PHYSIOLOGICAL ECOLOGY Life History of Podisus maculiventris (Heteroptera: ) Adult Females Under Different Constant Temperatures

JESUSA CRISOSTOMO LEGASPI

USDAÐARSÐCMAVE, Florida A&M UniversityCenter for Biological Control, 6383 Mahan Drive, Tallahassee, FL 32308

Environ. Entomol. 33(5): 1200Ð1206 (2004) ABSTRACT Life table analysis was performed on Podisus maculiventris (Say) adult females at constant temperatures of 16, 26, 30, and 36ЊC. Survivorship curves were linear type II, with steeper rates of decline at higher temperatures. Longevityat 16 ЊC (47.2 d) was signiÞcantlylonger than that at 26ЊC (14.3 d) or 30ЊC (12 d). Adults under the 36ЊC survived only4.9 d and laid no eggs. Percentage of eggs that hatched was relativelyconstant at Ϸ or about 40% at 16, 26, and 30ЊC. Numbers of egg clutches (ranging from 5.9 to 9.4), eggs per clutch (13.6Ð14.6), and eggs in the Þrst clutch (9.0Ð15.1) did not differ signiÞcantlyat these three temperatures. However, preoviposition period was signif- icantlylonger at 16 ЊC (20.3 d) than at 26ЊC (6.3 d) and 30ЊC (4.9 d). Number of eggs laid was related to bodyweight bythe equation E ϭϪ139.1 ϩ 3.49w, where E is number of eggs laid per female lifetime, and w is the weight of the predator female. Life table analysis of P. maculiventris female adults showed Њ that both net reproductive rate (R0) and gross reproductive rate (GRR) were highest at 26 C, estimated at 47.8 and 156.0 females per female, respectively. However, the shorter generation times at 30ЊC(T ϭ 42.2 d) resulted in higher values for the intrinsic rate of increase (r ϭ 0.09), the Þnite rate of increase (␭ ϭ 1.09), and doubling time (DT ϭ 7.7 d). Analysis of cumulative egg production suggests that 26ЊC maybe more suitable for maintaining colonies of P. maculiventris because of the sustained levels of egg production over a longer period, compared with the 30ЊC treatment.

KEY WORDS Podisus maculiventris, life history, life table

THE , Podisus maculiventris (Say) predator, and how theymaybe affected bytemper- (Heteroptera: Pentatomidae), is endemic throughout ature. North America and has been recorded in various Life table analysis is a standard ecological method crops, including soybean, Glycine max (L.) Merr.; al- for estimating demographic parameters related to falfa, Medicago sativa L.; and corn, Zea mays L. P. population dynamics. Computational methods for maculiventris is a polyphagous predator known to feed constructing life tables and estimating keyreproduc- on Ͼ75 species (McPherson 1980, McPherson tive parameters date back several decades (Birch et al. 1982), several of which are important pests 1948). Numerous published examples illustrate the (Waddill and Shepard 1975, Lopez et al. 1976). A practical use of life table analyses (Maia et al. 2000). considerable bodyof knowledge has been developed More speciÞcally, life tables facilitate the analysis and on the effects of different feeding regimens on its life understanding of insect population dynamics and the history, its reproduction, and trade-offs that occur effects of external factors, such as biological control under both laboratoryand Þeld conditions (Legaspi agents (Wittmeyer and Coudron 2001). In this study, and OÕNeil 1993, Wiedenmann et al. 1996, Legaspi and I present life table analyses of P. maculiventris female Legaspi 1998). Research has included both theoretical adults under four constant temperatures using as prey aspects of predator search and functional response the greater wax moth, Galleria mellonella (L.) (Lep- (Wiedenmann and OÕNeil 1991, 1992), as well as prac- idoptera: Pyralidae). tical use of P. maculiventris in applied biological con- trol programs (OÕNeil et al. 1996, OÕNeil 1997). How- Materials and Methods ever, limited information exists on life tables of this Effects of Temperature on Survivorship and Lon- gevity. P. maculiventris used in the experiment were The use of trade, Þrm, or corporation names in this publication is obtained from a laboratorycolonyat USDAÐARSÐ for the information and convenience of the reader. Such use does not constitute an ofÞcial endorsement or approval bythe USDA or the CMAVE/Florida A&M UniversityCenter for Biolog- ARS of anyproduct or service to the exclusion of others that maybe ical Control in Tallahassee, FL. Newlyemerged to suitable. 3-d-old P. maculiventris adult females were placed October 2004 LEGASPI:LIFE HISTORY OF P. maculiventris 1201

Fig. 1. (A) Survivorship curve of adult P. maculiventris as affected bytemperature. (B) Effect of temperature on longevity (F ϭ 17.3; df ϭ 3, 36; R2 ϭ 0.59; P Ͻ 0.01). Different letters indicate means are signiÞcantlydifferent at P ϭ 0.05 (TukeyÕs HSD). individuallyinto petri dishes (15 cm in diameter) lined was placed into each dish for a period of 3Ð4 d each with Þlter paper, and starved for 24 h before the start week to permit mating. Numbers of eggs laid and P. of the experiment. Theywere then provided daily maculiventris females dying were recorded daily until with Þve fourth to Þfth instars of G. mellonella (Rain- all females had died. All egg masses were removed, bow Mealworms & Crickets Co., Compton, CA) as counted, and held until hatching at laboratoryambi- prey. The average weight of the prey was 321.96 Ϯ ent temperature of 24Ð25ЊC. Egg hatch occurred on 11.59 (SE) mg and the mean length was 2.62 Ϯ 0.05 average after 5 d. Numbers of eggs that hatched were (SE) cm. A water source consisted of a cotton ball recorded and percentage hatching was calculated. dipped in water and placed in a small dish (3.5 cm in Each petri dish containing a single female was con- diameter). Bodyweights were recorded at the start of sidered one replicate. Ten replicates were used for the experiment byusing a Sartorius analyticalbalance each of four temperatures: 16, 26, 30, and 36ЊC. Con- (model BP221S, Sartorius Corp., Edgewood, NY) with stant temperature conditions were maintained inside a precision of Ϯ0.0001 g, and weights were recorded ThermoForma model 3740 growth chambers (Ther- at 5-d intervals until death. A young male (5Ð10 d old) moForma, Marietta, OH) with a photoperiod of 14:10 1202 ENVIRONMENTAL ENTOMOLOGY Vol. 33, no. 5

Fig. 2. (A) Effect of temperature (ЊC) on bodyweight (milligrams) of adult female P. maculiventris. (B) Final mean body weight (ϮSE) bytemperature ( F ϭ 4.35; df ϭ 3, 36; R2 ϭ 0.27; P ϭ 0.01). Means with different letters are signiÞcantlydifferent at P ϭ 0.05 (TukeyÕs HSD).

(L:D) h and mean of 60% RH. Temperature and rel- n ative humidityinside each chamber were monitored ϭ ͸ R0 lxmx [1] byHOBO recorders (Onset Computer Corp., Bourne, xϭ0 MA).

Life Table Calculations. Numerical methods for cal- where x is age group, lx is probabilityof surviving to culating life historyparameters maybe obtained from age x, mx is age-speciÞc fecundity, and n is the number standard biological texts (Southwood and Henderson of age groups. In this study, number of eggs laid at each 2000, Begon et al. 1990) and have been applied for age group was divided by2, to estimate number of eggs manyinsect species (Medeiros et al. 2000). The net that would result in females. This is probablya con- reproductive rate (R0) is the mean number of female servative estimate of female sex ratio, because Þeld progenyproduced bya single female during its mean studies suggest that natural populations are Ϸ65% fe- lifetime and was calculated as follows: male (Legaspi et al. 1996). The Gross reproductive October 2004 LEGASPI:LIFE HISTORY OF P. maculiventris 1203 rate (GRR), also expressed in units of number of females per female, was calculated as follows:

n ϭ ͸ GRR mx [2] xϭ0 The generation time (T) is an estimate in days of the mean period between birth of the parents and that of the offspring and was calculated as follows:

n T ϭ ͩ͸ xl m ͪͲ R [3] x x 0 xϭ0 An approximate estimate for the intrinsic rate of increase (r), expressed in numbers of females per Fig. 3. Total number of eggs laid as a function of adult female per day, was calculated as follows: female bodyweight E ϭϪ139.1 ϩ 3.49w, where E is number ͑ ͒ of eggs laid per female lifetime, and w is the weight of the ln R0 ϭ ϭ 2 ϭ Ͻ r ϭ [4] predator female (F 9.2; df 1, 28; R 0.25; P 0.01). T Dotted lines represent 95% CL.

The Þnite rate of increase, also expressed in females Њ per female per day, was estimated as follows: its effect on longevityand development. At 16 C, body weight increases slowly, but at a sustained rate be- ␭ ϭ exp͑r͒ [5] cause survival is longest at this temperature (Fig. 2A). In contrast, bodyweight seems to increase at a higher Doubling time (DT) is the estimated time in days rate at 26ЊC and 30ЊC, but the increase is not sustained required for the population to double and was calcu- because individuals do not survive for as long at these lated as follows: temperatures. The slow and short duration increase in ln͑2͒ weight at 36ЊC indicates this temperature is too high DT ϭ [6] for P. maculiventris females to either survive or de- r velop for anysigniÞcant period. Mean bodyweight at Statistical Analyses. All statistical tests were per- 36ЊC is signiÞcantlylower than the other temperature formed using Systat 10 software (Systat Software, Inc., treatments because the females were not able to sur- Richmond, CA). The effects of temperature on lon- vive and develop at this temperature extreme (Fig. gevity, numbers of egg clutches, eggs per clutch, eggs 2B). in the Þrst clutch laid, preoviposition period, and per- The pooled data on numbers of eggs laid as a func- centage of egg hatch were analyzed using one-way tion of bodyweight shows that heavier females also lay analysis of variance. Means were separated using the most eggs (Fig. 3), albeit with a low R2 value. The TukeyÕs honestly signiÞcant difference (HSD) test at regression equation for numbers of eggs as a function P ϭ 0.05. Percentage data were transformed using the of bodyweight is E ϭϪ139.1 ϩ 3.49w, where E is angular transformation before statistical analysis, but number of eggs laid per female lifetime, and w is the theyare presented as nontransformed means (Sokal weight of the predator female (F ϭ 9.2; df ϭ 1, 28; R2 and Rohlf 1995). Regression analysis was performed ϭ 0.25; P Ͻ 0.01). Zanuncio et al. (2000) found the on total number of eggs laid as a function of female same result using Podisus rostralis (Sta¨l). Heavier fe- bodyweight. males displayed shorter preoviposition periods, whereas the numbers of eggs produced per daywas positivelycorrelated with female weight. Therefore, Results and Discussion mass rearing programs for P. rostralis should focus on Effects of Temperature on Survivorship and Lon- the use of female parents weighing at least 60.0 mg gevity. P. maculiventris adult females displayed a typ- (Zanuncio et al. 2000). ical type II linear survivorship curve, characteristic of The effect of temperature on cumulative number of organisms that die at a constant rate (Begon et al. eggs laid is illustrated in Fig. 4A. At 16ЊC, egg laying is 1990) (Fig. 1A). Higher temperatures were associated delayed by a prolonged preoviposition period of Ϸ2 with steeper declines in adult survivorship, with long- wk. Eggs are laid at a lower rate compared with the est survival at 16ЊC, and highest mortalityrates at 36 ЊC. higher temperature treatments, but the ovipositional Temperature had a highlysigniÞcant effect on mean period is longer due to the longer duration times at this longevityof P. maculiventris females (F ϭ 17.3; df ϭ 3, temperature. Oviposition rates at 26 and 30ЊC are 36; R2 ϭ 0.59; P Ͻ 0.01) (Fig. 1B). Longevityat 16 ЊC similar over the Þrst 2-wk period, but theyare sus- was signiÞcantlylonger than that at other tempera- tained at higher rates at 26ЊC, which also exhibited a tures (TukeyÕs HSD, P Ͻ 0.01). longer ovipositional period. No eggs were laid at 36ЊC, The effect of temperature on mean bodyweight of which was too high for P. maculiventris adult females P. maculiventris females is probablycompounded by to survive and reproduce. Mean cumulative numbers 1204 ENVIRONMENTAL ENTOMOLOGY Vol. 33, no. 5

Table 2. Life table statistics for P. maculiventris adults under four constant temperatures

Parameter Temp (ЊC) 16 26 30 36

a R0 25.14 47.8 44.4 0.0 GRRb 41.3 156.0 117.7 0.0 Tc 64.2 44.8 42.2 rd 0.05 0.08 0.09 ␭e 1.05 1.08 1.09 DT f 13.9 8.6 7.7

a ϭ⌺ R0 lxmx expressed in units of females per female (assuming 1:1 sex ratio). b ϭ⌺ GRR mx in females per female. c ϭ ⌺ T ( xlxmx)/R0 in days. d ϭ r ln R0/T in females per female per day. e ␭ ϭ exp(r) in females per female per day. f DT ϭ ln (2)/r in days.

oviposition period was signiÞcantlylonger at 16 ЊC (20.3 d) than at 26ЊC (6.3 d) and 30ЊC (4.9 d). Life Table Calculations. Life table statistics for P. maculiventris female adults are summarized in Table 2. Њ Both R0 and GRR were highest at 26 C, estimated at 47.8 and 156.0 females per female, respectively. Gen- eration time (T) of 42.2 d was shortest at 30ЊC. Both r and ␭ were highest at 30ЊC, estimated at 0.09 and 1.09, respectively. Doubling time was fastest at 30ЊC and was estimated at 7.7 d. Reproductive parameters are marginallyhigher at 30 ЊC compared with the other temperatures tested. The higher sustained oviposition Fig. 4. (A) Cumulative number of eggs laid (summed rate displayed at 26ЊC is apparentlyoffset bythe across all replicates) as affected bytemperature. (B) Mean Њ cumulative numbers of eggs laid bytemperature (excluding shorter generation time at 30 C. individuals that laid no eggs) (F ϭ 0.75; df ϭ 2, 18; R2 ϭ 0.08; Wittmeyer and Coudron (2001) constructed life P ϭ 0.49). tables for P. maculiventris and tested for the effects of artiÞcial diets fed to larvae and adult predators on the reproductive parameters at 26 Ϯ 5ЊC. Insect-free diets of eggs per female ranged from 84.8 at 16ЊC to 158.9 at provided during both immature and adult stages re- 26ЊC; however, treatment effects were not signiÞ- sulted in longer developmental times and preoviposi- ϭ ϭ 2 ϭ ϭ cantlydifferent ( F 0.75; df 2, 18; R 0.08; P tion periods, and signiÞcantlyreduced R0 and r pa- 0.49) (Fig. 4B). rameters. When fed an insect diet of cabbage looper, Data on egg clutches and percentage egg hatch are Trichoplusia ni (Hu¨ bner) (Lepidoptera: Noctuidae), summarized in Table 1. Numbers of egg clutches during both immature and adult stages, the reproduc- (ranging from 5.9 at 16ЊC to 9.4 at 26ЊC), eggs per tive parameters for P. maculiventris were calculated as Њ Њ Ϯ ϭ Ϯ ϭ Ϯ clutch (13.6 at 16 C to 14.6 at 30 C), and eggs in the follows (X SD): R0 42.2 2.9, T 34.9 1.9, and Þrst clutch (9.0 at 16ЊC to 15.1 at 26ЊC) did not differ intrinsic rate of increase (r) ϭ 0.11 Ϯ 0.002. In a similar ϭ ϭ ϭ signiÞcantlyat these three temperatures. Westich and study, the values were R0 59.5, T 33.3, and r Hough-Goldstein (2001) also found that percentage of 1.001 (Coudron et al. 2002). Corresponding values for Њ ϭ ϭ egg hatch of P. maculiventris was not affected bytem- the 26 C treatment in this studywere R0 47.8, T perature, averaging 70% at both 18ЊC and 25ЊC. Pre- 44.8, and r ϭ 0.08, which indicated lower reproductive

(Table 1. Mean egg clutch data (؎SE

Measurement Temp (ЊC) Statistics 16 26 30 F df R2 P Egg clutches 5.86 Ϯ 1.34 9.43 Ϯ 2.89 7.12 Ϯ 2.2 0.63 2, 29 0.06 0.54 Eggs/clutch 13.578 Ϯ 1.34 14.21 Ϯ 1.58 14.62 Ϯ 0.75 0.12 2, 18 0.013 0.89 Eggs in Þrst clutch 9.0 Ϯ 2.3 15.1 Ϯ 2.54 10.25 Ϯ 1.45 2.34 2, 18 0.21 0.12 Days Þrst clutch laid 20.33 Ϯ 2.08a 6.29 Ϯ 1.11b 4.88 Ϯ 0.61b 42.23 2, 18 0.82 Ͻ0.01 % Egg hatch 45.8 Ϯ 14.1 42.3 Ϯ 10.6 37.9 Ϯ 8.9 0.22 2, 18 0.025 0.80

Data for the 36ЊC treatment was excluded from the analyses because no eggs were laid. Only nonzero replicates were included for other treatments. One-wayanalysisof variance was performed across rows for temperature effects on each factor. Different letters indicate means are signiÞcantlydifferent (TukeyÕsHSD) where treatment effects are signiÞcant. October 2004 LEGASPI:LIFE HISTORY OF P. maculiventris 1205 rates and longer generation times, suggesting that G. CMAVE/CESTA-CBC student apprentice) assisted in rear- mellonella was an inferior food source. Furthermore, ing a laboratorycolonyof P. maculiventris. Benjamin C. the following biological data were recorded byWitt- Legaspi, Jr., helped with statistical analysis of the data and meyer and Coudron (2001): developmental time (sec- provided useful discussions that greatlyimproved the manu- ond instar to adult) ϭ 17.8 Ϯ 0.3, weight (mg) ϭ 93.7 Ϯ script. Drs. Manuel Pescador and Lambert Kanga (Florida A&M University) reviewed an earlier version of this manu- 3.1, preoviposition period ϭ 7.3 Ϯ 0.3, and eggs per ϭ Ϯ script. Additional helpful comments were provided bytwo female 120.1 3.5. anonymous reviewers. Using a closelyrelated species, Medeiros et al. (2000) constructed life fertilitytables for Podisus ni- grispinus (Dallas) at a constant temperature of 25ЊC. References Cited Each female oviposited a mean of 188.5 eggs, with a mean longevityof 31.2 d. The R was 31.9 females per Aldrich, J. R., and W. W. Cantelo. 1999. Suppression of 0 Colorado potato beetle infestation bypheromone-medi- female, T was 47.4 d, DT was 9.5 d, r was 0.073, and ␭ ated augmentation of the predatoryspined soldier bug, Þnite rate of increase ( ) was 1.08. These values are Podisus maculiventris (Say) (Heteroptera: Pentatomi- similar to those obtained in this studyfor P. macu- dae). Agric. For. Entomol. 1: 209Ð217. liventris at 26ЊC (Table 2). In a subsequent study Begon, M., J. L. Harper, and C. R. Townsend. 1990. Ecology: (Medeiros et al. 2003), life table parameters of P. individuals, populations and communities, 2nd ed. Black- nigrispinus were measured at 20, 23, 25, 28, 30 and 33 Ϯ well, Cambridge, MA. 0.2ЊC (60 Ϯ 10% RH, photoperiod of 14:10 [L:D] h) by Birch, L. C. 1948. The intrinsic rate of natural increase of an using Alabama argillacea (Hu¨ bner) (Lepidoptera: insect population. J. Anim. Ecol. 17: 15Ð26. Noctuidae) as prey. GRR ranged from 1.6 (at 33ЊC) to Coudron, T. A., J. Wittmeyer, and Y. Kim. 2002. Life history Њ Њ Њ and cost analysis for continuous rearing of Podisus macu- 366.6 (28 C); R0 from 0.02 (33 C) to189.5 (28 C) fe- liventris (Say) (Heteroptera: Pentatomidae) on a zoo- males per female; T from 33.3 (33ЊC) to 85.5 (20ЊC) Њ Њ phytophagous artiÞcial diet. J. Econ. Entomol. 95: 1159Ð days; DT from 0.82 (33 C) to 17.8 (20 C) d; r from 0.13 1168. (33ЊC) to 0.12 (28ЊC) per day; ␭ from 0.88 (33ЊC) to de Clercq, P., K. Wyckhuys, H. de Oliveira, and J. Klapwijk. 1.12 (28ЊC) females per female per day. Population 2002. Predation by Podisus maculiventris on different life growth rates were highest between 28 and 30ЊC, with stages of Nezara viridula. Fla. Entomol. 85: 197Ð202. 33ЊC proving detrimental to predator reproduction. As Legaspi, J. C., and R. J. O’Neil. 1993. Life historyof Podisus in this study, the higher temperature used was sub- maculiventris given low numbers of Epilachna varivestis optimal. as prey. Environ. Entomol. 22: 1192Ð1200. Legaspi, J. C., and B. C. Legaspi, Jr. 1998. Life-historytrade- In published studies, previous workers maintained offs in , with emphasis on Podisus maculiventris their laboratorycolonies of P. maculiventris at close to Њ (Heteroptera: Pentatomidae), pp. 71Ð87. In M. Coll and 26 C, perhaps because this temperature maybe opti- J. R. Ruberson [eds.], PredatoryHeteroptera: their ecol- mal for insect growth and development in general. ogyand use in biological control. Thomas SayPublica- Examples of environmental conditions selected in- tions in Entomology, Lanham, MD. clude 23 Ϯ 1ЊC (65 Ϯ 10% RH, photoperiod of 16:8 Legaspi, J. C., R. J. O’Neil, and B. C. Legaspi, Jr. 1996. Trade- [L:D] h; de Clercq et al. 2002); 24 Ϯ 1ЊC (40Ð70% RH, offs in bodyweights, egg loads, and fat reserves of Þeld- photoperiod of 14:10 [L:D] h; Legaspi and OÕNeil collected Podisus maculiventris (Heteroptera: Pentato- 1993); 25ЊC (photoperiod of 18:6 [L:D] h; Westich and midae). Environ. Entomol. 25: 155Ð164. Њ Lopez, J. D., R. L. Ridgway, and R. E. Pinnel. 1976. Com- Hough-Goldstein 2001); 26 C (65% RH, photoperiod parative efÞcacyof four insect predators of the bollworm of 16:8 [L:D] h; Aldrich and Cantelo 1999); 26 Ϯ 2ЊC Ϯ and tobacco budworm. Environ. Entomol. 5: 1160Ð1164. (60 10% RH, photoperiod of 16:8 [L:D] h; SantÕ Ana Maia, A. de H. N., A.J.B. Luiz, and C. Campanhola. 2000. and Dickens 1998). Life table statistics such as those Statistical inference on associated fertilitylife table pa- calculated in this studymayprovide useful values for rameters using jackknife technique: computational as- summarizing the reproductive capacities of insects. pects. J. Econ. Entomol. 93: 511Ð518. However, theyalso maybe misleading when applied McPherson, J. E. 1980. A list of the preyspecies of Podisus to a situation, such as selecting an optimal temperature maculiventris (: Pentatomidae). Great Lakes for mass rearing a test insect, or simplymaintaining a Entomol. 13: 18Ð24. McPherson, R. M., J. C. Smith, and W. A. Allen. 1982. In- colonyfor experimental purposes. Examination of the Њ cidence of predators in different soybean crop- life table data indicates that 30 C yields the numeri- ping systems. Environ. Entomol. 11: 685Ð689. callybest reproductive values. Inspection of cumula- Medeiros, R. S., F. S. Ramalho, W. P. Lemos, and J. C. tive eggs laid with time mayindicate a more favorable Zanuncio. 2000. Age-dependent fecundityand life-fer- reproductive trend of prolonged egg production over tilitytables for Podisus nigrispinus (Dallas) (Het., Pen- a longer period. Therefore, 26ЊC mayindeed be a more tatomidae). J. Appl. Entomol. 124: 319Ð324. suitable temperature for maintaining a colonyof P. Medeiros, R. S., F. S. Ramalho, J. C. Zanuncio, and J. E. maculiventris than 30ЊC. Serra˜o. 2003. Effect of temperature on life table param- eters of Podisus nigrispinus (Het., Pentatomidae) fed with Alabama argillacea (Lep., Noctuidae) larvae. J. Appl. Acknowledgments Entomol. 127: 209. O’Neil, R. J. 1997. Functional response and search strategy I thank Mohamed Soumare (Florida A&M University) and of Podisus maculiventris (Heteroptera: Pentatomidae) at- Ignacio Baez (USDAÐARSÐCMAVE/CESTAÐCBC) for tacking Colorado potato beetle (Coleoptera: Chrysomeli- technical assistance. Elizabeth Aninakwa (USDAÐARSÐ dae). Environ. Entomol. 26: 1183Ð1190. 1206 ENVIRONMENTAL ENTOMOLOGY Vol. 33, no. 5

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