Lower Thermal Threshold Research Articles

Effect of temperature on the development, reproduction and survival of Tetramoera schistaceana (Lepidoptera: Tortricidae)

Tetramoera schistaceana Snellen is an important stem borer of sugarcane, which causes severe damage to sugarcane in China. Temperature is a key factor affecting its development and reproduction. Development duration, reproduction and survival rate of T. schistaceana were determined at five different temperatures (20, 23, 26, 29 and 32 °C) in this study. Results showed that temperature had significant effects on the development duration, survival rate and reproduction of T. schistaceana. The development rate of T. schistaceana for each stage increased linearly with increasing temperatures between 20 and 32 °C. Egg hatching rate, larval pupation rate and pupal eclosion rate were the highest between 23 and 26 °C. The lower thermal threshold (T0) for egg, larva, pupa, pre-adult and whole generation were 9.98, 9.80, 9.47, 9.50 and 8.87 °C, respectively and the thermal constant (K) for the development of the respective life cycle stages of were 89.29 for eggs, 400.00 for larvae, 151.52 for pupae, 625.00 for pre-adult and 666.67DD for whole generation, respectively. The average fecundity per female was also the highest between 23 and 26 °C. Therefore the optimum temperature range for the development and reproduction of T. schistaceana was between 23 and 26 °C.

Temperature-dependent development and life tables of Palpita unionalis (Lepidoptera: Pyralidae)

Abstract Palpita unionalis Hubner (Lepidoptera: Pyralidae) is one of the primary pests in olive orchards, damaging buds and fruits of the olive tree. The present study investigated the biology of P. unionalis across a temperature gradient and elaborated on the corresponding life tables for a better understanding of its population dynamics in the environment. The biology of the pest was studied at six temperatures (17, 20, 22, 25, 27, and 30 °C). The duration and survival of immature stages, sex ratio, and survival of emerged adults were evaluated. The female fecundity and longevity (pre-oviposition, oviposition, and post-oviposition periods) were calculated. The life tables were elaborated from these parameters. The life cycle of P. unionalis was significantly longer at 17 °C and shorter at 30 °C. Larval survival was significantly reduced at 30 °C, however, adult survival was at a maximum, yet their sex ratio was not affected by temperature. The lower temperature, 20 °C, was optimal for fecundity (586.3 eggs), which was reflected in the highest net reproductive rate (105.7 offspring per individual). The thermal constant (K) and the lower thermal threshold (t 0) for egg to adult period were 582.9° days and 7.1 °C, respectively. Based on the current study, it is concluded from the parameters of biology and life tables that temperature has a significant role in the population growth of P. unionalis. This should be considered throughout the monitoring and management of P. unionalis at different agro-ecologies in the context of global warming.

Mode Transition Induced by Gas Heating Along the Discharge Channel in Capacitively Coupled Atmospheric Pressure Micro Plasma Jets

The effects of neutral gas heating along the direction of the gas flow inside the discharge channel of a parallel plate micro atmospheric pressure plasma jet, the COST-jet, on the spatio-temporal dynamics of energetic electrons are investigated by experiments and simulations. The plasma source is driven by a single frequency sinusoidal voltage waveform at 13.56 MHz in helium with an admixture (0.05–0.2%) of nitrogen. Optical emission spectroscopy measurements are applied to determine the spatio-temporally resolved electron impact excitation dynamics from the ground state into the He I (3s)3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^3$$\\end{document}S1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_1$$\\end{document} state and the rotational temperature of nitrogen molecules at different positions along the direction of the gas flow inside the 30 mm long discharge channel. The gas temperature, which is assumed to be equal to the N2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document} rotational temperature, is found to increase along the discharge channel. This effect is attenuated as the nitrogen concentration is increased in the gas mixture, leading to an eventually constant temperature profile. The experimental data also reveal a plasma operating mode transition along the discharge channel from the Ω\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Omega$$\\end{document}- to the Penning-mode and show good agreement with the results of 1d3v kinetic simulations, which spatially resolve the inter-electrode space and use the gas temperature as an input value. The simulations demonstrate that the increase of the gas temperature leads to the observed mode transition. The results suggest the possibility of using the nitrogen admixture and the feed gas temperature as additional control parameters, (i) to tailor the plasma operating mode along the direction of the gas flow so that the production of specific radicals is optimized; and (ii) to control the final gas temperature of the effluent. The latter could be particularly interesting for biological applications, where the upper gas temperature limit is dictated by the rather low thermal damage threshold of the treated material.

Warning of warming limpets: sea temperature effects upon intertidal rocky assemblages

Abstract Limpets (Patella spp.) are marine gastropods that inhabit rocky shores along the coasts of Europe, the Mediterranean, Macaronesia and the north-west coast of Africa. Being considered key species, limpets have an important role regulating algal assemblages in coastal communities. The goal of this work was to evaluate the influence of sea temperature on the respiration rate of four limpet species occurring in mainland Portugal, in line with predictions from the metabolic theory of ecology. The individuals were collected from rocky shores in Portugal and exposed to sea temperatures ranging from 6–28°C for respiration rate assessments. Following the estimation of the relationship between oxygen consumption and temperature the activation energy was calculated. In parallel, low and high thermal thresholds were determined for three of the species. The results indicated that P. ulyssiponensis oxygen consumption increased linearly with sea temperature and the remaining species presented the same tendency. The values of activation energy ranged between 0.33–0.76 eV. For P. ulyssiponensis, the highest activation energy indicated that this species is more sensitive to temperature variations while for the tested temperatures it presented a higher thermal tolerance limit than the other species. Such findings indicate that P. ulyssiponensis is the most susceptible of these species to climate change, in line with the tolerance–plasticity trade-off hypothesis. This work provides a good starting point for understanding the effect of sea temperature on oxygen consumption in Patella spp. and for comprehending sensitivity of limpets to temperature increases under future climate change scenarios.

Broadband‐Tunable Third‐Harmonic Generation Using Phase‐Change Chalcogenides

Despite remarkable progress in passive nonlinear nanophotonics, dynamically controlled ultracompact nonlinear optical sources with high efficiency remain elusive. Nonvolatility, large refractive index contrast between amorphous and crystalline phases, low thermal threshold for crystallization, and particularly high‐third‐order nonlinear optical susceptibility of phase‐change alloy Ge2Sb2Te5 (GST) make it a promising candidate for active subwavelength metaphotonic structures for realization of third‐harmonic generation (THG) devices. Herein, a GST‐based asymmetric Fabry–Perot cavity is numerically designed and experimentally demonstrated to show a dynamically reconfigurable structure with a large shift of the THG resonant band. In addition, continuous resonant spectral shifting bridged by a precisely controlled semicrystalline phase of GST is realized. Tunable THG with the fundamental wavelength ranging from 1150 to 1400 nm is presented, which corresponds to a broadband THG source in the violet‐blue visible wavelength range. Herein, the potential of GST subwavelength structures as a reliable platform for realization of the broadband‐tunable frequency‐conversion sources for applications such as THG microscopy and optical communication is indicated.

Methods for estimating and modelling spruce budworm development rates at constant temperatures

Abstract We describe an experimental protocol for measuring the response of spruce budworm postdiapause larval development to temperature. This protocol is specifically designed to include measurements of development near their upper and lower thermal thresholds. The application of this protocol to a laboratory colony allowed for the first experimental evidence that spruce budworm larval development occurs at temperatures as low as 5 °C and as high as 35 °C, and it provides data to fit stage-specific development models. Our protocol is also designed to minimise mortality near the thermal development thresholds, thus allowing for multigenerational studies. We observed developmental plasticity in larvae reared at constant temperatures, particularly the occurrence of up to 42% of some individuals requiring only five instars to complete development compared to the expected six instars. The occurrence exhibited no clear relation to temperature. Although this protocol is specifically designed for spruce budworm, it provides a template for the study of other species’ developmental responses to temperature.

Effect of Different Thermal Conditions on Biology and Number of Generations of Palpita forficifera (Lepidoptera: Crambidae)

Palpita forficifera Munroe (Lepidoptera: Crambidae) is the principal pest in olive groves in Brazil and Uruguay, damaging buds and fruits. Therefore, this work was undertaken to understand the biology of P. forficifera at different temperatures, to determine thermal requirements, and to estimate the number of annual generations in different olive groves located in Brazil and Uruguay. The study was performed at 10, 15, 20, 25, 30, and 35 °C, 60 ± 10% RH, and a 14:10 h (L:D) photoperiod. The duration and survival stages of development, sex ratio, fecundity, and fertility were determined, and we elaborated the fertility life table at different temperatures. We also determined the thermal requirements, and the number of annual generations in olive producing areas were estimated. All immature stages of P. forficifera were affected negatively by the temperature at 10 and 35 °C, whereas 25 and 30 °C provided the shortest egg-to-adult periods. However, larval viability was affected at 30 °C (48.7%). Highest fecundity (325.5 eggs) was found for P. forficifera females kept at 25 °C. Additionally, the highest net reproduction rates (Ro) and intrinsic population growth rates (Rm) were verified at 25 and 30 °C. Lower thermal threshold (Tb) and thermal constant (K) for the egg-to-adult period were 10.7 °C and 549.45 degree-d, respectively. Based on the thermal requirements, P. forficifera can produce 4.0 to 6.3 generations per yr in the olive producing regions of Brazil and Uruguay. Results of the present study are important for understanding the occurrence of P. forficifera under field conditions and to aid strategic management designs.

<p><strong>Temperature-dependent development and reproduction of </strong><strong><em>Oligonychus punicae</em></strong><strong> (Acari: Tetranychidae) on Eucalyptus</strong></p>

Temperature plays an important role in the development and reproduction of mites. The present study assesses how temperature affects the biology (development and survival of immatures) and life table parameters of Oligonychus punicae. This study also determines the mite thermal requirements (thermal requirement and development base temperature). The experiments were conducted in an air-conditioned chamber under different temperatures (21, 25, 29, 33, and 37ºC). The period of each stage (egg to adult) of O. punicae at different temperatures was used to determine the thermal constant and the lower thermal limit of development. The duration of the periods of pre-oviposition, oviposition, post-oviposition, fecundity, and longevity was recorded. The life table at different temperatures was created using data from the biological cycle. There was an inverse relationship between the development time of O. punicae and temperatures. However, there was no hatching of eggs at 37ºC. All O. punicae eggs resulted in females. The survival analysis for the immature and adult (female) stages of O. punicae showed a decreased life span with increasing temperatures. For the egg-adult period, the lower thermal threshold and the thermal constant for females of O. punicae were 10.34ºC and 163.93 degree-days, respectively. Temperature affected the periods of pre-oviposition, oviposition, and fecundity of adult females of O. punicae, tending to decrease with increasing temperatures. Specific fecundity varied over the oviposition period, decreasing with increasing temperatures. The net reproduction rate decreased significantly following temperatures 21°C to 33°C. The increase in temperature results in a significantly shorter average generation time. The intrinsic rate of increase ranged from 0.15 to 0.20. The finite rates of increase were all greater than 1.00. The effects of temperature on the development of O. punicae varies according to the stage of development. The optimum temperature for O. punicae is between 25 and 29ºC.

Phenotypic Plasticity of the Thermal Reaction Norms for Development in the Multicolored Asian Lady Beetle, Harmonia axyridis (Pallas) (Coleoptera, Coccinellidae)

Phenotypic plasticity of insect thermal reaction norms (TRNs) (the lower thermal threshold, coefficient of thermal sensitivity, and sum of degree-days) ensures precise adjustment of the seasonal cycle to local environments by changing the pattern of temperature-dependence of developmental rate. In different geographic populations the plasticity of TRNs can be manifested in different ways. We investigated the photoperiodic and diet-induced plasticity of TRNs, body mass and structural size (hind femur length) of the multicolored Asian ladybird, Harmonia axyridis, from native (Irkutsk) and invasive (Sochi) laboratory populations. Each population was tested in 16 experimental treatments that represented combinations of 4 temperatures (17, 20, 24, and 28°C), 2 photoperiods (10 and 16 h of light per day), and 2 larval diets (frozen eggs of the grain moth Sitotroga cerealella and larvae and adults of the green peach aphid Myzus persicae). The lady beetle eggs developed at a temperature of 20°C; first instar larvae were distributed among experimental treatments. We have demonstrated that under both photoperiodic regimes larval feeding on a low-quality diet (grain moth eggs) resulted in a disproportional (more strongly manifested at a low temperature) retardation of preimaginal development of individuals from both populations. The lower temperature thresholds for preimaginal development were also greater on the inferior diet. When fed on grain moth eggs, larvae from the Irkutsk population showed weaker temperature-sensitivity of development, whereas in the Sochi population the slope of the TRN did not differ between the two diets. In contrast, H. axyridis from Irkutsk showed practically no photoperiodic plasticity of TRN, whereas those from Sochi were sensitive to photoperiod on both diets. Under short-day conditions, the lower temperature threshold in the latter population was smaller and temperature-sensitivity was weaker so that at the temperatures of 17 and 20°C, development under short-day conditions was faster than that under long-day conditions, whereas at 28°C, on the contrary, it was slightly slower. In both studied populations the thermal plasticity of adult body mass and hind femur length was manifested in different ways and to varying degrees, depending on the larval photoperiodic conditions and diet. Adult body mass could decrease or increase with larval developmental temperature or show no change. Despite being maintained in the laboratory for many generations, the H. axyridis populations from Sochi and Irkutsk have retained differences in physiological responses to photoperiodic conditions and larval diet.

Effect of temperature on the development time and life‐time fecundity ofTrichopria anastrephaeparasitizingDrosophila suzukii

AbstractThe aim of this study was to evaluate the effect of temperature (10, 15, 20, 25, 30 and 35°C), on the development time and life‐time fecundity ofTrichopria anastrephaeLima, 1940 (Hymenoptera: Diapriidae) parasitizingDrosophila suzukii(Matsumura, 1931) (Diptera: Drosophilidae).D. suzukiipupae that were up to 24‐hr old were submitted toT. anastrephaeparasitism for 24 hr. They were placed in plastic containers (50 ml) (ten pupae per container) in climatic chambers at temperatures of 10, 15, 20, 25, 30 and 35°C ± 1°C with a relative humidity of 70% ± 10% and a 12 hr photoperiod. For the adult phase,T. anastrephaecouples that were up to 24 hr old were each placed in plastic cages (300 ml) and kept at the same temperatures cited above until their deaths. The higher numbers of parasitism and offspring production were obtained at temperatures between 15 and 25ºC. At the temperatures of 10 and 35ºC, there was no emergence of individuals. The lower thermal threshold (Tt) for the egg to adult period was ≈ 14.6°C for males and females with thermal constants (K) of 384.61 and 432.90, respectively. In terms of the fertility life table,T. anastrephaeat 20 and 25°C presented shorter generation time (T) and higher net reproductive rates (Ro) in relation to other temperatures. The data show the ability ofT. anastrephaeto adapt to different thermal conditions, which is important for biological control programmes ofD. suzukii.

Effect of temperature on development and reproduction of Tetranychus kanzawai (Tetranychidae) fed on apple leaves

ABSTRACTThe effect of six constant temperatures (15°C, 20°C, 25°C, 30°C, 35°C and 37.5°C) on life table parameters of Tetranychus kanzawai Kishida (Tetranychidae) fed on apple (Malus domestica Borkh.: Rosaceae) leaves was studied. Total immature developmental time of females at the mentioned temperatures was 38.02, 21.80, 10.99, 8.42, 6.65 and 7.35 days, respectively. The estimated k for the total developmental time of females and males using the linear model was 156.25 and 153.84 DD, respectively. The lower thermal threshold for total immature stages of females was calculated as 11.56°C and 11.41°C by linear and Lactin models, respectively. Using SSI model, the estimated TL, TH and TФ for total immature stages of females were 9.02°C, 37.15°C, and 22.50°C, respectively. The intrinsic rate of increase (r), increased with the raising of temperature from 0.043 day−1 at 15°C to 0.252 day−1 at 30°C, then decreased to 0.134 day−1 at 37.5°C. The presented information in this study can be used to predict the occurrence, number of generations, and population dynamics of this pest.

Effects of Temperature on Demographic Parameters of Bryobia praetiosa (Acari: Tetranychidae).

The clover mite, Bryobia praetiosa Koch (Acari: Tetranychidae), is an agricultural pest, as well as a frequent invader of hospitals and homes. However, its adaptability to different temperatures is not well understood. We used age- and stage-specific life tables to investigate the effects of temperature on demographic parameters of B. praetiosa from 15 to 35°C under a long-day photoperiod (16:8 [L:D] h). The clover mite is a thelytokous species (consisting of only females) due to its infection with the symbiotic bacterium Wolbachia. The egg-to-adult development time of female B. praetiosa decreased as the temperature increased from 15 to 32.5°C. At 35°C, females laid eggs, but no eggs hatched. The lower thermal threshold (t0) and the thermal constant (K) for egg-to-adult females were 8.7°C and 274.1 degree-days, respectively. The intrinsic optimum temperature (TØ) was 22.4°C. The oviposition period decreased with increasing temperature. Fecundity was highest at 20°C and extremely low at 30°C. The net reproductive rate (R0) decreased as the temperature increased from 15 to 30°C, but no significant difference was observed between 15 and 20°C. The intrinsic rate of natural increase (r) varied from 0.0721/d at 15°C to 0.1679/d at 25°C, and then decreased to 0.1203/d at 30°C. These results should be useful in developing management strategies for B. praetiosa.

Seasonal occurrence and development of three closely related Oligonychus species (Acari: Tetranychidae) and their associated natural enemies on fagaceous trees.

We compared the life cycles and diapause attributes among three closely related spider mites, Oligonychus castaneae on Castanea crenata, and O. gotohi and O. amiensis on Lithocarpus edulis. The lower thermal thresholds from egg to egg were 10.5, 8.5 and 8.9°C, respectively, and the thermal constants were 177.8, 229.5 and 232.5 degree-days, respectively. The cumulative hatching rates of diapause eggs of O. castaneae and O. gotohi increased as the season progressed in and after early-to-mid January, which indicates diapause termination. In contrast, O. amiensis showed higher hatching rates in December and January, but hatchability gradually decreased in and after February because some of the eggs died from the cold. Oligonychus castaneae and O. gotohi females produced diapause eggs in response to the short photoperiod in late September to early October and in early-to-late October, respectively, which corresponded to the times predicted by the critical photoperiods (at 15°C) of 12h 15min and 11h 15min for the respective species. Oligonychus castaneae showed at least a single population peak over the 3-year observation period, but the time of peak population varied from mid-July to mid-September. The population of O. gotohi was higher between November and May when diapause eggs were present on host plants in early winter and the first-generation females laid eggs on leaves in spring. The population of O. amiensis, which is a non-diapause species, was only high between September and December, because eggs were laid on leaves in autumn to winter and then gradually disappeared and/or died during winter. Natural enemies were observed as the number of spider mites declined, and the density suppression effect by natural enemies was confirmed in the field.

Review of mechanisms and recent advances in cancer photo thermal therapy

Abstract. Cancer is a major health problem all over the world. Photo thermal therapy (PTT) is a non-invasive method in cancer treatment. In PTT, the laser light usually in near-infra red region is absorbed and converted to heat in the cancerous tissue. The temperature above 40 ° C in PTT can induce some effects including irreversible damage to proteins, changes in enzyme structures, failed dual DNA repair, and lack of glucose. Low thermal threshold, low pH, and hypoxia condition of cancer cells can be exploited for PTT. But the remaining challenges facing researchers in cancer treatment are limited access, treatment resistant property, cancer metastasis and recurrence as well as normal cell damages. The purpose of this paper is to evaluate the PTT mechanisms and review the novel approaches of PTT in cancer treatment. In last decade, the PTT efficacy has been increased due to recent advances in nanotechnology. Use of nanoparticles (NPs) such as carbon-based NPs, metal NPs (e.g. gold, iron, and palladium) intensifies PTT efficacy due to surface plasmon resonance (SPR) property. Using SPR property and therefore improving the treatment efficiency, less intensive laser can be used for PTT. Therefore, concern about damage to normal cells has been considerably addressed. PTT based on NPs also can reduce the limited access in conventional PTT. Owing to enhanced permeability and retention effect of the NPs in tumors, tumors that are deeper than 3-5 cm can be treated efficiently. Using a proper active targeting of NPs for PTT, we can selectively target the cancer cells including the metastatic ones. PTT in accompany with the NPs can generate intense and sub-cellular localized heat in abnormal cells; therefore, the tumors resistance to PTT have been diminished thorough combination of PTT and chemo/radiotherapy. In conclusion, based recent advances especially in nanotechnology, PTT is a simple & non-invasive treatment that can provide a better output, and can reduce the costs, side effects, and other limitations in cancer treatment.

The Relation Between Developmental Stages of the Predator, Rodalia cardinals (Mulsant) Reared on Icerya purchasi Maskell and the Required Thermal Units

Laboratory experiments were carried out in the Insectary of Economic Entomology Department Faculty of Agriculture, Mansoura University study the relationship betweenthe developmental stages of the predator, Rodalia cardinals (Mulsant)and the required thermal units at threeconstant temperatures, (15, 25 and 30˚C) on the third nymphal instar of Icerya purchasi Maskell. The results indicated that, the duration of the predator was longer at 15˚C. As temperature increased from 15 to 30˚C the developmental aspects of R. cardinals decreased. The lower thermal threshold for thedifferent stages were 10.5, 8.5, 5.3, 5.2, 5.4, 6.9, 0.8 and 1.3˚Cfor egg stage, larval stage, pupal stage, preoviposition period, oviposition period, postoviposition period, adult female longevity and adult male longevity, respectively. The heat units required for the development of eggs was 56.2 DD unite, while for larvae, pupae, adult female and adult male were 211.3, 114.7, 969.3 and 664.4, consecutively. The results revealed that, the longevity of the predator adult stage decreased with increasing the temperature degrees. The highest consumption rate per female was at 15 ˚C comparing with the other temperature degrees. The highest number of deposited eggs per female was 25 ˚C with the value of 443.71 eggs/ female. Obtained results provide essential information for predicting the field population of the predator R. cardinals, releasing time on certain mealybug species for controlling this pest and it's recommended to be an item of integrated pest management programs in Egyptian field designed to control certain mealybug species.

Effect of temperature on diapause termination and post-diapause development in Eotetranychus smithi (Acari: Tetranychidae).

Previous studies on the spider mite Eotetranychus smithi Pritchard &Baker have shown that diapause in eggs is induced by low temperature alone and that females developed at ≤17.5°C laid diapause eggs, regardless of the photoperiod. In this study, diapause eggs were kept at 5°C and a photoperiod of 16L:8D for 0-120days and then maintained at 25°C to know the effect of chilling on diapause termination. Diapause eggs mostly hatched when they were maintained at 25°C after chilling for 30-90days at 5°C, which suggests that diapause termination is favored by low temperatures. To clarify the hatching conditions after diapause termination, diapause eggs kept at 5°C for 45days were subsequently maintained at various constant temperatures (from 15 to 25°C) under a long-day photoperiod (16L:8D). The hatchability at all temperatures tested was high (>90%) and did not significantly differ among the high temperatures. Duration of embryonic development was shorter with increasing warming temperature after chilling. The lower thermal threshold (t) and thermal constant (k) for post-diapause egg development were 10.5°C and 76.9 degree-days, respectively. Females, which developed from diapause eggs that were chilled at 5°C for 45days and then maintained at 15°C, laid only non-diapause eggs, which indicates that they were prevented from re-entering diapause even under diapause-inducing conditions (15°C). Thus, temperature is the main factor to control diapause termination and post-diapause development, which has also been found for other spider mites that enter diapause at the egg stage.

Relationship Between Developmental Stages of Predator nephus includens (kisch) (coleoptera: coccinellidae) Reared on Certain Mealy Bug Species and the Required Thermal Units.

The present work was conducted to study the relationship between the developmental stages of the predator Nephus includens (Kisch) (Coleoptera: Coccinellidae) and the required thermal units at three constant temperatures, (20, 25 and 30oC) on certain mealy bug species (Planococcus citri Risso, Icerya seychellarum (Westwood) and Maconellicoccus hirsutus (Green). The results indicated that, the duration of the predator was longer at 20oC. As temperature increased from 20-30oC the longevity decreased, the lower thermal threshold for the development of N. includens 10.9, 10.6 and 11.1oC for eggs , 6.4, 2.1 and 0.7oC for larvae, 8.4, 5.6 and 11.9oC for pupa while it were 0.1, 3.2 and 1.9oC for the total duration from (egg to adult). The heat units requirement for the development of eggs were 90.1, 92.4 and 91.5 DD's , for larvae were 387.7, 328.1 and 382.5 DD's, for the pupa 325.8, 308.1 and 390.1 DD's while it were 713.8, 674.2 and 765.3 DD's for the development period of P. citri, I. seychellarum and M. hirtsutus respectively. The lower thermal threshold for longevity (female and male) of N. includens were 12.8 & 18.4, 10.9 and 13.2& 22.8 & 48.7, meanwhile, the heat units requirement for longevity of (female and male) were 2779.8 & 2513.7, 2709.9 and 2380.7 & 2432.4 & 4206.2 on the same mealy bug species, respectively. The average of total consumption per larva was the highest at 25 + 1oC and when this predator fed on the mealy bug species P. citri during its larval stage. The results revealed that, the longevity of the predator adult stage decreased with increasing the temperature degrees. The highest consumption rate per female was at 30 + 1oC comparing with the other temperature degrees. The number of deposited eggs per female was the highest (185.74 + 1.92 eggs) when female reared on P. citri at 25 + 1oC. Obtained results provide essential information for predicting the field population of the predator N. includens, releasing time on certain mealy bug species for controlling these pests and it's recommended to be an item of Integrated Pest Management Programs in Egyptian field designed to control certain mealy bug species.

Temperature-dependent development of diapausing larvae of Chilo partellus (Swinhoe) (Lepidoptera: Crambidae)

Temperature-dependent development rate, percent diapause induction (hibernation at low temperature and aestivation at high temperature), and survival of diapausing larvae of Chilo partellus (Swinhoe, 1885) were examined on 13 constant temperatures ranging from 8 to 40°C. Development of hibernating and aestivating larvae occurred from 10 to 25°C and 27–38°C, respectively. However, no development occurred at 8°C and 40°C. To determine actual thermal conditions that affect development and trigger both kind of diapause (hibernation and aestivation), various thermal parameters were estimated by fitting the development rate data to two linear (Ordinary equation and Ikemoto & Takai) models and thirteen non-linear models. The lower thermal thresholds (Tmin) for development of diapausing larvae of C. partellus were calculated as 9.60°C and 10.29°C using the ordinary linear model and Ikemoto & Takai model, respectively. Similarly, the thermal constants (K) estimated using the ordinary linear model was 333.33 degree-days and that estimated with Ikemoto & Takai model was 338.92 degree-days. Among the non-linear models, Lactin-2 followed by Lactin-1 were found to be the best as these models estimated the critical temperatures (Tmin, Tmax and Topt) similar to those of observed values. Conclusively, the Ikemoto & Takai linear model and Lactin-2 followed by Lactin-1 non-linear models are useful and efficient for describing temperature-dependent development and estimating the temperature thresholds of diapausing larvae of C. partellus. Our findings provided fundamental information for estimation of thermal requirement and temperature based development models for diapausing larvae of C. partellus. This information will be highly useful for predicting the occurrence, seasonal emergence, number of generations and population dynamics of C. partellus.

Impact of constant versus fluctuating temperatures on the development and life history parameters of Tetranychus urticae (Acari: Tetranychidae).

The impact of daily temperature fluctuations on arthropod life history parameters is inadequately studied compared with the ample amount of research that has been conducted on the effects of constant temperatures. Fluctuating temperatures are likely to be more realistic, as they are ecologically more similar to what these arthropods experience in nature. Here, we compared the impact of 11 constant temperatures that ranged from 10 to 35°C with fluctuating temperatures with the same corresponding mean temperature and an amplitude of 10°C between high (12h) and low (12h) temperatures on the development and life history parameters of Tetranychus urticae under continuous light conditions. No eggs hatched at constant 10°C, whereas 81.5% of eggs successfully completed development at fluctuating 10°C (15/5°C). Egg-to-female adult development was faster under fluctuating temperatures from 12.5 to 27.5°C than under constant temperatures, whereas the opposite trend was observed at >30°C. The lower thermal thresholds (T) were 11.63 and 8.63°C, and thermal constants (K) were 127.81 and 150.69 degree-days for egg-to-female adults at constant and fluctuating temperatures, respectively. The numbers of oviposition days were significantly higher at fluctuating 15°C than at the corresponding constant temperature, whereas the opposite trend was observed from 20 to 30°C. The intrinsic rate of increase (r) was higher at fluctuating than at constant 15°C. The net reproductive rate (R 0) was also higher at fluctuating than at constant 15 and 35°C, but showed an opposite trend at 20 and 25°C. We conclude that fluctuating temperatures should be considered to accurately predict spider mite population dynamics in nature.

Temperature thresholds for the onset of xylogenesis in alpine shrubs on the Tibetan Plateau

The threshold minimum air temperature driving xylem growth of alpine Rhododendron aganniphum is lower than that commonly observed at the treeline of conifers. Understanding how alpine shrubs grow and which environmental factors drive their biomass gain could help to functionally differentiate trees and shrubs. The cambium is the main meristem responsible for wood formation in trees and shrubs. Thus, a better knowledge of cambium growth dynamics in alpine shrubs would allow explaining why shrubs displace trees above the treeline. Here, we aim to investigate the timings and dynamics of xylogenesis and to identify the thermal thresholds controlling the onset of xylem growth of Rhododendron aganniphum, a tall shrub growing above the alpine treeline on the Tibetan Plateau. Timings of xylogenesis and radial growth rates were assessed from anatomical observations of the developing xylem during three growing seasons (2011, 2012, and 2013). The threshold temperature at which xylogenesis had a 0.5 probability of being active was calculated with logistic regressions. The onset of xylogenesis was observed between mid and late June, whereas the end of xylogenesis lasted from mid to late September. Overall, the duration of xylem growth lasted 88–101 days, and 94 % of the ring was formed from June to August. The threshold for the onset of xylem growth was observed at 2.0 ± 0.6 °C for the minimum air temperature, lower than that commonly observed for treeline conifers (ca. 6 °C). This low thermal threshold allows alpine shrubs to have a growing season long enough to complete xylem production and maturation during the warmest summer months. Our results suggest that the time required to complete xylogenesis is critical to understand why shrubs displace trees above the treeline.