Effect of temperature on the ovipositional biology and egg viability of the cattle tickBoophilus annulatus (Acari: Ixodidae)

The effect of temperature on the ovipositional biology ofBoophilus annulatus (Say) was determined under laboratory conditions. Engorged females subjected to constant temperatures of 12 and 45°C died without ovipositing, while females held at 15 and 40°C laid eggs which did not hatch. The preoviposition period at 25–40°C was 2–3 days; however, significant increases occurred at 20°C (5.2 days) and at 15°C (16.3 days). The number of eggs laid per female was ca. 2700 at temperatures of 25–35°C, but decreased significantly at 20°C (ca. 2300 eggs/female), 15°C (ca. 1800 eggs/female), and at 40°C (ca. 300 eggs/female). No differences were observed in the Conversion Efficiency Index (CEI) values at temperatures of 20–30°C (ca. 50%), while temperatures of 15 and 40°C produced the lowest CEI values at 35.6 and 4.9%, respectively. Hatch-ability of eggs was ca. 80% at temperatures of 20–35°C. Incubation period of eggs ranged from 52.2 days at 20°C to 16.2 days at 35°C. The thermal threshold for egg development determined by linear regression was 12.9°C. Females subjected to four fluctuating temperature regimes produced no differences in number of eggs/female (ca. 2400), CEI (ca. 50%), or hatchability of eggs (ca. 75%). Preoviposition period and incubation were significantly affected by a change in the thermoperiod, becoming longer in duration as the temperatures were decreased. From studying females exposed for various intervals from 0 to 105 days at 12°C, indications were that the longer the exposure period the more adverse the effects were on oviposition and egg-hatch. Correspondingly, exposure of eggs to a temperature of 15°C for up to 105 days gave indications that the longer the eggs remained at 15°C, the lower the hatch would be after transfer back to a temperature of 25°C.     

Ovipositional Phenology and Behavior of the Spruce Cone Fly, Strobilomyia neanthracina (Diptera: Anthomyiidae)

The behavior of Strobilomyia neanthracina Michelsen, a phytophage infesting spruce (Picea spp.) seed cones, was observed at a field site in northern Ontario and in cages in a greenhouse to investigate spatiotemporal aspects of mating, host location, and oviposition. In the field, adults emerged from 21 to 24 May 1996, which coincided with bud burst of Picea glauca (Moench) Voss seed cones. For 4 days following emergence, Strobilomyia flies could no longer be seen at a monitored P. glauca tree and may have been on a mating or dispersal flight. Subsequently, females but not males were seen again and the oviposition period of ca. 3 weeks began. Mating was observed only in the greenhouse, mostly (i.e., 65%) at age 5–9 days. Although copulations lasted 11–45 min, these females laid infertile eggs only, beginning at age 4 days. No sperm was found in the spermathecal capsules of females, suggesting that no sperm had been transferred during these copulations. In both the field and the greenhouse, ovipositional sequences that resulted in egg deposition occurred throughout the day but few sequences were observed before 1000, probably because flies were not very active at air temperatures below 14°C (most sequences occurred at 25–27°C). In the greenhouse, the typical ovipositional sequence lasted an average of 7 min and consisted of landing on the cone and examining it with the proboscis and sometimes the ovipositor, egg deposition, and postovipositional behaviors such as tapping (touching the cone surface with the flabellum ca. 5 times s ^–1 ), which possibly represents a host marking behavior. In the field, tapping was seen less frequently than in the greenhouse but occurred significantly (P = 0.014) more often after sequences that resulted in egg deposition than after sequences that did not. Eggs hatched after 4–5 days at 20°C. In the greenhouse, the median longevity of females and males was 24 and 17 days, respectively.     

Factors affecting oviposition and fecundity in the grain miteAcarus siro L. (Acarina:Acaridae), especially temperature and relative humidity

Oviposition and fecundity in the grain miteAcarus siro were studied at 5–30°C and 62.5–90% RH. At and above 20°C, 80% RH, mating and oviposition occurred soon after emergence, but at lower temperatures and humidities egg laying was progressively delayed from one to several days. Females needed to mate repeatedly in order to achieve maximum egg production, optimum conditions for which were 15°C, 90% RH, where total output per female averaged 435 with a maximum of 858. Oviposition rates were highest at higher temperatures, the mean daily rate at 20 and 25°C, 90% RH, rising to maximum levels of 28/29 eggs per female per day on day six.Oviposition followed clearly defined patterns, favourable conditions producing rapid increases in the mean daily oviposition rate to high peak levels reached at an early stage in the oviposition period. Less favourable conditions resulted in reduced outputs and lower, more uniform rates of egg laying. The mean oviposition period, varying with humidity, fell from 72–122 days at 5°C to 9–13 days at 30°C and the mean incubation period from 42–70 days at 5°C to 3–4 days at 30°C. Egg viability increased with increasing humidity but was little affected by temperature and unaffected by age of the female at time of oviposition.Males tended to live longer than females at most conditions; longevity—depending on humidity—averaging 13–15 days at 30°C and 129–175 days at 5°C. Adult life for females averaged 12–19 days at 30°C and 88–169 days at 5°C. An index of suitability, calculated from egg number, viability and duration of the egg stage and oviposition period, indicated that the most favourable conditions for oviposition and hatching were 20–25°C and 80–90% RH.     

Effects of temperature and diet on oviposition rate and development time of the New Zealand flower thrips, Thrips obscuratus

The life history of New Zealand flower thrips (Thrips obscuratus (Crawford), Thysanoptera: Thripidae) was studied using a simple laboratory rearing method. The effects of temperature and diet on oviposition rate and development time were examined. Oviposition rate increased with increasing temperature between 10°C and 25°C. Development time for individual instars and for total development decreased with increasing temperature between 10°C and 27°C. Total development time ranged from 50 days at 10°C (female) to 10 days at 27°C (male). The relationship between temperature and development rate was expressed as a straight line such that lower thresholds of development of between 4.2°C and 6.3°C were established for life stages. Adult lifespan increased with decreasing temperature between 10°C and 25°C and females lived longer than males. At 10°C and 25°C females lived for an average of 34 and 3 weeks respectively. Thrips supplied with pollen exhibited highest and sustained levels of egg production in comparison to other diets. Larval mortality was lowest and development time fastest on diets of pollen and sucrose or fruit juice in comparison to other plant tissues. Larval development time was similar on four species of pollen.     

Temperature influence on the reproduction of Podisus nigrispinus, a predator of the noctuid larva Alabama argillacea

The influence of temperature on thereproduction and longevity of Podisusnigrispinus (Dallas) (Heteroptera:Pentatomidae) fed with Alabamaargillacea (Hübner) (Lepidoptera:Noctuidae) larvae was studied. This predatorwas reared at constant temperatures of 20, 23,25, 28, 30 and 33 ± 0.2 °C, all atrelative humidity of 60 ± 10%, and aphotoperiod of L:D 14:10. Fecundity of P.nigrispinus at the various temperatures rangedfrom 401.2 (33 °C) to 841.3 (28 °C) eggs/female. The preoviposition,oviposition peak, and declining ovipositionperiods of P. nigrispinus were affectedby temperature [preoviposition period: 4.0 (33 °C) to 13.2 (20 °C) days;duration of oviposition peak period: 9.0 (33 °C) to 33.0 (20 °C) days; andduration of declining oviposition period: 16.0(33 °C) to 46.0 (20 °C) days].Longevity of females and males of P.nigrispinus ranged from 28.4 (33 °C) to88.6 (20 °C) days, and from 42.7 (33 °C); to 114.3 (20 °C) days,respectively. These data are useful in relationto the development of population dynamicsmodels to underpin programmes of biologicalcontrol.     

Survival of Coregonus albula (L.) (Teleostei) embryos incubated at different thermal conditions

Eggs of Coregonus albula were incubated at constant temperatures: 1.1, 2.0, 2.9, 4.9, 6.6, 8.4, and 9.9 °C, and the percentage of normal hatch was 20.6, 11.8, 30.4, 61.0, 51.7, 32.6, and 14.6%, respectively. The lower and upper median tolerance limit (TL 50) defined as the interpolated temperature at which embryos survival to hatch was 50% of the highest response (61% at 4.9 °C) were 2.9 and 8.5 °C, respectively. The optimum temperature range delimited by lower and upper TL 75 was encompassed by 4.0 and 7.2 °C.Eggs of C. albula incubated at variable temperature in a commercial hatchery showed a very high survival (up to 76%). Similarly low survival observed during hatching of embryos at constant temperatures of 1.1 and 2.0 °C could be hightened (to about 90%) by raising the temperature in the beginning of hatching period. This phenomenon was utilized in the technique of delaying C. albula embryos' mass hatching for the purpose of synchronization in time of stocking the lakes with the time of appearence of good thermal and food conditions for C. albula larvae.The conception of the optimal thermal conditions for Coregoninae embryogenesis was developed as the course of incubation temperature, securing the highest survival rate during embryogenesis and also during the larval period.     

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

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

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

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

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

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

Effect of temperature on reproductive parameters and longevity of <Emphasis Type="Italic">Tyrophagus putrescentiae</Emphasis> (Acari: Acaridae)

The effect of temperature on reproductive parameters and longevity of the mold mite, Tyrophagus putrescentiae (Schrank) was examined at seven constant temperatures, ranging from 10 to 34 °C, and a relative humidity of 90±5%. Preoviposition period and fecundity were adversely affected by extreme temperatures and the oviposition period increased as temperature was reduced. Different patterns were observed for longevity data for males and females, with greater longevities for males at intermediate temperatures and more similar values for both sexes at extreme temperatures. Polynomial and non-linear models provided a good fit of the relationship of reproductive and longevity parameters with temperature. The effect of temperature on the intrinsic rate of increase of T. putrescentiae populations was established by the non-linear Lactin model. The optimum temperature for development was obtained at 30 °C. At this temperature, the population doubling time is 1.75 days. The lower and upper thresholds for T. putrescentiae populations were established at 10.4 and 34.8 °C, respectively. Altogether, these data provide basic information to develop sound physical control strategies of the mold mite.     

Biology, life table and host specificity of the mushroom pest, Brennandania lambi (Acari: Pygmephoroidea)

Biology and life table parameters of Brennandania lambi (Krczal) were studied at different temperatures while feeding on white mushroom (Agaricus bisporus) mycelium cultured on mushroom compost. The duration of egg and larva development, preoviposition and oviposition period, female longevity, and the time to 50% mortality declined as temperature increased from 16 to 28°C. The threshold temperature of development (female) was 9°C and the thermal constant for completion of development (female) was 195 day-degrees. At 16, 20, 24 and 28°C, the total fecundity (eggs/female) was 71, 67, 66 and 57, respectively and the daily fecundity rate (eggs/female/day) was 5.6, 8.7, 8.7 and 9.1, respectively. The sex ratio (female/male) ranged from 1.9 to 2.1 at 16–28°C. At 16, 20, 24 and 28°C, the intrinsic rate of natural increase (r _m) was 0.11, 0.18, 0.22 and 0.27, respectively, and the population doubling time was 6.1, 3.9, 3.2 and 2.5 days, respectively. All life stages of the mite died when exposed to 35°C constant temperature for 24h, or to 32°C constant temperature for 12 days or to 31–35°C (average 32.9°C) ambient temperature for 4 days. Brennandania lambi completed development only when fed on Ag. bisporus mycelium growing on mushroom compost. It could not survive on mushroom mycelia of Auricularia auricula, Au. polytricha, Ganoderma lucidum, Hericium erinaceus, Lentinus edodes, Pleurotus ostreatus, P. sajor-caju and Tremella fuciformis.     

Reproduction,survival, and life table parameters of the predatory mite <Emphasis Type="Italic">Cheyletus malaccensis</Emphasis> (Acari: Cheyletidae) at various constant temperatures

Reproduction, survival, and life table parameters of the predatory mite Cheyletus malaccensis Oudemans were evaluated at six constant temperatures: 17.5, 20, 25, 30, 32.5 and 35°C, feeding on Tyrophagus putrescentiae (Schrank). Preoviposition period of fertilized and virgin females varied with temperature from ca. 9 days at 17.5°C to ca. 1.5 day at 32.5°C and then increased to ca. 3 days at 35°C. Virgin female oviposition period was significantly shorter than for fertilized females at the temperatures examined with the exception of 17.5°C. The mean total number of eggs per fertilized (169.7 ± 6.6) and virgin female (60.7 ± 4.3) was highest at the temperature of 30°C. The data indicated a significant positive and nearly doubling effect of fertilization on female fecundity at the temperatures examined with the exception of 17.5°C. Age-specific fecundity was described by a temperature dependent model from which the maximum daily fecundity rate was estimated for fertilized and virgin females at 10.3 (at 30°C) and 6.8 (at 32.5°C) eggs/female, respectively. Virgin female longevity was significantly shorter than for fertilized females at 20, 30 and 32.5°C, and decreased from ca. 57 days at 17.5°C to ca. 17 days at 35°C. The Weibull function that was used to describe the age specific survival of fertilized and virgin females produced excellent fits to the survival data. Estimates of intrinsic rate of increase, net reproductive rate, mean generation time, doubling time and finite rate of increase, were obtained. The r_m value increased with temperature from 0.03 (day⁻¹) at 17.5°C to 0.21 (day⁻¹) at 32.5°C, after which it decreased to 0.15 (day⁻¹) at 35°C. These data indicate that C. malaccensis can reproduce at temperatures between 17.5 and 35°C and can be used for biological control of astigmatid mites within the temperature range where the pest occurs.     

Reproductive bionomics of the soft tick, Ornithodoros turicata (Acari: Argasidae)

The effects of different temperatures and relative humidities (RHs) were tested on various reproductive parameters of Ornithodoros turicata, an argasid tick that inhabits gopher tortoise burrows in Florida, USA. The pre-oviposition, oviposition and incubation periods of the ticks decreased as temperature increased. These periods were also affected by the RH. The number of eggs oviposited was affected significantly by the combined effect of temperature and RH. Fewer eggs were laid by ticks in the 24°C regimes and the 27°C/95%RH regime compared to those in the other temperature/RH groups. There was an inverse relationship between the number of eggs oviposited and the percentage of hatched larvae that was correlated with the temperature and RH. Ticks reared at 27°C/90%RH and 30°C/90%RH laid more eggs than those reared in the other combinations of temperature and humidity but fewer larvae hatched from these eggs. The reproductive fitness index (RFI) values were highest in females held in the 24°C groups and the 30°C/95%RH group, although significantly more larvae hatched at the lower temperatures. The optimum reproductive conditions for O. turicata under laboratory conditions appear to be 24°C and 90–95%RH. While mating occurred at all temperatures, none of the females laid eggs at 22°C. The ticks may move preferentially to low temperatures when not feeding to remain above the critical equilibrium humidity and/or below the critical metabolic level necessary for prolonged survival. However, most female ticks oviposited after 45 days when moved to 27°C/95%RH. Ornithodoros turicata females may have a limited capability to delay oviposition until an optimal microenvironment for egg deposition can be located in the burrow.     

Influence of temperature and relative humidity on the development ofAmblyseius alstoniae (Acari: Phytoseiidae)

Reproduction and development ofAmblyseius alstoniae Gupta is significantly affected by temperature and relative humidity (rh), optimum being a temperature of 25°C andrh of 70%. At this combination, the viability of eggs, fecundity and daily egg production were higher, oviposition period and longevity were of longer duration, and mortality was minimal. Increase or decrease in these temperature andrh levels leads to a drop in fecundity, longevity and oviposition period and an increase in mortality. Longevity of females is always greater than that of males, irrespective of temperature andrh. Female: male ratio decreases with increase in temperature, irrespective ofrh.     

Influence of food and temperature on development and oviposition ofEuseius stipulatus andTyphlodromus phialatus (Acari: Phytoseiidae)

The influence of feeding and temperature on life table parameters ofEuseius stipulatus (Athias-Henriot) andTyphlodromus phialatus Athias-Henriot was determined in laboratory tests. Both phytoseiids developed and reproduced readily when fed onCarpobrotus edulis (L.) pollen andPanonychus citri (McGregor) Intrinsic rates of increase (r _m ) at 25°C forE. stipulatus andT. phialatus were 0.197 and 0.126, and, when fed onP. citri, 0.129 and 0.144, respectively.Tetranychus urticae Koch offered as prey allowed normal development and oviposition ofT. phialatus, but no eggs were laid byE. stipulatus when fed on this spider mite. Eggs and honeydew ofAleurothrixus floccosus Mask. furnished sufficient nutrition for development of immatures ofE. stipulatus. Larvae ofPlanoccocus citri Risso, and honeydew and eggs ofA. floccosus, allowed adult survival but no egg-laying of the predaceous mites.Lorryia formosa Cooreman was not a favoured prey species.Life tables were calculated forE. stipulatus fed on pollen andT. phialatus fed onP. citri at constant temperatures of 18, 25, and 32°C. Maximum development was reached at 32°C, withr _m values of 0.225 forE. stipulatus and 0.179 forT. phialatus. In general, both phytoseiids showed medium to high total number of eggs per female and long oviposition periods when compared with other phytoseiid species.When mating took place at 32°C,E. stipulatus females were not able to lay eggs, thus suggesting an interference of high temperatures with fertilization in this species. No hatching was observed in eggs of either species when kept at relative humidities of 50% or lower. The possible significance of these responses is discussed in relation to population trends observed in the field.     

Environmental influences on fecundity, egg viability and egg cannibalism in the scale insect predator, Chilocorus nigritus

The effects of temperature on age-specific fecundity, egg viability and egg cannibalism were examined in the coccidophagous coccinellid, Chilocorus nigritus being fed on the cyanophyllum scale, Abgrallaspis cyanophylli. There were no significant differences in lifetime fecundity or oviposition rate at constant temperatures in the range of 20 to 30°C although there was a trend for both parameters to increase with increasing temperatures. Total fecundity ranged from five to 1890 eggs per female whilst the oviposition rate varied from 0.2–12.1 eggs day^-1. Egg viability was significantly greater at 26 and 30°C (63 and 74%, respectively) than at lower temperatures (18 to 30%) whilst egg cannibalism was highest at 24 and 26°C (being the mid range of the temperatures tested). Mean pre-oviposition periods varied from 54 days at 20°C to 8.2 days at 30°C. The effect of relative humidities in the range of 33% to 75% on oviposition rate, egg viability and egg cannibalism was measured and found to have no significant effect on either parameter.     

Development and reproductive biology of Laricobius nigrinus, a potential biological control agent of Adelges tsugae

Biological studies on Laricobius nigrinus Fender (Coleoptera: Derodontidae) were conducted in the laboratory to obtain basic information on this littleknown predator. Laricobius nigrinus is acandidate biological control agent of thehemlock woolly adelgid, Adelges tsugaeAnnand (Homoptera: Adelgidae), an exotic peston eastern (Tsuga canadensis (L.)Carrière) and Carolina (T.caroliniana Engelmann) hemlocks in the easternUnited States. It is univoltine andundergoes an aestival diapause. Post-aestivation activity period was 36.6 and30.8 weeks for males and females, respectively. Adult activity and oviposition are wellsynchronized with the over-wintering generationof A. tsugae. Mean lifetime fecunditywas 100.8 eggs over a mean duration of 13.2weeks oviposition period. Within thetemperature range (12–18°C) studied,development was fastest at 18°C. Meandevelopment time from egg to adult was 88.8,64.8 and 46.6 days at 12, 15 and 18°C,respectively. Laricobius nigrinus hasfour larval instars. Mean larval consumptionwas 225.9 and 252.3 A. tsugae eggs at 12and 18°C, respectively. Thesefindings provide essential data on the rate ofdevelopment and feeding capacity of L. nigrinusat temperatures typical of ambientconditions during late winter/early spring inVirginia. Its rapid development at18°C indicates that it has potential asa biological control agent of A. tsugaebecause of its synchrony with the developmentof the over-wintering generation of A. tsugaein eastern United States.     

Isolation of thermostable D-hydantoinase-producing thermophilicBacillus sp SD-1

Summary A thermophilic bacterium which showed highest thermostability and activity of the hydantoinase was isolated from 1m000 thermophiles and identified to beBacillus sp. SD-1 according to morphological and physiological characteristics. The optimal growth temperature of the bacterium was about 60°C. The hydantoinase ofBacillus sp. SD-1 was strictly D-specific, and optimal pH and temperature were determined to be about 8.0 and 70°C, respectively. The D-hydantoinase was stable upto 70°C, and half-life of the enzyme was about 20 min at 80°C.     

Biology ofEuseius mesembrinus (Acari: Phytoseiidae): Life tables on ice plant pollen at different temperatures with notes on behavior and food range

Euseius mesembrinus (Dean) (Acari: Phytoseiidae) was recently reported on Florida citrus for the first time. This mite was able to develop and reproduce when fed plant pollen of Spanish needle,Bidens pilosa L. and ice plant,Malephora crocea (Jacq.) or three spider mite species (Acari: Tetranychidae) including all stages ofTetranychus urticae Koch,Eutetranychus banksi (McGregor), and larval and nymphal stages only ofPanonychus citri (McGregor).The biology ofE. mesembrinus was studied under laboratory conditions while being fed pollen ofM. crocea. The developmental time for immature stages at 18, 22, 26, and 30°C was 11.50, 7.47, 4.54, and 4.40 days, respectively. This pattern fits a log-probit model withr ²=0.940. Eggs hatched, but mortality in other stages was high at 34°C. The intrinsic rate of natural increase was 0.146, 0.250, and 0.246 at 22, 26, and 30°C. The optimum temperature for this phytoseiid to develop and increase on ice plant pollen was in the range of 26 to 30°C.Florida Agricultural Experiment Station Journal Series No. 7429.     

Effect of temperature on reproduction and embryonic development of the cabbage stem flea beetle,Psylliodes chrysocephala L., (Coleoptera: Chrysomelidae)

The cabbage stem flea beetle, Psylliodes chrysocephala (L.) (Coleoptera: Chrysomelidae), is a major pest of winter oilseed rape. Despite the importance of this pest, detailed information on reproduction to predict risk of crop damage is lacking. This study investigates the effect of temperature on parameters of reproduction, egg development and viability at five constant temperatures. Significant temperature effects were found on the pre‐oviposition period, total number of eggs laid, daily oviposition rate, female longevity, egg‐development rate and viability. The mean length of the pre‐oviposition period ranged from 93.1 days at 4°C to 14.6 days at 20°C. Analysis of total number of eggs laid and daily oviposition rate during female lifespan estimated the highest total number of eggs laid (696 eggs/female) at 16°C and the highest oviposition rate (6.8 eggs/female and day) at 20°C. The daily oviposition rate at 20°C was not significantly higher than 5.4 eggs/female and day at 16°C. Female longevity was significantly longer at 4°C, shorter at 20°C and not significantly different between 8, 12 and 16°C. Estimated 50% survival time of females was 239, 153, 195, 186 and 78 days at 4, 8, 12, 16 and 20°C, respectively. A linear model of egg development at 8–20°C estimated the lower developmental threshold to be 5.1°C and the thermal constant for development 184.9 degree‐days. The percentage of eggs hatching was significantly lower at 4°C than at all other temperatures tested. The estimated mean hatching percentages were 47.3%, 70.0%, 72.4%, 66.2% and 67.9% at 4, 8, 12, 16 and 20°C, respectively. These results can be used to predict the start and intensity of egg‐laying in the autumn and the appearance of larvae in the field from knowledge about time of field invasion and from monitoring the weather.