Developmental Threshold Temperature Research Articles

Shifting of the life cycle and life‐history traits of the fall webworm in relation to climate change

AbstractThe effects of global warming on the life cycle and life‐history traits of the fall webworm, Hyphantria cunea (Drury) (Lepidoptera: Arctiidae), were investigated in Fukui, Japan. Our previous studies showed that the Fukui population had a predominantly bivoltine life cycle, but recently the life cycle has changed. In the present study, the life‐history traits of individuals collected in 2002 in Fukui were clarified and compared to those in the previous studies. The lower threshold temperature for development and the thermal constant for one generation were 10.6 °C and 724.4 degree days, respectively. Although these developmental parameters were not investigated in the previous studies, the difference of the developmental period between the present and previous results was negligible in the larval and pupal stages at 20 °C. The critical photoperiod for diapause induction was 14 h 29 min at 20 °C and 14 h 10 min at 25 °C. The critical photoperiod at 25 °C was shortened to 14 min from that of the previous studies for individuals collected in 1995. The incidence of pupal diapause in the second generation was investigated in individuals that were collected as fourth and fifth instars in the field. Some portion of individuals averted diapause even if they were kept under a short photoperiod of L14:D10 at 25 °C after collection. These results, together with climate data and field observations in Fukui, suggest that at least a part of the population has three generations per year at present. This shift of the life cycle occurred within 7 years and is probably related to global warming in recent years.

BIOLOGY, THERMAL REQUIREMENTS, AND ESTIMATION OF THE NUMBER OF GENERATIONS OF ZAPRIONUS INDIANUS (DIPTERA: DROSOPHILIDAE) FOR THE MAIN FIG PRODUCING REGIONS OF BRAZIL

The African fig fly, Zaprionus indianus, was first recorded in fig orchards in Brazil in 1999, at the Valinhos region, in the State of São Paulo. In view of the scarcity of biological data on this insect in Brazil, the objective of this research was to study the biology, temperature requirements, and to estimate the number of Z. indianus annual generations for the main fig producing regions of Brazil, aimed at controlling the pest. The insects were reared on artificial diet at constant temperatures of 18, 20, 22, 25, 28, 30, and 32°C, relative humidity 80 ± 10%, and 14-h photophase. Duration of the development stages was variable with temperature, being longer at the lower temperatures. Temperature also influenced viability during the larval and pupal stages and the egg-adult biological cycle, with significant differences between 32°C and the other temperature conditions. The lower temperature development threshold (TT) and thermal constant (K) values for the egg, larval, and pupal stages were 9.7 and 10.5; 9.2 and 148.6, and 10.7°C and 66.25 DD, respectively, for a total thermal constant of 262.2 DD for the egg-adult biological cycle. Based on a lower temperature development threshold of 7.9°C., Z. indianus may have up to 16.6, 12.4, and 12.7 annual generations in the regions of Valinhos-SP, Pelotas-RS, and São Sebastião do Paraíso-MG, respectively, which are traditionally known as fig producing regions in the country.

보리두갈래진딧물 [Schizaphis graminum (Rondani)]의 온도발육과 발육모형

The development of Schizaphis graminum (Rondani) was studied at various constant temperatures ranging from 15 to , with RH, and a photoperiod of 16L:8D. Mortality of the stage nymphs were similar at most temperature ranges while at high temperature of , more stage individuals died. The total developmental time ranged from 13.8 days at to 4.9 days at suggesting that the higher the temperature, the faster the development. However, at higher end temperature of the development took 6.4 days. The lower developmental threshold temperature and effective accumulative temperatures for the total immature stage were and 105.9 day-degrees, respectively and the nonlinear shape of temperature related development was well described by the modified Sharpe and DeMichele model. The normalized cumulative frequency distributions of developmental period for each life stage were fitted to the three-parameter Weibull function. The attendance of shortened developmental times was apparent with nymph, and total nymph stages in descending order. The coefficient of determination ranged between 0.80 and 0.87.

Development, Survival, and Reproduction of the Predatory Mite <I>Kampimodromus aberrans</I> (Acari: Phytoseiidae) at Different Constant Temperatures

Development, survival, and reproduction of the predatory mite Kampimodromus aberrans Oudemans were studied at constant temperatures in the range from 15 to 35 degrees C under laboratory conditions. Larval developmental rate for both males and females increased gradually from 15 to 35 degrees C and decreased at higher temperatures. Lactin's nonlinear model described with adequate accuracy the relationship between developmental rate and temperature. The model predicted that lower and upper threshold temperatures for preimaginal development ranged from 9.8 to 11.8 degrees C and from 37.2 to 39.8 degrees C, respectively. The intrinsic rate of population increase (rm) at the different temperatures ranged from 0.0442 to 0.1575, with the highest value recorded at 25 degrees C. At 33 degrees C a negative rm value was estimated. The rm values determined at different temperatures were fitted to Lactin's nonlinear model, and the lower and upper threshold and the optimal temperatures for population increase were 10.5, 32.4, and 27.6 degrees C, respectively. These data indicate that K. aberrans may be better adapted to intermediate temperatures around 27 degrees C and, therefore, could be a useful biocontrol agent of spider mites during spring and early summer when such temperatures are prevalent in northern Greece. The results could also be useful in developing a population model for K. aberrans under field conditions.

Environmental change and the phenology of European aphids

AbstractAphids, because of their short generation time and low developmental threshold temperatures, are an insect group expected to respond particularly strongly to environmental changes. Forty years of standardized, daily data on the abundance of flying aphids have been brought together from countries throughout Europe, through the EU Thematic Network ‘EXAMINE’. Relationships between phenology, represented by date of first appearance in a year in a suction trap, of 29 aphid species and environmental data have been quantified using the residual maximum likelihood (REML) methodology. These relationships have been used with climate change scenario data to suggest plausible changes in aphid phenology. In general, the date of first record of aphid species in suction traps is expected to advance, the rate of advance varying with location and species, but averaging 8 days over the next 50 years. Strong relationships between aphid phenology and environmental variables have been found for many species, but they are notably weaker in species living all year on trees. Canonical variate analysis and principal coordinate analysis were used to determine ordinations of the 29 species on the basis of the presence/absence of explanatory variables in the REML models. There was strong discrimination between species with different life cycle strategies and between species feeding on herbs and trees, suggesting the possible value of trait‐based groupings in predicting responses to environmental changes.

Life Table Analysis for <I>Cactoblastis cactorum</I> Immatures and Female Adults under Five Constant Temperatures: Implications for Pest Management

Abstract The cactus moth, Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae), was reported in Florida in 1989, and it is expanding its geographical range to threaten Opuntia cactus (Cactaceae) in the southwestern United States, into Mexico, where it is an important economic crop. Laboratory life history studies were conducted at 18, 22, 26, 30, and 34°C to understand cactus moth biology and to develop strategies for control. Duration of immature stages was generally longest at 18°C, declining significantly at 22°C, and shortest at 26, 30, and 34°C. Total immature developmental time from eggs to pupae was ≈180 d at 18°C, 116 at 22°C, and ranged from 65 to 72 d at 26–34°C. Developmental rate for egg-to-pupal stages was estimated using the logistic equation, rate = 0.0165/(1 + (T/20.7093)−5.8823). Percentage survival of immatures was usually lowest at the temperature extremes tested (18 and 34°C), but they did not differ between the sexes. Estimated lower developmental threshold temperature was 13.3°C, re...

A developmental database to support insect phenology models

Insect phenology models are widely used for decision support in pest management and more recently in phytosanitary risk assessments. The development of generic and flexible modeling tools means that phenology models can be quickly created using an insect's developmental threshold temperatures and degree-day requirements. To assist scientists and field practioners in the rapid development and deployment of phenology models, an Insect Development Database containing the developmental requirements for over 500 insect species was created.

Effect of temperature on the life history of Eretmocerus sp. nr. furuhashii, a parasitoid of Bemisia tabaci

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.

Modeling Leafhopper Nymphs in Temperate Vineyards for Optimal Sampling

Abstract Cicadellids (Homoptera: Cicadellidae) are occasional pests of vineyards in temperate areas, and unchecked populations can build up to high densities to cause leaf burn followed by defoliation and yield loss. Therefore, an optimal sampling scheme would allow determination of risk at minimal cost. Because the development of leafhopper nymphs and feeding injury is closely tied to temperature, a model driven by the accumulation of degree-days was developed to predict leafhopper cumulative abundance at 5, 50, and 95% levels in vineyards. The model was based on 22 data sets collected over 7 yr in three vineyards in southern Quebec. It was based on the cumulative abundance of nymphs of the eastern grape leafhopper; the grapevine leafhopper; the threebanded leafhopper; the Virginia creeper leafhopper; and Erythroneura vitifex Fitch. The lower threshold temperature for development was 8°C. Paired t-tests and the forecasting efficiency confirmed the validity of the model. The model indicated that monitorin...

Biologia e exigências térmicas de Aedes aegypti (L.) (Diptera: Culicidae) provenientes de quatro regiões bioclimáticas da Paraíba

The present work aimed at estimating the thermal requirements for the development and the number of generations per year of Aedes aegypti (L.) under natural conditions. The life cycle of A. aegypti populations was studied at constant temperatures of 18, 22, 26, 30 and 34 degrees C, and 12 h photophase. The development period, egg viability and larval and pupal survival were evaluated daily as well as adult longevity and fecundity. The low threshold temperature of development (Tb) and the thermal constant (K) were determined. The number of generations per year in laboratory and field were also estimated. The favorable temperature to A. aegypti development is between 21 degrees C and 29 degrees C, and to longevity and fecundity is between 22 degrees C and 30 degrees C. The egg to adult basal temperature, thermal constant and the number of generations in field were, in order, 9.5, 8.5, 3.4, 7.1, 13.5 degrees C; 244.5, 273.9, 298.5, 280.9 and 161.8 degree-days; and 21.9, 23.8, 24.2, 21.1 and 22.1 generations in populations from Boqueirão, Brejo dos Santos, Campina Grande, Itaporanga and Remígio.

The effects of food and the sum of effective temperature on the embryonic development of the seahorse, Hippocampus kuda Bleeker

The effect of different food (live Acetes spp., live Mysis spp., frozen Mysis spp., and mixed food of 50% live Acetes spp. and 50% frozen Mysis spp.) on gonad development of seahorses, Hippocampus kuda Bleeker, was evaluated in this experiment. The developmental durations of testes and ovary of seahorses were significantly different among the four experimental treatments. The live Acetes spp. treatment presented the shortest developmental durations to stage V, which were 87.6 ± 3.84 days and 89.2 ± 3.71 days, respectively, for ovary and testes. The frozen Mysis spp. treatment had the longest developmental durations ( F 3,15 = 13.284, P < 0.05). The relationship between developmental duration of the ovary and gonad developmental stages could be formulated: Y 1 = 12.04 x + 24.36 ( r 2 = 0.9722, n = 16, P < 0.05). The gonadosomatic index (GSI) of parent seahorses among the four treatments differed significantly ( F 3,15 = 18.364, P < 0.05). The standard GSI of seahorses fed live Acetes spp. was 15.64 ± 1.65%, which was the highest. Feeding live food had a significant effect on the fecundity and spawning of seahorses. The fecundity and spawning number of the live Acetes spp. treatment were 598 ± 45.49 and 552 ± 49.19 individuals, respectively, which were dramatically higher than those of frozen treatment ( F 3,19 = 34.152, P < 0.05). Live food also had a similar effect on the fertilization and hatching rate during the embryonic development of seahorses ( F 3,19 = 11.386, P < 0.05). Food treatment could also induce an indirect effect on survival rate of juveniles through gonadal and embryonic development of the parents ( F 3,15 = 14.519, P < 0.05). In this experiment, the mortality within parent seahorses in the frozen Mysis spp. treatment was the highest (15.1 ± 6.55%), and the survival of juveniles was the highest in the live Acetes spp. treatment (90.4 ± 2.26% at 10 days). In conclusion, feeding live Acetes spp. significantly benefited the gonadal and embryonic development of H. kuda. The effect of temperature (22 °C, 24 °C, 26 °C, 28 °C, 30 °C and 32 °C) on the hatching time of H. kuda was also studied. We demonstrated that the higher the temperature, the shorter the hatching time, as well as the higher the hatching speed. The relationship between hatching time and temperature could be expressed: T = − 39.337 t + 677.75 ( r 2 = 0.9755, n = 30, P < 0.05). In this finding, we provided the sum of effective temperature (SET) and threshold temperature of embryonic development of H. kuda (14066.9 °C h − 1 and 13.7 °C, respectively). This new information on the effect of feeding type and culture temperature is beneficial for the commercial rearing and breeding industry of this species.

Effects of Temperature on Development ofPhormia regina(Diptera: Calliphoridae) and Use of Developmental Data in Determining Time Intervals in Forensic Entomology

Precise developmental data for forensic indicator blow fly species are essential for accuracy in the estimate of the post-mortem interval (PMI). Why, then, does the determination of the PMI result in conflicting time frames when published conspecific developmental data are used? To answer this question, we conducted constant temperature trials between the developmental minimum temperature and upper threshold temperatures (8-32°C) on the forensically important blow fly species Phormia regina (Meigen) (Diptera: Calliphoridae). Flies were reared using two designs to quantify sources of variation. We measured rearing container temperatures and internal growth chamber temperatures by using thermocouples to accurately record temperatures experienced by larvae and to construct a degree-day model. Differences in experimental design, as seen across temperature studies for this fly species, did not significantly impact larval development. We also found that using set chamber temperatures rather than rearing container temperatures altered the final degree-day model. Using any minimum threshold (including an empirically determined true minimum) other than that from linear interpolation (x-intercept) violated degree-day assumptions and invalidated estimates of the PMI. We observed the minimum developmental temperature to be higher (14°C) than that generated under the x-intercept method (5.46°C) by using data from oviposition to adult emergence. This difference along with the noted difference in accumulated degree-days (using different base temperatures) suggests a need for additional experimentation on other forensically important fly species at low temperature thresholds to help with development of curvilinear models. Former and current estimates of the PMI may be inaccurate if the process to determine the time frame ignored degree-day model assumptions or was based upon questionable data sets.

Effects of Temperature on Development of &lt;I&gt;Phormia regina&lt;/I&gt; (Diptera: Calliphoridae) and Use of Developmental Data in Determining Time Intervals in Forensic Entomology

Precise developmental data for forensic indicator blow fly species are essential for accuracy in the estimate of the post-mortem interval (PMI). Why, then, does the determination of the PMI result in conflicting time frames when published conspecific developmental data are used? To answer this question, we conducted constant temperature trials between the developmental minimum temperature and upper threshold temperatures (8-32 degrees C) on the forensically important blow fly species Phormia regina (Meigen) (Diptera: Calliphoridae). Flies were reared using two designs to quantify sources of variation. We measured rearing container temperatures and internal growth chamber temperatures by using thermocouples to accurately record temperatures experienced by larvae and to construct a degree-day model. Differences in experimental design, as seen across temperature studies for this fly species, did not significantly impact larval development. We also found that using set chamber temperatures rather than rearing container temperatures altered the final degree-day model. Using any minimum threshold (including an empirically determined true minimum) other than that from linear interpolation (x-intercept) violated degree-day assumptions and invalidated estimates of the PMI. We observed the minimum developmental temperature to be higher (14 degrees C) than that generated under the x-intercept method (5.46 degrees C) by using data from oviposition to adult emergence. This difference along with the noted difference in accumulated degree-days (using different base temperatures) suggests a need for additional experimentation on other forensically important fly species at low temperature thresholds to help with development of curvilinear models. Former and current estimates of the PMI may be inaccurate if the process to determine the time frame ignored degree-day model assumptions or was based upon questionable data sets.

Development and Reproduction of the Egg Parasitoid, &lt;I&gt;Gonatocerus ashmeadi&lt;/I&gt; Girault (Hymenoptera: Mymaridae), as a Function of Temperature

The development, fecundity, and life table parameters of Gonatocerus ashmeadi Girault, an egg parasitoid of the glassy-winged sharpshooter, Homalodisca coagulata (Say), were studied in the laboratory at six constant temperatures between 12 and 32°C. At 12°C, the parasitoid failed to develop beyond the third instar, and durations of the egg stage and the first and second instars were prolonged. Development from the egg stage to adult emergence varied from 27.1 d at 16°C to 9.5 d at 28°C. Temperature thresholds for development ranged from 3.8°C for first-instar larvae to 12.8°C for the pupal stage. The thermal constants were lowest for the second-instar larvae (26.7 DD) and highest for the pupae (75.4 DD). Nearly 207 DD were required above the lower temperature threshold of 8.5°C to complete development from egg to adult. The optimum temperature for egg to adult development was 29.2°C. Survival from egg to adult was 67.4% at 16°C and ranged from 83.4 to 86.7% between 20 and 32°C. At 16–32°C, the population had a type I survivorship pattern. At 16°C, longevity of adult females and males averaged 27.1 and 19.0 d, respectively, but declined to 6.4 and 6.9 d at 32°C. At 20–32°C, peak adult emergence occurred on the first day of emergence, but at 16°C, it was greatest on the second day. When exposed to temperatures ranging from 16 to 32°C, the female:male sex ratio was similar, ranging from 3.4 to 5.6. Lifetime fecundity was greatest at 24°C and lowest at 32°C, with the maximum net reproduction also occurring at 24°C. Greatest intrinsic and finite rates of increase, shortest population doubling time, and mean generation time occurred when G. ashmeadi was held at 28°C. The parameters defined in this study can influence geographical distribution and are important for the mass-rearing this wasp as biological control agent for the glassy-winged sharpshooter.

Physiological and morphological development of Anagyrus ananatis at constant temperatures

The lower developmental temperature threshold (T0) and the Degree Days (DD) required for the encyrtid endoparasitoid Anagyrus ananatis Gahan to develop from egg to adult on the pink pineapple mealybug (PPM), Dysmicoccus brevipes (Cockerell) (Hemiptera: Pseudococcidae), were determined. The T0 was estimated to be about 12.65 °C for both females and males. In contrast, females and males required about 275 and 265 DD, respectively, to complete development from egg to adult. Temperatures from 19 to 29 °C were optimal for mass rearing of A. ananatis, with the optimal temperature being around 24 °C. At this temperature, A. ananatis could complete almost two generations in the time it takes PPM to complete only one generation. Although A. ananatis is a koinobiont, the mealybug host was killed within a few (6–8) days after parasitization. The developmental stages of A. ananatis were described (e.g., appearance, size, color) and their time periods quantified when reared on PPM at 23.5 ± 0.5°C. Encyrtiform eggs were inserted through the dorsal surface of the PPM and were attached to the host via a slender stalk. This immature parasitoid remained attached to the host cuticle via the stalk until entering the prepupal stage. The host mealybug mummified during the parasitoid’s prepupal stage. First adult eclosion occurred at 24 days post-parasitization.

The effect of temperature on the development of Angiostrongylus cantonensis (Chen 1935) in Pomacea canaliculata (Lamarck 1822)

Angiostrongyliasis cantonensis, clinically presented as eosinophilic meningitis, is a snail-borne parasitic disease. We studied the effects of different temperatures on the larval development of Angiostrongylus cantonensis in the freshwater snail Pomacea canaliculata. Six groups of snails were infected and each group was cultured under different temperature conditions. At predefined intervals, four snails from each group were dissected to examine the larval development. The development-time curve of each group was drawn according to the fraction of third-stage larvae present. The developmental time was defined as the time needed until 50% of the first-stage larvae developed into third-stage larvae. A linear regression model was established based on the time (D; in days) and the corresponding temperature (T; in degrees Celsius): DT = 15.04 x D + 262.53. The threshold temperature for larval development was 15.04 degrees C and the thermal constant was 262.53 degree-days. These parameters could be helpful in estimating the number of parasite generations in a year and the impact of climate change on the distribution of A. cantonensis.

Life-history parameters and population dynamics of Ericaphis fimbriata (Hemiptera: Aphididae) on blueberry, Vaccinium corymbosum

AbstractDevelopment rate and age-specific fecundity and survival of Ericaphis fimbriata (Richards) virginoparae were determined during the spring on young leaves of blueberry, Vaccinium corymbosum L., as functions of temperature. The same traits were measured during the summer and the autumn on both young and mature leaves at 21.2 °C. The temperature threshold for development was 4.1 ± 0.5 °C (SE). For apterae, development time from birth to adult was 157.7 ± 5.9 day-degrees (dd). Proportional lengths of instars I–IV were 0.16, 0.14, 0.34, and 0.36, respectively. Adult life was 434.5 ± 17.5 dd and proportional lengths of the pre-reproductive, reproductive, and post-reproductive periods were 0.05, 0.74, and 0.21, respectively. Mean fecundity was 23.6 ± 1.0 nymphs per female. Mean survival was 602.9 ± 14.6 dd, and more than 80% of apterae survived the peak reproductive period. Alate fecundity was 16.5 ± 3.2 nymphs per female and alate survival was 460.9 ± 47.5 dd. Leaf type and season of measurement had significant effects on development time and fecundity: development time was 158.2 dd (+4.9 upper asymmetric SE) on young V. corymbosum ‘Duke’ leaves in the spring but 312.4 dd (–16.9 lower asymmetric SE) on mature ‘Bluecrop’ leaves, the dominant leaf type, from a commercial field in the summer. Fecundity for the respective leaf types and seasons was 16.7 (–1.6) and 1.4 (+0.5) nymphs per female. From summer to autumn, development time increased on young ‘Duke’ and ‘Bluecrop’ leaves but decreased on mature ‘Bluecrop’ leaves; fecundity decreased on young ‘Duke’ and ‘Bluecrop’ leaves but remained at low levels on mature ‘Bluecrop’ leaves. A simulation model showed that seasonal changes in development time and fecundity were capable of reducing population growth rates to near zero depending on aphid distribution with respect to young and mature leaves. The results support a combined bottom-up and top-down view of aphid population regulation and suggest that control efforts should focus on the spring, when the population growth rate is maximal.

Development and survival of the cheese mites, Acarus farris and Tyrophagus neiswanderi (Acari: Acaridae), at constant temperatures and 90% relative humidity

Two species of acarid mites, Acarus farris and Tyrophagus neiswanderi, have been identified infesting Cabrales cheese in an Asturian maturing cave, the former being the prevalent species. The developmental rate and survival of immature stages of these mites were examined at constant temperatures, ranging from 7 to 29.7 °C for A. farris, and 10 to 31 °C for T. neiswanderi, and a relative humidity (r.h.) of 90±5%. The larval stage of A. farris was particularly susceptible to low and high temperatures with 81.7% and 95.2% mortality at 7 and 29.7 °C, respectively. Tyrophagus neiswanderi larvae also showed the greatest mortality at extreme temperatures among immature stages, though at a lower level than for A. farris (8.6% and 25.6% at 10 and 31 °C, respectively). The optimal temperature for development appeared to be 27–28 °C for both species and the developmental rates were higher for A. farris than T. neiswanderi within the range of the cooler temperatures prevalent in the cheese-maturing caves. The nonlinear Logan type-III model provided the best fit for the relationship between developmental rates and temperature ( R a 2>0.99) for all immature stages of A. farris, whereas the development of T. neiswanderi was better described by the Lactin model ( R a 2>0.97). The lower and upper developmental threshold temperatures predicted for each stage of A. farris were 3–4 °C lower than those predicted for T. neiswanderi. The differential temperature-development rate for each species might explain the greater abundance of A. farris compared to T. neiswanderi. Furthermore, manipulation of temperature based on modeling predictions may well be used to control mite populations during the cheese maturing process.

Developmental parameters and voltinism of the painted apple moth, Teia anartoides Walker (Lepidoptera: Lymantriidae) in New Zealand

Key developmental parameters, including the lower threshold temperature for development and thermal accumulation requirements, of T. anartoides reared on an artificial diet were determined. The median number of days required to complete development was measured for each life stage at constant mean temperatures of 6.7, 10.2, 12.6, 17.7, 21.9, 22.5 and 30°C. Rate of development was a linear function of temperature over a range that can be realistically expected in New Zealand, and minimum rates of development were estimated by extrapolation. Eggs failed to emerge at temperatures below 10.2°C. Some neonate larvae survived for 60 days at 6.7°C, but failed to develop. At higher temperatures, larvae usually developed through 4 and 5 instars to males and females respectively, with generation developmental times of 71 and 76 days at 17.7°C, and 33 and 34 days at 30°C (for males and females respectively). Optimum temperatures for development lay between 17.7 and 22.5°C. Female developmental requirements above a base temperature of 9.6°C were 616 day-degrees per generation, consisting of 119 day-degrees for egg hatch plus 497 day-degrees for larval and pupal development. Historical weather data from sites around New Zealand suggest that T. anartoides might develop through 1.4 generations/year in the south of the South Island and 4 generations/year in the north of the North Island. The data indicate that the moth might realistically establish at any coastal site around New Zealand, and vary from uni-voltine in the south to tri-voltine in the north, depending on a number of factors including host plant.

Comparative studies on populations of Pauesia juniperorum (Hymenoptera: Braconidae), a biological control agent for Cinara cupressivora (Hemiptera: Aphididae)

Pauesia juniperorum (Starý), a solitary endoparasitoid which attacks several Cinara spp. in the subgenus Cupressobium, was introduced into Africa for the control of the cypress aphid Cinara cupressivora Watson & Voegtlin (previously identified as Cinara cupressi (Buckton)) and is now established. Data on its biology including a comparison of populations from different hosts and geographical locations are presented. From the UK this consisted of populations reared from Cinara cupressivora, Cinara fresai Blanchard and Cinara juniperi De Geer, and from France, Cinara ?fresai. Between different populations, the duration of development varied within a narrow range (15.5-18.1 days) at 22 degrees C. Data on duration of development over a range of temperatures (15-26 degrees C) for two populations, from the UK and France ranged between 14.0-31.4 days for males and 14.7-32.8 days for females. The threshold temperature for development was 6.2 degrees C and 4.1 degrees C for the populations from the UK and France, respectively. The mean egg load for different populations ranged between 46.4 and 78.5 eggs. The host species had a significant effect on egg load which was directly related to size of the respective host aphids. The lowest egg load was recorded on specimens reared from C. cupressivora which was the smallest aphid. The population from the UK had a higher intrinsic rate of increase (0.232) than the one from France (0.207).