Size-Dependent Feeding and Reproduction by Boll Weevil (Coleoptera: Curculionidae)

University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln

U.S. Department of Agriculture: Agricultural Publications from USDA-ARS / UNL Faculty Research Service, Lincoln, Nebraska

2005

S. M. Greenberg Kika de la Garza Subtropical Agricultural Research Center, [email protected]

D. W. Spurgeon USDA-ARS

Thomas W. Sappington USDA-ARS, [email protected]

M. Sétamou USDA-ARS

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Greenberg, S. M.; Spurgeon, D. W.; Sappington, Thomas W.; and Sétamou, M., "Size-Dependent Feeding and Reproduction by Boll Weevil (Coleoptera: Curculionidae)" (2005). Publications from USDA-ARS / UNL Faculty. 730. https://digitalcommons.unl.edu/usdaarsfacpub/730

This Article is brought to you for free and open access by the U.S. Department of Agriculture: Agricultural Research Service, Lincoln, Nebraska at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Publications from USDA-ARS / UNL Faculty by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. ECOLOGY AND BEHAVIOR Size-Dependent Feeding and Reproduction by Boll Weevil (Coleoptera: Curculionidae)

1 2 3 4 S. M. GREENBERG, D. W. SPURGEON, T. W. SAPPINGTON, AND M. SE´ TAMOU

Areawide Pest Management Research Unit, USDAÐARS, 2413 East Highway 83, Weslaco, TX 78596

J. Econ. Entomol. 98(3): 749Ð756 (2005) ABSTRACT The considerable variation in adult size of the boll weevil, Anthonomus grandis grandis Boheman, has been well documented, but the inßuences of adult size on reproductive rate are not known. We examined the relationship between the size of boll weevils and their feeding and oviposition. Weevils weighed to the nearest milligram were grouped into Þve categories based on pupal weight: Յ5, 6Ð10, 11Ð15, 16Ð20, and Ͼ20 mg. Numbers of lifetime punctures produced in ßower buds (squares) of cotton, Gossypium hirsutum L., by both sexes of adults tended to increase with pupal weight. Boll weevil females with pupal weights Ͼ10 mg produced progeny with signiÞcantly higher survival to adulthood and also produced a higher percentage of female progeny than those with pupal weights Յ10 mg. The population growth indices for females having pupal weights Ͼ10 mg averaged 1.8-fold higher than those of females weighing Յ10 mg. Survivorship of adults of both sexes also tended to increase with pupal weight. The percentage of females laying eggs on any given day averaged 2.1 times higher when their pupal weights were Ͼ10 mg than when their pupal weights were Յ10 mg. Although small size negatively affected female reproductive potential, even extremely small females produced some viable offspring. However, the penalties of small adult size, in terms of longevity and reproductive potential, suggest that cultural practices that result in the production of small adults may be used to impact weevil populations.

KEY WORDS Anthonomus grandis grandis, boll weevil, reproductive indices, cotton

THE CONSIDERABLE VARIATION IN adult size of the boll tion of this premise, Reardon and Spurgeon (2002) weevil, Anthonomus grandis grandis Boheman, is well removed larvae from food at different times to deter- documented (Mally 1901, Newell et al. 1926, Little and mine the critical weight beyond which development Martin 1942). Most studies have considered the source to adulthood would occur without further feeding. of this variation to be dietary, with limited food quality Although their conclusions questioned the promi- or availability resulting in smaller weevils. In partic- nence of the role of square desiccation in the produc- ular, the production of small adult weevils has been tion of mortality, the results emphasized that variation associated with the infestation of undersized ßower in access to a food supply among larvae could result in buds (squares) of cotton, Gossypium hirsutum L.) a wide (1.61Ð21.49 mg) range of adult sizes. Based on (Mally 1901, Smith 1921, Bailey et al. 1967), although observations of infested square collections (D.W.S., there is an indication that this relationship may vary unpublished data), the production of small adult wee- among species of cotton (Black and Leigh 1963). vils is likely to occur most often early in the growing Other conditions also may impact the diet to produce season when available squares are small, and near the small adults. Curry et al. (1982) constructed a model time of crop maturity, when the numbers of squares of boll weevil mortality based on the desiccation rates are limited, weevil populations are high, and most of abscised squares. The premise of this model was that squares are heavily fed upon. rapid square desiccation would result in starvation of Substantial effort has been devoted to understand- the developing boll weevil larva. During an examina- ing the factors that contribute to natural mortality in the boll weevil (Smith 1936; Sturm and Sterling 1986, This article reports the results of research only. Mention of a 1990; Sturm et al. 1990), and the manipulation of these proprietary product does not constitute an endorsement or a recom- factors through cultural practices has been investi- mendation by the USDA for its use. 1 Corresponding author, e-mail: [email protected]. gated in some production systems (Slosser 1981, 2 Areawide Pest Management Research Unit, USDAÐARS, College Slosser et al. 1986). However, the emphasis of most of Station, TX 77845. these efforts was on increasing mortality in the boll 3 Current address: Corn Insects and Crop Genetics Research Unit, weevil population without regard to the potential im- USDAÐARS, Ames, IA 50011. 4 Subtropical Agricultural Research Center, USDAÐARS, Weslaco, pacts of an altered size distribution of adults. Because TX 78596. no previous study has examined the population level 750 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 98, no. 3 consequences of variable adult size, our objective was the ßower bud and with bracteoles intact) daily until to examine the respective relationships between pupal weevil death. Squares were removed and examined weight and subsequent feeding and reproductive ac- each day for feeding and oviposition punctures (fe- tivities of boll weevils. males) or only for feeding punctures (males). Un- sealed punctures were considered as feeding punctures. Oviposition punctures were distinguished by a Materials and Methods frass plug and/or a waxy substance either closing the Experimental Insects and Reproductive Condition- puncture or present on the periphery of the puncture. ing. Adult boll weevils were obtained from infested Everett and Ray (1962) reported a correlation be- squares collected from the ground in cotton Þelds in tween the numbers of sealed punctures and the num- the Lower Rio Grande Valley of Texas in the 2001 and bers of eggs that weevils deposited. Therefore, we 2002 growing seasons. Squares were carefully dis- used the numbers of sealed punctures as a relative sected to conÞrm infestation, and those with live third estimate of egg numbers. instars were closed and held within screened cages in In addition to monitoring feeding and oviposition, an environmental chamber at 28 Ϯ 1ЊC, 65% RH, and the percentage of eggs that ultimately produced an a photoperiod of 14:10 (L:D) h. Temperature and adult, and the sex ratio of adult progeny, were esti- humidity were monitored by a Fisher-brand traceable mated from cohorts of squares. relative humidity meter with temperature readout Distinct cohorts of randomly selected oviposition- (catalog no. 11-661-12; Control Company, Friends- punctured squares were periodically obtained from wood, TX). When Ϸ60% of boll weevil larvae had each pupal weight category. To avoid underestimating pupated, the pupae were harvested, weighed to the the production of adults because of larval cannibalism, nearest milligram, and placed individually in petri only squares containing a single oviposition puncture dishes (35 by 10 mm) containing a thin layer of moist were selected. The number of oviposition-punctured vermiculite. squares in each cohort varied based on their availabil- Pupal weight categories were Յ5, 6Ð10, 11Ð15, 16Ð ity. Totals of 12, 24, 21, 19, and 14 cohorts containing 20, and Ͼ20 mg. Because the sizes of pupae available 70, 133, 111, 159, and 117 oviposition-punctured in naturally infested squares varied seasonally, weevils squares, respectively, were obtained from pupal assigned to different weight classes were generally weight classes of Յ5, 6Ð10, 11Ð15, 16Ð20, and Ͼ20 mg. obtained from different square collections. Adult wee- Each cohort was held in a 150 by 20-mm plastic petri vils corresponding to pupal weight classes of Յ5 and dish vented as described previously. Square cohorts 6Ð10 mg were obtained from square collections be- were maintained under the same environmental con- tween 15 April and 31 May, and in September. Adults ditions as the adults. Plates were observed daily for corresponding to other pupal weight classes were ob- newly emerged adults beginning on day 12 and until tained from square collections in June through August. day 20 after oviposition. After day 20, squares were Pupae were examined daily until adult eclosion. opened to determine whether additional live weevils Adults were sexed as described by Sappington and remained. Spurgeon (2000), and males were marked with a red Finally, individual oviposition-punctured squares paint pen on the right elytron. Newly eclosed weevils were periodically collected from each pupal weight from the same pupal weight categories were held in class (until a total of 10 adults were obtained per male-female pairs in 90 by 15-mm plastic petri dishes weight class) for estimation of weevil developmental in an environmental chamber maintained at 28 Ϯ 1ЊC, time. These squares were maintained under the same 65% RH, and a photoperiod of 14:10 (L:D) h. Daily for environmental conditions as the square cohorts, ex- 5 d, each pair was provided with Þve undamaged cept that they were held singly so the developmental cotton squares (7Ð9 mm in diameter at the widest part time from egg to adult emergence could be deter- of the ßower bud and with intact bracteoles) and a mined. cotton wick saturated with water. We assumed all Statistical Analyses. Because pupae, both within and females were mated by the end of this 5-d conditioning among weight classes, were collected at various times period. and no single collection yielded pupae of all weight Experimental Procedure. Observations were made classes, collections within a weight class were pooled on groups of weevils distinguished by their pupal for analysis. Before feeding and oviposition data were weights. Because weevils of different weight classes pooled, they were examined for homogeneity of vari- generally became available at different times, individ- ance within each pupal weight class. Based on Fisher ual male and female weevils were incorporated into tests (Sokal and Rohlf 1995), data for feeding punc- Ͻ ϭ Ͼ the experiment until sample sizes of 30, 36, 40, 41, and tures of males (Fcalculated 1.61; df 9, 19; P 0.05), 25 weevils of each sex were attained for respective and total punctures (feeding plus oviposition punc- Յ Ͼ Ͻ ϭ Ͼ weight classes of 5, 6Ð10, 11Ð15, 16Ð20, and 20 mg. tures) of females (Fcalculated 1.53; df 9, 19; P After the conditioning period to allow mating and 0.05) exhibited homogeneous variances. preoviposition development, each weevil was held Total lifetime punctures were examined by two- individually in a 150 by 20-mm plastic petri dish with way analysis of variance (ANOVA) by using PROC a 40-mm diameter nylon screen window on top. Each GLM of SAS (SAS Institute 1999), with weevil sex, weevil was provided Þve uninfested greenhouse- pupal weight class, and their interaction as model grown squares (7Ð9 mm diameter at the widest part of effects. Data for lifetime oviposition, female adult lon- June 2005 GREENBERG ET AL.: BOLL WEEVIL PUPAL WEIGHT AND REPRODUCTION 751

total longevity in days. The proportions of days on which females oviposited were then compared among pupal weight classes using a log likelihood G-test (Zar 1999). The proportions of females laying one or more eggs during their lifetimes were similarly compared among pupal weight classes by using a log-likelihood G-test. Each respective relationship between female pupal weight and total oviposition punctures, total feeding punctures, the ratio of oviposition punctures to total punctures, and the proportion of squares with one or more punctures, was described by a simple linear regression calculated using PROC GLM (SAS Insti- tute 1999). The numbers of oviposition punctures observed for each weevil each day were examined by repeated measures analysis using PROC MIXED (Lit- Fig. 1. Mean Ϯ SE lifetime total punctures by boll weevil tell et al. 1997). The model used a compound symme- females and males within different pupal weight classes. try covariance structure and contained terms for time Means followed by the same uppercase letter within each (day), pupal weight, and their interaction. weight class are not signiÞcantly different between sexes, and means followed by the same lowercase letter within each The inßuence of pupal weight on patterns of sub- sex are not signiÞcantly different between weight classes sequent adult survival was examined separately for (TukeyÐKramer). each weevil sex. Homogeneity of survival curves among pupal weight classes was tested with the log- rank ␹2 statistic of the LIFETEST procedure of SAS gevity, total developmental time of progeny (egg to (SAS Institute 1999). Subsequently, a closed testing adult emergence), percentage of emergence, and per- procedure (Hommel 1988) was used to determine centage of progeny that were female, were examined whether survival curves for different weight classes by one-way analyses of variance using PROC GLM could be distinguished. (SAS Institute 1999) to determine the inßuence of An estimate of boll weevil population growth rate pupal weight. When signiÞcant F values were ob- was obtained for females corresponding to each pupal tained, means were separated using the TukeyÐ weight class by calculating life table statistics. For each Kramer test (TUKEY option of the LSMEANS state- treatment, the jackknife program of Hulting et al. ment, SAS Institute 1999). Percentage data were (1990) was used to calculate the net reproductive rate analyzed as arcsine square-root-transformed propor- (Ro), the intrinsic rate of natural increase (rm), the tions (Sokal and Rohlf 1995), but results are presented Þnite capacity of increase (␭, deÞned as the number as untransformed means. of times a population multiplies itself per unit of time), Because we observed differences among pupal the mean generation time (T), the doubling time weight classes in both lifetime oviposition and female (DT) of the population, and the total progeny pro- longevity, the relationships between these two param- duced per female. eters were explored by covariance analysis by using PROC MIXED (Littell et al. 1997). The model included lifetime oviposition as the dependent variable, Results pupal weight class as the independent variable, and longevity as a covariate. Relationships corresponding The number of lifetime punctures differed between to the respective pupal weight classes were examined sexes (F ϭ 17.3; df ϭ 1, 334; P Ͻ 0.01) and among pupal for coincidence of the regression lines, and for com- weight classes (F ϭ 21.8; df ϭ 4, 334; P Ͻ 0.01). The mon slopes. Differences among the slopes of regres- average number of total punctures produced by fe- sions corresponding to individual weight classes were males, including both feeding and oviposition punc- then assessed through pairwise comparisons using the tures (302.6 Ϯ 24.0), was 1.6-fold higher than the total ESTIMATE statement in PROC MIXED. made by males (190.4 Ϯ 9.5). Lifetime punctures The proportion of days on which each female ovi- tended to increase with pupal weight (Fig. 1). The posited was calculated by dividing the number of days interaction between pupal weight class and weevil sex during which each female laid one or more eggs by the was not signiÞcant (F ϭ 0.9; df ϭ 4, 334; P ϭ 0.50),

Table 1. Regression parameters relating female boll weevil pupal weight (pwt) to daily oviposition punctures (OP), daily feeding (punctures (FP), ratio of oviposition punctures to total punctures (OP/͓OP؉FP͔), and total squares attacked (SA

2 Relation n Slope (SE) Pslope Intercept (SE) Pintercept R pwt-OP 170 0.232 (0.032) Ͻ0.01 Ϫ0.175 (0.474) 0.71 0.233 pwt-FP 170 0.116 (0.041) Ͻ0.01 5.218 (0.598) Ͻ0.01 0.046 pwt-OP/͓OPϩFP͔ 170 0.016 (0.002) Ͻ0.01 0.033 (0.024) 0.17 0.350 pwt-SA 170 0.019 (0.002) Ͻ0.01 0.345 (0.035) Ͻ0.01 0.258 752 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 98, no. 3

Table 2. Effects of boll weevil female pupal weight on the Table 4. Regression equations relating adult longevity to life- emergence and development time of progeny, and on the percent- time oviposition for female boll weevils corresponding to different age of female progeny pupal weight classes

Pupal Completed Developmental Female Pupal n Slope (SE) P Intercept (SE) P wt(mg) development (%) time(d) progeny(%) wt(mg) slope intercept Յ5 38.5 Ϯ 7.4b 16.9 Ϯ 0.5a 28.0 Ϯ 10.9b Յ5 30 1.72 (2.94)ab 0.56 Ϫ6.11 (28.98) 0.83 6Ð10 44.2 Ϯ 5.0b 15.9 Ϯ 0.5a 40.6 Ϯ 2.8ab 6Ð10 36 5.08 (0.89)a Ͻ0.01 Ϫ47.30 (22.95) 0.04 11Ð15 73.6 Ϯ 5.8a 16.7 Ϯ 0.5a 58.3 Ϯ 7.8a 11Ð15 40 4.06 (0.59)a Ͻ0.01 Ϫ0.11 (24.01) Ͼ0.99 16Ð20 72.8 Ϯ 5.3a 15.4 Ϯ 0.3a 62.5 Ϯ 3.9a 16Ð20 41 2.34 (0.56)b Ͻ0.01 53.44 (24.03) 0.03 Ͼ20 66.1 Ϯ 3.3a 15.0 Ϯ 0.4a 67.2 Ϯ 4.1a Ͼ20 25 1.56 (0.54)b Ͻ0.01 64.82 (29.35) 0.03

Means Ϯ SE within a column followed by different letters are Slopes (SE) within a column followed by different letters are signiÞcantly different (TukeyÐKramer). signiÞcantly different (comparison-wise error rate 0.05). indicating that the effects of pupal weight class on 3). Lifetime oviposition also increased with pupal lifetime production of punctures was similar for both weight class up to the 11Ð15 mg class (F ϭ 9.3; df ϭ 4, sexes. 167; P Ͻ 0.01; Table 3). The total number of lifetime Average daily oviposition increased with female pu- oviposition punctures produced by females with pupal pal weight (F ϭ 52.4; df ϭ 1, 170; P Ͻ 0.01; Table 1). weights Ͼ10 mg were Ϸ16-fold higher than for females Similarly, increases in female pupal weight were ac- weighing Ͻ5 mg. companied by increases in the average daily number Analyses of covariance indicated the relationships of feeding punctures (F ϭ 8.0; df ϭ 1, 170; P Ͻ 0.01), between lifetime oviposition (y) and longevity (x) the ratio of oviposition punctures to total punctures were not described by a common, coincident regres- (F ϭ 93.3; df ϭ 1, 170; P Ͻ 0.01), and the average sion for all weight classes (F ϭ 21.25; df ϭ 5, 162; P Ͻ proportion of squares that were attacked each day 0.01) and that at least one of the regression slopes (F ϭ 59.3; df ϭ 1, 170; P Ͻ 0.01) (Table 1). Overall, differed from those of the other weight classes (F ϭ 40.2 Ϯ 3.5% of the squares provided were punctured 4.30; df ϭ 4, 162; P Ͻ 0.01). Lifetime oviposition was by females with pupal weights Յ5 mg, whereas 50.1 Ϯ not statistically related to longevity for weevils of the 4.0, 63.1 Ϯ 4.0, 67.9 Ϯ 3.4, and 71.0 Ϯ 3.6% of squares lowest pupal weight class (Table 4). The lack of this were punctured by females in respective weight relationship likely resulted from the substantial per- classes of 6Ð10, 11Ð15, 16Ð20, and Ͼ20 mg. centage of weevils in this weight class that did not The percentage of progeny that developed to adult- oviposit (45%) at any time during the study. For wee- hood differed among pupal weight classes of the fe- vils associated with pupal weights Ͼ5 mg, slopes of the male parents (F ϭ 7.8; df ϭ 4, 85; P Ͻ 0.01). Oviposition regressions relating oviposition to longevity tended to by females with pupal weights Ͼ10 mg produced a decrease with increasing pupal weight class (Table 4). signiÞcantly higher percentage of eggs yielding adult Thus, an inßuence of longevity on lifetime oviposition progeny compared with smaller females (Table 2). was observed for all weight classes Ͼ5 mg, but this Female pupal weight class also inßuenced the pro- inßuence was diminished at pupal weights Ͼ15 mg. portion of progeny that were female (F ϭ 4.9; df ϭ 4, The percentage of days on which females oviposited 85; P Ͻ 0.01). Females with pupal weights Ͼ10 mg during their lifetime increased with higher pupal produced a higher percentage of female progeny than weight (G ϭ 111.6, df ϭ 4, P Ͻ 0.01). On average, those with pupal weights Յ5 mg. However, the size of females weighing Յ5 mg oviposited on 37.2% of days female parents did not signiÞcantly inßuence off- of their lifetime. Females in weight classes of 6Ð10, spring developmental time (F ϭ 3.1; df ϭ 4, 45; P ϭ 11Ð15, 16Ð20, and Ͼ20 mg laid eggs on 43.8, 74.6, 81.3, 0.523; Table 2). and 93.3% of days in their lifetimes, respectively. The Adult female longevity increased with pupal weight, proportion of females that were gravid (oviposited at with females obtained from pupae weighing Ͼ10 mg least once) also increased with pupal weight (G ϭ living signiÞcantly longer than those obtained from 10.6, df ϭ 2, P Ͻ 0.01). Approximately 54.7, 75.0, and smaller pupae (F ϭ 11.9; df ϭ 4, 167; P Ͻ 0.01; Table 90.0% of females in pupal weight classes of Յ5, 6Ð10, and 11Ð15 mg, respectively, oviposited at least once. All females weighing Ն16 mg oviposited at least once. Table 3. Effects of boll weevil female pupal weight on longevity Oviposition was signiÞcantly inßuenced by both and lifetime oviposition time (days postconditioning) (F ϭ 3.9; df ϭ 118, 1,903; Pupal Oviposition P Ͻ 0.01) and female pupal weight class (F ϭ 18.4; df ϭ Longevity(d) wt(mg) punctures 4, 107; P Ͻ 0.01) (Fig. 2). In addition, the time by pupal ϭ ϭ Յ5 8.2 Ϯ 1.0b 8.2 Ϯ 2.9c weight class interaction was signiÞcant (F 1.5; df 6Ð10 19.9 Ϯ 2.8b 54.0 Ϯ 17.6b 298, 2,918; P Ͻ 0.01), indicating that the temporal 11Ð15 32.6 Ϯ 3.7a 135.4 Ϯ 21.2a pattern of oviposition activity differed among female 16Ð20 35.4 Ϯ 3.8a 136.0 Ϯ 20.4a pupal weight classes. For females with pupal weights Ͼ20 43.6 Ϯ 6.6a 132.9 Ϯ 18.0a Յ5 mg, oviposition did not begin until day 8 after the Means Ϯ SE within a column followed by different letters are conditioning period, after which the average number signiÞcantly different (TukeyÐKramer) of oviposition punctures slowly increased to a plateau June 2005 GREENBERG ET AL.: BOLL WEEVIL PUPAL WEIGHT AND REPRODUCTION 753

Fig. 2. Lifetime proÞles of daily mean Ϯ SE oviposition activity of boll weevil females in response to different categories of pupal weight (A) Յ5 mg, (B) 6Ð10 mg, (C) 11Ð15 mg, (D) 16Ð20 mg, and (E) Ͼ20 mg. of Ϸ1 egg per day for Ϸ10 d, with a short (3 d) peak classes of 11Ð15 and 16Ð20 mg, oviposition began ear- at Ϸ5 eggs per day, followed by a rapid decline in lier (days 2 and 3 after the conditioning period, re- oviposition (Fig. 2A). No females in this pupal weight spectively), the plateau preceding peak oviposition class laid eggs beyond day 25. A similar pattern of was less distinct, and oviposition rates were generally oviposition was observed for females in the pupal higher than for the smaller weevils (Fig. 2C and D). weight class from 6 to 10 mg, except the duration of However, in both classes the period of peak oviposi- each of the phases of the pattern (plateau, peak, and tion was Ϸ20 d, followed by a gradual decline in decline) were greatly lengthened, and the oviposition oviposition until beyond day 80. The peak in ovipo- rates were higher, compared with the smaller females sition for the heaviest weevils (pupal weights Ͼ20 mg) (Fig. 2B). The last egg laid by a female in the 6Ð10-mg occurred earlier and for a shorter duration than for class was oviposited on day 85. For females in weight smaller weevils, but these heavier females continued 754 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 98, no. 3

df ϭ 1, P Ͻ 0.01, Fig. 3B). Survivorship of males within the 6Ð10-mg pupal weight class was similar to that for males in the 11Ð15-mg class but was less than for weevils in heavier weight classes (␹2 Ն 6.4, df ϭ 1, P Յ 0.01). Survivorship of males associated with pupal weights Ͼ10 mg was similar among weight classes (␹2 Յ 2.4, df ϭ 1, P Ն 0.11). The values of life table statistics calculated for boll weevil females differed among pupal weight categories (Table 5). Populations of boll weevils with pupal weights Ͼ10 mg are predicted to grow at signiÞcantly

higher mean constant exponential rates (rm) than those with pupal weights Յ10 mg. Life table calcula- tions indicated that boll weevil populations with pupal weights of Ͼ10 mg will increase an average 8.4-fold

each generation (Ro) higher than for females with weights Յ5 mg or 6Ð10 mg. The DT of weevils with pupal weights Յ5 mg could not be estimated because

the population was not increasing (rm was not different from zero).

Discussion Positive relationships between adult or pupal weight or size and resulting egg complement or fecundity have been reported in several Lepidoptera (Bragg 1970, Miller et al. 1982, Wagner et al. 1987, Spurgeon et al. 1995, Greenberg et al. 2001), Diptera Fig. 3. Survivorship (percentage of live weevils) proÞles (Hawley 1985, Krainacker et al. 1989), and Hymenop- of boll weevil (A) females and (B) males in relation to tera (Zhang and Wagner 1991, Eliason and McCul- different categories of pupal weight. lough 1997). Many authors have reported that among arthropod predators and parasitoids there is often a to produce approximately one to three eggs per day for positive correlation between body size or weight and nearly 120 d (Fig. 2E). reproductive potential (OÕNeill and Skinner 1990, Weevil survivorship (percentage of weevils remain- Croft and Copland 1993, Zheng et al. 1993, Greenberg ing alive each day) varied signiÞcantly among pupal et al. 1995). Comparatively few studies have explored weight classes for both females (␹2 ϭ 107.2, df ϭ 4, P Ͻ this relationship within the Coleoptera. Pupal weight 0.01) and males (␹2 ϭ 53.9, df ϭ 4, P Ͻ 0.01). The was not a good indicator of fecundity or adult lon- pairwise comparisons revealed that survivorship of gevity for the cottonwood leaf beetle, Chrysomela females with pupal weights Յ5 mg was the lowest of scripta F. (Coyle et al. 1999), but larval development the Þve weight categories (␹2 Ն 24.7, df ϭ 1, P Ͻ 0.01, rate and survival of progeny to adulthood in the coc- Fig. 3A). Survivorships of females with pupal weights cinellids Adelia bipunctata (L.) and Coccinella trans- Յ10 mg were signiÞcantly lower than those of females versalis F. were inßuenced by the weights of the par- with pupal weights Ͼ10 mg (␹2 Ն 8.2, df ϭ 1, P Ͻ 0.01). ents (Francis et al. 2001, Omkar and James 2004). However, individuals within weight categories 11Ð15, In our study on the boll weevil, we found no neg- 16Ð20, and Ͼ20 mg had comparable survivorships (␹2 ative impact of small parent size on developmental Յ 2.5, df ϭ 1, P Ͼ 0.11). Comparisons of male survi- rate, but small size of the female parent was associated vorship indicated trends similar to those for females. with reduced survival and emergence of adult prog- Survivorship of males with pupal weights Յ5mgwas eny, and with reductions in the proportions of progeny lower than for other pupal weight classes (␹2 Ն 10.8, that were female. Our analyses detected relationships

Table 5. Life table statistics of boll weevil females as affected by the pupal weights (values in parentheses are 95% conﬁdence intervals)

␭ Pupal wt (mg) Ro rm TDT Յ5 1.3 (0.4Ð2.2) 0.023 (Ϫ0.03Ð0.09) 1.02 (0.97Ð1.09) 12.5 (Ϫ2.61Ð16.98) 6Ð10 12.0 (4.2Ð19.8) 0.132 (0.10Ð0.17) 1.14 (1.10Ð1.18) 18.8 (14.69Ð23.46) 5.2 (3.6Ð6.7) 11Ð15 57.7 (38.5Ð77.0) 0.218 (0.19Ð0.25) 1.24 (1.21Ð1.28) 18.6 (16.20Ð21.12) 3.2 (2.8Ð3.6) 16Ð20 63.2 (44.2Ð82.1) 0.231 (0.19Ð0.27) 1.26 (1.21Ð1.31) 18.0 (14.91Ð21.08) 3.0 (2.5Ð3.5) Ͼ20 47.0 (34.8Ð59.1) 0.201 (0.13Ð0.26) 1.22 (1.13Ð1.30) 19.2 (13.07Ð25.16) 3.3 (3.4Ð4.6)

␭ Ro, net reproductive rate; rm, intrinsic rate of increase; , Þnite rate of increase; T, mean period over which progeny are produced (days); DT, doubling time of the population (days). June 2005 GREENBERG ET AL.: BOLL WEEVIL PUPAL WEIGHT AND REPRODUCTION 755 between female pupal weight and mean numbers of Acknowledgments feeding punctures per day, oviposition punctures per We acknowledge the technical assistance of J. Alejandro, day, the proportion of oviposition punctures to total J. Caballero, R. Domingues, and L. Leal. We are grateful to punctures, and the proportion of squares attacked. Drs. E. Villavaso (USDAÐARS, Biological Control and Mass However, Þt of these relationships indicated by re- Rearing Research Unit, Mississippi State, MS) and K. R. spective R2 values were relatively poor. These poor Þts Summy (Department of Biology, University of Texas Pan may suggest that other, unidentiÞed factors inßuenced American, Edinburg, TX) for critical reviews of the manu- these responses during the experiment. More likely, script. this variation in response was indicative of the variation among weevils obtained from similarly sized pupae. References Cited More importantly, our results demonstrate severe Bailey, J. C., F. G. Maxwell, and J. N. Jenkins. 1967. Boll penalties for the smallest adults in terms of longevity, weevil antibiosis with selected cotton lines utilizing egg- oviposition rates, survival of progeny, proportion of implantation techniques. J. Econ. Entomol. 60: 1275Ð1279. progeny that are female, and duration of the oviposi- Black, J. H., and T. F. Leigh. 1963. The biology of the boll tion period. Because many of these effects are multi- weevil in relation to cotton type. J. Econ. Entomol. 56: plicative, their joint impacts on population growth can 789Ð790. be substantial. For example, the number of female Bragg, D. E. 1970. Insemination and fecundity in the arti- choke plume moth, Platyptilia carduidactyla (Lepidop- progeny produced per a Þxed number of eggs was Ϸ tera: Pterophoridae). Ann. Entomol. Soc. Am. 63: 334Ð 4.1-fold higher for weevils in the highest pupal 335. weight class (Ͼ20 mg) compared with weevils in the Coyle, D. R., J. D. McMillin, and E. R. Hart. 1999. Pupal and lowest weight class (Յ5 mg) because weevils in the adult parameters as potential indicators of cottonwood latter group suffered reduced survival of progeny and leaf beetle (Coleoptera: Chrysomelidae) fecundity and a reduced proportion of progeny that were female. longevity. J. Econ. Entomol. 93: 713Ð720. When these penalties are combined with an Ϸ16-fold Croft, P., and Copland, M. 1993. Size and fecundity in Das- difference in oviposition between the two extreme nusa sibirica Telenga. Bull. OILB/SROP 16: 53Ð56. Curry, G. L., J. R. Cate, and P.J.H. Sharpe. 1982. Cotton bud weight classes, the total difference in the lifetime drying: contributions of boll weevil mortality. Environ. production of female progeny by weevils of the two Entomol. 11: 344Ð350. weight classes is Ϸ64-fold. Eliason, E. A., and D. G. McCullough. 1997. Survival and Although the boll weevil commonly exhibits wide fecundity of three insects reared on four varieties of variation in adult size, our study is the Þrst to examine scotch pine Christmas trees. J. Econ. Entomol. 90: 1598Ð the reproductive consequences of small parent size. 1608. These consequences are sufÞciently severe to have Everett, T. R., and J. O. Ray. 1962. The utility of sealed substantial population impacts for the smallest adult punctures for studying fecundity and egg laying by the boll weevil. J. Econ. Entomol. 55: 634Ð637. weevils. Although small size negatively affected fe- Francis, F., E. Haubruge, P. Hastir, and C. Gaspar. 2001. male reproductive potential, it did not preclude re- Effect of aphid host plant on development and repro- production even for weevils in the lowest weight class. duction of the third trophic level, the predator Adalia However, the penalties imposed on the smallest wee- bipunctata (Coleoptera: Coccinellidae). Environ. Ento- vils were so severe that life table analyses could not mol. 30: 947Ð952. detect a population increase for this group. Fuchs, T. W., D. R. Rummel, and E. P. Boring, III. 1998. Considerable effort has been devoted to investigat- Delayed uniform planting for areawide boll weevil sup- pression. Southwest. Entomol. 23: 325Ð333. ing cultural means of maximizing mortality of devel- Greenberg, S. M., T. W. Sappington, B. C. Legaspi, Jr., T.-X. oping boll weevil larvae. None of these efforts recog- Liu, and M. Se´tamou. 2001. 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