Depth of pupation of the wild olive fruit fly, Bactrocera (Dacus) oleae (Gmel.) (Dipt., Tephritidae), as affected by soil abiotic factors

Abstract:  The influence of four abiotic factors (temperature, soil type, compaction, moisture) on the pupation depth of the wild Bactrocera ( Dacus ) oleae (Gmel.) larvae was studied using soils sampled in the field. Two temperatures (25 and 12°C), three different soil types (alluvial deposits, soil from decaying of limestone, soil from decaying of flysch), two compaction levels (low and high) and two moisture levels (10 and 50% field capacity) were tested in a factorial experiment with a total of 96 experimental units. Five larvae were placed on the soil surface of each test container and when burrowing was completed pupae were retrieved and pupation depth was recorded. The majority of larvae pupated in the top 3 cm and the mean depth of all units was 1.16 cm. The means differed significantly depending on soil type, moisture, the temperature–soil type interaction and the soil type–moisture interaction. Larvae pupated at a greater depth in limestone than in the other two soils. Depths were greater in soils at 50% field capacity than in those at 10% field capacity. In limestone and flysch the depth was greater at 25°C whereas no differences were found in alluvial soil. Different moisture levels had diverse effects in the three soil types; in alluvial soil and in flysch the increased moisture resulted in greater values but in limestone these were slightly lower. These results can be used in developing non chemical control measures and designing efficient sampling techniques for the insect in the ground.     

Biology of Diaphorina citri (Hem., Psyllidae) on different hosts and at different temperatures

Abstract:  The objective of this work was to study the effect of different hosts and temperatures on Diaphorina citri Kuwayama (Hem., Psyllidae) biology. Citrus limonia (Rangpur lime), Murraya paniculata (orange jessamine) and Citrus sunki (Sunki mandarin) were used as hosts. Measurements included duration and viability of the egg and nymphal stages, sex ratio, fecundity and longevity. In order to verify the effect of temperature on D. citri biology, the duration and viability of its developmental stages and biological cycle were compared at seven different temperature conditions. Durations of the embryonic and nymphal stages were similar for Rangpur lime, orange jessamine and mandarin. However, the nymphal viability obtained on mandarin was lower than the values obtained on the other hosts. Fecundity was higher on orange jessamine and, in all instances, females had greater longevity than males. A fixed number of instars (five) was obtained on the three hosts. Rangpur lime and orange jessamine provided better D. citri development when compared with mandarin. Duration of the egg and nymphal stages varied from 2.6 to 7.7 and from 9.4 to 35.8 days, respectively, at temperatures from 18 to 32°C. Egg viability was higher than 81.6% at the temperature range studied (18–32°C); nymphal viability was higher than 70% at the 18–30°C range, differing from viability at 32°C, which was dramatically reduced. The D. citri lower temperature development threshold (TT) and thermal constant ( K ) values for the egg, nymphal and biological cycle (egg–adult) stages were 12.0°C and 52.6 Degree-Day (DD); 13.9°C and 156.9 DD; and 13.5°C and 210.9 DD respectively.     

Influence of soil moisture on egg cold hardiness in the migratory locust Locusta migratoria (Orthoptera: Acridiidae)

Abstract.  The present study investigates the influence of environmental moisture on cold hardiness of the migratory locust, Locusta migratoria . The water content of locust eggs kept in soil at 30 °C varies according to the moisture content of the substrate. In turn, it can significantly affect the supercooling point of locust eggs (range from −26 to −14.8 °C) and the mortality when exposed to subzero temperatures. Environmental moisture influences the supercooling capacity of eggs and their survival at low temperature. When locust eggs of the same water content are exposed to subzero temperatures under different soil moistures, their mortality varies between short-time exposure and long-time exposure at subzero temperatures. Given a short-time exposure, mortality in wet soil is lower than in dry soil due to the buffering effect of soil water against temperature change. The pattern of egg mortality is reversed after long-time exposure at low temperature, suggesting that inoculative freezing may be an important mortality factor. It is suggested that interactions between soil moisture and low temperature can influence the cold hardiness of locust eggs, and partial dehydration is beneficial to over-wintering eggs of the migratory locust.     

The importance of temperature and moisture to the egg-laying behaviour of a pest slug, Deroceras reticulatum

Oviposition behaviour is important when modelling the population dynamics of many invertebrates. The numbers of eggs laid are frequently used to describe fecundity, but this measure may differ significantly from realised fecundity. Oviposition has been shown to be important when describing the dynamics of slug populations, which are important agricultural pests. The numbers of eggs laid by Deroceras reticulatum and their viability were measured across a range of 16 temperature (4, 10, 15 and 23°C) by moisture (33%, 42%, 53% and 58% by dry soil weight) experimental combinations. A fitted quadratic response surface model was used to estimate how D. reticulatum adjusted its egg laying to the surrounding temperature and moisture conditions, with most eggs being laid at a combination of 53% soil moisture and 18°C. The number and proportion of viable eggs also covaried with temperature and moisture, suggesting that D. reticulatum may alter their investment in reproduction to maximise their fitness. We have shown that the number of viable eggs differs from the total number of eggs laid by D. reticulatum . Changes in egg viability with temperature and moisture may also be seen in other species and should be considered when modelling populations of egg-laying invertebrates.     

The influence of temperature on the life cycle and occurrence of three species of lake-dwelling leeches (Annelida: Hirudinea)

The influence of constant temperatures on the growth, maturation and reproduction of field-collected and F, generation Helobdella stagnalis, Glossiphonia complanata and Erpobdella octoculata was investigated. Leech material from a lowland, productive lake and from an upland, unproductive lake was cultured at each of the temperatures: l·5,5·5,8, 10·5, 13,16, 19 and 23°C. Field-collected and F₁ generation H. stagnalis and E. octoculata matured and produced eggs and young over the range 10·5–23°C, whereas the range for egg production was 8–23°C for field-collected G. complanata, F, generation leeches failing to mature at any temperature due to an additional limiting factor being involved.
Optimal temperatures for cocoon/egg production were observed for E. octoculata, but egg production was similar at all temperatures for G. complanata and H. stagnalis. In contrast, the viability of eggs was greater at certain temperatures for the last two species but was similar at all temperatures for E. octoculata. Differences in egg production between field-collected and F, generation leeches are discussed. Rising temperatures accelerated rates of egg hatching, and of growth and maturation of leeches. The observed differences in survival of leeches at the various temperatures are discussed. Ecotypic adaptation to temperature within the small geographical area of Britain may not occur. It is concluded that though temperature may be a contributory factor determining distribution and abundance in British lakes, other causative factors, such as the occurrence and abundance of food organisms, are more likely to be implicated.     

Factors Affecting Biological Control of Sclerotinia sclerotiorum by Fungal Antagonists

Studies were conducted to determine the effects of soil moisture (9, 16 or 24% w/w) and temperature (5, 15, 20 or 25°C) on the control of sclerotia of Sclerotinia sclerotiorum by five fungal agents in sterile and natural field soil. All five biocontrol agents were effective in reducing the survival of sclerotia of S. sclerotiorum in sterile soil under dry (9% moisture) or wet (24% moisture) conditions at 20°C, but only Coniothyrium minitans was effective in natural soil. Coniothyrium minitans was the most effective in reducing sclerotial viability at the temperature range of 15–25°C. Trichoderma virens was effective against sclerotia of S. sclerotiorum to a lesser extent than C. minitans , and in non-autoclaved soil, it performed best at 25°C. Although Epicoccum purpurascens , Talaromyces flavus and Trichothecium roseum were effective against sclerotia of S. sclerotiorum in some instances, they were less effective than C. minitans and T. virens . Sclerotia of S. sclerotiorum conditioned for myceliogenic germination were more vulnerable to attack by the biocontrol agents than dormant sclerotia. The implications are discussed with respect to enhancement of biological control of crop diseases caused by S. sclerotiorum in different geographic regions.     

THE EFFECTS OF TEMPERATURE AND HUMIDITY ON THE RATE OF DEVELOPMENT AND THE MORTALITY OF TRIBOLIUM CONFUSUM DUVAL (COLEOPTERA, TENEBRIONIDAE)

The speed of development and the developmental mortality of Tribolium confusum were studied over a series of constant temperatures between 15° and 40° C. at 10, 30, 70 and 90% R.H. using wheatfeed as food.
Eggs did not hatch at 15° or 40° C. at any humidity. At 37.5° C. about 60% of eggs hatched and at all other conditions about 90% hatched. The effect of temperature on the duration of the egg period is shown graphically, the shortest period being at 35° C. Humidity does not affect the egg period.
Larvae failed to develop to pupae at 17.5° C., at 10% R.H. at 20° C, and at 10 and 90% R.H. at 37.5° C. The rate of larval development was affected by both temperature and humidity being quickest at the higher humidities and at about 32.5° C. Larval mortality was less than 16% except at 37.5° C., at 10% R.H. or less, and at 20°C., 90% R.H.
The duration of the pupal period was not affected by humidity and was shortest at 37.5°C. The total developmental period is compared with that of T. castaneum over the range of temperature and humidity conditions in which both species can grow. The optimum for developmental speed and the maximum and the minimum temperatures at which development is possible were all about 2.5°C. lower for T. confusum than for T. castaneum. The developmental periods for the two species were equal at temperatures between 23 and 27°C., depending on humidity. At lower temperatures, T. confusum developed the more quickly and at higher temperatures the more slowly.     

Effect of temperature on the biology of Creontiades dilutus (Stål) (Heteroptera: Miridae)

The egg and nymphal development, fecundity and survival of the green mirid, Creontiades dilutus were examined at a range of temperatures and a modified day-degree model fitted to the data. Day degree (DD) requirements for egg and nymphal development, and threshold temperatures were calculated from the fitted lines. Female fecundity and longevity, egg and nymphal development, and survival of C. dilutus were significantly influenced by temperature. Eggs and nymphs failed to complete development at temperatures below 17 and at 38°C. Females also failed to produce any eggs at 11 and 38°C. The optimum temperature range for female fecundity was found to be 26–32°C. The optimum temperature for the development of eggs was calculated from the model as 30.5°C and for nymphs as 31.5°C. The threshold temperature for development was 15.8°C for egg and 15.1°C for nymph; 69.4 and 156.7 DD were required for completing the egg and the nymphal development, respectively. At the optimum temperature, it was estimated that development from egg to adult took 15 days. Survival was highest at 26°C for eggs and at 30–32°C for nymphs.     

Euplectrus melanocephalus Girault (Hymenoptera: Eulophidae), an ectoparasitoid of larvae of fruit-piercing moths (Lepidoptera: Noctuidae: Catocalinae) from northern Queensland

Euplectrus melanocephalus is a gregarious, primary ectoparasitoid of larvae of the fruit-piercing moth genus Eudocima Billberg (Noctuidae: Catocalinae). In northern Queensland, E. melanocephalus parasitised second- and third-instar larvae of Eud. aurantia (Moore), Eud. cocalus (Cramer) , Eud. fullonia (Clerck), Eud. iridescens (Lucas), Eud. jordani (Holland) and Eud. materna (L.). In the laboratory, E. melanocephalus also parasitised Eud. salaminia (Cramer) but failed to oviposit on larvae of two other noctuids, Erebus terminitincta (Gaede) (Catocalinae) and Spodoptera litura (F.) (Amphipyrinae). When parasitising Eud. materna , eggs of E. melanocephalus were deposited dorsolaterally on one of the first five abdominal segments of second- and third-instar larvae. Fourth instars were occasionally parasitised when the density of parasitoids was increased, but successful development to adults was markedly reduced. Pupation took place between the leaf substrate and host. Female parasitoids provided with honey survived 21 days (range = 1–42) and deposited 112 eggs (range = 11–196), while development from egg to adult occupied 12–13 days at 25°C. The minimum temperature threshold for oviposition was 17.5°C, while minimum and maximum development thresholds for larvae were 18.5°C and 30°C, respectively. Studies on the parasitoid/host interactions of E. melanocephalus indicate that it is adapted principally to the larvae of Eudocima spp.     

The relationship between egg size and embryonic and larval development in the freshwater shrimp Paratya australiensis Kemp (Decapoda: Atyidae)

1. Paratya australiensis egg and clutch sizes vary between lower and upper altitude sites within headwater streams of the Conondale Range, Queensland, Australia. The adaptive significance of this variation is examined by comparing the development of large eggs from upper sites with small eggs from lower sites at ambient temperatures in the laboratory. 2. Embryonic duration was not dependent on egg size, but was a function of temperature (28 days at 18 °C, but only 22 days at 21 °C). However, larvae developing from large eggs were significantly larger at all stages of development, larval duration was shorter and growth rate was faster than that of larvae from small eggs. 3. It is suggested that the larger, more rapidly developing larvae at upper altitude sites have a greater chance of maintaining position within headwater sections of the stream. This is important as physical barriers such as waterfalls may severely restrict upstream movement. At lower altitude sites, maintaining position may not be as critical as there are no major barriers to upstream movement following downstream displacement. The influence of temperature may also be important as larger eggs may be an adaptation to compensate for slower development of eggs and larvae at cooler, upper altitude sites. The advantage in completing larval development quickly is that larvae would have less risk of removal by spates occurring late in the breeding season.     

Shoot temperatures and thermal tolerances for succulent species of Haworthia and Lithops

Abstract. Temperatures of small succulent plants, such as species in the genera Haworthia and Lithops , are highly influenced by temperatures of the surrounding soil. Indeed, the minimum and the maximum temperatures of the upper leaf epidermis of Haworthia retusa. H. turgida. Lithops leslei , and L. turbiniformis were generally within 1°C of the accompanying soil surface temperatures. An energybudget model closely predicted such soil-to-plant temperature differences as well as the effect of the greater convective exchange for the protruding Haworthia species compared with the Lithops species, which were flush with the soil surface. Although a lower shortwave absorptance would reduce maximum shoot temperatures, the shortwave absorptances of all four species were similar to those of the soil in their respective native habitats in South Africa. Tolerances of the four species to low and to high temperatures at three different day/night air temperatures (15°C/5°C, 30°C/20°C, and 45°C/35°C) were analysed using cellular accumulation of a vital stain, neutral red. Chlorenchyma cells were slightly more tolerant of extreme temperatures than were cells of the water-storage parenchyma. In this regard, H. retusa survived low and high temperatures that killed the water-storage parenchyma but not the chlorenchyma. Acclimation to low temperatures and to high temperatures, which was exhibited by all four species, led to estimated tolerances to 1 h at −16°C and 68°C. Although the low temperature tolerance is not particularly noteworthy, very few vascular plants are reportedly able to tolerate such high temperatures.     

Influence of Environmental Factors on the Hatch and Survival of Meloidogyne incognita

The influence of soil temperature and moisture on Meloidogyne incognita (Kofoid and White) Chitwood was examined in relation to hatching and survival of second-stage juveniles (J2). Nematodes were cultured on cotton (Gossypium hirsutum L. cv. Acala SJ2) under field conditions to provide populations similar to those found in the field in late autumn. Egg masses were placed in a temperature range (9-12 C and 21 C), and hatch was measured over a period equivalent to 20 degree days > 10 C (DD10). Hatch occurred below the reported 18 C activity threshold, was restricted below 12 C, and was inhibited below 10 C. Soil moisture influence on hatch was measured by placing egg masses in Hesperia sandy loam and subjecting them to suction pressures ranging from -1.1 bars to -4 .5 bars. Suction potentials of less than -2 bars reduced hatch and less than -3 bars inhibited hatch. J2 were placed in sandy loam soil with soil moisture near field capacity, and their motility was measured over a period of 500 DD10. In the absence of a host, more than 90% of J2 became nonmotile over this period.     

Incubation temperatures, sex ratios and sex determination in a population of Nile crocodiles (Crocodylus niloticus)

A demographic study of the Nile crocodile Crocodylus niloticus at Lake Ngezi, Zimbabwe, revealed that females predominated in all size classes and among embryos. The sex of C. niloticus was shown to be determined by the temperature of egg incubation in constant temperature laboratory experiments. At 31 °C and below only females were produced. The threshold temperature for maleness was between 31 ° and 34 °C, but appeared to vary between clutches. The duration of the incubation period varied with temperature and was 110 days at 28 °C, falling to 85 days at 34 °C. Incubation temperature affected hatchling length, but not mass. Hatchlings from incubation at 34 °C were shorter on average than those from incubation at 28 °C and 31 °C, but by three months had outgrown them. There was no sex-related difference in length in a random sample of 200 two-year-old C. niloticus on a crocodile farm. Mean temperatures in wild nests were consistently lower than 31 °C and therefore the male threshold as determined in the laboratory. Embryonic development was slow and hatching success poor. The shallowest eggs in a nest had higher mean temperatures and more advanced embryos than the deepest eggs. They also experienced daily temperature fluctuations of up to 10 °C during which the maximum occasionally rose to 35 °C. Constant temperature incubation was not a good model of field conditions, but the correlation between nest temperatures and embryonic sex is consistent with temperature-dependent sex determination in the wild.     

Modeling egg development of the pest Clavipalpus ursinus (Coleoptera: Melolonthidae) using a temperature‐dependent approach

Abstract Predicting the population dynamics of insects in natural conditions is essential for their management or preservation, and temperature‐dependent development models contribute to achieving this. In this research the effects of temperature and soil moisture content on egg development and hatching of Clavipalpus ursinus (Blanchard) were evaluated. The eggs were exposed to seven temperature treatments with averages of 7.2, 13.0, 15.5, 19.7, 20.6, 22.0 and 25.3°C, in combination with three soil moisture contents of 40%, 60% and 80%. A linear and two non‐linear (Lactin and Briere) models were evaluated in order to determine the thermal requirements of this developmental stage. Temperature affected significantly the time of development and egg hatching, while no significant effect was observed for moisture content. Thermal requirements were set as: 7.2°C for lower developmental threshold, 20.6°C for optimum developmental threshold, 25.3°C for maximum temperature and 344.83 degree‐days for the thermal constant. The linear model described satisfactorily egg development at intermediate temperatures; nevertheless, a slightly better fit of the observed data was obtained with the Lactin model. Egg development took place inside a narrow range of temperatures. Consequently, an increment of soil temperature could generate a negative impact on the population size of this species or changes in its biological parameters.     

The effect of soil temperature,moisture and nitrogen on Striga asiatica (L.) Kuntze seed germination,viability and emergence on sorghum (Sorghum bicolor L. Moench) roots under field conditions

Experiments were conducted in a Striga-sick field to study the effect of soil temperature, moisture and nitrogen on Striga parasitism on sorghum. Striga seeds contained in nylon bags and buried at 2 cm in the soil, were exposed to different temperature and moisture treatments. Clear polythene, hay mulch and bare soil treatments were used to vary soil temperature. These treatments gave mean maximum temperatures of 60°, 48° and 37°C, respectively at 2-cm soil depth. Irrigation levels of 0, 30 and 60 mm were applied to change soil moisture. Striga seed germination, viability and emergence were studied. After 34 days of preconditioning, the exhumed Striga seeds from polythene-covered plots (solarized plots) did not germinate or retain viability when these seeds were exposed to sorghum root exudate. However, seeds similarly buried under hay mulch or bare soil, with mean maximum soil temperatures of 48° and 37°C, respectively, had similar germination and viability percentages. Of these 75% germinated and 85% of them were viable, regardless of the temperature treatment. Although seeds stored at high temperature and humidity (solarization) were killed, more Striga plants emerged under the polythene treatment compared to hay mulch and bare soil treatments. The observed Striga plants in the polythene mulch treatment were, therefore, assumed to have come from deeper layers where solarization was not effective. Irrigation treatments did not have significant effects on Striga seed germination and viability, but a slightly higher number of plants emerged at 60-mm irrigation level than at 30-mm and 0-mm. Striga emergence, on the other hand, was directly related to the rate of N application. Nitrogen rates of 0, 25, 50 and 100 kg ha^–1 resulted in the emergence of 11, 34, 38 and 40 Striga plants per plot, respectively. Despite the high infestation at high N levels, sorghum plants did not show a loss of vigor. Nitrogen application, therefore, does not reduce Striga incidence, but seems to neutralize the harmful effects of Striga without reducing the extent of parasitism.     

Body-temperatures and torpor in Sminthopsis crassicaudata and S. larapinta (Marsupialia–Dasyuridae)

Body-temperatures in two species of insectivorous marsupial mice (family Dasyuridae) were measured using a rectal thermistor. In Sminthopsis crassicaudata at 21°C, body-temperatures ranged from–5–31 - 1° C (432 measurements on 12 mice). A diurnal temperature cycle with a mean amplitude of 0.79°C was revealed, with temperatures at a maximum at 02.00 hours and a minimum at 10.00 hours. Mean body-temperatures of sibs showed significant differences; in one litter a difference of 2.7°C was demonstrated. In S. larapinta , the diurnal temperature cycle was greater with a mean amplitude of 4.24°C. Body-temperatures ranged from 38.8–22.9°C.
Changes in surface-temperature (Ts) in unrestrained animals during entry into and arousal from torpor, were measured using thermocouples fitted inside the nest-box and a recording potentiometer. S. larapinta had a daily torpor with or without food at room temperature, while in S. crassicaudata torpor could only be induced by lack of food. The lowest T_s reached were 18° and 17°C respectively. It is suggested that the torpor-mechanism may have evolved in these species to meet temporary or seasonal shortages of food.     

Variability In the rate of egg development of the stonefly, Nemoura cinerea (Plecoptera)

SUMMARY. 1. The egg development of the widely distributed European stonefly. Nemoura cinerea Retzius. was investigated in the laboratory. There was a significant relationship between water temperature (T°C) and incubation period (Ydays), expressed by the regression equation: Y = 239 T^−0.85 (r²= 0.85. P<0.001).
2. The number of day-degrees above 0°C required for hatching showed a curvilinear relationship with water temperature, with a minimum requirement around 12°C.
3. Nemoura cinerea shows more variation in the rate of egg development than most other stoneflies. This, in part, explains the wide size range in nymphal populations and the species' extended emergence period. Flexibility in life cycle and asynchrony in egg development enable this species to colonize a wide range of freshwater habitats.     

基于植被和环境因子的亚高山森林土壤水源涵养功能空间尺度上推模型构建——以岷江上游杂谷脑流域为例

土壤层水源涵养功能是森林水源涵养功能的主体。目前关于森林土壤水源涵养功能的研究主要集中在林地或坡面尺度上。由于流域尺度,尤其是环境空间异质性强的西南亚高山区流域,如何将林地尺度实测结果上推至流域或更大空间尺度仍是生态水文领域面临的巨大挑战之一。以川西岷江上游杂谷脑流域为研究对象,融合多种森林类型样地实测与流域尺度多源遥感数据,构建了基于植被和环境因子的林地-流域森林土壤水源涵养功能尺度转换模型,实现了流域尺度土壤水源涵养功能快速评价及其空间分布预测。样地尺度研究结果表明各类型森林的土壤水文特性各异,总体表现为天然林优于人工林,混交林优于单纯林。林地土壤持水能力受到区域气候、植被、土壤及地形等因子的共同影响,其中风速、NDVI及林龄与土壤最大持水量、毛管持水量及非毛管持水量均呈极显著正相关（P<0.01）。基于关键植被和环境因子构建的林地-流域土壤水源涵养功能尺度上推模型精度较高,土壤最大持水量、土壤毛管持水量和土壤非毛管持水量模型拟合优度R²分别为0.700、0.720和0.908;土壤最大持水量、土壤毛管持水量和土壤非毛管持水量的模型预测值与野外实测值的相关系数介于0.69-0.79之间,平均误差均低于20%,表明模型预测结果可靠。利用构建的土壤水源涵养功能尺度上推模型,估算得出流域尺度森林土壤持水量的空间分布,其结果表明杂谷脑流域森林土壤持水量空间分异明显,海拔较高区域森林土壤持水量最高,其次为距道路和河流有一定距离的缓坡地带,下游干旱河谷地区土壤持水量最低。本研究为亚高山森林生态功能的恢复和提升提供了科学依据和评价工具。     

Cotton (Gossypium barbadense) production as affected by climatic factors and soil moisture status

This study investigates the statistical relationship between climatic variables and aspects of cotton production (Gossypium barbadense), and the effects of climatic factors prevailing prior to flowering or subsequent to boll setting on flower and boll production and retention in cotton. Also, the study covers the predicted effects of climatic factors during convenient intervals (in days) on cotton flower and boll production compared with daily observations. Further, cotton flower and boll production as affected by climatic factors and soil moisture status has been considered. Evaporation, sunshine duration, relative humidity, surface soil temperature at 1800 h, and maximum air temperature, are the important climatic factors that significantly affect flower and boll production. The least important variables were found to be surface soil temperature at 0600 h and minimum temperature. The 5-day interval was found to be more adequately and sensibly related to yield parameters. Evaporation; minimum humidity and sunshine duration were the most effective climatic factors during preceding and succeeding periods on boll production and retention. There was a negative correlation between flower and boll production and either evaporation or sunshine duration, while that correlation with minimum relative humidity was positive. The soil moisture status showed low and insignificant correlation with flower and boll production. Higher minimum relative humidity, short period of sunshine duration, and low temperatures enhanced flower and boll formation.     

THE EFFECT OF TEMPERATURE AND HUMIDITY ON THE RATE OF DEVELOPMENT AND MORTALITY OF TRIBOLIUM CASTANEUM (HERBST) (COLEOPTERA, TENEBRIONIDAE)

The speed of development and the developmental mortality of Tribolium castaneum were studied over a series of temperatures between 15 and 40°C. at 10, 30, 70 and 90% R.H. using wheatfeed as food.
Eggs did not hatch at any humidity at 17·5°C. or less, nor at 10% R.H. at 40°C. At all other conditions about 80% of eggs hatched. Humidity does not affect the duration of the egg period. The effect of temperature on the egg period is shown graphically, the shortest period occurring at 37·5°C.
Larvae fail to develop into normal adults at 20°C. and also fail at 90 and 30% R.H. at 40°C. At 20°C. and 70% R.H. pupae may be formed but they do not become normal adults. The rate of larval development is affected by both temperature and humidity. Development is quickest at the highest humidity used at any temperature and at 35°C. for each humidity. Larval mortality is less than 20% except at 40°C. and at combinations of low humidity and low temperature. The results correspond with published results using similar foodstuffs.
Groundnuts were used as a food in a series of experiments at 30°C. and another series at 70% R.H. Larvae on this food were much more susceptible to the effects of humidity and were unable to develop at 20 or 40°C. at 70% R.H. In all conditions development was slower and mortality higher than on wheatfeed.
The pupal period is not affected by humidity and is shortest at 37·5°C.
The conditions in which Park found that cultures of T. castaneum became extinct, 24°C. and 30% R.H., lie inside the zone in which development is possible. The possible causes for this discrepancy are discussed.