Effects of temperature on the establishment potential in the U.K. of the non-native glasshouse biocontrol agent Macrolophus caliginosus

Abstract This study investigated the effect of temperature on the development and winter survival of the predatory mirid Macrolophus caliginosus Wagner, recently introduced into the U.K. as a biocontrol agent for glasshouse whitefly Trialeurodes vaporariorum . The developmental threshold for M. caliginosus calculated by three methods was between 7.3 and 8.4 °C, with a day-degree requirement per generation varying between 472 and 524 day-degrees. It was estimated that under outdoor conditions M. caliginosus could complete two generations per year in the U.K. All life stages of M. caliginosus had supercooling points around −20 °C, with some pre-freeze mortality evident in both acute and chronic low temperature exposures. Acclimation increased survival of nymphal M. caliginosus from approximately 24–52 days when exposed to a constant 0 °C. Provision of prey extended survival of nymphs in the laboratory at a constant 5 °C from 39 to 64 days and in the field by c . 150 days. The results are discussed in the context of the occurrence and establishment of M. caliginosus in the U.K. and the need to develop a reliable risk assessment system for non-native species used in glasshouse biocontrol.     

Adult mortality and oviposition rates in field and captive populations of the blowfly Lucilia sericata

Abstract.  1. Adult mortality and oviposition rates were determined for populations of the blowfly Lucilia sericata (Meigen) (Diptera: Calliphoridae). This species is of economic importance as the primary agent of sheep myiasis throughout north-western Europe.
2. Populations of marked flies in six, 1 m³, outdoor field cages and unmarked wild flies at two farms in south-west England were studied simultaneously between May and September 1998.
3. In the field, wild female L. sericata were caught and aged using a combination of wing-fray and ovarian dissection techniques. Survivorship analysis gave estimates of mortality of 1.94% (± 0.037) and 2.09% (± 0.044) per day-degree and mean life expectancy of 51.5 and 47.9 day-degrees above a threshold of 11 °C, at the two farms studied. Mean lifetime reproductive output in the field was estimated to be 159.6 and 138.4 eggs per female at the two farms respectively.
4. The survivorship of cohorts of marked female flies in cages was followed by counting the number of dead individuals each day; the mortality rate of these flies was 0.81% per day-degree (± 3.49 × 10⁻⁴%) and the mean life expectancy was 123.1 day-degrees above a threshold of 11 °C. Mortality rate was shown to increase significantly with average ambient temperature and relative humidity lagged for two sample periods (approximately 10 days). Oviposition rate also increased with average temperature but declined with average relative humidity. A best-fit multiple regression model incorporating both ambient temperature and humidity explained 60.5% of the variance in the pattern of oviposition.
5. The differences between the field and cage populations highlight the caution required when extrapolating life-history parameters from artificial to natural habitats.     

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.     

Effect of temperature on life table parameters of Podisus nigrispinus (Het., Pentatomidae) fed with Alabama argillacea (Lep., Noctuidae) larvae

Abstract: The influence of temperature on life table parameters of Podisus nigrispinus (Dallas) (Het., Pentatomidae) fed with Alabama argillacea (Hübner) (Lep., Noctuidae) larvae was studied. This predator was kept at constant temperatures of 20, 23, 25, 28, 30 and 33±0.2°C, at relative humidity of 60±10% and photoperiod of L : D 14 : 10. Gross (GRR) and net ( R ₀) reproductive rates of P. nigrispinus ranged from 1.6 to 366.6 and from 0.02 to 189.5 females/female at temperatures of 33 and 28°C, respectively; generation time ( T  ) ranged from 33.3 (33°C) to 85.5 (20°C) days; doubling time ( D ) from 0.82 (33°C) to 17.8 (20°C) days; intrinsic rate of increase ( r _m ) from −0.13 (33°C) to 0.12 (28°C) per day; and the finite rate of increase ( λ ) from 0.88 (33°C) to 1.12 (28°C) females/female added to the population per day. The ideal age to release P. nigrispinus should be when this predator presents higher reproductive values (VR _x ); that is, its adults are about 7 days old, independent of prevailing temperature. Population growth of P. nigrispinus was affected by temperature with maximum numerical response between 28 and 30°C. The negative population growth shown at 33°C may not occur in natural conditions due to milder microclimate in the cotton agroecosystem and due to oscillations of temperature in the course of the day.     

Assessment of temperature effects on the development and fecundity of Pullus mediterraneus (Col., Coccinellidae) and consumption of Saissetia oleae eggs (Hom., Coccoida)

Eggs, larval and nymphal periods and fecundity of Pullus mediterraneus were examined under 16 h light : 8 h dark combined with six constant temperatures: 15, 20, 25, 30, 35 and 40°C. Eggs of Saissetia oleae were used as prey. The developmental time at 15, 20, 25, 30 and 35°C was 17.23, 4.5, 2.64, 1.67, 1.28 days for eggs and 98.47, 68.88, 53.94, 28.96, 36.51 days for larval–pupal duration, respectively. At 7°C no eggs hatched, and at 40°C all the stages died after 36 h of maximum exposure except the three last stages. The fecundity of females rearing at different temperatures ranged between 1.7 eggs at 15°C and 601.86 eggs at 30°C. The pre-oviposition period ranged between 23.75 days at 15°C and 3.47 days at 35°C. The consumption of S. oleae eggs by the larvae reached 597.69 eggs during the pre-imaginal development. Females attacked more eggs than males averaging 77.69 ± 22.34 eggs per 4 day period compared with 46.97 ± 10.12 eggs per 4 day period for males.     

Influence of rearing temperature during the larval and nursery periods on growth and sex differentiation in two Mediterranean strains of Dicentrarchus labrax

European sea bass Dicentrarchus labrax of the north‐western (NW) and south‐eastern (SE) Mediterranean Sea strains were exposed to different temperatures (13, 17 or 21° C) during the larval rearing (11–51 days post hatching, dph) or nursery periods (55–95 dph), in order to examine the effects of temperature on sex differentiation and subsequent growth during the first year of life. Higher growth was observed during exposure to higher temperatures, but fish of the NW strain exposed to 13 or 17° C during larval rearing exhibited compensatory growth once exposure to the lower temperatures finished, and as a result their final size at 300 dph was similar or greater to the group exposed to 21° C. Fish exposed to 17° C during the nursery period also had similar size to fish exposed to 21° C after 300 days of rearing, but the fish exposed to 13° C remained significantly smaller (ANOVA, n  = 55–100, P  < 0·05). There were significant differences in the sex ratio among the fish exposed to different temperatures during the two periods of rearing, with high temperature (21° C) resulting in a significantly higher percentage of males in the population, both in the NW (ANOVA, n  = 2, P  < 0·04) and SE populations (ANOVA, n  = 2, P  < 0·01). The masculinization effect of high temperature was significantly stronger during the larval rearing stage, both in the NW (ANOVA, n  = 2, P  < 0·005) and SE populations (ANOVA, n  = 2, P  < 0·01). None of the temperature manipulations could produce 100% females, suggesting that there is a part of the genetic component in sex differentiation which is not labile to environmental influence.     

Influence of temperature on biofilm formation by Listeria monocytogenes on various food-contact surfaces: relationship with motility and cell surface hydrophobicity

Aims:  To assess the ability of Listeria monocytogenes to form biofilm on different food-contact surfaces with regard to different temperatures, cellular hydrophobicity and motility.
Methods and Results:  Forty-four L. monocytogenes strains from food and food environment were tested for biofilm formation by crystal violet staining. Biofilm levels were significantly higher on glass at 4, 12 and 22°C, as compared with polystyrene and stainless steel. At 37°C, L. monocytogenes produced biofilm at significantly higher levels on glass and stainless steel, as compared with polystyrene. Hydrophobicity was significantly ( P  < 0·05) higher at 37°C than at 4, 12 and 22°C. Thirty (68·2%) of 44 strains tested showed swimming at 22°C and 4 (9·1%) of those were also motile at 12°C. No correlation was observed between swimming and biofilm production.
Conclusions:  L. monocytogenes can adhere to and form biofilms on food-processing surfaces. Biofilm formation is significantly influenced by temperature, probably modifying cell surface hydrophobicity.
Significance and Impacts of the Study:  Biofilm formation creates major problems in the food industry because it may represent an important source of food contamination. Our results are therefore important in finding ways to prevent contamination because they contribute to a better understanding on how L. monocytogenes can establish biofilms in food industry and therefore survive in the processing environment.     

Experimental systems and a mathematical model for studying temperature effects on pollen-tube growth and fertilization in plum

Abstract. Cross and self pollen tubes were cultured in 'Victoria' plum flowers ( Prunus domestica L.) at 5, 10, 15 and 20°C. Pollen-tube lengths measured at intervals were fitted by S-shaped growth curves (logistic function) and the parameters of the curves used to derive a generalized model for pollen-tube growth based on accumulated temperatures. Above the threshold of 2.5°C, maximum growth rate was 0.34 mm per day-degree and the tubes reached half their final length at 16.6 day-degrees above 2.5°C. The model indicates that fertilization of plum flowers requires 16–20 d at a constant temperature of 5°C after pollination, but only 3–4 d at 15°C. Mathematical expressions based on the model are given for estimating pollen-tube penetration and growth rate from values of cumulated temperature since pollination, and for estimating the cumulated temperature necessary for pollen tubes to penetrate a given distance. Pollen-tube growth rates were the same in detached flowers, flowers attached to twigs, and flowers on young, grafted trees in pots. In detached flowers growth stopped before fertilization could occur, but some embryo sacs were fertilized in both the remaining treatments. Accurate pollen-tube growth assessments can therefore be made with detached flowers which are most convenient to use and can be accommodated in small incubators. Studies on fertilization, however, must use flowers on bulky and expensive grafted trees.     

Seed germination ecology of Portulaca oleracea L.: an important weed of rice and upland crops

Portulaca oleracea , a C₄ species, is reported to be a serious weed in 45 crops in 81 countries. Experiments were conducted in the laboratory, the screenhouse and the field to determine the influence of environmental factors on seed germination and seedling emergence of P. oleracea . In the laboratory, germination in the dark was low and was not influenced by the tested temperatures (35/25°C, 30/20°C and 25/15°C alternating day/night temperatures). In the light/dark regime, however, germination was lower at 25/15°C and 35/25°C than at 30/20°C (70%, 75% and 81% germination, respectively). In conditions of 106 mM sodium chloride or −0.34 MPa osmotic potential, seeds germinated to only 50% of maximum germination of the control. Germination was not influenced by buffered pH solutions ranging from 5 to 9. In the screenhouse, germination was greatest for seeds placed on the soil surface, but emergence declined with increasing seed burial depth in soil; no seedlings emerged from the depth of 2 cm. Seedling emergence and seedling dry matter were markedly reduced by the addition of rice residue to the soil surface at rates equivalent to 4 to 6 t ha⁻¹. In the field, seedling emergence of P. oleracea was greater under zero till (ZT) (17–20%) than under minimum tillage (6–10%), a likely reflection of low seed burial and exposure of seeds to light with a ZT system. This study identifies some of the factors enabling P. oleracea to be a widespread weed in the humid tropics, and the information could contribute to improved control strategies.     

Biological parameters of Thripobius semiluteus Bouček (Hym., Eulophidae), a larval endoparasitoid of Heliothrips haemorrhoidalis (Bouché) (Thysan., Thripidae)

Abstract:  The endoparasitoid Thripobius semiluteus Bouček was recently introduced to Italy from Israel for the biological control of Heliothrips haemorrhoidalis (Bouché). In this study, some aspects of the biology of T. semiluteus were determined in the laboratory. Developmental time (egg to adult), potential fecundity, realized fecundity, progeny, daily rate of deposition of eggs and several demographic growth parameters were evaluated. Studies of the longevity of fed and starved adults at seven temperatures (3, 10, 15, 20, 23, 25 and 30 ± 1°C) showed that fed T. semiluteus lived longest at 15°C (36.45 days) and shortest at 3°C (1.45 days). Longevity was reduced significantly at higher and lower temperatures than 15°C and when honey was not provided. Development time was measured at six temperatures. Pupae did not complete development at 10°C. The lower theoretical temperature threshold was 9.0°C; the optimum developmental temperature and the upper lethal threshold were 28.0°C and 34.1°C respectively. The most rapid development was found at 30°C, but waSPS suffered significantly higher mortality at this temperature than at other temperatures. Ovigeny index showed that T. semiluteus is synovigenic, with a mean realized fecundity of 78.8 eggs per female. The mean progeny was 68.2 adults per female on fed adults.     

Effect of Temperature on the Formation of Microsclerotia of Verticillium dahliae

Microsclerotium formation by six isolates of Verticillium dahliae was studied at different temperatures both in vitro and in Arabidopsis thaliana . In vitro mycelial growth was optimal at 25°C, but microsclerotium formation was greatest at 20°C (two isolates) or 15–20°C (one isolate). Seedlings of A. thaliana were root-dipped in a conidial suspension, planted, and either placed at 5, 10, 15, or 25°C, or left at 20°C until the onset of senescence, after which some of the plants were placed at 5, 10, 15, or 25°C. The amount of microsclerotia per unit of shoot weight was assessed in relation to isolate and temperature. The optimal temperature for production of microsclerotia was 15–25°C. Two isolates each produced about 10 times more microsclerotia than each of the other four isolates. For these isolates, high R ²_adj.-values of 0.77 and 0.66 were obtained, with temperature and its square as highly significant (P   < 0.001) independent variables. R ²_adj.-values for the other isolates varied between 0.28 and 0.39. Moving plants to different temperatures at the onset of senescence led to microsclerotial densities that were intermediate between densities on plants that had grown at constantly 20°C and plants grown at other temperatures. This suggests that vascular colonization rate and rate of microsclerotium formation are similarly affected by temperature. The senescence rate of plants appeared unimportant except for plants grown at 25°C, which showed the highest amounts of microsclerotia per unit of plant weight in the most rapidly senescing plants.     

Interspecific competition between Cephalonomia stephanoderis and Prorops nasuta (Hym.,Bethylidae), parasitoids of the coffee berry borer, Hypothenemus hampei (Col., Scolytidae)

The competition between Cephalonomia stephanoderis and Prorops nasuta was studied in the laboratory, using coffee fruits infested with the host of these parasitoids, the coffee berry borer Hypothenemus hampei . Experiments were performed under different conditions, using: (a) three temperatures; (b) five densities of infested coffee fruits; and (c) introducing the parasitoids at different times. The effect of competition was determined according to the production of the progeny. When cultured together at the same time, C. stephanoderis produced in general, more progeny than P. nasuta under conditions of 29°C and alternating temperatures of 18–29°C. Nevertheless, there were significant differences at densities of 1 : 3, fruits : parasitoids ( F _0.05=8.9; d.f.=1, 12; P < 0.05) and 1 : 5 ( F _0.05=7.56; d.f.=1, 12; P < 0.05) at 29°C. Under alternating temperatures, there were differences at the same ratios as above in favour of C. stephanoderis , 1 : 3 ( F _0.05=20.08; d.f.=1, 12; P < 0.05) and 1 : 5 ( F _0.05=20.21; d.f.=1, 12; P < 0.05). Prorops nasuta was clearly more successful in all densities at 18°C. When C. stephanoderis was introduced 10 days before P. nasuta , the progeny production was markedly higher in eight from 10 densities at temperatures of 29°C and 18–29°C. Despite being introduced 10 days later, P. nasuta showed better performance at 18°C. When P. nasuta was introduced 10 days earlier than C. stephanoderis , there were significant differences in progeny production in favour of P. nasuta in 13 of 15 fruit densities under the three temperatures. Both parasitoids avoided ovipositing on previously parasitized hosts. Aggressive behaviour or interference was not observed when they were outside coffee fruits.     

Plasma osmolarity, glucose concentration and erythrocyte responses of two Antarctic nototheniid fishes to acute and chronic thermal change

Haematocrit, haemoglobin concentration, plasma osmolarity and plasma glucose concentration of the Antarctic nototheniid fishes Pagothenia borchgrevinki and Trematomus bernacchii were monitored during 24 h periods of exposure to 3 and 6° C. The same haematological variables were also measured in P. borchgrevinki following a 5–6 week period of 4° C acclimation. The first plasma glucose measurements in acutely thermally‐stressed Antarctic nototheniids revealed a delayed hyperglycaemia which related well to the relatively slow stress‐related elevation of plasma cortisol in these species. Plasma osmolarity of both species was unchanged by acute 3° C exposure, but exhibited a delayed and transient increase during acute exposure to 6° C. Haematocrit was unaltered in T. bernacchii during the acute temperature increases but was elevated in the relatively active P. borchgrevinki . Following 5–6 weeks of warm‐acclimation (4° C) the plasma glucose concentration, haematocrit and haemoglobin concentration of P. borchgrevinki were not significantly different from fish at −1° C, but plasma osmolarity decreased toward the level found in temperate‐water teleosts.     

Growth and food choice by two species of limnephilid caddis larvae given natural and artiflcial foods

SUMMARY 1. Larvae of the caddisfly Limnephilus externus grew faster than those of Nemotaulius hostilis in a permanent pond in southern Alberta.
2. We investigated whether this was due to more efficient food processing by L. externus , whether their growth coincided with high environmental temperatures, or whether they had the ability to choose and exploit higher quality food.
3. Of five foods used, protein content was highest in wheat flakes, similar in alder, bur-reed and willow leaves, and lowest in the moss Leptodictyum .
4. Both species grew faster and survived better on the wheat flakes, but there was no statistically significant difference between species on the same food when reared at 4 or 8°C in the laboratory.
5. At 16°C L. externus grew better than N. hostilis when fed wheat, but N. hostilis survived better on alder. Both species had higher survival and growth rates per day-degree at 8 and 4 than at 16°C.
6. Thus, faster growth rates of L. externtus in the field appear to be due simply to higher temperatures during the larval growth period. Indeed, N. hostilis had a significantly higher growth rate per day-degree in a field experiment.
7. In food preference experiments, L. externus chose wheat first, moss second, alder third, and willow last; N. hostilis chose alder first, bur-reed second, moss third, and wheat last.
8. Protein content, leaf texture, microbial conditioning, and an interaction between larval behaviours selecting for food quality and case materials, are potential factors that influence'food preference'results.     

Daily ration and prey size of juvenile piscivore Japanese Spanish mackerel

Daily ration of juvenile Japanese Spanish mackerel Scomberomorus niphonius (32·1–33·1 mm standard length, L _S) was estimated at three temperatures (18·6, 19·5 and 21·2° C) in the laboratory. Gastric evacuation rate ranged between 0·398 (18·6° C) and 0·431 (21·2° C). Diel change in instantaneous consumption rate indicated that juvenile Japanese Spanish mackerel are daylight feeders. The estimated values of the daily ration ranged between 66·1%(18·6° C) and 82·6%(21·2° C) of body mass. These per cent values of daily ration were converted to daily consumption in mg (28 mg at 18·6° C to 34 mg at 21·2° C) using the mean dry body mass of juvenile Japanese Spanish mackerel of 30 mm (42·1 mg). Stomach content analysis of wild specimens collected in the Seto Inland Sea, south‐western Japan, revealed that the majority of wild Japanese Spanish mackerel larvae and juveniles ingested fish larvae with a body size >50% of the predator L _S. Based on the predator‐prey size relationship, the daily consumption of a Japanese Spanish mackerel juvenile of 30 mm was equivalent to 5·1 (18·6° C) to 6·4 (21·2° C) Japanese anchovy Engraulis japonicus larvae which was the dominant prey organism in stomachs of the wild Japanese Spanish mackerel.     

Biological studies of the Australian predatory mite Typhlodromips montdorensis (Schicha) (Acari: Phytoseiidae), a potential biocontrol agent for western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae)

Abstract The biology of the Australian phytoseiid mite Typhlodromips montdorensis is described from material collected in Queensland and South Australia in 1994−1996. At 25°C, when fed on cumbungi ( Typha sp.) pollen, the life cycle was completed in approximately 7 days, with an intrinsic rate of natural increase ( r _m ) of 0.32. Female−male pairs produced a mean total of 52.7 eggs within 28 days of oviposition. Females that were deprived of males after first mating stopped laying eggs after 7−19 days; however, if another male was added, they resumed egg laying and produced, on average, a total of 49.4 eggs. The sex ratio was 2.24 females to one male. At 25°C, fecundity on a diet of thrips larvae (first-instar Frankliniella schultzei Trybom) was high, ranging from 2.72 to 3.58 eggs per day on the third day, depending on previous diet. Consumption rate of thrips was also high, with an average of 7.23−14.44 first-instar larvae eaten per day on the third day, depending again on previous diet and also on number of thrips larvae made available. The species was also observed to feed on: (i) broad mite, Polyphago­tarsonemus latus (Banks); (ii) tomato russet mite, Aculops lycopersici (Massee); and (iii) two-spotted mite, Tetranychus urticae Koch. No diapause was observed under conditions of 25°C, 8 h light and 10°C, 16 h dark. Eggs were sensitive to low humidity, with 50% failing to hatch below 70.8% relative humidity. This species is of interest as a candidate biological control agent for thrips, broad mite and tomato russet mite in protected crops.     

Biological studies of the Australian predatory mite Typhlodromalus lailae (Schicha) (Acari: Phytoseiidae)

Abstract The biology of the Australian phytoseiid mite Typhlodromalus lailae is described from material collected in Western Australia and New South Wales in 1994. At 25°C, when fed on cumbungi ( Typha sp.) pollen, the life cycle is completed in approximately 6 days, with an intrinsic rate of natural increase ( r _m ), of 0.38. Female−male pairs produced a mean total of 44.6 eggs within 22 days of oviposition, with 39% of these females living in excess of 29 days. Females that were deprived of males after first mating stopped laying eggs after 4−9 days, but if another male was added they resumed egg laying and produced close to a full complement of eggs (mean 42 eggs). At 25°C, fecundity on a diet of cumbungi pollen or thrips larvae (first-instar Frankliniella schutzei Trybom) was high, averaging 3.71 and 3.33 eggs per day, respectively, over a 3-day period. The sex ratio was approximately 1.5 females to 1 male. Consumption rate of thrips was also high, with an average of approximately seven first-instar or two second-instar F. schultzei larvae eaten per day. The species was also observed to feed on broad mite, Polyphagotarsonemus latus (Banks), and tomato russet mite, Aculops lycopersici (Massee). No diapause was observed under conditions of 25°C 8 h light and 10°C 16 h dark. Eggs were sensitive to low humidity, with 50% failing to hatch below 71.1% relative humidity. This species is of interest as a candidate biological control agent for thrips, broad mite and tomato russet mite in protected crops.     

Development time and survival of Verrallina funerea (Theobald) (Diptera: Culicidae) immatures and other brackish water mosquito species in southeast Queensland, Australia

Abstract  Verrallina funerea (Theobald) is a brackish water mosquito that is recognised as an important pest and vector in southeast Queensland, Australia. Immature development time and survival of Ve. funerea was defined in the laboratory in response to a range of temperatures (17–34°C) and salinities (0–35 parts per thousand (p.p.t)). The expression of autogeny in this species was also assessed. Salinity only had a slight effect on mean development time from hatching to adult emergence (7.0–7.4 d at salinities of 0, 17.5 and 31.5 p.p.t) and survival was uniformly high (97.5–99.0%). Mean development times were shorter at 26, 29 and 32°C (7.0, 6.8 and 6.8 d, respectively) and longest at 17°C (12.2 d). The threshold temperature ( t ) was 5.8°C and the thermal constant ( K ) was 142.9 degree-days above t . Survival to adulthood decreased from >95% (at 17–29°C) to 78% (at 32°C) and 0% (at 34°C). No expression of autogeny was observed. Immature development times of Ve. funerea , Ochlerotatus vigilax (Skuse) and Oc. procax (Skuse) were then determined under field conditions at Maroochy Shire. Following tide and rain inundation, cohorts of newly hatched larvae were monitored daily by dipping, and time until pupation was noted. Tidal inundation triggered hatching of Ve. funerea and Oc. vigilax larvae whereas Oc. procax larvae were found only after rain inundation. Estimates of Ve. funerea and Oc. vigilax field development times were similar (8–9 d) while Oc. procax development time was slightly longer (9–10 d). Based on these survey results, control activities targeting Ve. funerea must be initiated 4 d (if using Bacillus thuringiensis var. israelensis de Barjac) or 5 d (if using s -methoprene) after inundation. However, Casuarina glauca Sieber canopy and branchlets covering breeding habitats may present a problem for the penetration of such treatments.     

Influence of temperature on life-table parameters of Stethorus gilvifrons (Mulsant) (Coleoptera: Coccinellidae) fed on Tetranychus urticae Koch

The influence of temperature on life-table parameters, fecundity and survivorship of the predatory ladybird, Stethorus gilvifrons , fed on Tetranychus urticae was determined at seven constant temperatures of 15°C, 20°C, 25°C, 28°C, 30°C, 35°C and 40°C. No development was observed at 40°C, thus being regarded as the threshold for the development of S. gilvifrons . The results indicate a significant decrease in male and female longevity with increasing temperature from 15°C to 35°C. The longest and shortest longevity were 18.40 and 12.75 days for males and 17.40 and 8.80 days for females, respectively. The intrinsic rate of natural increase ( r _m ) and the net reproductive rate ( R ₀) of S. gilvifrons linearly increased with increasing temperatures from 15°C to 35°C, while the mean generation time ( T ) and doubling time (DT) decreased linearly within this temperature range. The highest values of r _m (0.240 females/female/day) and R ₀ (59.27 females/female) and the lowest mean generation time (17.01 days) and DT (2.88 days) were recorded at 35°C. The maximum (185.50 eggs) and minimum (25.50 eggs) measurement of total fecundity was also recorded at 35°C and 15°C, respectively. The results indicate that temperature greatly affected fecundity, survivorship and life-table parameters of S. gilvifrons , and that 35°C is a suitable temperature for population growth of this predator.