Optimum Temperature For Development Research Articles

Does the temperature–size rule apply to idiobiont parasitoids?

AbstractIn most ectotherms, several life‐history traits, including body size, respond to environmental conditions through the temperature–size rule (TSR). The mechanisms underlying the TSR are still being debated, but studying idiobiont insect parasitoids, which develop with a fixed amount of resources, may shed light on this relationship. In this study, we conducted experiments to determine how the developmental temperature affects various characteristics of male and female Trichogramma euproctidis (Girault) (Hymenoptera: Trichogrammatidae), an idiobiont egg parasitoid of Lepidoptera. The study tested various hypotheses, including the cellular or oxygen diffusion hypotheses and the resource acquisition hypothesis, to understand whether T. euproctidis follows the TSR. The developmental time of both male and female T. euproctidis decreased with increasing temperature. Both males and females displayed a unimodal distribution for size, dry mass, and lipid content, with individuals at lower and higher temperatures being smaller, weighing less, and containing fewer lipids. Female lifetime fecundity increased from 13 to 24 °C and then decreased at 31 °C. Additionally, the number and size of gametes in male and female T. euproctidis displayed a unimodal distribution with increasing temperature. Trichogramma euproctidis deviates from the TSR as it follows a non‐linear reaction norm with an optimal developmental temperature. This result supports the hypothesis that for species following TSR and having unlimited access to food resources, the resource acquisition hypothesis is a significant mechanism explaining the TSR. With climate change affecting temperature, understanding the TSR is crucial, and research on insect parasitoids may help reveal how the interplay between environmental temperature and resource allocation affects the TSR in natural populations.

Population and spatial ecology of horseshoe crabs (Limulidae) in a nursery ground at Pulau Bedukang, Brunei Bay, Borneo

Abstract. Rozaini AF, Laurie KH, Marshall DJ. 2023. Population and spatial ecology of horseshoe crabs (Limulidae) in a nursery ground at Pulau Bedukang, Brunei Bay, Borneo. Biodiversitas 24: 4485-4492. Suitable nursery habitat to support populations of juvenile horseshoe crabs is becoming threatened globally. There are currently no formal studies on juvenile populations of the horseshoe crabs (Limulidae) for Brunei Darussalam (Brunei, Borneo). We investigated body size structure, population cohort and ecological distribution of juvenile horseshoe crabs associated with a mudflat on Pulau Bedukang, in Brunei Bay. Seventy juveniles were retrieved during four sampling days covering two seasons and four study sites. Carcinoscorpius rotundicauda and Tachypleus gigas were common, whereas only two individuals of Tachypleus tridentatus were found. Carapace width (size) was similar in the common species and there was no difference in juvenile size between the seasons and study sites. Body weight to carapace width relationships showed that the species grew at similar rates, although C. rotundicauda developed faster, producing 14 compared to the eight pre-migration mudflat instars produced by T. gigas. Species densities were similar, and there was no spatial separation of species or juvenile size across the mudflat or in relation to the mangrove forest edge. Nearest-neighbor (NN) analysis showed that individual crabs were generally dispersed. Their mudflat cohabitation suggests physiological and behavioral plesiomorphies for common optimal developmental salinity and temperature conditions. This study provides baseline information for comparison with other regional studies and for local conservation planning.

Sub-lethal effects of spinetoram application interacts with temperature in complex ways to influence respiratory metabolism, life history and macronutrient composition in false codling moth (Thaumatotibia leucotreta)

In many pests, insecticide efficacy is dependent on environmental conditions, including ambient temperature. However, it remains unknown if thermal history alters sub-lethal effects to potentially enhance or reduce pesticide resistance in the false codling moth (FCM), Thaumatotibia leucotreta. Here, using FCM, a pest of economic importance in South Africa infesting several commercial food crops, we report results of sub-lethal exposure to spinetoram, an insecticide that disrupts the nervous system. We investigate whether insecticide efficacy is temperature dependent or perhaps interacts with thermal history by testing the effect of a combination of a sub-lethal dose of spinetoram (4 mg/100 ml) and developmental temperature acclimation (22˚C and 28˚C, i.e., a few degrees above or below optimal development temperatures) on the metabolic rate, life history traits and body composition of FCM in the laboratory. A sub-lethal dose of spinetoram reduced metabolic rate of FCM pupae significantly, led to smaller pupal mass and decreased emergence rates. Additionally, males acclimated at 28 °C had a significantly higher emergence rate compared to males acclimated at 22 °C. Body water, body lipids and body protein reserves of adult FCM tended to be higher in the insecticide treatment compared to the control in the 22 °C acclimation group. In the 28 °C acclimation group, body water, lipids and proteins were lower in the insecticide treatment versus the control. Furthermore, sex influenced both emergence rate and body composition with the direction of change depending on insecticide and temperature treatments. Overall, a sub-lethal dose of spinetoram negatively affects body composition and life history traits but interacts with temperature in complex ways. Therefore, both lethal and sub-lethal effects of spinetoram on FCM, in combination with information on the thermal environment experienced by the pest, should be taken into consideration when pest control decisions are made.

Estivation and Postestivation Development of Hemlock Woolly Adelgid (Adelges tsugae) (Hemiptera: Adelgidae) at Different Temperatures.

Hemlock woolly adelgid (Adelges tsugae) is the most important pest of hemlocks in the eastern United States, where it completes three generations a year. We investigated the impact of temperature (8, 12, 16, and 20°C) on the estivation and postaestivation stages of the A. tsugae sistens generation. Temperature significantly impacted development and survival of this generation. The highest mortality occurred at the coolest temperature (8°C). Adelges tsugae developed rapidly as the temperature increased and optimum temperatures for development ranged between 17 and 22°C for the different instars. The estimated lower temperature threshold was 0°C for second instar nymphs and 3 -5°C for the other instars and the preoviposition period. Estivating first-instar sistentes resumed development (as evidenced by segments becoming visible) after 40-100 d at the constant temperatures (fastest at 16°C) then required only 105 degree-days (DD) for 50% of the individuals to molt. Subsequent instars developed rapidly (another 470 DD total to reach adult), and oviposition began at ~623 DD from the time the first instars resumed development. This study provides valuable data required to develop an annual phenology model for A. tsugae which will assist in timing monitoring and control treatments.

Effects of Temperature on the Development and Survival of Cricket Species; Acheta domesticus and Gryllus bimaculatus (Orthoptera: Gryllidae)

Temperature plays an important role in the development and survival of insects. The effects of temperature on the development of two cricket species, Acheta domesticus and Gryllus bimaculatus were determined at six constant temperatures (18, 22, 26, 30, 34 and 380C). Parameters for stage-specific development such as fecundity, weight and fat content, structural body size, sex ratio, development time, and longevity were investigated. Relative humidity, light intensity, and photoperiod were set at 60-90 %, 500 ± 25 Lux, and 12:12 L:D, respectively. The results indicated that the duration of eggs and nymphal stages were significantly influenced by increased temperature. The egg-to-adult developmental period of Acheta domesticus declined from 200.5 days to 66.26 days as the temperature increased from 180C to 30 °C while that for Gryllus bimaculatus decreased from 231.82 to 62.22 days as the temperature increased from 18 to 34°C. The optimum temperature estimated for egg-to-adult ranged from 26˚C to 34˚C. Longevity of both females and males was significantly higher (female: F5, 401 = 7.5, P < 0.001; male: F5, 401 = 6.4, P < 0.001) at 18oC than at other temperatures, with the shortest recorded for Acheta domesticus (female: 20.19 days; male: 26.67 days) and Gryllus bimaculatus (Females: 25.56 days; Males: 27.49 days) at 38oC. Fecundity was highest at 26°C (1360 eggs/female/generation) and lowest at 18°C (101 eggs/female/generation) for Acheta domesticus. For Gryllus bimaculatus, the highest fecundity was recorded at 30°C (1722 eggs/female/generation) and the lowest at 18°C (123 eggs/female/generation). The optimal developmental temperature for crickets was determined to range from 26°C to 34°C. Understanding the impacts of temperature on the development of crickets would provide information on how climate change shapes insect ecologies and enable the development of forecasting models.

Thermal Biology of Liorhyssus hyalinus (Hemiptera: Rhopalidae) and Nysius simulans (Hemiptera: Lygaeidae), Fed on the Milky Stage of Maize Grains.

When quinoa, Chenopodium quinoa Willd., is cultivated in South America outside of its Andean origin, the heteropterans Liorhyssus hyalinus (Fabricius) and Nysius simulans Stål may emerge as important pests. Here we studied the development and reproduction of both species at different constant temperatures in the laboratory. Egg and nymphal development were investigated at 18, 22, 26, 30, 34, and 36°C. For both species, egg incubation time significantly decreased as the temperature increased. Nymphs did not successfully develop at 18°C and the total nymphal time significantly decreased as the temperature increased from 22 to 36°C. Based on a linear day-degree (DD) model, the lower developmental threshold (LDT) temperatures for eggs and nymphs were estimated to be 16.0 and 17.9°C for L. hyalinus, and 16.1 and 19.7°C for N. simulans, respectively. Thermal requirements for egg and nymphal development were 68.6 and 114.8 DD for L. hyalinus, and 77.7 and 190.3 DD for N. simulans, respectively. Reproduction and adult longevity were studied at 22, 26, 30, and 34°C. For both species preoviposition time decreased as temperature increased, and the oviposition period was longest at 26°C. The highest fecundity and egg viability were observed at 30°C, whereas longevities were higher at 22–26°C than at 30–34°C. As the lowest tested temperatures were not suitable to both heteropterans and 30°C was found to be the optimal temperature for development and reproduction, peak densities are expected in warm areas and seasons.

Virulence of native isolates of entomopathogenic fungi (Hypocreales) against the “sweetpotato whitefly” Bemisia tabaci (Hemiptera: Aleyrodidae), including the effects of temperature and fungicides

Hypocrella, Moelleriella and related species in the Hypocreales (Ascomycota, Sordariomycetes) cause epizootics of whiteflies and scale insects in nature. However, studies on their host specificity, virulence, infection cycles, optimal development under laboratory conditions, and compatibility with other control methods, are unexplored for most species. Under laboratory conditions, the virulence of several isolates of field-collected hypocrealean fungi (Hypocrella, Moelleriella, Regiocrella, and Verticillium) was determined on Bemisia tabaci eggs and 4th instar nymphs. In addition to virulence, the effect of temperature and two commercial fungicides on growth rates and germination of the isolates was evaluated. None of the isolates infected the eggs, while M. libera, M. ochracea, and M. turbinata caused high nymphal mortality. Moelleriella libera was the most virulent isolate. At all temperatures, M. libera, Regiocrella sp. (P17H20), and Verticillium cf. pseudohemipterigenum had the highest germination and growth rates. The optimal growth temperature depended on the isolate, but at 23 °C and 25 °C, the probability of spore germination was higher for most isolates. Finally, the fungicides azoxystrobin and chlorothalonil inhibited growth rates and conidial germination at 24 and 48 h of exposure. This research produces vital knowledge on the virulence and infection cycles of poorly studied native species of entomopathogenic fungi. In addition, the results provide information on the optimal temperature for development in laboratory conditions and susceptibility to fungicides, which could contribute to future biological control strategies.

Acclimation to low pH does not affect the thermal tolerance of Arbacia lixula progeny.

As the ocean warms, the thermal tolerance of marine invertebrates is key to determining their distributional change, where acclimation to low pH may impact the thermal range of optimal development. We compared thermal tolerance of progeny from a low pH-acclimated sea urchin (Arbacia lixula) population from the CO2 vents of Ischia (Italy) and a nearby population living at ambient pH. The percentages of normally developing gastrulae and two-armed larvae were determined across 10 temperatures representing present and future temperature conditions (16-34°C). Vent-acclimated sea urchins showed a greater percentage of normal development at 24 h, with a larger optimal developmental temperature range than control sea urchins (12.3°C versus 5.4°C range, respectively). At 48 h, upper lethal temperatures for 50% survival with respect to ambient temperatures were similar between control (+6.8°C) and vent (+6.2°C) populations. Thus, acclimation to low pH did not impact the broad thermal tolerance of A. lixula progeny. With A. lixula's barrens-forming abilities, its wide thermotolerance and its capacity to acclimate to low pH, this species will continue to be an important ecological engineer in Mediterranean macroalgal ecosystems in a changing ocean.

Modeling Temperature-Dependent Development Rate in Insects and Implications of Experimental Design.

Characterizing the temperature-dependent development rate requires empirical data acquired by rearing individuals at different temperatures. Many mathematical models can be fitted to empirical data, making model comparison a mandatory step, yet model selection practices widely vary. We present guidelines for model selection using statistical criteria and the assessment of biological relevance of fits, exemplified throughout a Lepidoptera pest dataset. We also used in silico experiments to explore how experimental design and species attributes impact estimation accuracy of biological traits. Our results suggested that the uncertainty in model predictions was mostly determined by the rearing effort and the variance in development times of individuals. We found that a higher number of tested temperatures instead of a higher sample size per temperature may lead to more accurate estimations of model parameters. Our simulations suggested that an inappropriate model choice can lead to biased estimated values of biological traits (defined as attributes of temperature dependent development rate, i.e., optimal temperature for development and critical thresholds), highlighting the need for standardized model selection methods. Therefore, our results have direct implications for future studies on the temperature-dependent development rate of insects.

Evaluation of linear and nonlinear models for temperature driven development of Spodoptera litura (Fabricius) on soybean crop


 The tobacco caterpillar, Spodoptera litura, a major pest of soybean in India is under surveillance in all soybean growing areas in Maharashtra in order to issue alerts to farmers and prevent economic losses. In this context, two linear models were fitted to developmental data of S. litura life stages reared on soybean at five constant temperatures viz. 15, 20, 25, 30 and 35°C through laboratory experiments. Optimum temperature for development (Topt) and upper temperature threshold (Tmax) were estimated from three nonlinear models by additionally including developmental response at >35°C. Topt estimates for the total immature development were 34.5°C (Lactin-2), 33.7°C (Briere-1) and 33.2°C (Simplified Beta type function) while Tmax estimates were in the range of 38 to 40°C. Application of a thermodynamic non-linear model (Optim SSI) gave estimate ofintrinsic optimum temperature (Tφ) for development of egg (28.3°C), larva (27.5°C) and pupal stage (30.3°C). The phenology model of S. litura on soybean based on estimated developmental threshold temperatures and thermal constants was validated using available field surveillance data to facilitate informed pest management decisions.

Spatial and temporal variation in phenotypes and fitness in response to developmental thermal environments

AbstractPhenotypic variation within populations is influenced by the environment via plasticity and natural selection. How phenotypes respond to the environment can vary among traits, populations and life stages in ways that can influence fitness.Plastic responses during early development are particularly important because they can affect components of fitness throughout an individual's life. Consequently, how natural selection shapes developmental plasticity could be influenced by fitness consequences across different life stages. Moreover, spatial variation in selection pressures could generate differences in plastic responses among populations.To gain insight into sources of variation in phenotypes and survival, we used a laboratory egg incubation experiment using brown anole lizardsAnolis sagreifrom mainland (ancestral) and island (descendent) populations, combined with a mark–release–recapture experiment in the field. Our study was designed to (a) quantify the effects developmental temperature on embryo development and offspring morphology, (b) assess how developmental temperature influences offspring survival across different life stages and (c) quantify how thermal reaction norms vary among ancestral and descendant populations.Developmental temperature influenced offspring morphology, but thermal reaction norms of embryos showed little variation among populations. Developmental temperature influenced offspring survival, but the patterns differed between embryo and hatchling stages; the optimal temperature for embryos was about 5℃ lower than that for hatchlings. High temperatures were thermally stressful to embryos, but they reduced incubation duration and led to early hatching. In turn, earlier hatching increased the probability of survival to adulthood. Moreover, the effect of developmental temperature on hatchling survival was most pronounced for offspring that hatched late in the season.The difference in optimal developmental temperatures between life stages may be driven by physiological tolerance for embryos and by ecological factors for hatchlings. Moreover, the fitness consequences of the developmental environment depend on the phenology of hatching. Overall, these results highlight how the developmental environment can differentially affect fitness across life stages and show that temporal thermal heterogeneity can influence survival of embryos, but the consequences on post‐hatching stages may vary at different times of the season.A freePlain Language Summarycan be found within the Supporting Information of this article.

Thermal development of the endoparasitoid Aphelinus maculatus Yasnosh (Hymenoptera: Aphelinidae) parasitizing Myzus persicae Sulzer (Homoptera: Aphididae).

The aphid parasitoid, Aphelinus maculatus Yasnosh, was first documented in China in 2016. It is important to make clear of the effects of temperatures on the development of this aphid parasitoid for the future using as a aphid biological control agent. So the thermal requirements, lower developmental threshold (t), thermal constant (K), upper developmental threshold (Tm) and optimum developmental temperature (To) for the egg-mummy, mummy-adult and egg-adult periods of A. maculatus were established under the laboratory conditions. The studies were conducted at five constant temperatures (13, 18, 23, 28, and 33°C) and with a 16L: 8D photoperiod. Lower developmental threshold (t) and thermal constant (K) were estimated by fitting linear model. Upper developmental threshold (Tm) and optimal developmental temperature (To) were estimated by fitting Logan I non-linear model. The results turned out that the lower (t) and the upper developmental thresholds (Tm) for egg-adult period were 5.59°C and 28.17°C, respectively. The thermal constants (K) for egg-mummy, mummy-adult, and egg-adult periods were estimated at 121.51, 127.88, and 243.90 degree-days, respectively. The optimal developmental temperature (To) for egg-adult period was 27.45°C calculated by the model, but the survival rate was only 40.68% at the temperature of 28°C. The highest survival rate was 74.32% at temperature of 23°C, implying that A. maculatus preferentially developed at the temperate regions of temperature.

Effects of temperature on the development and reproduction of sugarcane top borer Scirpophaga excerptalis (Lepidoptera: Pyralidae)

• The top borer Scirpophaga excerptalis is a major pests of sugarcane in Guangxi, China. • Temperature has a critical impact on developmental rate of S. excerptalis. • Developmental rate of different stages of S. excerptalis was reduced by increasing of temperatures during experiments. • Temperature has a key role in reproduction and development of S. excerptalis . To determine the effects of temperature on the development and reproduction of top borer Scirpophaga excerptalis Walker (Lepidoptera: Pyralidae), the durations of different developmental stages and reproductive capacity of S . excerptalis were measured at 20, 23, 26, 29 and 32℃. The results showed that the average durations of various developmental stages of S. excerptalis shortened with increasing temperatures from 20 to 32℃. The durations to complete one life cycle were 113.17 days at 20℃, and 39.50 days at 32℃. The developmental rate of each stage and generation was positively correlated with the temperature, which was consistent with the Logistic regression model. The temperature thresholds for egg, larval, pupal and preoviposition stages and the total cycle were 13.73, 14.73, 13.91, 13.66 and 14.10℃, respectively. The effective accumulative temperature was 112.62, 370.01, 188.17, 23.82 and 718.07 degree-days (DD), respectively. The adult longevity shortened with increasing temperatures, and the highest number of eggs laid per female was 204.74 eggs at 29℃. The survival rates of eggs, larvae and the whole generation were the highest at 26℃, which were 87.25%, 56.67% and 37.21%, respectively while the highest survival rate of the pupa was 76.69% at 29℃. There was no significant difference for the total cycle at 23-29℃. The results indicated that temperature was the key factor affecting the development and reproduction of S. excerptalis , and the optimum temperature for development and reproduction ranged from 23 to 29℃.

Modeling the impact of temperature on the population abundance of the ambrosia beetle Xyleborus affinis (Curculionidae: Scolytinae) under laboratory-reared conditions.

Modeling the impact of temperature on each life stage of a beetle population represents a continuing challenge. This study evaluates the effects of five temperature treatments (20, 23, 26, 29 and 32°C) on population abundance and timing of a colony of ambrosia beetles Xyleborus affinis reared under laboratory conditions and use this data to develop demographic and phenological models. Abundances at each life stage (eggs, larvae, pupae and adult) were examined through periodic destructive sampling; given that it was not possible to track individuals. To assess the effects of temperature on oviposition, development and survival rates we developed a novel estimation strategy based on cohorts, which does not require individual developmental data. Since oviposition was entirely unwitnessed, we assessed competing empirical ovipositional models. Rates of development were computed using a modal rate curve for each life stage, and rates were projected to cohorts in life stages assuming log-normal developmental variance. Temperature-driven survival rates were assumed to be logistic with a quadratic exponent to capture modal temperature dependence. Parameters were estimated simultaneously using minimum negative log posterior likelihood, assuming Poisson distribution of observations and using priors to inform unobserved developmental rates and enforce mechanistic constraints on oviposition models. A parabolic function best described oviposition rate. Optimal developmental temperatures were 30.5°C, 29°C and 27.5°C, with maximum developmental rates of 0.26/day, 0.12/day and 0.23/day for eggs, larvae and pupae, respectively. The survival rates in the range 20-29 °C were equal to 1 in the eggs-to-larvae transition, from 0.72 to 0.35 in larvae-to-pupae transition, and from 0.2 to 0.89 in pupae-to-adults transition. This procedure effectively characterized the direct thermal effects on development and survival of each life stage in the X. affinis under laboratory conditions and would be suitable for estimating temperature dependence for other species in which individual observations are not possible.

Mild Abiotic Stress Affects Development and Stimulates Hormesis of Hemp Aphid Phorodon cannabis.

Simple SummaryFor centuries, hemp has been used by humans as a source of natural fiber. Nowadays, it is a multipurpose crop with many uses, but the most valuable are hemp metabolites including terpenes and cannabinoids. During the cultivation of hemp, farmers encounter wilting plants, inhabited by the hemp aphid—a persistent plant-damaging insect. The species lives mainly on the undersides of leaves and on flower stalks and feeds on the phloem sap. We studied the effects of temperature and the herbicide used by farmers in routine hemp cultivation on the population biology of hemp aphids. Hemp aphids thrived best at moderate temperatures between 20 and 25 °C. At this temperature range, they lived for about 25 days, during which they reproduced for 15 days, producing between 54.5 and 111.6 nymphs in total per female. At 28 °C, aphid survival and reproductive capacity were much lower. Treatment of plants with herbicide caused mild stress in aphids and resulted in increased aphid reproduction and a change in their behavior; aphids settled on lower parts of the plant rather than on the top part of the plant (growing point), which is normal in untreated plants. This new knowledge may help to manage the hemp aphid and reduce damage to hemp crops in the future.The hemp aphid Phorodon cannabis Passerini is a well- known (Asia, Europe) or newly emerging (North America) insect. It is a monophagous insect pest causing considerable damage in field and glasshouse cultivations. The aim of this work was to study the effects of meteorological (temperature) and agronomical (herbicide) factors on the biology of the hemp aphid. In one experiment, hemp plants were kept at constant temperatures ranging from 20 to 30 °C, and aphid survival and fecundity were measured. In a related experiment conducted at 20 °C, plants were treated with field-appropriate rates of a selective graminicide containing quizalofop-P-tefuryl (40 gL−1, 4.38%, HRAC group 1), commonly used to control weeds in hemp, and aphid enzyme activity was measured in addition to population parameters. We found that hemp aphids could live, feed and reproduce within the whole studied range of temperatures, demonstrating its great evolutionary plasticity. However, the optimal temperature for development was 25 °C, at which the insect lived and reproduced for 25 and 15 days, respectively, with an average fecundity of 7.5 nymphs per reproduction day. The herbicide treatment increased the activity of superoxide dismutase (SOD), catalase (CAT), β-glucosidase, S-glutathione transferase (GST), oxidoreductive peroxidase (POD), and polyphenol oxidase (PPO) in the aphids, but only on certain days after treatment, which indicates a mild stress in aphid tissues, related to a higher reproduction and changed feeding behavior; aphids moved from the actively growing tips compared to untreated plants. The results of these experiments are discussed in terms of the impact on the future management of this pest.

Biological and Biochemical Impacts of Temperature on Spodoptera littoralis (Boisduval)

Background: The Egyptian cotton leafworm, Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae), is one of the most destructive agricultural lepidopteran pests in Egypt, attacking several important crops all year round. S. littoralis can have two to seven generations per year, depending on the climate of the region; for example, changes in temperature affect all life processes of S. littoralis. Methods: The development, survival, and fecundity of S. littoralis at one of five constant temperatures as well as their effects on the biochemical impacts were investigated. Results: The results showed that the duration of developmental stage (eggs, instars, pupae), longevity, and fecundity significantly decreased with increasing temperature from 15 to 35 oC. Larvae emerged fastest from the eggs at 25 °C. The percentage of oviposited females was 46, 58, 74.5, 66.5, and 50% at 15, 20, 25, 30, and 35 °C, respectively. The results also showed that the fourth larval instars of S. littoralis at 25 oC had a higher level of proteins, lipids, carbohydrates, and free amino acids in comparison with those larvae at 35 oC. Therefore, temperature rise leads to increasing metabolic rate, and decreasing the development period. Conclusion: Thus, 25 °C was the optimum temperature for development, fecundity, rates of biochemical and physiological reactions of S. littoralis.

Aspects of the development of Ixodes anatis under different environmental conditions in the laboratory and in the field

BackgroundNumerous laboratory and fewer field-based studies have found that ixodid ticks develop more quickly and survive better at temperatures between 18 °C and 26 °C and relative humidity (RH) between 75 and 94%. Ixodes anatis Chilton, 1904, is an endophilic, nidicolous species endemic to North Island brown kiwi (Apteryx mantelli) (NIBK) and the tokoeka (Apteryx australis), and little is known about the environmental conditions required for its development. The aims of this study were to determine and compare the conditions of temperature and RH that ensure the best survival of the kiwi tick and the shortest interstadial periods, in laboratory conditions and outdoors inside artificial kiwi burrows.MethodsFree-walking engorged ticks were collected off wild kiwi hosts and placed in the laboratory under various fixed temperature and humidity regimes. In addition, sets of the collected ticks at different developmental stages were placed in artificial kiwi burrows. In both settings, we recorded the times taken for the ticks to moult to the next stage.ResultsLarvae and nymphs both showed optimum development at between 10 °C and 20 °C, which is lower than the optimum temperature for development in many other species of ixodid ticks. However, larvae moulted quicker and survived better when saturation deficits were < 1–2 mmHg (RH > 94%); in comparison, the optimum saturation deficits for nymph development were 1–10 mmHg.ConclusionsOur results suggest that the kiwi tick has adapted to the stable, but relatively cool and humid conditions in kiwi burrows, reflecting the evolutionary consequences of its association with the kiwi.Graphical

Pest survey card on Spodoptera frugiperda

This pest survey card was prepared in the context of the EFSA mandate on plant pest surveillance (M-2017-0137), at the request of the European Commission. Its purpose is to guide the Member States in preparing data and information for Spodoptera frugiperda surveys. These are required to design statistically sound and risk-based pest surveys, in line with current international standards.Spodopterafrugiperdais a regulated priority Union quarantine pest in the EU and Member States are therefore required to perform annual surveys. Emergency measures are in place to prevent the introduction into and the spread within the EU. Spodoptera frugiperda is not known to occur in the EU, but it could become established in some coastal Mediterranean regions that remain frost-free all year. Climate is therefore a limiting factor for the establishment of the pest. The optimum temperature for development from egg to adult is 28°C.Spodopterafrugiperda is a polyphagous pest and detection surveys should mainly target maize, rice and sorghum, while delimiting surveys should cover all host species in the survey area. Due to the high spread capacity of the adults, detection of the mothat low levels of population is crucial to avoid further spread of the pest.Detection surveys tosubstantiate pest freedom should be based on a trapping strategy.After a finding, trapping should be intensified in the neighbouring fields and combined with the visualexamination of host plants for the symptoms and early stages of S. frugiperda. Morphological and molecular procedures are both available for the identification of S. frugiperda. If experience is lacking or the purpose is to identify the early stages of the pest, molecular methods are preferred over the morphological ones.

Effect of short-term high-temperatures on the growth, development and reproduction in the fruit fly, Bactrocera tau (Diptera: Tephritidae)

Bactrocera tau (Walker) (Diptera: Tephritidae) is an economically important invasive pest, that is capable of seriously reducing the quality and yield of vegetables and fruits, it was first recorded from Fujian province in 1849 and later introduced to Yunnan province in 1912 as a result in trade fruits and vegetables of China. In recent years, with the onset of global climate change and the accompanying increase in the greenhouse effect, elevated climatic temperatures have become one of the main environmental factors affecting growth and reproduction in insects, and the optimal developmental temperature of B. tau was found to be from 25 °C to 31 °C, the growth, development and reproduction of B. tau are normal under the optimal temperature conditions. In order to determine the repercussions that elevated temperature have on B. tau, we assessed the effects that short-term (12 h) high-temperature exposures (34 °C, 36 °C, 38 °C, 40 °C, 42 °C, 44 °C, 46 °C, and 48 °C) had on the growth, development and reproduction of B. tau at different developmental stages of the fly. The results showed that the survival rate of B. tau gradually decreased in all stages following exposure to short-term high-temperatures. The pupal stage was the least sensitive to increased temperatures. The pupae withstood the highest lethal temperature, having an LT50 of 42.060 °C, followed by female adults (40.447 °C), male adults (40.013 °C), and larvae (36.740 °C). The egg stage, which was the most susceptible to heat increases, had the lowest LT50 (38.310 °C). No significant effects were observed in the developmental stages of B. tau at temperatures from 24 °C to 38 °C. The development duration was significantly prolonged at 40 °C (P < 0.05) in the eggs (2.830d), larvae (7.330d), and pupae (8.170d) (P < 0.05). B. tau was unable to survive at temperatures above 42 °C. The pre-oviposition of female adults was extended, the average egg number per female showed a downward trend, the longevity of adults gradually shortened, and the ratio of female to male offspring increased as temperature increments were increased. In summary, short-term high-temperatures over 42 °C were not suitable for successful development of B. tau, while short-term high-temperatures over 40 °C were not suitable for successful reproduction in B. tau.

The Effects of Constant and Fluctuating Temperatures on Development of Diaphorina citri (Hemiptera: Liviidae), the Asian Citrus Psyllid.

The effects of six average daily temperatures, 15, 20, 25, 30, 32, and 35°C, that were either constant or fluctuating over 24 h on development times of California-sourced Diaphorina citri Kuwayama nymphs were examined. Thermal performance curves for immature stages of D. citri were characterized using one linear and six nonlinear models (i.e., Ratkowsky, Lobry-Rosso-Flandrois, Lactin-2, Brière-2, Beta, and Performance-2). Daily thermal fluctuations had significant effects on development times of D. citri nymphs, which differed across experimental temperatures. Diaphorina citri nymphs reared at constant temperatures completed development faster than those reared under fluctuating profiles with equivalent temperature means. Linear model estimates of degree-days required for completion of cumulative development of D. citri were 25% lower for constant temperatures when compared with fluctuating temperature regimens. Nonlinear model estimations of optimum developmental temperature and upper theoretical temperature bounds for development were similar for individuals reared under constant and fluctuating temperatures. Nevertheless, the estimated values of lower theoretical temperature limits above which development occurred were lower under fluctuating than constant temperatures. A meta-analysis of published D. citri temperature-dependent development literature, synthesizing datasets of five globally distributed populations (Brazil, California, China, Florida, and Japan) reared under different constant temperatures on six different host plants (i.e., Citrus limonia, C. sinensis cv Natal, C. sinensis cv. Pêra, C. reticulata, Fortunella margarita, and Murraya paniculata), together with the results of this study (C. volkameriana), revealed convergence in estimates of developmental parameters. These results have implications for predicting D. citri invasion and establishment risk and subsequent population performance across various climactic gradients and geographic regions.