. crinicornis may be exhibiting similar in- Lambert, L. 1994. Grape colaspis, pp. 56–57. In L.G. Higley and creases in activity at night that facilitates movement from D. J. Boethel (eds.), Handbook of soybean insect pests. Entomo- logical Society of America, Lanham,MD. more protected to more exposed areas within a habitat. It is unclear what mechanisms drive this diel pattern, but Lewis, T., and L. R. Taylor. 1965. Diurnal periodicity of flight by . Trans. R. Entomol. Soc. Lond. 116: 393–476. vegetation architecture and associated interactions with environmental conditions may play a role. Sweep-netting Lindsay, D. R. 1943. The biology and morphology of Colaspis flav- ida (Say). Ph.D. dissertation, Iowa State College, Ames, IA. in clover and soybean fields and whole-plant-count sam- Lopez, A. N., H.A.A. Castillo, D. Carmona, P. L. Manetti, E. pling in cornfields were both effective sampling methods Mondino, and A. M. Vincini. 2002. Biological aspects of Co- for Colaspis adults. However, because activity and behav- laspis bridarollii (Bechyne) (Coleoptera: Chrysomelidae: Eu- iors of Colaspis beetles were influenced by time of day in molpinae) in Argentina. Coleopts. Bull. 56: 259–269. this study, use of a consistent sampling time within a diel May, L. M. 1979. Insect thermoregulation. Annu. Rev. Entomol. period would be recommended for future population stud- 24: 313–349. ies or IPM decision-making. This study demonstrates the Miwa, K. 2014. Natural history, phylogenetic relationships, and importance of night-time sampling to facilitate more com- pest potential of Colaspis Fabricius species (Coleoptera: Chrys- plete understanding of the biology of Colaspis beetles. As omelidae) in Nebraska. Ph. D. dissertation, University of Ne- more species are studied, it will become more apparent braska–Lincoln, Lincoln,NE. whether or not heightened night-time activity patterns Miwa, K., and L. J. Meinke. 2015. Developmental biology and ef- are common within the genus. fects of adult diet on consumption, longevity, and fecundity of Colaspis crinicornis (Coleoptera: Chrysomelidae). J. Insect Sci. 15: 78; doi: 10.1093/jisesa/iev062. Morris, R. F. 1960. Sampling insect populations. Annu. Rev. En- Acknowledgments — We would like to acknowledge E. G. 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