Effects of temperature on the development,growth, and survival of larvae and pupae of a north-temperate chrysomelid beetle

Summary Developoment, growth, and survival of larvae and pupae of the red turnip beetle, Entomoscelis americana Brown, were studied in 10 constant and four alternating temperature regimes (10 to 32.5° C), in field-cages, and in natural populations in Manitoba. This beetle has a northtemperate distribution in North America. Larval and pupal development occurs in spring and normally is completed before the end of June. Growth and development occurred at all constant temperatures tested, but survival was low at the extreme temperatures. Therefore, the threshold and upper limit were near 10 and 32.5° C. The developmental times of the sexes did not differ and decreased with temperature, except possibly at 32.5° C. The average weight of adult females increased with temperature up to 32.5° C and those of males up to 25° C. Considering developmental rate, survival, adult weight, and incidence of malformed adults, the optimum temperature was estimated to be near 27.5° C.Development was accelerated significantly (6 to 9%) in alternating regimes with temperatures differing by 10° C, but not in regimes differing by 5 and 15° C. All alternating regimes increased adult weight, 5 to 17% for females and 2 to 10% for males. Field cage studies confirmed the increase in adult weight, but not the acceleration in development.A three-parameter normal function described accurately the relationship between developmental rate and constant temperature. A computer simulation model based on this equation estimated developmental times in field cages to within one to five days. For natural populations the model overestimated the developmental times by five to 16 days. The discrepancies between model estimates and observed developmental times in natural populations apparently were due to the elevation of larval and pupal body temperatures above air temperatures by behavioral thermoregulation. The elevation of body temperature was estimated to be equivalent to the addition of 5 to 6° C to the maximum daily air temperature. The adaptations and responses of this beetle to the cool spring temperatures of the north-temperate region are discussed.Contribution No. 1164, Agriculture Canada, Research Station, Winnipeg, Manitoba, Canada     

温度对美洲斑潜蝇发育、存活和繁殖的影响

探讨了在光照周期为14L◊10D、R.H.为70%±5%的恒温(12～35℃)条件下美洲斑潜蝇的发育、繁殖和存活,求得美洲斑潜蝇世代的发育起点温度与有效积温分别为8.77℃和295.69日度,给出了温度与各虫态发育速率间的函数关系。20～27.5℃时存活率较高,死亡主要发生在蛹期,35℃下蛹不能羽化。成虫寿命随温度的升高而缩短;种群增长指数于27.5℃时达到最高。     

Influence of temperature on survival, growth and fecundity of the freshwater snail Indoplanorbis exustus (Deshayes).

To note the effect of temperature on survival, growth and fecundity, newly hatched (zero day old) snails Indoplanorbis exustus were cultured at 10 degrees, 15 degrees, 20 degrees, 25 degrees, 30 degrees and 35 degrees C constant temperatures and room temperature (17.5 degrees-32.5 degrees C). Individuals exposed to 10 degrees C died within 3 days while those reared at 15 degrees, 20 degrees, 25 degrees, 30 degrees, 35 degrees C and room temperature survived for a period of 6, 27, 18, 16, 12 and 17 weeks respectively. An individual added on an average 0.21 mm and 0.45 mg, 0.35 mm and 7.94 mg, 0.63 mm and 15.5 mg, 0.81 mm and 27.18 mg, 1.07 mm and 41.48 mg and 0.78 mm and 31.2 mg to the shell diameter and body weight respectively at those temperatures per week. The snails cultured at 15 degrees C died prior to attainment of sexual maturity. On an average, an individual produced 31.9 and 582.77, 54.86 and 902.18, 56.01 and 968.45, 49.32 and 798.68 and 62.34 and 1143.97 capsules and eggs respectively at 20 degrees, 25 degrees, 30 degrees, 35 degrees C and room temperature (17.5 degrees-32.5 degrees C).     

Effects of constant and changing temperature conditions on diapause induction in Helicoverpa armigera (Lepidoptera: Noctuidae)

The effects of photoperiod and temperature on the induction and termination of facultative pupal diapause in Helicoverpa armigera (Lepidoptera: Noctuidae) were investigated under laboratory conditions. Exposing H. armigera larvae to both constant and fluctuating temperature regimes with a mean of 25°C and 20°C resulted in a type-III photoperiodic response curve of a short-long day insect. The long-day critical daylengths for diapause induction were ten hours and 12 hours at the constant temperatures of 25°C and 20°C, respectively. Higher incidences of diapause and higher values both for the longer and the shorter critical photoperiods for diapause induction were observed at fluctuating regimes compared with the corresponding constant ones. At alternating temperatures, the incidence of diapause ranged from 4.2% to 33.3% and was determined by the temperature amplitude of the thermoperiod and by the interaction of cryophase or thermophase with the photoperiod. Helicoverpa armigera larvae seem to respond to photoperiodic stimuli at temperatures >15°C and <30°C; all insects entered diapause at a constant temperature of 15°C, whereas none did so at a constant temperature of 30°C under all the photoperiodic regimes examined. Although chilling was not a prerequisite for diapause termination, exposure of diapausing pupae to chilling conditions significantly accelerated diapause development and the time of adult emergence. Therefore, temperature may be the primary factor controlling the termination of diapause in H. armigera.     

Development, survival and reproduction of black citrus aphid, Toxoptera aurantii (Hemiptera: Aphididae), as a function of temperature

The development, survival, and reproduction of the black citrus aphid Toxoptera aurantii (Boyer de Fonscolombe) were evaluated at ten constant temperatures (4, 7, 10, 15, 20, 25, 28, 30, 32 and 35 degrees C). Development was limited at 4 and 35 degrees C. Between 7 and 32 degrees C, developmental periods of immature stages varied from 44.2 days at 7 degrees C to 5.3 days at 28 degrees C. Overall immature development required 129.9 degree-days above 3.8 degrees C. The upper temperature thresholds of 32.3, 28.6, 29.3, 27.2, and 28.6 degrees C were determined from a non-linear biophysical model for the development of instars 1-4 and overall immature stages, respectively. Immature survivorship varied from 82.1 to 97.7% within the temperature range of 10-30 degrees C. However, immature survivorship was reduced to 26.3% at 7 degrees C and 33.1% at 32 degrees C. Mean adult longevity was the longest (44.2 days) at 15 degrees C and the shortest (6.2 days) at 32 degrees C. The predicted upper temperature limit for adult survivorship was at 32.3 degrees C. Total nymph production increased from 16.3 nymphs per female at 10 degrees C to 58.7 nymphs per female at 20 degrees C, declining to 6.1 nymphs per female at 32 degrees C. The estimation of lower and upper temperature limits for reproduction was at 8.2 and 32.5 degrees C, respectively. The population reared at 28 degrees C had the highest intrinsic rate of increase (0.394), the shortest population doubling time (1.8 days), and shortest mean generation time (9.5 days) compared with the populations reared at six other temperatures. The population reared at 20 degrees C had the highest net reproductive rate (54.6). The theoretical lower and upper temperature limits for population development, survival and reproduction were estimated at 9.4 and 30.4 degrees C, respectively. The biology of T. aurantii was also compared with three other citrus aphid species.     

Development, survival, and reproduction of the psocid Liposcelis yunnaniensis (Psocoptera: Liposcelididae) at constant temperatures

We investigated the effects often constant temperatures (20.0, 22.5, 25.0, 27.5, 30.0, 32.5, 35.0, 37.5, 39.0, and 41.0 degrees C) on the development, survival, and reproduction of the psocid Liposcelis yunnaniensis Li & Li (Psocoptera: Liposcelididae). At 39.0 and 41.0 degrees C, none of individuals could develop successfully or reproduce. From 20 to 37.5 degrees C, the development period from egg to adult ranged from 64.3 d at 20 degrees C to 16.1 d at 35 degrees C. The lower developmental threshold for egg, nymph, and combined immature stages were estimated at 15.08, 15.13, and 14.77 degrees C, respectively. After emergence the females went through a preoviposition period that ranged from 18.5 d at 22.5 degrees C to 3.11 d at 35 degrees C, whereas it was 16.3 d at 20 degrees C. Liposcelis yunnaniensis produced most eggs at 35 degrees C and the fewest at 22.5 degrees C. The population reared at 35 degrees C had the highest intrinsic rate of increase, shorter mean generation time, and shortest population doubling time compared with other temperatures. According to Weibull frequency distribution, L. yunnaniensis reared at all the temperatures had type III survivorship curves (c < 1.0). Based on life-table parameter estimations, we suggest that optimum range of temperatures for this species is from 25 to 37.5 degrees C. These data give us useful information on population biology of L. yunnaniensis and can be used to better manage this species.     

Pupal diapause of Helicoverpa armigera (Lepidoptera: Noctuidae): sensitive stage for thermal induction in the Okayama (western Japan) population

Helicoverpa armigera (Hübner) exhibits a facultative pupal diapause, which depends on temperature and photoperiod. Pupal diapause is induced at 20 degrees C by short photoperiods and inhibited by long photoperiods during the larval stage. However, in some pupae (35% of males and 57% of females) of a non-selected field population from Okayama Prefecture (34.6 degrees N), diapause is not induced by short photoperiods. In the present experiment, the importance of temperature for diapause induction was studied in the non-diapausing strain, which was selected from such individuals reared at 20 degrees C under a short photoperiod of 10L:14D. Furthermore, the sensitive stage for thermal determination of pupal diapause was determined by transferring larvae of various instars and pupae between 20 degrees C and 15 degrees C. Diapause was induced by 15 degrees C without respect to photoperiod. When larvae or pupae reared from eggs at 20 degrees C under a short or a long photoperiod were transferred to 15 degrees C in the periods of the middle fifth instar to the first three days after pupation, the diapause induction rate was significantly reduced in both males and females, especially in females. In contrast, when larvae or pupae reared at 15 degrees C were transferred to 20 degrees C in the same periods, diapause was induced in males, but not in females. However, the diapause induction rate of pupae transferred to 20 degrees C on the fourth day after pupation was significantly increased in females. The results show that temperature is the major diapause cue in the photoperiod-insensitive strain and the periods of middle fifth larval instar to early pupal stage are the thermal sensitive stages for pupal diapause induction with some different responses to temperatures between males and females in H. armigera.     

Influence of temperature on developmental rate,wing length,and larval head capsule size of pestiferous midge Chironomus crassicaudatus (Diptera: Chironomidae)

Larvae of Chironomus crassicaudatus Malloch were reared individually at nine constant temperatures from 12.5 to 32.5 degrees C (2.5 degrees C increments) for 120 d. Duration of immature stages (egg, four instars, and pupa), head capsule width of fourth instars, and wing length were recorded. Some adults emerged at all temperatures, except at 12.5 degrees C where individuals developed to fourth instars during the experiment. Sharpe and DeMichele's four-parameter model with high-temperature inhibition described the temperature-dependent developmental rates. The slowest development was observed at 15 degrees C, with developmental rate peaking between 25 and 27.5 degrees C. Developmental rate increased rapidly with increasing temperature up to 20 degrees C, slowed between 20 and 27.5 degrees C, and decreased at temperatures >27.5 degrees C. No developmental inhibition at high temperatures was observed in eggs. The most apparent high-temperature inhibition of development was recorded in fourth instars, which comprised the largest proportion of developmental time. Males developed faster than females, but females had wider larval head capsules and longer wings than males. Adult size was negatively related with temperature in both sexes, but this relationship was steeper in males than in females. Larval size peaked at 20 degrees C, whereas the head capsule width was reduced at temperatures higher and lower than 20 degrees C.     

Reproduction,survival, and life table parameters of the predatory mite <Emphasis Type="Italic">Cheyletus malaccensis</Emphasis> (Acari: Cheyletidae) at various constant temperatures

Reproduction, survival, and life table parameters of the predatory mite Cheyletus malaccensis Oudemans were evaluated at six constant temperatures: 17.5, 20, 25, 30, 32.5 and 35°C, feeding on Tyrophagus putrescentiae (Schrank). Preoviposition period of fertilized and virgin females varied with temperature from ca. 9 days at 17.5°C to ca. 1.5 day at 32.5°C and then increased to ca. 3 days at 35°C. Virgin female oviposition period was significantly shorter than for fertilized females at the temperatures examined with the exception of 17.5°C. The mean total number of eggs per fertilized (169.7 ± 6.6) and virgin female (60.7 ± 4.3) was highest at the temperature of 30°C. The data indicated a significant positive and nearly doubling effect of fertilization on female fecundity at the temperatures examined with the exception of 17.5°C. Age-specific fecundity was described by a temperature dependent model from which the maximum daily fecundity rate was estimated for fertilized and virgin females at 10.3 (at 30°C) and 6.8 (at 32.5°C) eggs/female, respectively. Virgin female longevity was significantly shorter than for fertilized females at 20, 30 and 32.5°C, and decreased from ca. 57 days at 17.5°C to ca. 17 days at 35°C. The Weibull function that was used to describe the age specific survival of fertilized and virgin females produced excellent fits to the survival data. Estimates of intrinsic rate of increase, net reproductive rate, mean generation time, doubling time and finite rate of increase, were obtained. The r_m value increased with temperature from 0.03 (day⁻¹) at 17.5°C to 0.21 (day⁻¹) at 32.5°C, after which it decreased to 0.15 (day⁻¹) at 35°C. These data indicate that C. malaccensis can reproduce at temperatures between 17.5 and 35°C and can be used for biological control of astigmatid mites within the temperature range where the pest occurs.     

Temperature-dependent development and life table parameters of Octodonta nipae (Coleoptera: Chrysomelidae)

The effect of temperature on the development, survivorship, fecundity, and life table parameters of Octodonta nipae (Maulik) (Coleoptera: Chrysomelidae), was studied at seven constant temperatures of 17.5, 20, 22.5, 25, 27.5, 30, and 32.5°C. Preliminary experiments showed that no development was observed at 15 and 35°C. All individuals completed development and females laid eggs from 20 to 30°C. There was a significant decrease in male and female longevity with increasing temperatures from 20 to 30°C. The longest and shortest longevity were 203.5 and 73.7 d for males, and 178.7 and 57.6 d for females, respectively. Females produced on average 62.7, 88.9, 116.8, 70.0, and 47.3 eggs and the life expectancy for a newborn egg was 171.6, 148.7, 114.9, 89.2, and 94.8 d at 20, 22.5, 25, 27.5 and 30°C, respectively. Life history data were analyzed by using an age-stage, two-sex life table. The intrinsic rate of increase (r) and the finite rate of increase (λ) of O. nipae increased with increasing temperatures from 20 to 30°C, while the mean generation time (T) decreased within this temperature range. The r was 0.0155, 0.0249, 0.0339, 0.0361, and 0.0383 d(-1) at 20, 22.5, 25, 27.5, and 30°C, respectively. The net reproductive rate (r(0)) was highest at 25°C (35.0 offspring), and lowest at 20°C (17.0 offspring). T was shortest at 30°C (76.4 d). The results showed that temperature greatly affected the fecundity and life table parameters of O. nipae, and a suitable temperature for population development and fecundity was at 25°C. The life table data can be used for the projection of population growth and evaluation of control programs.     

Effects of temperature on the immature development of the stone leek leafminer Liriomyza chinensis (Diptera: Agromyzidae)

The effect of nine constant temperatures (15, 17.5, 20, 22.5, 25, 27.5 30, 32.5, and 35 degrees C) on the development of the stone leek leafminer, Liriomyza chinensis (Kato), on Japanese bunching onion, Allium fistulosum L., was studied in the laboratory. Developmental times for immature stages were inversely proportional to temperature between 15 and 30 degrees C but increased at 32.5 degrees C. Total developmental times from egg to adult emergence decreased from 69.6 to 17.1 d for temperatures from 15 to 30 degrees C, with pupae requiring more time for development than the combined egg and larva stages. Both linear and nonlinear (Logan equation VI) models provided a reliable fit of development rates versus temperature for all immature stages. The lower developmental thresholds that were estimated from linear regression equations for the egg, first, second, and third instars, total larva, egg-larval, pupa, and total combined immature stages were 12.1, 10.6, 13.6, 8, 9.6, 11.3, 11.2, and 11.4 degrees C, respectively. The degree-day accumulation was calculated as 312.5 DD for development from egg to adult emergence. By fitting the nonlinear models to the data, the upper and optimal temperatures for egg, larva, pupa, and total immature stages were calculated as 37.8 and 31.7, 34.9 and 30.1, 35.8 and 30.6, and 35.0 and 30.9 degrees C, respectively. These data are useful for predicting population dynamics of L. chinensis under field conditions and determining the maximum proportion of susceptible individuals for facilitating improved timing of application of control measures.     

Effects of alternating temperatures onAcarus siro L. (Acari: Acaridae)

Fecundity, longevity and survival to adulthood ofAcarus siro (L.) at constant and alternating temperatures were compared. Both fecundity and longevity were affected by alternating temperatures but the effect of the frequency of alternations was not significant. Significantly higher fecundity and longer life spans were recorded at constant temperatures of 14 and 21°C than at 28°C or at alternating temperature regimes. Alternating temperature regimes in comparison to constant regimes did not significantly change the number of males and females surviving to adulthood or the sex ratio. However, the lowest number of adults surviving was recorded when temperatures were changed every 12 h and the highest at a constant temperature of 14°C.     

Temperature and humidity affecting development, survival and weight loss of the pupal stage of Drosophila melanogaster, and the influence of alternating temperature on the larvae

1. 1. The mean durations of development in the pupae of Drosophila melanogaster (Meigen) and their survival were measured at combinations of six constant temperatures (15, 20, 22.5, 25, 27.5 and 30°C) and up to 11 levels of relative humidity. The thermal survival range for the pupae is between 15 and 30°C, and the humidity viable range is between 60 and 100% RH.

2. 2. The percentage water loss of the pupae was measured at six constant temperatures and four levels of relative humidity. There was a rapid increase in the percentage of water lost during the first 24 h exposure at all tested conditions. However, pupae reared at 100% RH at each constant temperature, sustained the lowest water loss. The percentage water loss increased as temperature increased, as humidity decreased and also with time.

3. 3. The duration of larval development studied at six constant temperatures (15, 20, 22.5, 25, 27.5 and 30°C) was inversely related to temperature. A wide range of alternating temperature regimes had a small, though statistically significant, accelerative effect on larval developmental time. Thus, the present results may be used as a basis for modelling development under changing temperatures, with the assumption that the developmental rate is nearly identical to that from a series of constant temperatures.

     

Thermal Requirements and Parasitism Capacity of Trissolcus brochymenae (Ashmead) (Hymenoptera: Scelionidae) Under Constant and Fluctuating Temperatures, and Assessment of Development in Field Conditions

In order to understand the relative importance of Trissolcus brochymenae , a common egg parasitoid of the predatory stinkbug Podisus nigrispinus in areas where this predator is released, the thermal requirements and developmental periods (egg to adult) at constant (17, 20, 25, 28 and 32°C) and fluctuating (10-20, 13-23, 15-25, 17-27, 20-30 and 25-35°C) temperatures, and the effect of constant and fluctuating temperatures systems on the longevity and parasitism capacity of T. brochymenae were investigated. Based on thermal requirements of the parasitoid and field day/night temperature variation in the regions where P. nigrispinus was released, we calculated monthly and yearly number of generations of the parasitoid. Parameters of biological and thermal requirements of T. brochymenae were not affected when the insects were reared under constant or fluctuating temperatures. It was shown that males have a shorter developmental period and lower thermal requirements than females. The lowest parasitism capacity and shortest longevity of T. brochymenae were observed under fluctuating temperature regimes of 10-20oC and 25-35°C. A higher parasitism capacity was obtained under a 20-30°C regime (96.0 ±33.6 offspring per female), while longevity was longer at a constant temperature of 27°C (17.6 ±0.6 days). T. brochymenae showed a continuous development during all seasons through the year under field conditions, accomplishing 2.7, 2.4, 2.9 generations per month in the CAF, Pains, and Refloralje areas. An average of 26.4 and 25.8, 25.8 and 25.3, and 24.7 and 23.6 generations per year under constant and fluctuating temperatures systems was estimated for the CAF, Pains, and Refloralje areas, respectively. No significant difference between thermal systems in each area was observed; however, a significantly smaller number of generations per year were estimated to occur in the Refloralje area. Implications of these results for the forecasting of parasitoid population development and its impact on the host stinkbug predator are discussed.     

A true summer diapause induced by high temperatures in the cotton bollworm, Helicoverpa armigera (Lepidoptera: Noctuidae)

Summer diapause in the cotton bollworm, Helicoverpa armigera (Hübner), which prolongs the pupal stage, particularly in males, is induced by high temperatures. In the laboratory, summer-diapausing pupae of H. armigera were induced at high temperatures (33-39 degrees C) with a photoperiod of LD8:16; winter-diapausing and non-diapausing pupae, cultured at 20 degrees C with a photoperiod of LD8:16 and at 27 degrees C, LD16:8, respectively, acted as a control. Retention time of eye spots, weight, and lipid and glycogen levels were compared. At high temperatures, both body weight and energy storage capacity were much higher in summer-diapausing pupae than in non-diapausing pupae reared at 33-39 degrees C. At temperatures (>33 degrees C) high enough to maintain summer diapause, the eye spots of summer-diapausing pupae did not move during the 30-day experiment. However, eye spots of summer-diapausing pupae placed at 30 degrees C began to move about 10 days after they were transferred, significantly later than in non-diapausing pupae reared at 33-39 degrees C or non-diapausing pupae reared at 27 degrees C, which initiated eye spot movement 2 days after pupation. The differences in retention time of eye spots between summer- and winter-diapausing pupae shows that winter diapause is more intense than summer diapause in this insect. The weight loss, and lipid and glycogen metabolism curves indicate that the summer-diapausing pupae's metabolism is very low. We conclude that summer diapause in the cotton bollworm is a true diapause and that the summer diapause enables the cotton bollworm to withstand the high temperatures of summer.     

Interactions between size and temperature influence fecundity and longevity of a tortricid moth,Zeiraphera canadensis

Females of Zeiraphera canadensis Mut. & Free., the spruce bud moth, were reared in the laboratory at constant and alternating temperatures, and in an outdoor insectary, to (1) determine the effects of temperature, age and size on several reproductive parameters and, (2) to test the hypothesis that body size-temperature interactions influence longevity and realized fecundity. Egg maturation was linearly related to age and large moths developed eggs at a higher rate than small ones. Mcan lifetime oviposition rate reached a maximum and remained stable at temperatures 20° C while the mean lifetime rate of egg maturation increased linearly with temperature, indicating that higher temperatures adversely affect oviposition. The production of nonviable eggs increased with age but also with temperature, suggesting high temperature (25° C) reduces egg quality and/or hinders fertilization. The realized fecundity and longevity of females reared under an alternating temperature regime (mean 20° C) was significantly less than that of females reared at constant 20° C. Similar realized fecundity, longevity and mean lifetime oviposition rates for females reared at temperatures alternating between 10 and 25° C (mean 20° C) and those at constant 25° C reflected the inability of females to recover from elevated diurnal temperatures. Longevity was positively related to female body size at constant 15 and 20° C but the relationships were negative for moths exposed to diurnal temperatures equal to or exceeding 25° C. Due to the reduced longevity of large moths at high temperatures, linear regressions between size and realized fecundity were only significant at constant temperatures 20° C. At higher temperatures, the size-fecundity relationship became curvilinear as a result of the diminished reproductive output of large individuals. Reduced fecundity and longevity of large females at high temperatures may have been due to elevated internal temperatures of large-bodied moths. Large females in a controlled-environment chamber maintained at 25° C developed an internal temperature excess (i.e. temperature above ambient) of nearly 2° C while small-bodied females exceeded ambient by only 0.3° C. However, when held at 20° C, the temperature excess of large-bodied moths was much less than 1° C and small-bodied females did not differ from ambient. Such interactions between temperature and body size suggest that there should be stabilizing selection toward moderate-sized individuals and may explain the absence of size-related effects on fecundity and longevity previously reported for several other lepidopterans.     

Heat and cold-induced male sterility in Drosophila buzzatii: genetic variation among populations for the duration of sterility

Here we studied three phenotypic traits in Drosophila buzzatii that are strongly effected by temperature, and are expected to be closely associated with fitness in nature. The traits measured were thermal threshold of male sterility, time for males to gain fertility when reared at a sterility-inducing temperature and transferred to 25 degrees C on eclosion and survival after development. The last two traits were measured under four temperature regimes, constant 12 degrees C, 25 degrees C, 31 degrees C, and fluctuating 25 degrees C (18 h) and 38 degrees C (6 h). We looked for genetic variation in these traits and relations among them in four lines of D. buzzatii originating from Argentina and Tenerife. The thermal threshold of heat-induced male sterility was found to lie within the range of 30.0-31.0 degrees C. When measuring the time for males to gain fertility, males reared at a nonstressful temperature (25 degrees C) were fertile 58-67 h after emergence with only minor differences among lines. When reared constant 31 degrees C, males were fertile 174-225 h after hatching. The Argentinean lines were significantly faster in recovering from sterility than were the lines from Tenerife. When reared in a fluctuating temperature regime, differences among lines increased, dividing the lines into three significantly different groups, with a sterility period of 135-215 h. When reared at 12 degrees C from the pupal stage, males were fertile after 106-130 h with significant difference in the variance but not in the mean duration of sterility. Significant differences in viability were found among development temperatures, but not among lines, and viability and the duration of sterility seem to be genetically independent.     

Influence of temperature on the development, reproduction and longevity of Ceratothripoides claratris (Thysanoptera: Thripidae) on tomatoes

Ceratothripoides claratris (Shumsher) is a serious pest attacking tomatoes in Thailand. Temperature-dependent development of C. claratris was studied at seven constant temperatures, i.e. 22, 25, 27, 30, 34, 35 and 40 degrees C. Pre-adult survivorship was greatest (95%) at 25 and 30 degrees C and shortest at 22 degrees C. Egg-to-adult time decreased within the range of 20 to 30 degrees C and at 34 degrees C it started to increase. The lower thermal threshold for egg-to-adult development was estimated at 16 and 18 degrees C by linear regression and the modified Logan model, respectively. The optimum temperature for egg-to-adult development was estimated at 32-33 degrees C by the modified Logan model. The influence of temperature on reproduction and longevity of C. claratris was determined at 25, 30 and 35 and 40 degrees C. Both inseminated and virgin females failed to reproduce at 40 degrees C. Virgin females produced only male offspring, confirming arrhenotoky. The sex ratio of the offspring of fertilized females was strongly female-biased, except at 25 degrees C. Mean total fecundity per female and mean daily total fecundity per female were highest for both virgin and inseminated females at 30 degrees C. Female longevity was longest at 25 degrees C and shortest at 40 degrees C. Male longevity was longest at 30 degrees C and shortest at 40 degrees C. The net reproductive rate (R0) and intrinsic rate of natural increase (rm) was greatest at 30 degrees C while, mean generation time (G) and the doubling time (t) were highest at 25 degrees C. The finite rate of increase (lambda) was fairly constant (1.1-1.5 days) over the three temperatures tested. The pest potential of C. claratris for tropical Asia is discussed.     

Developmental and reproductive biology of Scirtothrips perseae (Thysanoptera: Thripidae): a new avocado pest in California

The developmental and reproductive biology of a new avocado pest, Scirtothrips perseae Nakahara, was determined in the laboratory at five constant temperatures, 15, 20, 25, 27.5 and 30 degrees C. At 20 degrees C, S. perseae exhibited greatest larval to adult survivorship (41%), and mated females produced a greater proportion of female offspring at this temperature when compared to 15, 25, 27.5 and 30 degrees C. Average lifetime fecundity and preoviposition period was greatest at 15 degrees C at 39.6 eggs per female and 17.6 days, respectively. Jackknifed estimates of net reproduction (Ro), capacity for increase (rc), intrinsic rate of increase (rm), and finite rate of increase (lambda) were all significantly greater at 20 degrees C than corresponding values at 15, 25 and 27.5 degrees C. Population doubling time (Td) was significantly lower at 20 degrees C, indicating S. perseae populations can double 33-71% faster at this temperature in comparison to 15, 25 and 27.5 degrees C. Mean adult longevity decreased with increasing temperature, from a maximum of 52.4 days at 15 degrees C to a minimum of 2.4 days at 30 degrees C. Developmental rates increased linearly with increasing temperatures for eggs and rates were non-linear for development of first and second instar larvae, propupae, pupae, and for egg to adult development. Linear regression and fitting of the modified Logan model to developmental rate data for egg to adult development estimated that 344.8 day degrees were required above a minimum threshold of 6.9 degrees C to complete development. An upper developmental threshold was estimated at 37.6 degrees C with an optimal temperature of 30.5 degrees C for egg to adult development. Unmated females produced only male offspring confirming arrhenotoky in S. perseae.     

Temperature-dependent development of Chilocorus bipustulatus (Coleoptera: Coccinellidae)

The effect of temperature on development and survival of Chilocorus bipustulatus L. (Coleoptera: Coccinellidae), a predator of many scale insects, was studied under laboratory conditions. The duration of development of egg, first, second, third, and fourth larval instars, pupa, and preovioposition period at seven constant temperatures (15, 17.5, 20, 25, 30, 32.5, and 35°C) was measured. Development time decreased significantly with increasing temperature within the range 15-30°C. Survival was higher at medium temperatures (17.5-30(ο)C) in comparison with that at more extreme temperature regimens (15 and >30(ο)C). Egg and first 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 35.2-37.9 and 11.1-13.0°C, respectively. The optimum temperature for development (where maximum rate of development occurs) was estimated at between 33.6 and 34.7°C. The thermal constant for total development was estimated 474.7 degree-days.