Differences in cold tolerance,desiccation resistance,and cryoprotectant production between three populations of <Emphasis Type="Italic">Eurosta solidaginis</Emphasis> collected from different latitudes

Possible links between cold-tolerance and desiccation resistance were examined between larvae of the goldenrod gall fly collected from Michigan, southern Ohio, and Alabama locations as their host plant senesced. After acclimation to 5°C, Michigan-collected larvae were more cold-tolerant (25% survival after a 96 h exposure to −40°C) than larvae from Ohio (10% survival) and Alabama (0% survival). Increased cold-tolerance was partially linked to higher concentrations of the cryoprotectant glycerol (Michigan: 500 ± 30 mmol; Ohio: 270 ± 20; Alabama: 220 ± 20). Moreover, cryoprotectants may have functioned to reduce rates of overall and cuticular water loss for Michigan larvae, 0.10 ± 0.01 and 0.037 ± 0.003 μg mm⁻² h⁻¹, respectively, values that were 40-44% lower than those for Ohio and Alabama larvae and may represent a link between desiccation resistance and cold-tolerance. After acclimation to 20°C, Alabama-collected larvae had metabolic rates that were 40% lower than those from Ohio and Michigan that averaged 0.100 ± 0.006 μl of CO₂ produced g⁻¹ h⁻¹. The lower metabolic rate of Alabama-collected larvae at 20°C likely resulted in reduced respiratory transpiration that may represent a mechanism to maintain water balance at the higher overwintering temperatures they typically experience.     

Progeny production and adult longevity of the mealybug parasitoidsAnagyrus pseudococci,Leptomastix dactylopii,andLeptomastidea abnormis [Hym.: Encyrtidae] in relation to temperature

Progeny production increased and adult longevity decreased with rising temperature within the range 18°C to 30°C for the 3 mealybug parasitoidsAnagyrus pseudococci (Girault),Leptomastix dactylopii Howard andLeptomastidea abnormis (Girault). The Weibull distribution gave a good fit to survival curves for the 3 parasitoids and statistical comparison of Weibullb andc parameters at different temperatures allowed changes in the scale and shape of the curves to be detected. In general, ♀♀ lived longer than ♂♂ for all 3 species, except at high temperature. FemaleL. abnormis attained their maximum progeny production at 24°C and maintained this level up to 34°C. They lived longer than the other 2 parasitoid species at 30°C and showed a type I survival curve throuhout the range of temperatures examined.A. pseudococci andL. dactylopii both required high temperatures (30°C) to attain their maximal progeny production, but werepseudococci tended towards type II, with a larger proportion of the population dying within the first few days.L. dactylopii lived longest at 26°C, with ♀♀ showing a type I survival curve at all temperatures and ♂ survival curves changing from type I to type II at 30°C. The implications of these findings for the population dynamics of the different parasitoids are briefly discussed.      

Effect of temperature on the development, fecundity, progeny sex ratio and life-table of Campoletis chlorideae, an endolarval parasitoid of the pod borer, Helicoverpa armigera

Development, survival, fecundity, progeny sex ratio (PSR) and age-specific life-table parameters of the parasitoid Campoletis chlorideae Uchida (Hymenoptera: Ichneumonidae) were examined at six different constant temperatures (12, 17, 22, 27, 32 and 37°C) in the laboratory [70 ± 10% RH and 10:14 h (light:dark) photoperiod]. Second instar larvae of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) were reared on chickpea (Cicer arietinum L.) and used as the host. Development times shortened as the temperature increased from 12 to 37°C. The estimated lower developmental threshold (tL) was 3.4°C. The thermal summation for total immature stages was 379.97 degree-days. A reciprocal relationship between temperature and longevity was observed in the range of 12–17°C. The maximum mortality of pupae (71.8%) occurred at 37°C. At 22°C, the yield of a female parasitoid averaged 137.3 ± 14.7 (mean ± SD) progeny, of which 89.6 ± 7.6 were daughters. The number of daughters produced decreased when the females were kept either above or below 22°C, although the PSR was female biased in the range of 17–27°C. The analyses of life-table parameters, developmental rates, reproduction, mortality and PSR suggest that maximum population growth (r _m ) is near 27°C. There was little variation observed in most of the desired qualities of C. chlorideae in the range of 17–27°C, and it appears that the parasitoid is adapted to a wide range of temperatures. We suggest that for maximum production the parasitoid should be reared at 22 ± 4°C and be released in areas where the temperature ranges between 17° and 27°C, as in the plains of northern India.     

Wind tunnel assays of olfactory responses of femaleRhagoletis pomonella flies to apple volatiles: effect of wind speed and odour release rate

Little is known about how adults of the corn leafhopper,Dalbulus maidis (DeLong & Wolcott), and its congeners survive subfreezing temperatures at high elevations during the dry winter in Mexico. In the laboratory, duration of survival at −5°C was measured for four MexicanDalbulus species:D. maidis, D. elimatus (Ball),D. gelbus DeLong andD. quinquenotatus DeLong & Nault; and a closely related North American species,Baldulus tripsaci Kramer & Whitcomb. Adult leafhoppers reared under environmental conditions that simulated the beginning of the dry winter season during October in Mexico (‘October-reared’) were at least twice as tolerant of −5°C than adults reared under environmental conditions that simulated the beginning of the wet summer season during June (‘June-reared’).Dalbulus species found primarily at high elevations, such asD. elimatus, were seven times more tolerant of −5°C thanD. quinquenotatus, a species which overwinters at low to mid elevations on itsTripsacum hosts. October-rearedD. maidis adults survived relatively short periods at −5°C (LT₅₀=8.9h) compared to October-rearedD. elimatus adults (LT₅₀=42.3h). This suggests that in Mexico,D. maidis either overwinters in protected habitats at higher elevations or it migrates to lower, frost-free regions. October-rearedB. tripsaci adults, which overwinter in the egg stage, were intolerant of −5°C (LT₅₀=2.6h). A conditioning period for 1 h at +5°C before and after exposure to −5°C significantly improved survival forD. maidis. Supercooling points (SCPs) were between −23 and −20°C, indicating that mortality of these leafhoppers at −5°C was due to cold shock injury rather than internal ice formation.     

The effect of temperature on growth characteristics and competitions of <Emphasis Type="Italic">Microcystis aeruginosa</Emphasis> and <Emphasis Type="Italic">Oscillatoria mougeotii</Emphasis> in a shallow,eutrophic lake simulator system

Blue-green algal blooms formed by Microcystis and Oscillatoria often occur in shallow eutrophic lakes, such as Lake Taihu (China) and Lake Kasumigaura (Japan). Growth characteristics and competitions between Microcystis aeruginosa and Oscillatoria mougeotii were investigated using lake simulator systems (microcosms) at various temperatures. Oscillatoria was the superior competitor, which suppressed Microcystis, when temperature was <20°C, whereas the opposite phenomenon occurred at 30°C. Oscillatoria had a long exponential phase (20 day) and a low growth rate of 0.22 day⁻¹ and 0.20 day⁻¹ at 15°C and 20°C, respectively, whereas Microcystis had a shorter exponential phase (2–3 days) at 30°C and a higher growth rate (0.86 day⁻¹). Interactions between the algae were stronger and more complex in the lake simulator system than flask systems. Algal growth in the lake simulator system was susceptible to light attenuation and pH change, and algae biomasses were lower than those in flasks. The outcome of competition between Microcystis and Oscillatoria at different temperatures agrees with field observations of algal communities in Lake Taihu, indicating that temperature is a significant factor affecting competition between Microcystis and Oscillatoria in shallow, eutrophic lakes.     

Thermal biology and establishment potential in temperate climates of the aphid parasitoid, <Emphasis Type="Italic">Lysiphlebus testaceipes</Emphasis>

Lysiphlebus testaceipes (Cresson) (Hymenoptera: Braconidae, Aphidiinae) is a parasitic wasp which plays an important role in the biological control of a number of aphid species. Through assessment of its thermal biology and low temperature tolerance, this study ascertains the establishment potential of L. testaceipes in cool temperate climates typical of northern Europe. The developmental threshold of L. testaceipes was 5.8°C. Rearing of parasitoids at shorter day lengths and lower temperatures indicated no ability to enter a diapause state. The supercooling points (SCP) of non-acclimated and acclimated parasitoid life stages were between −24.6°C and −17.7°C, with LTemp₅₀ temperatures approaching these values, indicating a high level of cold tolerance in short exposures. At 5°C the LTime₅₀ of acclimated larvae within parasitized aphids was 42.8 days. Acclimated pupae continued to develop with 54% adult emergence from mummies within 60 days. Acclimated parasitoid larvae and pupae, within living and mummified aphids, continued to develop during 70 days of winter field exposure and emerging adult parasitoids were reproductively viable under field conditions. These data indicate that where suitable host species are available throughout the year, L. testaceipes would be able to establish in northern Europe.     

Comparison of Searching Behaviour of Two Aphelinid Parasitoids of the Greenhouse Whitefly, Trialeurodes vaporariorum under Summer vs. Winter Conditions in a Temperate Climate

Searching behaviour of two aphelinid parasitoids, Encarsia formosa Gahan and Eretmocerus eremicus Rose and Zolnerowich, was compared in a controlled environment under simulated summer [high light intensity (83 ± 1 W/m²), and 24 ± 1°C] and winter [low light intensity (11 ± 0.5 W/m²), and 20 ± 1°C] greenhouse conditions on tomato leaflets, with and without a single 3rd instar whitefly host, Trialeurodes vaporariorum (Westwood), within a 4-cm tomato leaflet arena. Residence time of both parasitoid species was longer on infested leaflets vs. clean leaflets, and longer under winter than summer conditions. When parasitoids encountered a host on infested leaflets, residence time increased. In all cases, residence time of E. formosa was longer that of E. eremicus. Proportion of time spent searching (i.e. antennating leaf surface while walking or standing still) was longer on clean vs. infested leaflets for both E. formosa and E. eremicus. Walking speed by E. eremicus on clean leaflets was faster than E. formosa under both summer and winter conditions. Host handling time and proportion of host acceptance did not vary among parasitoids. These findings suggest that E. eremicus could be more efficient in host finding on tomato leaflets than E. formosa over all seasons, especially in the winter when natural light is limiting and where daylight temperatures are ≥20°C.     

European field collections and Canadian releases ofCeranthia samarensis (Dipt.: Tachinidae), a parasitoid of the gypsy moth

A programme to collect, import and release into Canada the gypsy moth parasitoid,Ceranthia samarensis (Diptera: Tachinidae) is described. The parasitoid's potential for biological control in Canada is also discussed. The parasitoid was collected in Europe by exposing experimental gypsy moth larvae in areas where local gypsy moth populations were at low densities. Following field exposure, the host larvae were returned to the laboratory and parasitoids reared from them. This technique has shown thatC. samarensis is the suffers 7–16% hyperparasitism. From 83–90% of theC. samarensis typically enter diapause as pharate adults within the puparia. Laboratory tests of post-exposure host rearing conditions indicate that constant temperatures disrupt the normal parasitoid diapause and that this effect can not be offset by use of either static long or short photoperiods or natural daylengths. Shipping and cold-storage procedures for puparia are described. Post-storage time to emergence of adultC. samarensis decreased with longer cold storage periods and with higher post-storage incubation temperatures. Emergence requires 112 degree-days above a threshold of 8°C after a period of at least 8 months cold storage. Releases of adultC. samarensis into field cages at four locations in southern Ontario are documented. While dissection of host larvae from the field cages has failed so far to demonstrate evidence of parasitism, we remain hopeful that some establishment of the parasitoid has occurred.      

Physiological differences in the growth of <Emphasis Type="Italic">Sargassum horneri</Emphasis> between the germling and adult stages

The effects of temperature, irradiance, and daylength on Sargassum horneri growth were examined at the germling and adult stages to discern their physiological differences. Temperature–irradiance (10, 15, 20, 25, 30°C × 20, 40, 80 μmol photons m⁻²s⁻¹) and daylength (8, 12, 16, 24 h) experiments were carried out. The germlings and blades of S. horneri grew over a wide range of temperatures (10–25°C), irradiances (20–80 μmol photons m⁻²s⁻¹), and daylengths (8–24 h). At the optimal growth conditions, the relative growth rates (RGR) of the germlings were 21% day⁻¹ (25°C, 20 μmol photons m⁻²s⁻¹) and 13% day⁻¹ (8 h daylength). In contrast, the RGRs of the blade weights were 4% day⁻¹ (15°C, 20 μmol photons m⁻²s⁻¹) and 5% day⁻¹ (12 h daylength). Negative growth rates were found at 20 μmol photons m⁻²s⁻¹ of 20°C and 25°C treatments after 12 days. This phenomenon coincides with the necrosis of S. horneri blades in field populations. In conclusion, we found physiological differences between S. horneri germlings and adults with respect to daylength and temperature optima. The growth of S. horneri germlings could be enhanced at 25°C, 20 μmol photons m⁻²s⁻¹, and 8 h daylength for construction of Sargassum beds and restoration of barren areas.     

Freezing and desiccation injury resistance in the filamentous green alga Klebsormidium from the Antarctic, Arctic and Slovakia

The freezing and desiccation tolerance of 12 Klebsormidium strains, isolated from various habitats (aeroterrestrial, terrestrial, and hydro-terrestrial) from distinct geographical regions (Antarctic — South Shetlands, King George Island, Arctic — Ellesmere Island, Svalbard, Central Europe — Slovakia) were studied. Each strain was exposed to several freezing (−4°C, −40°C, −196°C) and desiccation (+4°C and + 20°C) regimes, simulating both natural and semi-natural freeze-thaw and desiccation cycles. The level of resistance (or the survival capacity) was evaluated by chlorophyll a content, viability, and chlorophyll fluorescence evaluations. No statistical differences (Kruskal-Wallis tests) between strains originating from different regions were observed. All strains tested were highly resistant to both freezing and desiccation injuries. Freezing down to −196°C was the most harmful regime for all studied strains. Freezing at −4°C did not influence the survival of studied strains. Further, freezing down to −40°C (at a speed of 4°C/min) was not fatal for most of the strains. RDA analysis showed that certain Antarctic and Arctic strains did not survive desiccation at +4°C; however, freezing at −40°C, as well as desiccation at +20°C was not fatal to them. On the other hand, other strains from the Antarctic, the Arctic, and Central Europe (Slovakia) survived desiccation at temperatures of +4°C, and freezing down to −40°C. It appears that species of Klebsormidium which occupy an environment where both seasonal and diurnal variations of water availability prevail, are well adapted to freezing and desiccation injuries. Freezing and desiccation tolerance is not species-specific nor is the resilience only found in polar strains as it is also a feature of temperate strains. Presented at the International Symposium Biology and Taxonomy of Green Algae V, Smolenice, June 26–29, 2007, Slovakia. This paper is dedicated to the memory of the late Dr. Bohuslav Fott (1908–1976), Professor of Botany at the Charles University in Prague, to mark the centenary of his birth.     

Salinity and Temperature Effects on Germination for Three Salt-resistant Euhalophytes, Halostachys caspica, Kalidium foliatum and Halocnemum strobilaceum

The effects of three salinities (0, 100 and 500 mM NaCl) and four constant temperatures (10, 20, 30 and 35 °C) on seed germination of Halostachys caspica (M. B.) C. A. Mey., Kalidium foliatum (Pall.) Mop. and Halocnemum strobilaceum (Pall.) Bieb. were investigated. After seeds were treated with different concentrations of NaCl at constant temperatures of 10–35 °C for 16 days, ungerminated seeds were transferred to distilled water for 10 days to investigate the total germination; after this time, the ungerminated seeds from the 10 and 20 °C treatments were then moved to 35 °C for another 5 days to determine the final germination. The three plant species in the present experiment are salt-resistant euhalophytes growing in high saline soils in the Zhungur Basin in Xinjiang, a northwest province of China.Compared with germination under control conditions, germination percentages of all three species were not affected by 100 mM NaCl at 10–35 °C, while severely inhibited by 500 mM NaCl; germination percentages were very low at 10 °C up to 100 mM NaCl for all species; the optimum temperature for germination of H. caspica and K. foliatum was 20–30 °C, while 35 °C for H. strobilaceum, up to 100 mM NaCl; seeds did not suffer ion toxicity for all species, as evidenced by the high total germination after ungerminated seeds pretreated with 500 mM NaCl were transferred to distilled water at constant temperatures of 10–35 °C for 10 days, and the high final germination after the ungerminated seeds from the 10 and 20 °C treatments were subsequently moved to 35 °C for another 5 days; Halostachys caspica had greater sensitivity to increasing temperatures from 10 and 20 °C to 35 °C compared with the other two species.     

Temperature influences the performance and effectiveness of field and laboratory strains of the ichneumonid parasitoid, <Emphasis Type="Italic">Campoletis chlorideae</Emphasis>

To understand the influence of temperature on host–parasitoid interactions as a consequence of climatic change, we studied development, survival, and fecundity of field and laboratory strains of the Helicoverpa armigera larval endoparasitoid, Campoletis chlorideae at five different temperatures under laboratory conditions. Post-embryonic development period and degree-days required for completing the life cycle by both the strains decreased by 2.5 and 1.5 folds at 27°C compared to 18°C. Post embryonic development period showed a negative (r = −0.99, P < 0.001) and the development rate a positive (r = 0.99, P < 0.001) association with an increase in temperature. However, no parasitoid larvae survived in H. armigera larvae reared at 12 and 35°C after parasitization, suggesting that temperatures ≥35°C as a result of global warming will be lethal for development and survival of immature stages of C. chlorideae. Adult longevity was negatively associated (r = −0.91 to −0.96, P < 0.001) with temperatures between 12 and 35°C. The parasitoid adults stored at 12°C survived for longer period and exhibited higher fecundity than those kept at 27°C, but the efficiency of parasitism and adult emergence were quite low. Sex ratio of the progeny at 12°C was highly male-biased than the insects kept at 27°C. Laboratory strain of the parasitoid exhibited better survival, and the adults lived longer than the field strain at 18°C than at 27°C. Therefore, C. chlorideae adults stored at 18°C could be used for parasitism, while the immature stages should be reared at 27°C for mass production of the parasitoid for biological control of H. armigera.     

Effects of temperature and photoperiod on the development and oviposition ofApanteles sp. groupUltor [Hym.: Braconidae], a larval parasite of the carob mothEctomyelois ceratoniae [Lep.: Pyralidae]

Development of the solitary parasitoidApanteles sp. groupultor in larvae ofEctomyelois ceratoniae was investigated at different constant temperatures. Temperature had a significant effect upon parasitoid development during both host-internal and host-external phases. The duration of the host-internal phase varied from 41 days at 15–17°C to 8.6 days at 29°C, the duration of the host-external phase varied from 16.5 days at 16–17°C to 5.4 days at 29°C. Effect of photoperiod upon parasite development and parasitization of hosts were determined under daily photophases, of 24, 16, 12, 8 and 0 hours. No significant differences in oviposition rate were found among the 5 treatments. In any photoperiod studied, the parasite progeny developed normally without entering diapause.      

Effects of temperature and light on the growth and geosmin production of Lyngbya kuetzingii (Cyanophyta)

The effects of temperature and light on the growth and geosmin production of Lyngbya kuetzingii were determined. Of the three temperatures tested, 10, 25 and 35°C, the maximal geosmin concentration and geosmin productivity were yielded at 10°C, while the highest chl a production was observed at 25°C. In the studies on light intensity, the maximal geosmin concentration and geosmin productivity were observed at 10 μmol m⁻² s⁻¹, while the highest chl a production was at 20 μmol m⁻² s⁻¹. It was suggested that more geosmin was synthesized with lower chl a demand. Meanwhile, the relative amounts of extra- and intracellular geosmin were investigated. Under optimum growth conditions (20 μmol m⁻² s⁻¹, 25°C; BG-11 medium), the amounts of extracellular geosmin increased as the growth progressed and reached the maximum in the stationary phase, while the intracellular geosmin reached its maximum value in the late exponential phase, and then began to decline. However, under the low temperature (10°C) or light (10 μmol m⁻² s⁻¹) conditions, more intracellular geosmin was synthesized and mainly accumulated in the cells. The proportions of extracellular geosmin were high, to 33.33 and 32.27%, respectively, during the stationary phase at 35°C and 20 μmol m⁻² s⁻¹. It was indicated that low temperature or light could stimulate geosmin production and favor the accumulation of geosmin in cells, while more intracellular geosmin may be released into the medium at higher temperatures or optimum light intensity.     

Microbial population dynamics and temperature changes during fermentation of kimjang kimchi

A distinct subset of lactic acid bacteria that are greatly influenced by temperature play an important role during kimchi fermentation. However, microbial population dynamics and temperature control during kimjang kimchi fermentation, which is traditionally fermented underground, are not known. Here we show that Lactobacillus sakei predominates in kimjang kimchi, perhaps due to suitable fermentation (5∼9°C) and storage (−2°C) temperatures. The temperature of this kimchi gradually decreased to 3.2°C during the first 20 days of fermentation (−0.3°C/day) and then was stably maintained around 1.6°C, indicating that this simple approach is very efficient both for fermentation and storage. These findings provide important information towards the development of temperature controlling systems for kimchi fermentation.     

Temperature management strategy for efficient gene expression in a thermally inducible <Emphasis Type="Italic">Escherichia coli</Emphasis>/bacteriophage system

In a two-phase operation, E. coli containing λSNNU1 (Q ⁻ S ⁻) in the chromosome is typically cultured at 33°C and cloned gene expression is induced by elevating the temperature. At least 40°C is necessary for complete induction of cloned gene expression; however, temperatures above 40°C have been shown to inhibit cloned gene expression. This suggests that a three-phase operation, which has an induction phase between the growth and production phases, may result in higher gene expression. In this study, optimal temperature management strategies were investigated for the three-phase operation of cloned gene expression in thermally inducible E. coli/bacteriophage systems. The optimal temperature for the induction phase was determined to be 40°C. When the temperature of the production stage was 33°C, the optimal time period for the induction phase at 40°C was determined to be 60 min. In contrast, when the temperature of the production phase was 37°C, the optimal period for the induction phase at 40°C was 20∼30 min. When the three-phase temperature and temporal profile were set at a growth phase of 33°C, an induction phase at 40°C for 30 min, and a production phase at 37°C, the highest level of cloned gene expression was achieved.     

Temperatures lethal for citrus blackfly parasites,Encarsia opulenta andE. Smithi [Hym.: Aphelinidae]

Seasonally acclimatized adult and immature parasites of the citrus blackfly (CBF),Aleurocanthus woglumi Ashby, were exposed to high or low temperature extremes for 3 h periods. Death of all summer adults ofEncarsia opulenta Silvestri andE. smithi Silvestri occurred between 35° and 40°C. Within CBF hosts,E. opulenta were not able to emerge when temperatures reached between 45° and 50°C. In winter experiments adults of bothEncarsia species succumbed between −5° and −10°C. In a comparison of the 2 seasonal tests, a higher percentage ofE. smithi adults were able to survive both higher and lower temperatures thanE. opulenta, but the main interspecific difference was the ability ofE. opulenta within CBF to survive −10° to − 15°C whileE. smithi did not. Limited data forAmitus hesperidum Silvestri [Hym.: Platygasteridae] indicated that the immatures survived better at low, and not as well at high, temperatures as either species ofEncarsia. Florida Agricultural Experiment Station Journal Series # 5549.     

Oxygen consumption by ammocoetes of the lampreyGeotria australis in air

 When covered by moistened lint-free gauze, the larvae (ammocoetes) of the lamprey Geotria australis survived, without apparent discomfort, for 4 days in water-saturated air at 10, 15 and 20 °C. In air, the mean standard rates of O₂ consumption of medium to large ammocoetes of G. australis (xˉ=0.52 g) at 10, 15 and 20 °C were 14.5, 35.7 and 52.1 μl⋅g^-1⋅h^-1, respectively. At 15 °C, the slope of the relationship between log O₂ consumption (μl O₂⋅h^-1) and log body weight for ammocoetes over a wide range in body weight was 0.987. The Q ₁₀s for rate of O₂ consumption between 10 and 15 °C, 15 and 20 °C and 10 and 20 °C were 4.9, 2.9 and 3.6, respectively. Our results and observations of the ammocoetes suggest that, when out of water, larval G. australis derives most of its O₂ requirements from cutaneous respiration, particularly at lower temperatures. This would be facilitated by the small size and elongate shape (and thus a relatively high surface-to-volume ratio), low metabolic rate, thin dermis, extensive subdermal capillary network and high haemoglobin concentration of larval G. australis. Accepted: 28 March 1996     

Effect of temperature on the life history of <Emphasis Type="Italic">Eretmocerus</Emphasis> sp. nr. <Emphasis Type="Italic">furuhashii</Emphasis>, a parasitoid of <Emphasis Type="Italic">Bemisia tabaci</Emphasis>

Eretmocerus sp. nr. furuhashii (Hymenoptera: Aphelinidae) is an indigenous parasitoid of Bemisia tabaci (Gennadius)(Hemiptera: Aleyrodidae) from southern China; the effects of constant temperatures on the life history of E. sp. nr. furuhashii were examined in the laboratory. The developmental period ranged from 39.2 days at 20°C to 12.40 days at 32°C. A total of 263.4 degree-days were required to complete development with a lower developmental threshold temperature of 11.1°C. Of the eggs produced, 59.3% completed development at 20°C with completion increasing to 71.5% at 26°C. Adult female longevity was 10.8 days at 20°C and 5.2 days at 32°C while the mean daily offspring reproduced per female was highest at 29°C with 5.9 offspring. Adult oviposition peaked three days after emergence at 26, 29 and 32°C, and four days post-emergence at 20°C and 23°C. The total numbers of offspring produced per female ranged from 25.7 individuals at 32°C to 41.1 individuals at 20°C. The sex ratio had a female bias and ranged from 0.72 at 17°C to 0.51 at 35°C. The intrinsic rate of increase was 0.1727 at 29°C followed with 0.1606 at 32°C. Results indicated that E. sp. nr. furuhashii reaches its maximum biological potential at temperatures ranging from 26°C to 32°C.     

Uscana lariophaga, egg parasitoid of bruchid beetle storage pests of cowpea in West Africa: the effect of temperature and humidity

The stored-product bruchid pests,Callosobruchus maculatus (Fabricius) andBruchidius atrolineatus (Pic) cause considerable production losses in cowpea in West Africa.Uscana lariophage Steffan parasitizes the eggs of the bruchids both in the field and in storage. As chemical control of bruchids in traditional granaries is not appropriate for poor farmers, enhancement of the efficacy of the parasitoid by environmental manipulation has been investigated. The effect of temperature on the capacity ofU. lariophaga to parasitize eggs has been studied at eleven constant and three fluctuating temperatures within the range 10 to 45°C. Longevity of the female wasp decreased with increasing temperature. The rate of development increased linearly at temperatures from 17.5 to 35°C, but decreased from 35 to 40°C. Mortality of the developing wasp remained below 20% from 20 to 37.5°C, but outside this range, mortality reached 100% at 15 at 42.5°C. Most parasitization occurred at temperatures of 25 and 30°C. Sex ratio (percentage females) increased with temperature in the high temperature range. The intrinsic rate of increase (r_m) forU. lariophaga was highest in the temperature range from 30 to 37.5°C and was higher than that ofC. maculatus at all temperatures. While the r_m value ofC. maculatus did not vary much at temperatures from 25 to 35°C, the r_m value of the wasp doubled. Relative humidity did not effect longevity, egg-laying capacity, mortality, development time and sex ratio of the wasps withC. maculatus as host. However, withB. atrolineatus as the host, development time and mortality increased at lower relative humidity levels. The results indicate that temperature is the major regulating factor on the parasitoid. As the type of storage structure and its location (sun or shade) affects the temperature inside the store, ways are being investigated of manipulating the storage environment through temperature regulation to increase the impact of the parasitoid.