Effect of temperature on developmental time and longevity of Psyttalia cosyrae (Hymenoptera: Braconidae)

Psyttalia cosyrae (Wilkinson) (Hymenoptera: Braconidae) is a koinobiont, solitary larval-pupal parasitoid of Ceratitis cosyra (Walker) (Diptera: Tephritidae), and possibly other tephritid fruit flies. The effect of temperature on developmental time and longevity of this parasitoid was investigated and the thermal requirement at six constant temperatures (15±0.5, 20±0.5, 25±0.5, 27±0.5, 30±0.5, and 33±0.05°C) and 60-70% R.H was determined. The developmental rate increased with an increase in temperature. Females took a longer time to complete development than males at all temperatures tested. Development from egg to adult emergence required 244 degree-days (DD) above a thermal threshold of 11.9°C for both sexes pooled, 233 DD above 12.0°C for males and 256 DD above 11.6°C for females. Adult longevity was affected by temperature, and females lived longer than males at all temperatures tested.     

Temperature-dependent development and reproductive traits of <Emphasis Type="Italic">Tetranychus macfarlanei</Emphasis> (Acari: Tetranychidae)

Development and reproductive traits of Tetranychus macfarlanei Baker & Pritchard (Acari: Tetranychidae) were investigated on kidney bean, Phaseolus vulgaris L., at eleven constant temperatures. Tetranychus macfarlanei was able to develop and complete its life cycle at temperatures ranging from 17.5 to 37.5°C. At 15 and 40°C, a few eggs (2–4%) hatched but further development was arrested. Development from egg to adult was slowest at 17.5°C and fastest at 35°C for both females and males. Using Ikemoto and Takai’s linear model, the estimated lower developmental thresholds for egg-to-female adult, egg-to-male adult and egg-to-egg development were 12.9–13.0°C. The thermal constants for the respective stages were 110.85, 115.99 and 125.32 degree-days (DD). The intrinsic optimum temperatures (T _Φ) calculated by non-linear SSI model were determined as 24.4, 24.4 and 24.2°C for egg-to-female adult, egg-to-male adult and egg-to-egg development, respectively. The net reproductive rate (R ₀) was highest at 25°C (167.4 females per female) and lowest at 17.5°C (42.6 females per female). The intrinsic rate of natural increase, r _m, increased linearly with the rising of temperature from 0.102 at 17.5°C to 0.441 day⁻¹ at 35°C. These values suggested that T. macfarlanei could be growing quickly in response to increasing temperatures from 17.5 to 35°C and provide a basis for predicting its potential geographical range.     

Life table parameters of an indigenous strain of Neoseiulus californicus McGregor (Acari: Phytoseiidae) when fed Tetranychus urticae Koch (Acari: Tetranychidae)

The life table of the indigenous Neoseiulus californicus was studied at different temperatures and 65 ± 5% relative humidity under conditions of 16 h light : 8 h dark (LD 16:8). The total developmental period from egg to adult varied from 3.0 to 14.0 days at 15 to 35°C. Survival to adulthood ranges from 86.21 to 93.94%, with the highest rate at 25°C. The lower threshold temperature from egg to adult stages of females and males was 10.84 and 10.72°C, respectively, and the thermal constant was 57.14 degree‐days (DD) for females and 56.18 DD for males. Total number of eggs laid by each female was the highest (70.38 eggs) at 25°C, whereas average daily fecundity was the highest (3.69 eggs/female/day) at 30°C. The net reproductive rate was the highest (48.49) at 25°C and lowest (26.18) at 30°C. Mean generation time decreased from 19.04 to 11.47 days with increasing temperature from 20 to 30°C. Both intrinsic rate of natural increase (0.284) and finite rate of increase (1.32) were maximum at 30°C. Adult longevity was the highest (42.75 days for females and 32.60 days for males) at 20°C and lowest (22.70 days for females and 15.30 days for males) at 30°C. Sex ratio was female biased and was the highest (78.08) at 25°C and lowest (70.24) at 30°C. Developmental data of five constant temperatures, temperature thresholds and thermal requirements may be used to predict the occurrence, number of generations and population dynamics of N. californicus as an important biocontrol agent of Tetranychus urticae.     

Effects of temperature and other environmental factors on the post‐diapause development of walnut husk fly Rhagoletis completa (Diptera: Tephritidae)

To more effectively manage walnut husk fly Rhagoletis completa (Diptera: Tephritidae), in California walnut orchards, it is important to understand the factors that affect the timing of adult emergence. In the present study, we examine the effects of incubation temperature, pre‐chill and chill durations, latitude, cultivar and size on the post‐diapause development of R. completa puparia. The lower developmental threshold, upper developmental threshold and optimal temperature for puparial development are estimated to be 4, 34 and 26.6 °C, respectively. The thermal requirement for adult emergence after 120 days of chilling is estimated to be 2024 degree days. Percentage adult emergence declines at both higher and lower incubation temperatures. Chill duration at 5 °C for diapausing puparia has a nonlinear negative effect on the thermal requirement but no effect on percentage emergence. Insufficient chilling leads to poor synchronization of adult emergence. Greater pre‐chill duration at room temperature increases the thermal requirement and slightly decreased percentage emergence. Latitude has a negative effect on the thermal requirement. Puparia from northern California black walnut (Juglans hindsii) have a slightly greater thermal requirement than puparia from cultivated walnut (Julgans regia). There is no significant difference in puparial fresh weight or mean thermal requirement between males and females, although the positive correlation between thermal requirement and puparial fresh weight is stronger for females than males. The effects of temperature and other environmental factors on the post‐diapause development of R. completa are discussed in relation to observations from other Rhagoletis species.     

Physiological and morphological development of Anagyrus ananatis at constant temperatures

The lower developmental temperature threshold (T ₀) and the Degree Days (DD) required for the encyrtid endoparasitoid Anagyrus ananatis Gahan to develop from egg to adult on the pink pineapple mealybug (PPM), Dysmicoccus brevipes (Cockerell) (Hemiptera: Pseudococcidae), were determined. The T ₀ was estimated to be about 12.65 °C for both females and males. In contrast, females and males required about 275 and 265 DD, respectively, to complete development from egg to adult. Temperatures from 19 to 29 °C were optimal for mass rearing of A. ananatis, with the optimal temperature being around 24 °C. At this temperature, A. ananatis could complete almost two generations in the time it takes PPM to complete only one generation. Although A. ananatis is a koinobiont, the mealybug host was killed within a few (6–8) days after parasitization. The developmental stages of A. ananatis were described (e.g., appearance, size, color) and their time periods quantified when reared on PPM at 23.5 ± 0.5°C. Encyrtiform eggs were inserted through the dorsal surface of the PPM and were attached to the host via a slender stalk. This immature parasitoid remained attached to the host cuticle via the stalk until entering the prepupal stage. The host mealybug mummified during the parasitoid’s prepupal stage. First adult eclosion occurred at 24 days post-parasitization.     

Utilisation of morphological features in life table studies of Liriomyza huidobrensis (Dipt., Agromyzidae) developing in lettuce

Abstract: A method of distinguishing different larval instars of Liriomyza huidobrensis morphologically, using measurements of the cephalopharyngeal skeleton was developed. The growth ratios of cephalopharyngeal skeletons between first and second and second and third instar larvae were 1.80 and 1.47, respectively, enabling clear separation to be achieved for experimental work. Using this method the development rates of the immature stages of L. huidobrensis feeding on Lactuca sativa were determined under constant temperatures of 11, 16, 19, 26 and 28 ± 1°C and were shown to increase linearly with temperature over the range investigated. The theoretical lower threshold temperatures for development from oviposition to the end of each larval instar or pupal stage were 5.35, 6.30, 6.20 and 5.70°C, respectively. The overall threshold temperature for development from oviposition to 50% adult emergence (5.70°C) was used to calculate degree‐day (DD) requirements for development from oviposition to each larval instar or pupal eclosion, which were 84.3, 30.1, 58.9, 143.7 DD, respectively. The use of these data for optimizing the timing of application of control agents which are effective against specific developmental stages is discussed.     

Temperature-dependent life history of Oligonychus mangiferus (Acari: Tetranychidae) on Mangifera indica

The mango red spider mite, Oligonychus mangiferus (Rhaman and Sapra), is a major mango pest in Taiwan. This mite damages the leaves of the mango tree and affects the quality of the fruit. This study investigates the life history of the mango red spider mite on Mangifera indica L. cv. Irwin at five constant temperatures (17, 21, 25, 29, and 33 °C), under 80 ± 5 % RH and L12:D12 photoperiod conditions. An increase in temperature significantly decreased the developmental times for each stage and the overall immature period in females and males. The lower developmental thresholds of the immature stage were 12.5 and 12.4 °C for females and males, respectively. The thermal summations for the development of the immature stage were 185.9 and 175.7 degree-days for females and males, respectively. Based on the annual field temperature, an estimated 26 generations can reproduce in a mango orchard annually. The longevity of adults of both sexes decreased as temperature increased, and adult males lived longer than females. The preoviposition periods were shorter than 1 day when the temperature exceeded 25 °C. The development period and the oviposition period were shortest at 29 °C. At this point, daily fecundity was highest, and fecundity was second highest, resulting in the highest intrinsic rate of increase (r _m ), 0.182 day^?1. These life history traits are applied to improve the management of O. mangiferus.     

On the biology and thermal developmental requirements of the cotton mealybug,Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) in Egypt

This study evaluated the thermal requirements for development of the cotton mealybug Phenacoccus solenopsis depending on different biological parameters on Okra leaves Abelmoschus esculentusat under two constant temperatures (20 and 30 °C) at (RH 65%, 12:12 h. light/dark). The effect of temperature on eggs was ineffective since it hatched shortly to first nymphal instars after deposition. While the tested temperature caused significant effects on nymphal durations, pupation rate (pre-male stage), females emergence %, pre-oviposition, longevity, post-oviposition periods and fecundity in females (egg deposition, ovisacs numbers and hatchability %). The thermal constant and developmental zero were calculated to be 7.29 °C and 79.9 degree-days (DDs) for eggs, 11.67 °C and 272.9 DDs for nymphal stages, 11.06 °C and 46.4 DDs for males and then 3.31 °C and 554.1 DDs for females, respectively. The duration of the life cycle was 65.6 ± 10.36 days at 20 °C; this was shortened to 35.51 ± 1.12 days at 30 °C. The thermal requirements to complete the insect development for one generation was 8.2 °C for the developmental zero and 774.1 DDs for the thermal constant. Based on the thermal requirements values, the average life cycle duration from January to December 2016 was 61.78 days and the number of annual generations was 7.143 when the average annual temperature was 23.29 °C.     

The influence of temperature,photoperiod, and diet on development and reproduction in the four-spot lady beetle <Emphasis Type="Italic">Harmonia quadripunctata</Emphasis> (Pontoppidan) (Coleoptera,Coccinellidae)

This is the first report on the effects of temperature (from 17 to 30°C), photoperiod (from 10 to 16 h of light), and diet (the wheat aphid Schizaphis graminum and the green peach aphid Myzus persicae) on preimaginal developmental rates, adult body mass, preoviposition period, and female fecundity of the predatory lady beetle Harmonia quadripunctata (Pontoppidan) under the laboratory conditions. A constant temperature of 30°C was lethal to the embryos. Judging from the data obtained at 17, 20, and 25°C, the lower temperature threshold for total egg-to-adult development equaled 12.0°C and the respective sum of effective temperatures was 274 degree-days. Preimaginal development was somewhat faster under short-day conditions, the threshold for this quantitative photoperiodic response being approximately 14 h at the rearing temperatures of 20 and 25°C. At a temperature of 25°C, the mean body mass of newly emerged adults was greater for those individuals that during the larval stage had been fed on the green peach aphid (16.4 mg in males and 18.4 mg in females) than in those fed with the wheat aphid (13.8 mg in males and 15.3 mg in females). The preoviposition period (measured from adult emergence to the first egg laid) also depended on temperature and had a lower threshold of 13.4°C and a sum of effective temperatures of 152 degree-days. Maximum fecundity was observed at 25°C and 16-h day length; under these conditions, the oviposition period lasted over 100 d, and the average lifetime fecundity was about 800 eggs per female. Under short-day conditions, females of H. quadripunctata entered reproductive diapause. The photoperiodic threshold for this qualitative response at the temperatures of 20 and 25°C was about 14 h when fed on the peach aphid and 15 h when fed on the wheat aphid. Relatively small body size, low fecundity, and a strong photoperiodic response that hinders rapid adaptation to novel climates probably explain the fact that H. quadripunctata, in contrast to H. axyridis, has not become an aggressive invader.     

Temperature-dependent development of overwintering Sericinus montela Gray (Lepidoptera: Papilionidae) pupae and its validation

The developmental time and survival of overwintering Sericinus montela Gray pupae were studied at four constant temperatures (15.0, 20.0, 25.0, and 30.0 °C), 40 ± 10% relative humidity, and 10:14 h light:dark cycle. The developmental time of both sexes decreased with increasing temperature between 15.0 °C (70.18 days for females and 55.28 days for males) and 30.0 °C (19.60 days for females and 13.78 days for males). The development periods of females were longer than those of males at each constant temperature. The relationship between the developmental rate and temperature was fitted by a linear model and a nonlinear developmental rate model (Lactin 1). The mortality of overwintered S. montela pupae was lowest at 25.0 °C (16.7%) and highest at 15.0 °C (36.7%). The lower developmental thresholds were 12.38 and 12.16 °C for females and males, respectively. The distribution of development completion for females and males was described by the two-parameter Weibull distribution equation (r² = 0.87 for females and r² = 0.94 for males). The date for the cumulative 50% adult emergence was within one or two days of that predicted using the Lactin 1 model. The temperature-dependent developmental model for S. montela could be applied to predict the timing of spring emergence in different geographical locations and will be helpful in developing a full-cycle phenology model for S. montela.     

Temperature-dependent development and immature survival of an aphidophagous ladybeetle, Propylea dissecta (Mulsant)

Development and survival of the immature stages of an aphidophagous ladybeetle, Propylea dissecta (Mulsant) was investigated at five constant temperatures, viz. 20, 25, 27, 30 and 35°C, using Aphis gossypii Glover as prey. Developmental period of all the life stages were significantly affected with change in constant temperature and developmental rate increased with increase in temperature. Theoretical lower thermal threshold for complete development and thermal constant was 10.39°C and 465.11 Day‐degrees, respectively. Of the various life stages, first instar larvae were most susceptible to mortality at temperatures between 20 and 30°C, whilst pre‐pupae suffered least mortality. Egg‐mortality was maximum at 35°C. Female biased sex ratios were obtained at all five temperatures tested with higher proportion of females at the extremes of temperature, thus suggesting that females are more thermal‐tolerant. Lowest mortality of immature stages with maximum larval survival and adult emergence was recorded at 27°C, while reverse was the case at 35°C. Thus, 27°C may be considered best for the laboratory rearing of P. dissecta.     

Effects of different temperatures on the life history of Evania appendigaster L. (Hymenoptera: Evaniidae), a solitary oothecal parasitoid of Periplaneta americana L. (Dictyoptera: Blattidae)

The influence of temperatures on the life parameters of the solitary oothecal parasitoid Evania appendigaster, was investigated in the laboratory. Parasitized oothecae of Periplaneta americana were left to develop under seven constant temperatures: 15, 17, 20, 25, 30, 35, and 40 °C. At the end, we found that: (i) E. appendigaster was able to complete development within the temperature range of 17–34 °C; (ii) mean adult longevity decreased as temperature increased, with the temperature of 40 °C being fatal in a matter of hours; (iii) males lived longer than females between 15 and 30 °C; (iv) adult emergence rate was the highest at 25 °C, and (v) no wasps emerged at 15 or 40 °C. Non-emerged oothecae contained either unhatched eggs or dead larvae. We determined the theoretical lower developmental threshold and thermal constant for the complete development as 12.9 °C and 584.8 day-degrees for males, and 13.1 °C and 588.2 day-degrees for females, respectively. A good balance between faster development, maximum adult longevity and good egg viability was obtained between 25–30 °C, and that would be the best temperature range for rearing E. appendigaster.     

Age-specific fecundity and life table of Trissolcus semistriatus, an egg parasitoid of the sunn pest Eurygaster integriceps

The effects of temperature on age‐specific fecundity and life table parameters of the egg parasitoid Trissolcus semistriatus (Nees, 1834) (Hymenoptera: Scelionidae) were examined under four constant temperature conditions (17, 20, 26 and 32°C), using eggs of the sunn pest Eurygaster integriceps Puton, 1881 (Hemiptera: Scutelleridae), an important pest of wheat, as hosts. The intrinsic rate of increase increased linearly, while the mean generation time and the doubling time decreased with increases in temperature. The net reproductive rate, however, varied without clear correlation with temperature. Fecundity tended to be higher at higher temperatures. The total number of eggs per female was estimated as 52.0 and 116.4 eggs, respectively, at 17°C and 32°C, with the highest fecundity rate during the first day of oviposition. The oviposition rate fluctuated from 4.4 to 14.3 eggs per day. Oviposition and postoviposition periods and longevity decreased when temperature increased. Maximum longevity for females was 21.6 days at 20°C, and female parasitoids lived longer than males at all temperatures. The development period ranged from 7.1 days (32°C) to 35.6 days (17°C) for males and from 8.4 days (32°C) to 37.2 days (17°C) for females. The development of female T. semistriatus required 166.7 degree‐days (DD) above a theoretical threshold of 11.8°C and the development of males required 142.9 DD above 13.1°C. The numbers of generations per year for female and male T. semistriatus, given the temperature in Tekirdag, Turkey, were estimated to be 9.0 and 8.8, respectively. The potential of the egg parasitoid for the control of E. integriceps is discussed.     

Temperature‐dependent development of Neoseiulus barkeri (Acari: Phytoseiidae) on Tetranychus urticae (Acari: Tetranychidae) at seven constant temperatures

Abstract The effect of seven constant temperatures of 15, 20, 25, 27, 30, 35 and 37°C on developmental time of Neoseiulus barkeri Hughes were determined in laboratory conditions under 65%± 5% RH and a photoperiod of 12 : 12 (L : D) h on nymphal stages of Tetranychus urticae Koch. Total developmental time of females (from egg to adult emergence) at the above‐mentioned temperatures was 26.59, 14.43, 6.32, 5.64, 4.59, 3.98 and 4.67 days, respectively. Developmental rate of the N. barkeri increased as temperature increased from 15 to 35°C, but declined at 37°C. A linear and two nonlinear models were fitted to developmental rate of immature stages of N. barkeri to predict the developmental rate as a function of temperature, as well as to estimate the thermal constant (K) and critical temperatures (i.e., T_min, T_opt and T_max). The estimated values of the T_min and K for total developmental time using the linear model were 12.07°C and 86.20 degree‐days (DD), respectively. The T_min and T_max estimated by the Sharpe‐Schoolfield‐Ikemoto (SSI) model were 11.90°C and 37.41°C, respectively. The estimated T_opt for overall immature stage development of N. barkeri by the Lactin and SSI models were 33.89°C and 24.51°C, respectively. Based on the biological criteria of model evaluation, the linear and SSI models were found to be the best models for describing the developmental rate of overall immature stages of N. barkeri and estimating the temperature thresholds.     

Temperature-dependent ovariole and testis maturation in the yellow dung fly

Temperature is one of the abiotic environmental factors most strongly affecting animal behaviour, physiology, and life history. In insects, lower temperatures generally slow down most physiological processes, reducing growth rate and prolonging the juvenile period. Here, we investigate temperature‐dependent ovariole and testis maturation in the anautogenous yellow dung fly, Scathophaga stercoraria L. (Diptera: Scathophagidae), and relate it to corresponding temperature effects on pre‐adult development time and the adult pre‐reproductive period. Flies were reared in the laboratory at three constant temperatures (18, 22, and 26 °C), and the size of the developing ovarioles and testes (reflecting sperm production) was measured over time (i.e., age). Ovariole size increased asymptotically over the first 12 days of adult life, while the testes continued to fill after day 10. In accordance with the temperature‐size rule, warmer temperatures resulted in smaller ovarioles (eggs) and smaller testes, independent of body size. Warmer temperatures also greatly reduced pre‐adult development time by more than half, from 12 to 25 °C, the larger males always taking 1–3 days longer than the females. Corresponding temperature effects on the adult pre‐reproductive period were small (<1 day between 15 and 25 °C), with males taking 5–6 days and females 10–13 days to first reproduction. Time lost by males during the pre‐adult stage, when ovaries and testes are produced, can thus be more than compensated‐for by time gained during the pre‐reproductive period, when eggs and sperm are produced, so males can nevertheless start reproducing sooner than females.     

Effects of heat shock,heat exposure pattern,and heat hardening on survival of the sycamore lace bug,Corythucha ciliata

The sycamore lace bug, Corythucha ciliata (Say) (Hemiptera: Tingidae), is an invasive exotic pest on Platanus trees in China. This study assessed the thermotolerance of C. ciliata in the laboratory. Detailed experiments were conducted on the effects of high temperature (35, 37, 39, 41, 43, and 45 °C), duration of exposure (0.5, 1, 2, 4, 6, and 8 h), and developmental stage (egg, nymph, and adult) on survival of the bug. Meanwhile, the effects of heat hardening on survival at lethal temperature (exposure to 33, 35, 37, 39, and 41 °C for 1 h prior to transfer to 43 °C for 2 h) were also assessed for nymphs and adults. Survival of eggs, nymphs, and adults was not affected by temperatures between 35 and 39 °C, but declined rapidly with increasing duration of exposure (from 0.5 to 8 h) at temperatures ≥41 °C. The lethal temperature that caused mortality of 50% (Ltemp₅₀) of all developmental stages decreased with increasing duration of exposure from 0.5 to 8 h. The Ltemp₅₀ for nymphs was 44.3, 42.0, and 39.0 °C after 0.5, 2, and 8 h exposure, respectively. Thermotolerance was the highest in eggs, followed by adults and then nymphs. Thermotolerance was slightly greater for adult males than for adult females. The ability of nymphs, females, and males to survive exposure to 43 °C for 2 h significantly increased by heat hardening, i.e., by exposure to a non‐lethal high temperature for 1 h; the optimal heat‐hardening temperature was 37 °C. The results indicate that survival of C. ciliata at heat‐shock temperatures depended on both the temperature and the duration of exposure, and the tolerance to heat shock was enhanced by heat hardening. The thermotolerance of C. ciliata may partially explain why C. ciliata has been rapidly spreading on Platanus trees in southern provinces of China.     

INFLUENCE OF TEMPERATURE ON CERTAIN BIOLOGICAL ATTRIBUTES OF A LADYBEETLE COCCINELLA SEPTEMPUNCTATA LINNAEUS

Influence of temperature on certain biological attributes of an aphidophagous ladybeetle, Coccinella septempunctata Linnaeus, feeding on mustard aphid, Lipaphis erysimi (Kaltenbach), at five different temperatures, viz. 20, 25, 27, 30 and 35°C was investigated. Its developmental period was shortest (11.7 ± 0.09 days) at 35°C and longest (20.6 > 0.35 days) at 20°C. Developmental rate increased with increase in temperature. Hatching percent, larval survival, adult emergence and growth index were maximum at 30°C and minimum at 20°C. Oviposition period and fecundity were highest at 30°C and lowest at 20°C. A positive linear relationship exists between temperature and developmental rate and negative correlation between the duration of immature life stages and temperature. The proportion of developmental period allocated to each immature stage was found to be similar at each temperature regime. Thus, 30°C was found as the most suitable for C. septempunctata amongst the five temperatures tested.     

Effects of experimental warming on survival,phenology, and morphology of an aquatic insect (Odonata)

1. Organisms can respond to changing climatic conditions in multiple ways including changes in phenology, body size or morphology, and range shifts. Understanding how developmental temperatures affect insect life‐history timing and morphology is crucial because body size and morphology affect multiple aspects of life history, including dispersal ability, whereas phenology can shape population performance and community interactions. 2. It was experimentally assessed how developmental temperatures experienced by aquatic larvae affected survival, phenology, and adult morphology of dragonflies [Pachydiplax longipennis (Burmeister)]. Larvae were reared under three environmental temperatures: ambient, +2.5, and +5 °C, corresponding to temperature projections for our study area 50 and 100 years in the future, respectively. Experimental temperature treatments tracked naturally‐occurring variation. 3. Clear effects of temperature were found in the rearing environment on survival and phenology: dragonflies reared at the highest temperatures had the lowest survival rates and emerged from the larval stage approximately 3 weeks earlier than animals reared at ambient temperatures. There was no effect of rearing temperature on overall body size. Although neither the relative wing nor thorax size was affected by warming, a non‐significant trend towards an interaction between sex and warming in relative thorax size suggests that males may be more sensitive to warming than females, a pattern that should be investigated further. 4. Warming strongly affected survival in the larval stage and the phenology of adult emergence. Understanding how warming in the developmental environment affects later life‐history stages is critical to interpreting the consequences of warming for organismal performance.     

A comparative study of development and demographic parameters of <Emphasis Type="Italic">Tetranychus merganser</Emphasis> and <Emphasis Type="Italic">Tetranychus kanzawai</Emphasis> (Acari: Tetranychidae) at different temperatures

We investigated the effect of temperature on development and demographic parameters such as the intrinsic rate of natural increase (r _m) of the two spider mite species Tetranychus merganser Boudreaux and T. kanzawai Kishida at eleven constant temperatures ranging from 15 to 40°C at intervals of 2.5°C. Both male and female T. merganser and T. kanzawai completed development from egg to adult at temperatures ranging from 15 to 37.5°C. The longest developmental duration of immature stages was found at 15°C and the shortest developmental duration was found at 35°C for both species. Using linear and non-linear developmental rate models, the lower thermal thresholds for egg-to-adult (female and male) and egg-to-egg development were estimated as 12.2–12.3°C for T. merganser and as 10.8°C for T. kanzawai. The highest developmental rates were observed at around 35°C, whereas the upper developmental thresholds were around 40°C for both species. In fact, at 40°C, a few eggs of either species hatched, but no larvae reached the next stage. The r _m-values of T. merganser ranged from 0.072 (15°C) to 0.411 day⁻¹ (35°C), whereas those of T. kanzawai ranged from 0.104 (15°C) to 0.399 (30°C). The r _m-values were higher for T. kanzawai than for T. merganser at temperatures from 15 to 30°C, but not at 35°C (0.348 day⁻¹). Total fecundity of T. merganser was also higher than that of T. kanzawai at 35°C. These results indicate that higher temperatures favor T. merganser more than T. kanzawai.