MOLECULAR ECOLOGY AND EVOLUTION Temperature-Dependent Development of bipustulatus (Coleoptera: )

1 2 3 P. A. ELIOPOULOS, D. C. KONTODIMAS, AND G. J. STATHAS

Environ. Entomol. 39(4): 1352Ð1358 (2010); DOI: 10.1603/EN09364 ABSTRACT The effect of temperature on development and survival of Chilocorus bipustulatus L. (Coleoptera: Coccinellidae), a predator of many scale , was studied under laboratory condi- tions. The duration of development of egg, Þrst, second, third, and fourth larval instars, pupa, and preovioposition period at seven constant temperatures (15, 17.5, 20, 25, 30, 32.5, and 35ЊC) was measured. Development time decreased signiÞcantly with increasing temperature within the range 15Ð30ЊC. Survival was higher at medium temperatures (17.5Ð30␱C) in comparison with that at more extreme temperature regimens (15 and Ͼ30␱C). Egg and Þrst larval instars were the stages where C. bipustulatus suffered the highest mortality levels at all temperatures. The highest survival was recorded when experimental individuals were older than the third larval instar. Thermal requirements of development (developmental thresholds, thermal constant, optimum temperature) of C. bipustulatus were estimated with application of linear and one nonlinear models (Logan I). Upper and lower developmental thresholds ranged between 35.2Ð37.9 and 11.1Ð13.0ЊC, respectively. The optimum temperature for development (where maximum rate of development occurs) was estimated at between 33.6 and 34.7ЊC. The thermal constant for total development was estimated 474.7 degree-days.

KEY WORDS Chilocorus bipustulatus, biological control, development, temperature, thermal constant

The armored-scale ladybeetle Chilocorus bipustulatus Although developmental thresholds and day-de- L. (Coleoptera: Coccinellidae) is one of the most gree requirements for development of many and important predators of diaspidids, with intense pres- mealybug coccinellid predators have been estimated, ence not only in Greece (Argyriou et al. 1976; Argy- only a few data are available as far as diaspidid pred- riou and Katsoyannos 1977; Stathas et al. 2003, 2009) ators are concerned (Podoler and Henen 1983, Pon- but in the whole Palearctic region (Bodenheimer sonby and Copland 1996, Stathas 2000). 1951, Avidov and Harpaz 1969, Viggiani 1985). Apart The lack of experimental data about the effect of from armored scales, it may alternatively feed on other temperature on the development of C. bipustulatus, its scale families such as , Asterolecaniidae (Yi- importance as a biocontrol agent against diaspidids, non 1969), and Pseudococcidae (Avidov and Yinon and the signiÞcance that the effect of temperature on 1969). development has for biological control made us Prey species of C.bipustulatus are among the most determined to estimate the lower and upper devel- important pests on perennials and ornamental plants, opmental thresholds, as well as the optimum temper- common in all regions in the world. The presence of ature and day-degree requirements, for development armored scales on fruits and ornamentals affects their of this predator. Estimation of lower developmental appearance, rendering them unmarketable. They may threshold (t) and day-degree requirements for devel- also cause discolorations, deformations, skin scleriÞ- opment (or thermal constant [K]) for each develop- cation, and cavities on fruit surface. On the leaves, mental stage was undertaken by Þtting experimental they cause chlorosis, reduce photosynthesis and tran- data on a linear model. The upper developmental spiration, and encourage leaf senescence and abscis- threshold (Tm) and optimum temperature for devel- sion, followed by branch dieback, as a result of plant opment (To) were calculated by application of a non- sap sucking through their long, Þlamentous mouth- linear model (Logan I). Most of these parameters are parts (Katsoyannos 1996, Gill 1997). novel for C. bipustulatus.

1 Corresponding author: Technological Educational Institute of Materials and Methods Larissa, Department of Crop Production, 41 110 Larissa, Greece (e-mail: [email protected]). Chilocorus bipustulatus was reared on the oleander 2 Benaki Phytopathological Institute, Department of Agricultural scale Aspidiotus nerii Bouche (Hemiptera: Diaspidi- Entomology and Zoology, 8 St. Delta Str., 14561 KiÞssia, Greece. ´ 3 Technological Educational Institute of Kalamata, Department of dae) infesting potato tubes. The initial population of Crop Production, 24 100 Kalamata, Greece. both predator and prey originated from olive orchards

0046-225X/10/1352Ð1358$04.00/0 ᭧ 2010 Entomological Society of America August 2010 ELIOPOULOS ET AL.: DEVELOPMENT OF C. bipustulatus 1353

in Attiki, Greece. The duration of separate develop- 2 2 ym s S.Eb mental stages (egg, Þrst, second, third, and fourth S.E ϭ ͱ ϩ ͩ ͪ t b N ϫ y 2 b larval instars, and pupa) and adult preoviposition pe- m riod of C. bipustulatus was measured at seven constant S.E Ϯ Ϯ Ϯ Ϯ Ϯ ϭ b temperatures (15 1, 17.5 1, 20 1, 25 1, 30 and S.EK 2 1, 32.5 Ϯ 1, and 35 Ϯ 1ЊC). The relative humidity was b 65 Ϯ 5% and the photoperiod was 16-h light: 8-h where ym is the sample mean (mean value rate of darkness at all temperatures. All experimental indi- development as derived from the linear equation y ϭ viduals were kept in growth chambers with the desired a ϩ bT), b is the linear equation parameter, s2 is the temperature regimen according to experimental de- residual mean square, and ⌵ is the sample size (num- sign. All dishes with individuals of the same temper- ber of different temperatures used during study). Cal- ature treatment were kept in the same chamber and 2 culation of ym,s, and SEb was conducted with the were observed at the same time. statistical program JMP (SAS Institute 2007). To get experimental individuals, mated females Experimental data from all temperatures were transferred to oviposition cages and left undis- (15Ð32.5␱C) were Þtted to Logan I nonlinear model turbed for 24 h to lay their eggs on A. nerii. Afterward, (Logan et al. 1976): females were taken away, and eggs were collected and Tm Ϫ T put individually on petri dishes (9 cm in diameter and ␳T ␳Tm ͑ ͒ ϭ ␺ ϫ Ϫ ⌬ 1.6 cm high). Special care was taken so that experi- d T ͫe e T ͬ mental individuals were always supplied with an ex- cess of prey. Experimental individuals were checked where d(T) is the rate of development at temperature daily (every 12 h for individuals kept at 32.5 and 35ЊC), ⌻ (oC) (dÐ1), ␺ is a directly measurable rate of tem- and developmental stage was recorded. Data were perature-dependent physiological process at some ␳ taken from 25 individuals except those at 15, 32.5, and base temperature Tb, is a composite Q10 value for 35ЊC, where 50 individuals were studied (because of enzyme-catalyzed biochemical reactions, ⌻m is a max- increased egg mortality). imum temperature at which life processes can no For the preoviposition period study, newly emerged longer be maintained for prolonged periods of time, females were collected from the culture, paired with and ⌬⌻ is a temperature range, above the optimum 7- to 10-d-old males, and put on petri dishes with temperature for development and below Tm, over excess of prey. Pairs were checked daily, and initiation which the “thermal breakdown” becomes the over- of egg-laying was recorded. The study on the duration riding inßuence. of preoviposition period was carried out on 12 females The base temperature Tb is the minimum temper- Њ Њ ature used in the experiments, is inserted as a Þfth at 15 and 35 C, 14 females at 17.5 C, 15 females at 20, ␱ 30, and 32.5ЊC, and 16 females at 25ЊC. equation parameter, or can hypothesized as ⌻b ϭ 0 C. Lower and Upper Developmental Thresholds. Es- As stated by Lactin et al. (1995) and Got et al. (1997), timation of the lower developmental threshold was the model effectiveness is not affected by the hypoth- based on a linear model. Data obtained from the ex- esis of zero Tb. Taking also into account that the model periments were described by the linear regression is simpliÞed and easier for application, Tb was zero in ␺ ␳ ⌻ ⌬⌻ equation of the form: this study. Parameters , , m, and are not mea- sured directly but are estimated as parameters of non- y ϭ a ϩ bT linear regression where the Logan I equation is used as model. This nonlinear regression was carried out with the statistical program JMP (SAS Institute 2007). where y is the rate of development at temperature T The optimum temperature for development (⌻␱) and a and b are constants. Equation constants (a, b) was calculated by the equations of Logan et al. (1976): were estimated with least squares method using the statistical program JMP (SAS Institute 2007). Estima- ␧ ϫ ln( bo) tion of constants was based only on data obtained at To ϭ Tm ϫ ͩ1 ϩ␧ϫ ͪ, ␱ 1 Ϫ ␧ ϫ b 15Ð30 C, because the assumed linear relationship is o known to hold as an approximation for the median ⌬T ␧ϭ ϭ ␳ ϫ temperature range only (Campbell et al. 1974). Out- where: and bo Tm side of this range, the relationship is nonlinear (Mills Tm 1981). Statistical Analysis. Data (duration of develop- The regression line was extrapolated back and met ment) were subjected to analysis of variance the absicca at the developmental zero t, which was (ANOVA) with ␣ ϭ 0.05. Means were separated using calculated from t ϭϪa/b. The total quantity of ther- the TukeyÐKramer honestly signiÞcant difference mal energy required to complete development, the (HSD) test (Sokal and Rohlf 1995). The differences in thermal constant K, was calculated from the reciprocal survival percentages during total development among of the slope of the regression line (1/b) (Wiggles- treatments were determined by GLIMMIX procedure worth 1953, Campbell et al. 1974). (SAS Institute 2008). Statistical analysis was per- Values of SEs for parameters t and ⌲ were calculated formed using the statistical packages JMP (SAS Insti- from equations of Campbell et al. (1974): tute 2007) and SAS/STAT 9.2 (SAS Institute 2008). 1354 ENVIRONMENTAL ENTOMOLOGY Vol. 39, no. 4

Results ͔ ͔ ͔ ͔ ͔ 2 3 6 ͔ ͔ 22.5 ͔ 6 4 4 5 Ϫ Ϫ Ϫ Ϫ The effect of temperature on the development of C. Ϫ 3 Ϫ Ϫ Ϫ 3 ͓ ͓ 2 1.5 1.5 3 18 3 ͓ ͓ ͓ ͓ ͓ bipustulatus is presented in Table 1 and shows that the ͓ 10) 8) 6) 6) 5) 5) 5) 12) 0.9e 0.7e 0.5e 0.4e 1.7e 0.7e 0.9e

developmental period decreased with increasing tem- 0.3e ϭ ϭ ϭ ϭ ϭ ϭ ϭ ϭ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ n n n n n n n n Ϯ ( ( ( ( ( ( ( perature, as expected, within the range of favorable ( 5.0 3.4 2.2 3.8 4.0 4.7 1.8 temperatures. Duration of all developmental stages of 19.9 C. bipustulatus differed signiÞcantly among various ␱ ͔ ͔ ϭ ͔ ͔ temperatures from 15 to 30 C (Table 1): egg (F ͔ 2 3 6 ͔ ͔ 22 ͔ 6 4 4 5 Ϫ Ϫ Ϫ Ϫ 437.65, df ϭ 6,130, P Ͻ 0.0001), Þrst larval instar (F ϭ Ϫ 3 Ϫ Ϫ Ϫ 3 ͓ ͓ 2 1.5 1.5 3 16 3 ͓ ͓ ͓ ͓ ͓ 421.94, df ϭ 6,94, P Ͻ 0.0001), second larval instar ͓ 14) 9) 8) 7) 7) 7) 7) 15) 0.7e 0.8e 0.3e 0.5e 0.5e 2.0e 0.7e (F ϭ 224.98, df ϭ 6,79, P Ͻ 0.0001), third larval in- 1.0e ϭ ϭ ϭ ϭ ϭ ϭ ϭ ϭ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ n n n n n n n ϭ ϭ Ͻ n ( ( ( ( ( ( ( star (F 244.39, df 6,72, P 0.0001), fourth larval instar ( 4.8 3.1 1.8 2.0 3.6 3.9 4.5 (Fϭ345.50, df ϭ6,68, PϽ0.0001), pupa (Fϭ265.02, df ϭ 18.8 6,65, P Ͻ 0.0001), and total preimaginal period (F ϭ

664.00, df ϭ 6,65, P Ͻ 0.0001). The same pattern was ͔ ͔ ͔ ͔ ͔ ͔ 29 ͔ ͔ 7 5 3 4 6 6 7

recorded in the duration of preoviposition period of Ϫ Ϫ Ϫ Ϫ Ϫ Ϫ Ϫ Ϫ 5 3 2 2 5 4 4 24 ͓ ͓ ͓ ͓ ͓ ͓ ͓ the adult female (F ϭ 246.75, df ϭ 6,92, P Ͻ 0.0001). ͓ 20) 16) 14) 13) 12) 11) 15) 11)

No signiÞcant differences in duration of development 1.7e 0.5e 0.7e 0.5e 0.6e 0.4e 0.9e 0.9e ϭ ϭ ϭ ϭ ϭ ϭ ϭ ϭ

Ն Њ Ϯ n n n n n n n n Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ were recorded among temperatures 30 C. Ϯ ( ( ( ( ( ( ( ( 6.4 4.2 2.6 2.8 5.2 4.9 5.3 The linear regression equations and nonlinear 26.1 model parameters that describe the relationship be-

tween temperature and developmental rate as well as ͔ ͔ ͔ ͔ ͔ ͔ ͔ ͔ 43 C) 11 7 5 5 9 9 upper (Tm), lower (t), and optimum temperature 11 Њ Ϫ Ϫ Ϫ Ϫ Ϫ Ϫ Ϫ Ϫ 8 4 3 4 7 7 6 threshold (To) and day-degree requirements (K) for 37 ͓ ͓ ͓ ͓ ͓ ͓ ͓ ͓ each life stage and total immature development of C. 22) 19) 17) 16) 16) 16) 16) 16) 0.7d 0.7d 0.5d 0.6d 0.6d 1.4d 1.8d 0.8d ϭ ϭ ϭ ϭ ϭ ϭ ϭ ϭ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ bipustulatus are presented in Tables 2 and 3. The upper Ϯ 0.05. Values in brackets are min-max. n n n n n n n n Ϯ ( ( ( ( ( ( ( ( 9.3 5.7 4.4 7.9 7.5 and lower threshold and optimum temperature for 8.3 ϭ 3.9 38.7 Temperature ( development varied with developmental stage. How- ␣ ever, in most cases, the differences were minor. Eggs ͔ ͔ ͔ ͔ ͔ ͔ 17 ͔ ͔ 15 14 14 and preovipositing females were the most cold-toler- 72 12 8 9 Ϫ Ϫ Ϫ Ϫ Ϫ Ϫ Ϫ ant stages, provided that their lower thresholds (11.1 Ϫ 13 9 5 5 11 11 10 58 ͓ ͓ ͓ ͓ ͓ ͓ ͓ and 11.4ЊC) were notably lower than those of the ͓ 21) 17) 15) 14) 13) 12) 15) 12) 1.1c 1.1c 1.1c 1.1c 1.0c 1.3c 3.5c at various constant temperatures

other developmental stages. Pupae and preovipositing 1.0c ϭ ϭ ϭ ϭ ϭ ϭ ϭ ϭ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ n n n n n n n n Ϯ ( ( ( ( ( ( ( females also proved to be the most tolerant stages at ( 6.5 15.4 11.1 7.2 13.5 13.2 11.8 Њ 67.7 high temperatures (37.9 and 37.4 C). However, the ukey-Kramer HSD test, ⌻ A. nerii

rest of the preimaginal stages were more sensitive to ͔ ͔ ͔ ͔ ͔ ͔ ͔ ͔ 24 23 15 26 25 22 high temperatures, showing identical upper develop- 107 12 Ϫ Ϫ Ϫ Ϫ Ϫ Ϫ ϭ Њ Ϫ mental threshold (Tm 35.2 C). The thermal con- Ϫ 17 15 8 10 18 18 16 94 ͓ ͓ ͓ ͓ ͓ ͓ ͓ ͓

stant reached 474.7 degree-days for overall (egg to SE) fed on 4.4b 19) 13) 11) 10) 10) 10) 14) 10) 2.2b 2.4b 1.5b 1.6b 2.4b 2.7b 2.1b ؎ .(adult) development (Table 2 Ϯ ϭ ϭ ϭ ϭ ϭ ϭ ϭ ϭ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ n n n n n n n n ( ( ( ( ( ( ( The rate of development increased linearly with ( 20.9 17.9 10.2 12.3 20.5 21.0 18.9 101.5 temperature within the temperature range 15Ð30ЊC, as (mean indicated by the high values of coefÞcient of deter- 2 mination (R ϭ 0.8600Ð0.9736; Table 2), and declined ͔ ͔ ͔ ͔ ͔ ͔ ͔ ͔ 145 32 26 16 18 29 29 at higher temperatures (Fig. 1). Similarly, the nonlin- 26 Ϫ Ϫ Ϫ Ϫ Ϫ Ϫ Ϫ ear model (Logan I) proved to be very efÞcient in Ϫ 21 18 11 13 21 20 18 111 ͓ ͓ ͓ ͓ ͓ ͓ ͓ ͓ C. bipustulatus

describing the relationship of rate of development 15 17.5 20 25 30 32.5 35 12.2a 31) 19) 15) 13) 12) 11) 12) 11) 3.5a 2.3a 1.7a 2.1a 2.6a 2.9a with temperature (Table 3; Fig. 1), given that the 2.9a Ϯ ϭ ϭ ϭ ϭ ϭ ϭ ϭ ϭ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ n n n n n n n regression coefÞcient valued from 0.8403 to 0.9731. n ( ( ( ( ( ( ( ( Experimental individuals showed signiÞcantly higher survival at medium temperatures (17.5Ð30ЊC; 40Ð64%) in comparison with those kept at more ex- treme temperature regimens (15 and Ͼ30ЊC; 10Ð22%). The egg was the stage where C. bipustulatus had the highest mortality levels at all temperatures, taking into account that 12Ð80% of individuals did not manage to hatch irrespective of temperature. On the contrary, the highest survival was recorded during the pupal stage (91.7Ð100% at all temperatures). Stage of development no. of cohort adults.

The proportion of the total development time spent Table 1. Duration of development (d) of n, Values in the same row followed by the same letter are not signiÞcantly different, First 22.7 Second 13.9 Third 16.1 Fourth 25.8 Egg 27.8 Larval instar Pupa 25.4 Preoviposition period 21.5 in a particular developmental stage proved to be in- Total preimaginal development 133.7 August 2010 ELIOPOULOS ET AL.: DEVELOPMENT OF C. bipustulatus 1355

Table 2. Linear regression of developmental rate of C. bipustulatus on temperature

Stage of development Linear equation R2 t (ϮSE) K (ϮSE) Egg 1/D ϭ 0.09012T Ð 0.0080917 0.9463 11.1 Ϯ 0.2 123.6 Ϯ 2.8 Larval instar First 1/D ϭ 0.0140075T Ð 0.177466 0.9104 12.7 Ϯ 0.3 71.4 Ϯ 2.5 Second 1/D ϭ 0.0216309T Ð 0.267057 0.8654 12.3 Ϯ 0.4 46.2 Ϯ 2.1 Third 1/D ϭ 0.0209138T Ð 0.271553 0.8600 13.0 Ϯ 0.5 47.8 Ϯ 2.4 Fourth 1/D ϭ 0.0103719T Ð 0.126709 0.9590 12.2 Ϯ 0.3 96.4 Ϯ 2.5 Pupa 1/D ϭ 0.011579T Ð 0.147763 0.9016 12.8 Ϯ 0.4 86.4 Ϯ 3.7 Total preimaginal period 1/D ϭ 0.0021064T Ð 0.02605 0.9736 12.4 Ϯ 0.2 474.7 Ϯ 10.3 Preoviposition period 1/D ϭ 0.0098877T Ð 0.112453 0.8627 11.4 Ϯ 0.5 101.1 Ϯ 4.8

Data were obtained from Þve constant temperatures (15, 17.5, 20, 25, and 30ЊC). D, duration of development (d); T, temperature (ЊC); R2, coefÞcient of determination; t, lower developmental threshold (ЊC); ⌲, thermal constant (degree-days). dependent of temperature, provided that egg, larval, somphalus aonidum L., and A. nerii (Hemiptera: Di- and pupal stage of C. bipustulatus ranged between aspididae). The type of prey has a signiÞcant effect on 20.6Ð25.5, 55.9Ð60.0, and 18.8Ð20.7% of total preimagi- the duration of development of C. bipustulatus and its nal period, respectively, regardless of temperature. mortality (Uygun and Elekc¸iog˘lu 1998). This fact is also true for other coccinellids preying on (Omkar and Srivastava 2003, O¨ zder and Saglam 2003, Discussion ˘ Ali and Rizvi 2007) and mealybugs (Chong et al. 2005). There is little information available on the effect of Another factor that may have caused this variation is temperature on the development of C. bipustulatus. the genetic differences among populations with dif- Podoler and Henen (1983) reported that the com- ferent geographical origin, taking into consideration pleted its development (from egg to adult) in 80.5 d at that our population originated from Attiki (Central 18ЊC, 53.9 d at 22ЊC, 38.2 d at 24ЊC, 27.8 d at 26ЊC, 27.8 d Greece), whereas the Turkish population originated at 28ЊC, 31.2 d at 30ЊC, and 27.1 d at 32ЊC. They also from Adana Turkey (east Mediterranean region). It is estimated the lower developmental threshold and ther- well known that intraspeciÞc variation in develop- mal constant for each developmental stage from egg to mental traits, especially in critical temperatures, is adult using the law of heat summation according to the very common in Coccinellidae (Hone˘k and Kocourek Blu¨nckÐBodenheimer, which is practically the same 1988, Lamana and Miller 1998). These differences in equation as the linear model used in this study. The lower thermal requirements of populations from different developmental threshold provided by Podoler and origins within a species indicate the need to undertake Henen (1983) was 12.2, 8.5, 6.8, 3.0, 12.8, and 12.2ЊC and relative studies on native coccinellids when trying to the thermal constant was 112.1, 104.4, 65.5, 107.2, evaluate them as biological control agents. 92.8 and 104.6 DD for egg, Þrst, second, third, and Apart from that, data obtained from 32ЊC were in- fourth larval instar, and pupa, respectively. cluded on the linear equation for the estimation of the It is obvious that there are many differences among lower developmental threshold and thermal constant. the above-mentioned data with those of this study. However, this temperature is extreme for C. bipustu- This variation may be attributed to the different prey latus, as has been shown by this and older studies, and used in the earlier study, which was a mixture of lies within the range where the relationship of tem- diaspidids including Aonidiella aurantii (Mask.), Chry- perature and rate of development is nonlinear. Those values should not be included in the linear estimation Table 3. Parameter estimates of Logan I model for develop- of thermal values (Mills 1981). This is probably the ment of C. bipustulatus

␺␳ ⌬ 2 Stage of development Tm TTo R Table 4. Survivorship (percentages) of immature stages of C. Egg 0.0093 0.0959 35.2 0.1142 34.7 0.9101 bipustulatus fed on A. nerii at various constant temperatures Larval instar First 0.0112 0.1047 35.2 0.1436 34.6 0.8509 Stage of Temperature (ЊC) Second 0.0177 0.1053 35.2 0.1352 34.6 0.9059 development 15 17.5 20 25 30 32.5 35 Third 0.0135 0.1122 35.2 0.1403 34.6 0.8814 Egg 62.0 76.0 84.0 88.0 80.0 28.0 20.0 Fourth 0.0081 0.1082 35.2 0.1206 34.6 0.9475 Larval instar Pupa 0.0072 0.1162 37.9 2.2558 33.8 0.9150 First 61.3 68.4 81.0 86.4 80.0 64.3 80.0 Total preimaginal 0.0018 0.1039 35.2 0.1468 34.6 0.9731 Second 78.9 84.6 88.2 89.5 87.5 88.9 75.0 period Third 86.7 90.9 93.3 94.1 92.9 87.5 100.0 Fourth 92.3 100.0 92.9 100.0 92.3 100.0 83.3 Preoviposition period 0.0117 0.0943 37.2 1.6242 33.6 0.8403 Pupa 91.7 100.0 92.3 100.0 91.7 100.0 100.0 Total preimaginal 22.0d 40.0c 48.0ab 64.0a 44.0bc 14.0e 10.0e Data were obtained from seven constant temperatures (15, 17.5, 20, development 25, 30, 32.5, and 35ЊC). ␺ ␳ ⌻ ⌬ , , m, T, Logan equation parameters; To, optimum temperature Values of total preimaginal development followed by the same for development; R2, coefÞcient of determination for nonlinear re- letter are not signiÞcantly different (SAS/STAT 9.2, GLMMIX pro- gression. cedure, ␣ ϭ 0.05). 1356 ENVIRONMENTAL ENTOMOLOGY Vol. 39, no. 4

Fig. 1. Relationship of rate of development of C. bipustulatus with temperature described by the Logan I model (white circles represent the observed data).

reason for the extremely low value of many develop- When the same prey (A. nerii) was used, develop- mental thresholds of C. bipustulatus (8.5, 6.8, and ment from egg to adult and preoviposition period 3.0ЊC) reported by Podoler and Henen (1983). lasted 26 and 9.6 d, respectively, at 25ЊC (Uygun and August 2010 ELIOPOULOS ET AL.: DEVELOPMENT OF C. bipustulatus 1357

Elekc¸iog˘lu 1998). Similar values have been recorded tal conditions, as well as to set the best thermal con- in this study (29.4 and 8.3 d). In the same study, 16.6% dition for insect mass rearing (Perdikis and Lykoures- of newly hatched larvae did not reach adult stage at sis 2002). 25ЊC, which agrees with our data (15.8%). In conclusion, the results of this study provide use- Another interesting Þnding of this study was the fact ful data for establishing or mass rearing C. bipustulatus that the proportion of egg, larval, and pupal periods (i.e., mass culture methods could be enhanced by did not change notably, regardless of temperature. setting temperature conditions for rapid development These results are consistent with the suggestion that and maximum survival). Furthermore, the knowledge the proportion of the development times of preimagi- of the critical temperatures of C. bipustulatus is very nal stages for ladybird species is typical of each stage useful for determining the climatic conditions affect- and independent of temperature (Hodek and Hone˘k ing its efÞcacy against armored scales. Our Þndings 1996, Dixon 2000). indicate that C. bipustulatus could be a useful biolog- Eggs and preovipositing females proved to be the ical control agent against A. nerii and possibly other most tolerant stages in low temperatures (11.1 and diaspidid pests, under a wide range of temperatures, 11.4ЊC, respectively). This result comes in accordance especially in areas with a temperate climate. However, with the fact that the latter is the hibernating stage of for a more accurate evaluation of the impact of this C. bipustulatus in nature (Bodenheimer 1951, Avidov predator on its prey species, additional work on other and Yinon 1969, Katsoyannos 1996). biological parameters, apart from critical tempera- The Logan I model was very effective in describing tures and survival, such as fecundity, population dy- the effect of temperature on the rate of development namics, searching efÞciency, etc., is needed, especially of C. bipustulatus as is clearly indicated by the high under natural conditions where environmental het- values of the nonlinear regression coefÞcient (R2 ϭ erogeneity may inßuence and perhaps alter predator 0.8403Ð0.9731). This model has been successfully used and prey interactions. for describing the temperature-dependent develop- ment of coccinellids (Roy et al. 2002, Kontodimas et al. 2004). Acknowledgments This is the Þrst time that upper developmental We thank G. C. Fernandez and P. Shi for guidance with threshold and optimum temperature for development statistic analysis and the editor and anonymous reviewers for has been estimated for C. bipustulatus. Therefore, useful comments. these results broadened our knowledge of the critical temperatures of this predator. All developmental stages of C. bipustulatus seem to be very tolerant of References Cited warm conditions, especially for the temperate climate Ali, A., and P. Q. Rizvi. 2007. Development and predatory of the Mediterranean region. performance of Coccinella septempunctata L. (Co- Among indigenous predators of armored scales, the leoptera: Coccinellidae) on different aphid species. coccinellids Rhyzobius lophanthae Blaisdell and C. bi- J. Biol. Sci. 7: 1478Ð1483. pustulatus (Coleoptera: Coccinellidae) and the niti- Argyriou, L. C., and P. Katsoyannos. 1977. 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