The response of anther culture to culture temperature in Triticum aestivum

Summary The response of anther culture to culture temperature was studied in detail using many varieties, F₁ hybrids and pollen-derived lines of wheat (Triticum aestivum) as materials. The suitable culture temperature for inducing pollen callus (or embryoids) in wheat anther culture ranged from 26 °C to 30 °C, varying with genotypes. But for the great majority of wheat genotypes the suitable culture temperatures lay between 28 °C and 30°C. The most significant genotypic variation in the response to culture temperature was observed in the comparison between the culture at 33 °C for eight days followed by culture at 25 °C (or 26 °C) and the continuous culture at 25 °C (or 26 °C). This genotypic variation in the response to culture temperature is a heritable character which may be controlled by multiple genes. The effect of culture at 30 °C for eight days followed by culture at 26 °C was similar to, or in some cases, better than that of continuous culture at 28 °C, and the effect of culture at 32 °C for eight days followed by culture at 28 °C was similar to that of continuous culture at 30 °C. In the range from 26 °C to 32 °C, the overwhelming majority of pollen calli emerged before the 40th day after anther inoculation, and the higher the culture temperature, the earlier and more concentrated the emerging period of the pollen callus. The pollen callus obtained at high temperatures above 28 °C should be transferred in time onto the regeneration medium at 25°–27°C to induce shoots.     

Relationships between temperature, development and survival of different life stages of the tomato fruit fly, Neoceratitis cyanescens

The development and survival of female Neoceratitis cyanescens (Bezzi) (Diptera: Tephritidae) from egg to complete ovarian maturation were studied in the laboratory at five different constant temperatures: 15, 20, 25, 30, and 35 °C. The aim of this study was to get information on the influence of temperature on pre-mature stages, as a prerequisite to optimise rearing procedures and to understand temporal and geographical patterns of fruit fly occurrence. The developmental rate of the different life stages increased linearly with increasing temperatures up to 30 °C. The fastest development of pre-mature stages was recorded at 30 °C (22±1 days) and the slowest at 15 °C (98±3 days). The day-degrees requirements (K) to complete total development were 432.6 day-degrees. Lower temperature thresholds were 11.4, 11.9, 10.0, and 11.1 °C for egg, larval, pupal stages and ovarian maturation, respectively. The number of adults obtained from an initial batch of 100 eggs reached a maximum (64) at 25 °C. At 35 °C, no adults emerged. Larval developmental time was significantly shorter in green tomato fruits than in potato tubers at 15, 20, and 25 °C. Mortality rate of larvae was higher in green tomato fruits than in potato tubers at 25 and 30 °C.     

Bionomics and population growth statistics of apterous virginoparae of woolly apple aphid, Eriosoma lanigerum, at constant temperatures

Development, survival, reproduction and population growth statistics of apterous virginoparae of woolly apple aphid, Eriosoma lanigerum (Hausmann) (Hemiptera: Aphididae) at constant temperatures of 10, 13, 15, 20, 25, 30 and 32°C are reported. The developmental times of all life stages were inversely related to temperature ranging from 10 to 30°C. Span of total development (time from birth to adulthood) decreased from 57.8 days at 10°C to 11.7 days at 30°C and increased to 16.8 days at 32°C. A good linear model fit (R²>0.96) between developmental rate and temperature in the range 10–25°C was observed for all life stages. The lower developmental threshold was estimated at 5.8°C for instar I, 4.8°C for instar II, 4.9° for instar III and 4.4°C for instar IV. The lower temperature threshold for total development was estimated at 5.2°C. The upper developmental limit was found to be 32°C. Mean degree-day accumulations required for completion of instars I, II, III, IV and total development were: 125.6, 51.0, 47.7, 50.7 and 267.6, respectively. Fecundity, larviposition period and adult longevity were reduced with increasing temperature. Net reproductive rate was greatest at 15°C whereas intrinsic rate of increase peaked at 25°C. Optimal performance, as measured by fecundity, survival and intrinsic rate of increase, ocurred in the range 13–25°C.     

Biology of the shore fly Scatella stagnalis in rockwool under greenhouse conditions

The development times and survival of immature stages in rockwool and the fecundity and longevity of adult Scatella stagnalis were determined and stage-specific life-tables constructed for the species at constant 20 and 25 °C and at a fluctuating temperature (23–34 °C, mean 28.5 °C). Development time from egg to adult decreased with temperature, being 15.9±0.1 days at 20 °C, 11.4±0.1 days at 25 °C and 10.1±0.2 days at fluctuating temperature with mean of 28.5 °C. The lower threshold for egg-to-adult development was 6.4±2.7 °C and the total quantity of thermal energy required to complete development was 212.8±.0 °C. The proportion of females in two populations studied was 0.521. High temperature increased the mortality of pupae from 7% (20 °C) and 10% (25 °C) to 29% at 28.5 °C. At 25 °C, female longevity was 15.5±0.7 days and fecundity 315±19 eggs/female (20.4 eggs/female/day). Males lived for 22.0±1.1 days. At constant 25 °C, the net reproductive rate was 126.1 female eggs/female, generation time was 18.4 days, the doubling time of the population 5.3 days, and the intrinsic rate of increase (r _m) 0.263 day^–1.     

Life history of Euseius scutalis feeding on citrus red mite Panonychus citri at various temperatures

The aim of this study was todetermine the biology and reproductivepotential of Euseius scutalis(Athias-Henriot) (Acari: Phytoseiidae) atvarious temperatures. These data are of valuein relation to mass rearing and the developmentof population dynamics models. The developmenttime, survival and fecundity of E.scutalis were determined at 20, 25 and30 ± 1 °C, 65 ± 10% RH and 16:8photoperiod. Total development times of E.scutalis were 6.7, 4.9 and 4.2 days at 20, 25and 30 ± 1 °C, respectively, using adiet of all life stages of the spider mite Panonychus citri (McGregor) (Acari:Tetranychidae). In general, preoviposition andpostoviposition periods of E. scutaliswere shortened as temperature increased, butthe oviposition period was longer at 25 °C than at 20 and 30 °C. Theshortest survival time of E. scutalis, at30 °C, was 10.1 days, followed by 23.7days and 28.6 days at 20 and 25 °C,respectively. Mated females laid on average1.1, 1.4 and 1.7 eggs per female per day and21.5, 39.7 and 17.1 eggs over their entire lifetime at 20, 25 and 30 °C, respectively.The sex ratios of E. scutalis were2.11/1, 2.24/1 and 2.11/1 female/male at 20, 25and 30 °C, respectively. The intrinsicrate of natural increase (r _m) increasedwith rising temperatures from 0.166 at 20 °C to 0.295 females/female/day at 30 °C. The net reproductive rate (R ₀)was highest at 25 °C (26.03females/female) and lowest at 30 °C(12.95 females/female). Mean generation time(T ₀) was longest at 25 °C (17.50days) and shortest (9.53 days) at 30 °C.     

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     

A temperature effect on nondisjunction of the X chromosomes among eggs from agedDrosophila females

The effects of temperature and aging on the frequency of nondisjunction inDrosophila melanogaster eggs were investigated. At 25°C offspring arising from 3–5 day old control females had a nondisjunction frequency (0.943/1000 offspring) very similar to that for females who were 24–26 or 27 days old when eggs were collected (1.044/1000 offspring). When females were aged for the same length of time at 10°C the frequency of nondisjunctional exceptions increased to 3.368 per 1000 offspring. These results indicate that aging the females at 25°C does not increase the nondisjunction rate over that obtained from non-aged females raised at 25°. The increase in nondisjunction frequencies when the females were aged at 10°C reflects an influence of temperature on the meiotic process inDrosophila melanogaster. At the low temperature eggs were also aged since few or no eggs were laid during the aging process. Thus in addition to a temperature effect on nondisjunction rates at 10°C there may also be an age effect.     

Life history and demography of the predatory mite,Amblyseius longispinosus Evans

The life history and demography of Amblyseius longispinosus Evans were studied under laboratory conditions 25–28°C and 65–85% RH using the red form of the twospotted spider mite, Tetranychus urticae Koch complex as prey. The entire development from egg to adult averaged 102.5 h for both sexes with a survival rate of 90.0%. Immature females consumed more prey eggs than males, averaging 7.9 and 6.4 eggs/day, respectively. The embryonic development time for male eggs was longer (average 45.2 h) than for female eggs (average 42.6 h). The average duration of succeeding stages did not differ between the sexes: larva, 15.7; protonymph, 21.1; and deutonymph, 23.0 h. Larvae were not observed to feed. Statistically significant differences between sexes were noted with respect to consumption of the deutonymphs (female, average 4.0±0.2; male, average 2.9±0.3 eggs/day) but not of the protonymphs. Mating occurred on the same day as adult emergence and was repeated several times during the reproductive life. Egg laying started on the second day after emergence. Parameters relating to oviposition were: fecundity, gross (50.7) and net (43.3) eggs/female; hatchability, 99.6% (gross) and 99.5% (net); the oviposition lasted at most 28 days and showed a peak in the first week. Net reproductive rate (R₀) was 36.7 female offspring/female/generation time (T) of 9.0 days. The sex ratio was biased toward the females (71.9%), while the intrinsic rate of increase (r_m) was 0.4 with a doubling time (DT) of 1.7 days. Males lived longer (36 days) than females (30 days) with a LT₅₀ for males of 26 days and for females of 22 days.     

Temperature influence on life table statistics of the chicken miteDermanyssus gallinae (Acari: Dermanyssidae)

An age-specific life table for the chicken miteDermanyssus gallinae (DeGeer, 1778) was based on various observations carried out at 25°C. The generation time was calculated to be 16.8 days; the intrinsic rate of natural increase was 0.12 per day, and the net reproductive rate was 7.2. A nonlinear function was found satisfactory to describe the developmental rate of the different immature lifestages at temperatures below 40°C. The stage-specific survival of the immature life-stages was generally high between 10 and 37°C, but decreased quickly outside this temperature range. Most of the eggs were laid during the first three weeks of the adult life. The proportion of surviving females rapidly decreases after moulting to the adult stage. At a temperature of 30°C, the highest number of eggs (3 eggs per day) was laid.     

Biology of Ixodes Rubicundus Ticks under Laboratory Conditions: Observations on Oviposition and Egg Development

Observations on oviposition and egg development of Ixodes rubicundus were made under laboratory conditions. Engorged females were exposed to temperatures in the range 10–25°C and relative humidities (RHs) of 33 and 93%. The pre-oviposition period, oviposition period, incubation period, conversion efficiency index (CEI) values and fecundity were determined. The mean pre-oviposition period varied from 13.3 days (temperature 25°C and RH 33%) to 68.3 days (temperature 10°C and RH 93%). Oviposition extended from a mean of 39 days (temperature 25°C and RH 93%) to 201.7 days (temperature 10°C and RH 93%). The developmental zero temperature for the pre-oviposition period was 9.2°C. The mean total number of eggs produced by engorged I. rubicundus females varied from 2045.7 (temperature 10°C and RH 93%) to 3777.7 (temperature 20°C and RH 93%). Both female mass and RH significantly (p < 0.01) influenced the number of eggs produced. CEI values varied between 43.1–54.4% (RH 93%) and 34.1–42.5% (RH 33%). At 93% RH females produced between 14.2 and 17.7 eggs per mg body mass compared to the 13.2–14.6 eggs per mg body mass at 33% RH. The shortest mean incubation period recorded was 164.3 days (temperature 25°C and RH 93%). The developmental zero temperature for incubation was 6.5°C. Both the pre-oviposition and oviposition periods of I. rubicundus are more extended compared to other species of the genus. Ixodes rubicundus produces a large number of small eggs compared to other prostriate ticks.     

Influence of diet on life table parameters of <Emphasis Type="Italic">Iphiseius degenerans</Emphasis> (Acari: Phytoseiidae)

Studies on the reproduction, longevity and life table parameters of Iphiseius degenerans (Berlese) were carried out under laboratory conditions of 25 ± 1 °C, 75 ± 5% RH and 16L:8D h. As food sources for the predatory mite, Ricinus communis L. pollen, all stages of the spider mite Tetranychus urticae Koch, Frankliniella occidentalis (Pergande) larvae, and Ephestia kuehniella Zeller eggs were selected. All diets were accepted as food by the adult mites. Female longevity ranged from 29.5 to 42.4 days, the highest value was recorded on a diet of Ephestia eggs. The highest percentage of females escaping the experimental arena was observed on the diet consisting of thrips larvae. The highest oviposition rate (1.9 eggs/female.day) was recorded when the predator was fed on spider mites on an artificial substrate. For other diets, oviposition rates ranged from 1.0 to 1.3 eggs/female.day. The intrinsic rate of natural increase (r _m) of I. degenerans varied between 0.015 and 0.142 females/female.day. The diet consisting of castor bean pollen resulted in the highest population growth whereas the diet on spider mites brushed off onto a bean leaf arena resulted in the slowest population growth. This can be explained by the inability of the predator to cope with the webbing of T. urticae, and the high escape rate of the progeny when reared on spider mites. The percentage of females in the offspring ranged from 40 to 73%.This revised version was published online in May 2005 with a corrected cover date.     

Field and laboratory studies on the timing of oviposition and hatching of the western black-legged tick, Ixodes pacificus (Acari: Ixodidae)

The timing of oviposition and hatching of Ixodes pacificus was investigated in the field and at constant temperatures in the laboratory. Replete females held at temperatures between 9 and 29°C began depositing eggs a mean of 9–70 days after drop off. Egg masses held between 12 and 25°C commenced hatching 25–178 days after the onset of oviposition. Eggs held at 9 or 29°C did not hatch. The lower temperature thresholds for development (LTD) for oviposition and hatching were 6.5 and 9°C, respectively. The number of degree days required for oviposition and hatching was 173 and 588, respectively. Replete females placed in the field on 2 December through to 8 March deposited eggs from 2 February through to 24 April; the eggs commenced hatching between 2 July and 21 August. Unfed larvae from two of 20 egg masses survived through the winter and fed readily when exposed to deer mice (Peromyscus maniculatus) on 22 April. Replete larvae were returned to the field and moulted between 9 and 21 August. Larvae exposed to deer mice in August, 4 weeks after hatching, also fed readily. Although further studies are needed to clarify the timing of nymphal development, the present study suggests that I. pacificus requires more than 1 year to complete its life cycle.     

Effect of algal diet and temperature on the embryonic development time of the rotifer Brachionus plicatilis in culture

The embryonic development times of two strains of Brachionus plicatilis (Bs and S-1) cultured on three different algal diets (Nannochloris oculata, N. maculata and Nannochloropsis gaditana), have been determined at 20°C, 25°C and 30°C. As expected, the embryonic development times decreased with increasing temperature in all cases. However, embryos from adults fed on N. gaditana tended to develop more slowly than those of individuals fed on the other algal species. Mean egg volume was also affected by diet, larger eggs being produced by females fed on N. gaditana. No obvious relationship between egg size and temperature was detected.Two principal factors seemed to affect the embryonic development time. The first was temperature which acts through its well known effect on metabolic rates. The second was maternal diet which probably affects development time through its effect on yolk content, as reflected in the size of the egg.     

Biology of <Emphasis Type="Italic">Dermacentor silvarum</Emphasis> (Acari: Ixodidae) under laboratory conditions

The minimum life cycle of Dermacentor silvarum Olenev had a mean duration of 87.5 days (range 74–102 days) under laboratory conditions [(27±1 °C), 70% RH, 6 L: 18 D]. The mean time in (days) for the different stages of its cycle was as follows: incubation period of eggs was 15.3 days; prefeeding, feeding and premoulting periods of larvae and nymphs averaged 5.5, 4.0 and 7.3 days, and 5.2, 5.0 and 14.6 days, respectively; prefeeding, feeding, preoviposition and oviposition periods of female adults lasted for 7.8, 4.5, 4.3 and 14.0 days, respectively. There existed a highly significant correlation between engorged body weight of females and egg masses laid (r = 0.9877, p<0.001). The reproductive efficiency index (REI) and reproductive fitness index (RFI) in females were 11.09 and 9.58, respectively. No relationship between nymphal engorged body weight and resultant sexes was observed. Delayed feeding and non-oviposition (in June and July) existed in females, and low temperature (−10 °C) treatment for 45 days could terminate oviposition diapause. However, the egg masses laid by post-diapause females were significantly smaller than those laid by females engorged in March, April and May.     

Combined Effects of Algal (<Emphasis Type="Italic">Chlorella vulgaris</Emphasis>) Food Level and Temperature on the Demography of <Emphasis Type="Italic">Brachionus havanaensis</Emphasis> (Rotifera): a Life Table Study

We evaluated the combined effects of food (0.5 × 10⁶, 1.0 × 10⁶ and 2.0 × 10⁶ cells ml⁻¹ of Chlorella vulgaris) and temperature (15, 20 and 25 °C) on life history variables of B. havanaensis. Regardless of Chlorella density there was a steep fall in the survivorship of B. havanaensis at 25 °C. Both food level and temperature affected the fecundity of B. havanaensis. At any given food level, rotifers cultured at 15 °C showed extended but low offspring production. At 25 °C, offspring production was elevated, the duration of egg laying reduced and the fecundity was higher during the latter part of the reproductive period. The effect of food level was generally additive, at any given temperature, and higher densities of Chlorella resulted in higher offspring production. Average lifespan, life expectancy at birth and generation time were 2–3 times longer at 15 °C than at 25 °C. At 20 °C, these remained at intermediate levels. The shortest generation time (about 4 days) was observed at 25 °C. Gross and net reproductive rates and the rate of population increase (r) increased with increasing temperature and generally, at any given temperature, higher algal food levels contributed to higher values in these variables. The r varied from 0.11 to 0.66. The survival patterns and lower rates of reproduction at 15 °C suggest that the winter temperatures (10–15 °C) prevailing in many waterbodies in Mexico City allow this species to sustain throughout the year under natural conditions.     

The predatory mite Hypoaspis miles: temperature dependent life table characteristics on a diet of sciarid larvae, Bradysia paupera and B. tritici

Life table characteristics of Hypoaspis miles Berlese (Acarina: Hypoaspidae) fed on a mixture of Bradysia paupera Tuomikoski (Diptera: Sciaridae) and B. tritici Coquillet larvae were investigated in laboratory experiments at 4 temperatures (15, 20, 25, 30 °C) for development time, juvenile mortality, sex ratio, preoviposition period, oviposition period, postoviposition period, age-specific fecundity, and adult longevity. Juvenile development time decreased with increasing temperature from 46 days at 15 °C to 10 days at 30 °C. The lower temperature threshold was 9.9 °C and development required 205 °D. Juvenile mortality decreased from 52% at 15 °C to 3% at 25 °C and then increased to 24% at 30 °C. Preoviposition period varied with temperature from 12 days at 15 °C to 3 days at 25 °C and then increased to about 4 days at 30 °C. Oviposition period decreased with increasing temperature from 58 days at 15 °C to 25 days at 30 °C. The mean number of eggs per female per day increased from 0.4 at 15 °C to 2.3 at 25 °C and decreased to 1.3 at 30 °C. Age-specific fecundity was described by a temperature dependent model from which the maximum daily fecundity rate could be estimated to be attained at 25.6 °C. Female longevity was significantly shorter than for males, and decreased from 90 days at 15 °C to 34 days at 30 °C. Sex ratio was female-biased at all 4 temperatures and increased with temperature up to 25 °C, decreasing at 30 °C. Estimates of net reproductive rate, intrinsic rate of increase, finite rate of increase, mean generation time and doubling time were obtained. The r _m -value increased with temperature from 0.031 day^-1 at 15 °C to 0.133 day^-1 at 25 °C, after which it decreased to 0.112 day^-1 at 30 °C. The study showed that H. miles can develop and reproduce at temperatures between 15 and 30 °C. H. miles and sciarids have approximately the same optimum temperature and thresholds for development and reproduction and H. miles can be used for biological control of sciarids within the temperature range where the pest occurs.     

Temperature-induced changes in spider mite fitness: offsetting effects of development time, fecundity, and sex ratio

Temperature affects many life history parameters in poikilotherms. Temperature clearly affects development time and fecundity, which affect the intrinsic rate of increase. In haplodiploid mites, ambient temperature may also affect offspring sex ratio which, in turn, affects intrinsic rate of increase. The combined effect of all these processes determines the fitness of individual females. However, sex ratio also affects mating structure and, potentially, rate of local adaption. We investigated the direct effect of temperature variation on sex ratio, development time, and fecundity in the twospotted spider mite (Tetyranychus urticae), and calculated the effect of their interaction on mite intrinsic rate of increase. We conducted experiments at 2 temperatures and designed the experiment to separate pre-adult and adult sensitivity to temperature variation. Mites were reared from eggs to adult ecdysis at either 22°C or 32°C. Upon emergence as adults, these 2 groups were each split between 22°C and 32°C and allowed to oviposit. Not surprisingly, development from egg to adult was accelerated when mites were exposed to the higher temperature during offspring development, regardless of the temperature experienced by the mother during her development. Fecundity and the proportion of female offspring were affected by temperature only when mothers were exposed during both development and oviposition. About 12 offspring were gained and female bias was increased by 26% when the mother's development occurred at 22°C, whereas oviposition at 22°C added only 6 more offspring and increased female bias by only 7%. There was no correlation between sex ratio and fecundity; both were related to temperature but not to each other. Furthermore, development time, not fecundity or sex ratio, appeared to the main factor affecting the intrinsic rate of increase. Our results support other evidence that sex ratio varies independently of development time and fecundity.     

Life history study of Thrips setosus

Development, reproduction and population growth of Thrips setosus Moulton (Thysanoptera, Thripidae), reared on a leaf of kidney bean, was studied under six different constant temperatures, and the effect on reproduction of short photoperiod during immature stages was examined. Survival rates from hatch to adult were more than 67.5% at temperatures between 17.5 and 27.5 °C, but less than 55% at 30 °C. Developmental rates increased linearly as rearing temperature increased. A total of 181.1 degree-days, above a developmental zero of 12.5 °C, were required to complete development from egg to adult oviposition. These data were related to records of field temperatures in Kurashiki in western Japan, and an estimate produced that, under outdoor conditions, a maximum of between seven and 12 generations could have developed annually between 1990 and 1999. There were no significant differences in mean adult longevity and mean fecundity among three temperatures (20, 22.5 and 25 °C). The intrinsic rate of natural increase (r _m) was 0.1997 at 25 °C. Reproductive diapause was induced by a photoperiod less than 12 h at 20 °C.     

Effect of Temperature on Longevity and Productivity in Drosophila Ananassae: Evidence for Adaptive Plasticity and Trade-Off Between Longevity and Productivity

The genetic response of body size to temperature in the laboratory provides an interesting example of phenotypic plasticity. We found that females of Drosophila ananassae reared to adulthood at 18°C showed significant increase in body weight as compared to females reared at 25°C. At a given temperature, early productivity and lifetime productivity were the highest when the rearing and test temperature were the same. The effect of test temperature was highly significant for total productivity and early productivity. The interaction between test temperature and development temperature was also highly significant. Effect of development temperature was not significant. The females reared at 18°C showed greater body weight but their productivity was not significantly higher than smaller females reared at 25°C. Thus, the usually close relationship between size and fecundity is lost when the size change is due to rearing temperature. These findings provide evidence for adaptive plasticity in D. ananassae. We also found a negative correlation (trade-off) between longevity and productivity, the first report of such a trade-off between longevity and productivity in D. ananassae.     

Demographic analyses of organophosphate-resistant and susceptible strains of greenhouse whitefly, Trialeurodes vaporariorum, on three cotton cultivars

Laboratory experiments were conducted using organophosphate-resistant and susceptible strains of greenhouse whitefly, Trialeurodes vaporariorum Westwood, to assess age-specific vital rates in individually-held adults, and development and survival in preadults on three cotton cultivars at 27±1 °C, 50±10% RH, and a photoperiod of 16:8 (L:D). Female whiteflies lived longer than males, with a maximum life expectancy of 29 days. Heaviest egg laying occurred at ages between 7 and 18 days when individual whiteflies laid > 10 eggs/day. Greenhouse whitefly populations doubled weekly, with stable age distribution of 63% eggs, 28% larvae, 5% pupae, and 4% adults. Analysis of various life history parameters that combine aspects of survival, developmental rates, and fecundity indicated no consistent differences in reproductive fitness between the two greenhouse whitefly strains. Of the three cotton cultivars tested, Pima S-6 was most susceptible, Acala SJ-2 was intermediate and Gumbo 500 was most resistant to greenhouse whitefly. Resistance of Gumbo 500 was expressed as slower developmental rates, reduced survival to adulthood, lower reproductive rates, and lower intrinsic rate of increase.