Developmental rate estimation and life table analysis for Halyomorpha halys (Hemiptera: Pentatomidae)

Egg and nymphal development were studied under constant temperatures for the newly introduced pest species, Halyomorpha halys (St?l) (Hemiptera: Pentatomidae). Development was assessed at seven constant temperatures (15-35 degrees C). Development to adult was completed at temperatures between 17 and 33 degrees C, with egg hatch also occurring at 15 degrees C. The relationship between temperature and developmental rate was evaluated using three developmental models. Of the models evaluated, the Briere-1 model was the best fit for the empirical data of egg and total development and for providing accurate values for the temperature threshold. Application of the linear degree-day model estimated 537.63 DD are needed for total development (egg to imaginal ecdysis). An additional 147.65 DD are needed for the preoviposition period of the female. Reproductive parameters were evaluated at 25 degrees C and indicate a median number of 28 eggs per egg mass. Oviposition occurred at 4.32-d intervals, and a female can continue to oviposit throughout its lifespan. H. halys is univoltine in New Jersey and Pennsylvania, but if it spreads to warmer climates in the United States, it could have multiple generations per year.     

Developmental times and age-specific life tables for Lygus lineolaris (Heteroptera: Miridae), reared at multiple constant temperatures

Developmental times and survivorship of tarnished plant bug nymphs, Lygus lineolaris (Palisot de Beauvois), and longevity and reproduction of adult tarnished plant bug adults reared on green beans were studied at multiple constant temperatures. The developmental time for each life stage and the total time from egg to adult decreased with increasing temperature. Eggs required the longest time to develop followed by fifth instars and then first-instars. Total developmental time from egg to adult was shortest at 32°C, requiring 18.0 ± 0.3 d and 416.7 ± 31.3 DD above 7.9°C, the estimated minimum temperature for development from egg to adult. Sex did not affect total developmental times and did not affect median survival time. Adults lived significantly fewer days at high temperatures (30-32°C: 17-19 d) compared with temperatures below 30°C (range: 24.5-39.4 d) and the number of eggs laid per day increased from ≈ 4 at 18°C to a maximum of 9.5 eggs per day at 30°C. Total egg production over the lifetime of female tarnished plant bugs increased with temperature reaching a maximum of 175 eggs on average at 27°C, total egg production declined at temperatures above 27°C (30°C: 110.8, 32°C: 77.3 eggs per female). The highest net reproductive rate 74.5 (R(0)) was obtained from insects maintained at 27°C. The intrinsic rate of natural increase (r(m)) increased linearly with temperature to a maximum value of 0.1852 at 30°C, and then decreased at 32°C. Generation and doubling times of the population were shortest at 30°C, 21.0 and 3.7 d, respectively.     

环境因子对真水狼蛛胚胎发育的影响

研究了温度、相对湿度和光照时间对真水狼蛛（Pirata piraticus）胚胎发育的影响。结果表明,温度不仅影响真水狼蛛胚胎发育的全过程,也对胚胎发育的各阶段有影响,在20℃-35℃范围内,随着温度的升高,胚胎发育加快,卵的发育起点温度为11.9℃,低温下,卵的孵化整齐度高温下要高,28℃时,孵化率最高。为探讨真水狼蛛胚胎发育的影响因子和合适条件,考虑温度、相对湿度和光照时间3个因子的综合作用,按照二次正交旋转组合设计的要求安排实验,得出了影响胚胎发育历期、胚胎成形率和孵化率的二次回归模型,并分析了其影响因子,利用孵化率的回归模型,得到了真水狼蛛卵孵化的最优条件为温度为27℃-28.5℃,相对湿度为94％－97％,光照时间为14－17h。     

The relationship of egg size and incubation temperature to embryonic development time in univoltine and multivoltine aquatic insects

1. We used published data to investigate the combined influence of egg size and incubation temperature on embryonic development time for a broad assortment of aquatic insects at four different incubation temperatures (10, 15, 20 and 25 °C).
2. Embryonic development time (EDT) was positively correlated with egg size at each of the four temperatures, but with different relationships for univoltine and multivoltine aquatic insects. The relationships of embryonic development time to egg size expressed in degree-days did not significantly differ in slope ( P >0.50) or intercept ( P >0.05) for either univoltine or multivoltine aquatic insects at each of the four temperatures.
3. The relationship of embryonic development time (degree-days) to egg mass in multivoltine aquatic insects (EDT=885×0.19, P <0.0001, r 2=0.48) is similar in slope and intercept to that for other oviparous animals (i.e., zooplankton, fish, amphibians and reptiles), and to the relationship of embryonic development time to neonate mass in mammals. Univoltine species on average require 3–5 times longer to develop (EDT=14190×0.29, P <0.001, r 2=0.29) than most other animals of equivalent egg mass, but the relationship of embryonic development time to egg mass is similar in slope to that of most other animals. Together, these relationships provide a basis for evaluating differences in embryonic development time among aquatic insects.     

Egg Development in the Stonefly Pteronarcys californica Newport (Plecoptera: Pteronarcyidae)

Eggs of Pteronarcys californica Newport were incubated at fixed temperatures between 5 and 20°C in the laboratory and at field temperatures in the Crowsnest River, Alberta. The regression of rate of development on temperature between 5–15°C gave a developmental zero of 3.125°C. Within the range 10–20°C, highest hatching success and fewest days to median hatch occurred at 15.0 or 17.5°C, but physiological time (day-degrees) for egg hatching increased with temperature throughout, markedly so above 15°C. A minimum of 182 days was required for 50% hatch in the laboratory, with no observable development for approximately 80 days. Eggs placed in the river on 25 May 1993 started to hatch on 17 October 1993, and the pulse of larval recruitment in the field population occurred between April and August, 11 to 15 months after oviposition. Eggs hatched over periods of 130–322 days at different temperatures in the laboratory, and over an 11-month period in the field. The placement of diapause early in embryonic development is suggested as a cause of extended recruitment. The variety of embryonic development in Plecoptera is briefly reviewed.     

Development of Heterodera glycines Life Stages as Influenced by Temperature

The effects of temperature on rates of development of Heterodera glycines egg and juvenile stages were examined as a basis for predicting generation times of the nematode on soybean. The relationship of temperature to H. glycines embryonic development between 15 and 30 C was described by a linear model, The calculated basal temperature threshold was 5 C. Thermal optimum for embryogenesis and hatch with low mortality was 24 C. Development proceeded to first-stage juvenile at 10 C and to second-stage juvenile at 15-30 C. Hatch occurred at 20-30 C. At 36 C, development proceeded to the four-cell stage, then the eggs died. The range of diurnal soil temperature fluctuation and accumulated degree-days between 5 and 30 C (DD5/30) had an impact on rate of development of juveniles in soybean roots. From early June to early July, H. glycines required 534 + 24 DD5/30 (4 weeks) to complete a life cycle in the field. During the midseason (July and August), life cycles were completed in 3 weeks and 429 ± 24 DD5/30 were accumulated. Late in the season (September to November), declining soil temperatures were associated with generation times of 4 weeks and slower rates of development.     

Embryonic Developmental Temperatures Modulate Thermal Acclimation of Performance Curves in Tadpoles of the Frog Limnodynastes peronii

Performance curves of physiological rates are not fixed, and determining the extent to which thermal performance curves can change in response to environmental signals is essential to understand the effect of climate variability on populations. The aim of this study was to determine whether and how temperatures experienced during early embryonic development affect thermal performance curves of later life history stages in the frog Limnodynastes peronii. We tested the hypotheses that a) the embryonic environment affects mean trait values only; b) temperature at which performance of tadpoles is maximal shifts with egg incubation temperatures so that performance is maximised at the incubation temperatures, and c) incubation temperatures modulate the capacity for reversible acclimation in tadpoles. Growth rates were greater in warm (25°C) compared to cold (15°C) acclimated (6 weeks) tadpoles regardless of egg developmental temperatures (15°C or 25°C, representing seasonal means). The breadth of the performance curve of burst locomotor performance (measured at 10, 15, 20, 25, and 30°C, representing annual range) is greatest when egg developmental and acclimation temperatures coincide. The mode of the performance curves shifted with acclimation conditions and maximum performance was always at higher temperatures than acclimation conditions. Performance curves of glycolytic (lactate dehydrogenase activities) and mitochondrial (citrate synthase and cytochrome c oxidase) enzymes were modulated by interactions between egg incubation and acclimation temperatures. Lactate dehydrogenase activity paralleled patterns seen in burst locomotor performance, but oxygen consumption rates and mitochondrial enzyme activities did not mirror growth or locomotor performance. We show that embryonic developmental conditions can modulate performance curves of later life-history stages, thereby conferring flexibilty to respond to environmental conditions later in life.     

Influence of temperature and photoperiod on embryonic development in the dragonfly Sympetrum striolatum (Odonata: Libellulidae)

Temperature and photoperiod play major roles in insect ecology. Many insect species have fixed degree‐days for embryogenesis, with minimum and maximum temperature thresholds for egg and larval development and hatching. Often, photoperiodic changes trigger the transfer into the next life‐cycle stadium. However, it is not known whether this distinct pattern also exist in a species with a high level of phenotypic plasticity in life‐history traits. In the present study, eggs of the dragonfly Sympetrum striolatum Charpentier (Odonata: Libellulidae) are reared under different constant and fluctuating temperatures and photoperiodic conditions in several laboratory and field experiments. In general, and as expected, higher temperatures cause faster egg development. However, no general temperature or light‐days for eyespot development and hatching are found. The minimum temperature thresholds are distinguished for survival (2 °C), embryogenesis (6 °C) and larval hatching (above 6 °C). Low winter temperatures synchronize hatching. Above 36 °C, no eyespots are visible and no larvae hatch. In laboratory experiments, light is neither necessary for eyespot development, nor for hatching. By contrast to the laboratory experiments, the field experiment show that naturally changing temperature and photoperiod play a significant role in the seasonal regulation of embryonic development. The post‐eyespot development is more variable and influenced by temperature and photoperiod than the pre‐eyespot development. This developmental plasticity at the end of the embryogenesis might be a general pattern in the Libellulidae, helping them to cope with variation in environmental conditions.     

Parental identity influences progeny responses to incubation thermal stress in sockeye salmon Onchorhynchus nerka

The influence of individual parentage on progeny responses to early developmental temperature stress was examined in a cross-fertilization experiment using sockeye salmon Oncorhynchus nerka. Differences in survival, hatch timing and size were examined among five paternally linked and five maternally linked offspring families (Weaver Creek population, British Columbia, Canada) incubated at 12, 14 and 16° C from just after fertilization to hatch. Mean embryonic survival was significantly lower at 14 and 16° C; however, offspring families had substantially different survival responses across the thermal gradient (crossing reaction norms). Within temperature treatments, substantial variation in embryonic survival, alevin mass, time-to-hatch and hatch duration were attributable to family identity; however, most traits were governed by significant temperature-family interactions. For embryonic survival, large differences between families at 16° C were due to both female and male spawner influence, whereas inter-family differences were obscured at 14° C (high intra-family variation), and minimal at 12° C (only maternal influence detected). Despite post-hatch rearing under a common cool thermal regime, persistent effects of both temperature and parentage were detected in alevin and 3 week-old fry. Collectively, these findings highlight the crucial role that parental influences on offspring may have in shaping future selection within salmonid populations exposed to elevated thermal regimes. An increased understanding of parental and temperature influences and their persistence in early development will be essential to developing a more comprehensive view of population spawning success and determining the adaptive capacity of O. nerka populations in the face of environmental change.     

Embryonic developmental patterns and energy expenditure are affected by incubation temperature in wood ducks (Aix sponsa)

Recent research in birds has demonstrated that incubation temperature influences a suite of traits important for hatchling development and survival. We explored a possible mechanism for the effects on hatchling quality by determining whether incubation temperature influences embryonic energy expenditure of wood ducks (Aix sponsa). Because avian embryos are ectothermic, we hypothesized that eggs incubated at higher temperatures would have greater energy expenditure at any given day of incubation. However, because eggs incubated at lower temperatures take longer to hatch than embryos incubated at higher temperatures, we hypothesized that the former would expend more energy during incubation. We incubated eggs at three temperatures (35.0°, 35.9°, and 37.0°C) that fall within the range of temperatures of naturally incubated wood duck nests. We then measured the respiration of embryos every 3 d during incubation, immediately after ducks externally pipped, and immediately after hatching. As predicted, embryos incubated at the highest temperature had the highest metabolic rates on most days of incubation, and they exhibited faster rates of development. Yet, because of greater energy expended during the hatching process, embryos incubated at the lowest temperature expended 20%-37% more energy during incubation than did embryos incubated at the higher temperatures. Slower developmental rates and greater embryonic energy expenditure of embryos incubated at the lowest temperature could contribute to their poor physiological performance as ducklings compared with ducklings that hatch from eggs incubated at higher temperatures.     

Effects of temperature during early life history on embryonic and larval development and growth in haddock

The effect of incubation temperature (2, 4, 6, 8 and 10° C) on haddock Melanogrammus aeglefinus development and growth during the embryonic period and in subsequent ontogeny in a common post‐hatch thermal environment (6° C) was investigated. Hatching times were inversely proportional to incubation temperature and ranged from 20·3 days at 2° C to 9·1 days at 10° C. Growth rates were directly proportional to incubation temperature during both the embryonic and larval periods. There was a significant decline in growth rates following hatch in all temperature groups. Compared to the endogenously feeding embryos, growth rates in the exogenous period declined by 4·4‐fold at 4° C to 3·9‐fold at 8° C, indicative of the demarcation between the endogenous and exogenous feeding periods. Yolk utilization varied from 17 days at 2° C to 6 days at 10° C and followed a three‐stage sigmoidal pattern with the initial lag period inversely proportional to incubation temperature. Time to 50% yolk depletion varied inversely with temperature but occurred 1–1·5 days post‐hatch at all temperatures. Additionally, the period between 10 and 90% yolk depletion also decreased with increased temperature. Overall developmental rate was sequential with and directly proportional (2·3‐fold increase) to incubation temperature while the time spent in each developmental stage was inversely proportional to temperature. Larger embryos tended to be produced at lower temperatures but this pattern reversed following hatch, as larvae from higher temperature groups grew more rapidly than those from other temperature groups. Larvae from all temperatures achieved a similar length (c.total length 4·5 mm) upon complete yolk absorption. The study demonstrated the significant impact that temperature has upon developmental and growth rates in both endogenous and exogenous feeding periods. It also illustrated that temperature changes during embryogenesis had significant and persistent effects on growth in subsequent ontogeny.     

Reptilian viviparity in cold climates: testing the assumptions of an evolutionary hypothesis

Viviparity (live-bearing) in reptiles often is interpreted as an adaptation to cold climates. This hypothesis relies on (i) body temperatures of gravid females being higher than soil (nest) temperatures; (ii) embryonic development being accelerated by this temperature difference; and (iii) survivorship of hatchlings being increased if eggs hatch before the advent of cold weather in autumn. I gathered data to test these assumptions, using eight species of scincid lizards in a high-elevation area of southeastern Australia. Due to behavioural thermoregulation, body temperatures of gravid lizards average ca. 7°C higher than soil (nest) temperatures. Oviparous female lizards retain eggs in utero for ca. 50% of development. Laboratory studies show that a temperature increase from 17°C (mean nest temperature) to 24°C (mean lizard temperature) reduces incubation periods of eggs by >40 days in heliothermic species, and <20 days in a thigmothermic species. In the field, soil temperatures drop to lethally low levels shortly after the usual time of hatching. Simple calculations show that without the acceleration of development caused by uterine retention, eggs could not hatch prior to the onset of these low temperatures in the field. These results support the major assumptions of the “cold climate hypothesis” for the evolution of reptilian viviparity.     

Temperature-related development and population parameters for Typhlodromus pyri (Acari: Phytoseiidae) found in Oregon vineyards

The beneficial mite Typhlodromus pyri is a key predator of grapevine rust mite Calepitrimerus vitis in Pacific coastal vineyards. Rust mite feeding has been associated with damage such as stunted, deformed shoot growth and reductions in fruit yield. The life history traits of T. pyri were assessed at seven constant temperatures (12.5, 15, 17.5, 20, 25, 30 and 35 °C) to determine population parameters providing data to better predict biological control of C. vitis populations by T. pyri in vineyards. Successful development from the egg to adult stage was observed at temperatures ranging from 15 to 30 °C. Constant exposure to 12.5 and 35 °C resulted in 100 % mortality in immature T. pyri. Developmental times, fecundity and longevity were highest at 25 °C. The estimated minimum and maximum developmental thresholds were 7.24 and 42.56 °C, respectively. Intrinsic rate of increase (r ( m )) was positive from 15 to 30 °C indicating population growth within this range of temperatures. Net reproductive rate and intrinsic rate of increase were greatest at 25 °C. These developmental parameters can be used to estimate population growth, determine seasonal phenology and aid in conservation management of T. pyri. Results presented in this study will aid in evaluating the effectiveness of T. pyri as a key biological control agent of C. vitis during different periods of the growing season in Pacific Northwest vineyards.     

Temperature-dependent development and demography of Scymnus subvillosus (Coleoptera: Coccinellidae) reared on Hyalopterus pruni (Homoptera: Aphididae)

The development, survival, and fecundity of Scymnus subvillosus (Goeze) (Coleoptera: Coccinellidae) were studied at 20, 25, 30, and 35 degrees C, 60 +/- 5% RH, and a photoperiod of 16:8 (L:D) h (5,000 lux) under laboratory conditions. The total developmental time from egg hatch to adult eclosion ranged from 22.6 d at 20 degrees C to 10.6 d at 35 degrees C. The developmental rates of the egg stage, the larval stage, and total preadult stage at different temperatures increased linearly with increasing temperature. The thermal summation of the egg stage, the larval stage, and the total preadult stage was 77.5, 145.8 and 300 degree-days (DD), respectively. The developmental threshold of the egg stage, the larval stage, and the total preadult stage was 7.4, 4.1, and 7.1 degrees C, respectively. The life history raw data were analyzed using the age-stage, two-sex life table. The intrinsic rate of increase was 0.0845, 0.1138, 0.1395, and 0.0668 d(-1) at 20, 25, 30, and 35 degrees C, respectively. The net reproductive rate was highest at 25 degrees C (R0 = 78.7), and lowest at 35 degrees C (R0 = 4.7). The mean generation time was shortest at 35 degrees C (T = 23.9 d). The life table data can be used for the projection of population growth and designing mass rearing programs.     

Development of soybean aphid (Homoptera: Aphididae) on its primary overwintering host, Rhamnus cathartica

Thermally dependent development of soybean aphid (Aphis glycines Matsumura) and common buckthorn (Rhamnus cathartica L.) were examined in growth chambers in spring 2005. Models based on ambient air temperatures for all development events were developed. Adjusted models were developed to account for heat units acquired because of solar radiation. These models were tested at field sites in Guelph and Ridgetown, Ontario, Canada. It was found that egg hatch of aphids and bud swell of buckthorn coincided at low temperatures in growth chambers and in the field. Development thresholds of 9 and 10 degrees C were acquired for bud swell and egg hatch, respectively. Models based on ambient air temperatures were poor predictors of bud swell and egg hatch in the field, but models adjusted for solar radiation predicted these events just 1-4 d before they were observed at both sites. The results obtained have broad application for predicting aphid hatch on a regional basis.     

Experiments on the effects of food and density on voltinism in a stream-dwelling water strider (Aquarius remigis)

1. The stream water strider Aquarius remigis shows a latitudinal pattern of variation in voltinism. In general, populations with shorter growing seasons (e.g. in eastern Canada) tend to be univoltine (animals that reach adulthood in the summer overwinter before reproducing in the following spring), whereas populations with somewhat longer growing seasons (e.g. in the north-eastern United States) tend to be bivoltine. 2. This pattern was broken at our study site in the south-eastern United States (Kentucky) where A. remigis had a long growing season, but was almost always univoltine. In summer 1993, however, adult A. remigis in central Kentucky displayed a bivoltine reproductive cycle; i.e. individuals in some pools began breeding shortly after maturing to the adult stage. 3. A field survey documented a negative relationship between local water strider density and reproductive activity in prediapause adults. A laboratory experiment manipulating food availability and density, revealed that animals held at low density with high food levels displayed greater mating activity and egg production than did their counterparts at higher density or lower food levels. 4. A laboratory experiment also showed that high water strider density resulted in a greater frequency of very short pair durations (< 10 min). 5. Although the observed effects of density and food availability on mating activity of prediapause adults seem intuitively reasonable, they differ from the patterns observed in overwintered adults. The difference in reproduction patterns might be due to differences in selective pressures on prediapause vs. post-diapause adults.     

荔枝蒂蛀虫幼虫龄数及各发育阶段在不同温度下的发育历期

【目的】荔枝蒂蛀虫 Conopomorpha sinensis Bradley是荔枝龙眼上的主要害虫,以幼虫蛀果为害。本研究旨在明确荔枝蒂蛀虫幼虫龄数及不同温度下各虫态和各龄幼虫的发育历期,为该虫发生规律、预测预报和防控技术研究提供基础生物学数据。【方法】定期收集处于不同发育时期的荔枝蒂蛀虫幼虫,测量幼虫头壳宽度,对其进行频次分析,Crosby指数验证和曲线回归分析,以确定幼虫龄数。通过室内群体饲养的方法,测定了17~38℃区间8个温度梯度下荔枝蒂蛀虫各虫态和各龄幼虫的发育历期,并采用线性日度模型对其发育速率与温度的关系进行回归分析。【结果】根据荔枝蒂蛀虫幼虫头壳宽度频次分布图,其头壳宽度的频次分布可明显分为5个区域,说明其幼虫分5个龄期,符合Dyar定律。1-5龄幼虫的头壳宽度分别为：0.092~0.120, 0.140~0.206, 0.217~0.319, 0.356~0.523和0.582~0.728 mm。温度对荔枝蒂蛀虫卵、各龄幼虫和蛹的发育历期有明显影响,其发育历期均随温度的升高而缩短,其发育速率均与温度呈显著正相关,并符合线性回归模型。在20~32℃,荔枝蒂蛀虫可完成世代发育;在17℃时,该虫只能发育至3龄幼虫;在35℃时,蛹多不能羽化;在38℃时,卵多不能孵化。在20~32℃,其世代历期为41.16~19.34 d,蛹期为12.74~5.38 d,而产卵前期为4.75~4.22 d,温度对产卵前期无明显影响。在20~35℃,荔枝蒂蛀虫幼虫可正常发育,其1龄幼虫龄期为4.50~1.17 d,2龄幼虫期为2.09~1.40 d,3龄幼虫期为2.84~1.00 d,4龄幼虫期为3.41~1.18 d,5龄幼虫期为3.00~1.37 d,预蛹期为2.41~0.69 d。在17~35℃,荔枝蒂蛀虫卵可正常孵化,其卵期为7.73~2.09 d。【结论】荔枝蒂蛀虫幼虫分5个龄期,不同于前人所报道的4个龄期。在20~32℃温度范围内,卵、各龄幼虫和蛹的发育历期均随温度升高而缩短。本研究结果有助于荔枝蒂蛀虫预测预报方案的制定和实施。     

Seasonal variation in embryonic diapause of the striped ground cricket, Allonemobius fasciatus

ABSTRACT. The incidence and intensity of embryonic diapause in the striped ground cricket, Allonemobius fasciatus DeGeer (Gryllidae), is influenced by the date of oviposition and the incubation temperature. At 20C, embryos develop normally until the end of the appendage-formation stage when diapause occurs. The intensity of 'winter' diapause at this stage is greatest in eggs laid early in the season. Incubation at higher temperature induces a different and earlier 'summer' diapause. The higher the temperature the earlier the stage at which this developmental suppression is imposed. At 27 and 30C, some individuals develop without any interruption and hatch within 20 days. The proportion of these fast-developing eggs is low in summer but increases towards the end of the laying season. In nature, this species is univoltine and precocious hatching before winter is unlikely.
When embryos diapausing at an early stage at 27C are transferred to low temperatures, they resume development and enter winter diapause. The time required to reach the winter-diapause stage after transfer is inversely related to the temperature (30-30C). At 30C, sunmer diapause is neither induced nor maintained.     

A comparative study on effects of normal versus elevated temperatures during preimaginal and young adult period on body weight and fat body content of mature Coccinella septempunctata and Harmonia axyridis (Coleoptera: Coccinellidae)

Two climate chamber experiments were performed to simulate the effects of global warming on life table parameters of coccinellids. We investigated the effects of two daily temperature profiles during preimaginal development (larval and pupal) and the young adult period (first 10 d) on body weight and fat body content of adult Coccinella septempunctata L. and Harmonia axyridis (Pallas) fed English grain aphids [Sitobion avenae (F.)] ad libitum: 1) normal, i.e., current daily temperatures in central Europe (T0: mean, 17.8°C; maximum, 21.8°C; minimum, 13.4°C) and 2) increased by 3K (T3: mean, 20.8°C; maximum, 25.5°C; minimum, 15.7°C). The first experiment was performed at the same temperatures (T0 or T3) during both periods to establish the responses of the two species to temperature. The second was conducted to identify the period (preimaginal or adult) in which the responses occurred and to confirm the results of the first experiment. Compared with normal temperatures (T0), elevated temperatures (T3) resulted in significant decreases in preimaginal development time and increases in aphid consumption rates in both species. C. septempunctata (10-d-old adults) had the highest weights when reared at T3, H. axyridis at T0. C. septempunctata was significantly heavier than H. axyridis in most cases, particularly in females. The body fat content of C. septempunctata was higher than that of H. axyridis at T0 and T3 temperatures. At T3 temperatures, fat accumulation in C. septempunctata increased, whereas that in H. axyridis remained relatively low. Body weight and fat body content of 10-d-old adults of both species seemed to be determined by temperature conditions during preimaginal development.     

Effects of temperature on development of vedalia beetle, Rodolia cardinalis (Mulsant)

The effect of temperature on the development of the vedalia beetle, Rodolia cardinalis (Mulsant) (Coleoptera: Coccinellidae), fed Icerya purchasi Maskell (Homoptera: Margarodidae) under controlled laboratory conditions was studied. Adults exposed to temperatures of 25, 28, 31, 34, and 37 °C for 72 h showed 95–100% survival, however egg production was significantly reduced at 34 and 37 °C. In addition, eggs maintained at 34 °C showed reduced hatch and survival of larvae, and eggs held at 37 °C failed to hatch. The duration of each developmental stage and survival of each stage were measured at 10, 14, 18, 22, and 25 °C. There was no egg eclosion at 10 °C. The developmental time from egg to adult emergence decreased from 79 to 18 days for temperatures from 14 to 25 °C. The sex ratio was unaffected by these temperatures. The lower developmental temperature threshold of R. cardinalis was estimated to be 10.8 °C and the degree–day accumulation was calculated as 279 for development from egg to adult eclosion. These results will guide further research designed to optimize management of vedalia populations in the San Joaquin Valley of California.