Parental effects on embryonic viability and growth in Arctic charr Salvelinus alpinus at two incubation temperatures

The parental influences on three progeny traits (survival to eyed‐embryo stage, post‐hatching body length and yolk‐sac volume) of Arctic charr Salvelinus alpinus were studied under two thermal conditions (2 and 7° C) using a factorial mating design. The higher temperature resulted in elevated mortality rates and less advanced development at hatching. Survival was mostly attributable to maternal effects at both temperatures, but the variation among families was dependent on egg size only at the low temperature. No additive genetic variation (or pure sire effect) could be observed, whereas the non‐additive genetic effects (parental combination) contributed to offspring viability at 2° C. In contrast, any observable genetic variance in survival was lost at 7° C, most likely due to the increased environmental variance. Irrespective of temperature, dam and sire–dam interaction contributed significantly to the phenotypic variation in both larval length and yolk size. A significant proportion of the variation in larval length was also due to the sire effect at 2° C. Maternal effects were mediated partly through egg size, but as a whole, they decreased in importance at the high temperature, enabling a concomitant increase in non‐additive genetic effects. For larval length, however, the additive component, like maternal effects, decreased at 7° C. The present results suggest that an exposure to thermal stress during incubation can modify the genetic architecture of early developmental traits in S. alpinus and presumably constrain their short‐term adaptive potential and evolvability by increasing the amount of environmentally induced variation.     

Thermal reaction norms in two Coenagrion damselfly species: contrasting embryonic and larval life-history traits

1. We studied the temperature‐dependence of important life‐history traits both at the embryonic (egg hatching success, embryonic development time and hatchling size) and the larval stage (larval growth rate, larval survival and larval size after 100 days) using full‐sib families of two congeneric damselflies, Coenagrion hastulatum and Coenagrion puella, that differ in latitudinal distribution. Larvae were reared in the laboratory from the egg stage at four temperatures (12, 17, 22 and 27 °C). 2. The observed patterns of thermal plasticity in embryonic traits showed that the northern species was more successful than the southern species at lower temperatures, in line with the pattern of temperature adaptation in thermal reaction norms. 3. At the larval stage, we found no consistent pattern of latitudinal compensation. The thermal family reaction norms indicate, however, the potential for latitudinal compensation to evolve. We observed an ontogenetic shift in thermal optima for larval growth rate, with a higher optimal temperature for growth rate during the first 2 weeks of the larval stage. 4. This is the first indication of the existence of latitudinal compensation at the interspecific level in an invertebrate; it is stage‐specific, being present only in the embryonic stage. We argue that compensation in the embryonic stage may be much more likely than in the larvae and stress the importance of including more then one life‐history stage when drawing conclusions about the adaptiveness of patterns in thermal reaction norms.     

Temperature effects on egg and larval development and phenological forecasting of the smaller fruit tortrix,Grapholita lobarzewskii

The effects of temperature on egg and larval development of Grapholita lobarzewskii Nowicki (Lepidoptera: Tortricidae) were studied under controlled conditions to complement the basis for phenological forecasting and thus to optimize the timing of monitoring and control measures with respect to sustainable pest management. Egg development lasted on average 28.1 days at 12.7 °C and 5.5 days at 26.1 °C. Egg mortality was generally low, varying between 12 and 14% within a temperature range of 12.7–22.0 °C, but slightly increased to 20% at 26.1 °C. For egg development, a lower thermal threshold of 9.7 °C and a thermal constant of 90.6 degree days were established. Larval development took on average 76.0 days at 12.7 °C and 21.5 days at 26.1 °C. Larval mortality was 51% at 12.7 °C but only 6–12% at temperatures above 17 °C. The lower thermal threshold and the thermal constant for larval development were 7.6 °C and 389.2 degree days, respectively. Final larval weight increased with temperature from 18.6 mg at 12.7 °C to a maximum of 23.9 mg at 22.0 °C. Based on mortality rates, the optimal temperature range was between 12.7 and 22.0 °C for egg development and between 17.1 and 22.0 °C for larval development, which was confirmed based on the weight of fully grown larvae. These biological parameters of egg and larval development enabled us to parameterise a phenology model for G. lobarzewskii, which was incorporated into an existing decision support system for fruit pests. Precise forecasts of pest phenology facilitate the optimal timing of monitoring and control measures, improve their efficiency, and thereby contribute to sustainable crop protection.     

Effect of temperature on the morphometric development of eggs in the prawn Macrobrachium americanum (Caridea: Palaemonidae) and larval success under experimental conditions

Abstract

This study evaluated the effect of temperature on morphometric features of the egg during the embryonic development of the prawn Macrobrachium americanum and the relationship with hatching and the survival of the larvae. Berried females were grouped (n = 3) and reared at three different temperatures, 26, 29, and 33 °C, for which seven developmental stages were recognized. At each stage, the apical and sagittal diameters of the eggs were measured, the volume was calculated, and the weights were recorded. Additionally, the duration of embryonic development, hatching percentage, and larval survival were determined. At 29 and 33 °C, the eggs’ volume increased by 50%, but at 26 °C, the increase was 25%. Larvae from eggs incubated at 33 °C died one day after hatching. At 29 °C, larvae survived until Zoea VII. Larvae from eggs incubated at 26 °C died at the end of Zoea I. The number of days of embryonic development was 20.5 ± 1.5 (26 °C), 15 ± 1 (29 °C), and 12 ± 1 (33 °C). A temperature of 29 °C was the most favorable for embryonic development in M. americanum.     

The thermal tolerance of crown-of-thorns (Acanthaster planci) embryos and bipinnaria larvae: implications for spatial and temporal variation in adult populations

To understand the role of sea temperature on the population biology of the crown-of-thorns sea star Acanthaster planci, the thermal window for embryonic and larval development was investigated. In two experiments, the response of embryos and larvae across 12 temperatures from 19.4 to 36.5 °C was quantified as the percentage of individuals reaching cleavage stage embryos, blastula, gastrula, early-bipinnaria, late-bipinnaria larvae or abnormal. Measurements were made at 7 times up to 72 h post-fertilisation, with the morphometrics of larvae measured in the 72-h sample. Acanthaster planci developed at temperatures between 19.4 and 33.2 °C, with a thermal window for development to the late-bipinnaria stage between 25.6 and 31.6 °C. Development rate, normal development and larval size were optimal at 28.7 °C, with development rates remaining relatively constant up to 31.6 °C. Rates of abnormality increased steadily (early embryonic stages) above 28.7 °C and was 100 % at temperatures approaching 33 °C. These experiments provide a more detailed insight into the response of A. planci developmental stages to temperature. The present day distribution of the species in eastern Australia overlap with the optimal thermal window for development to the late-bipinnaria stage (≈25–32 °C), implying a role of temperature in controlling population distributions and abundances. Despite this, short- or long-term temperature increases may not be a major modulator of the crown-of-thorns recruitment success, population dynamics and distribution in the future as no significant change in development rates, larval survival and growth occurred within this thermal window. Therefore, moderate (1–2 °C) increases in sea temperatures caused by El Niño or near-future ocean warming may not drive an increase in developmental and settlement success. Indeed, without any acclimation to warmer temperatures expected under near-future warming (+2 to 4 °C), climate change could ultimately reduce larval survival due to elevated mortality above the optimal development temperature.     

High temperature tolerance and thermal-adaptability plasticity of Asian corn borer (Ostrinia furnacalis Guenée) after a single extreme heat wave at the egg stage

Due to ongoing climate change, short-term extreme heat waves in the summer are expected to be more frequent. Insect eggs are sensitive to thermal stress. This raises the question of whether herbivore insects' thermal adaptability would be changed after a single extreme heat wave at the egg stage. In this study, we examined the developmental performance of Ostrinia furnacalis Guenée at 25?°C, 27?°C, 29?°C or 31?°C after a single extreme heat wave (42?°C) for 0?h (control), 1?h, 2?h, or 3?h at the egg stage. The results showed that O. furnacalis at the egg or larval stage was more sensitive to a single heat wave than it was at the pupae or adult stage. After a single heat wave, O. furnacalis showed a reduced egg-hatching rate or reduced larval survival rate, but the optimum temperature for egg hatching and larval survival was higher than that in the control. The upper temperature threshold and optimum temperature for larval development in the control were higher than that after a single extreme heat wave. Both male and female pupal weight decreased with increasing temperature, and pupal weight decreased faster in females than in males. The Cox proportional hazard model showed that when O. furnacalis developed at 25?°C, the instantaneous death risk of adults with a 3?h heat wave at the egg stage was higher than that of the control, but when O. furnacalis developed at 29?°C and 31?°C, the instantaneous death risk of adults after a heat wave was significantly lower than that of the control. Our study highlights the effect of a single heat wave on O. furnacalis eggs and the subsequent development of survival individuals.     

Cooler temperatures increase sensitivity to ultraviolet B radiation in embryos and larvae of the frog Limnodynastes peronii

Recent studies suggest that complex interacting processes are driving global amphibian declines. Increased ultraviolet B (UVB) radiation in the solar spectrum associated with ozone depletion has been implicated in declines, and evidence suggests that the effects of UVB radiation on amphibians may be greater at cooler temperatures. We tested the thermal sensitivity of UVB effects on amphibians in a controlled factorial experiment using the striped marsh frog, Limnodynastes peronii as a model species. We compared survival, growth and locomotor performance of embryonic and larval L. peronii reared under low and high UVB exposures at both 20 and 30 °C. Embryonic and larval L. peronii proved extremely sensitive to UVB damage and exhibited greater sensitivity at 20 °C compared with 30 °C. Embryonic survival to Gosner stage 25 was unaffected by UVB exposure at 30 °C, but at 20 °C survival was reduced to 52% under high UVB. Larval survival exhibited a similar trend. At 20 °C, all tadpoles survived under low UVB, whereas under high UVB there was 100% mortality after 15 days of exposure. At 30 °C, 86% survived under low UVB, but only 46% survived under high UVB. Sublethal effects such as, embryonic malformation, retarded larval growth and reduced larval swimming performance were also greater at 20 °C compared with 30 °C. Our results strongly indicate that UVB damage in amphibians is markedly increased at cooler temperatures. Thus, populations of UVB sensitive species occurring at cold climates may be at greater risk of declines due to increased solar UVB radiation.     

Carry‐over effects of multiple stressors on benthic embryos are mediated by larval exposure to elevated UVB and temperature

Damaging effects of UVB in conjunction with other stressors associated with global change are well‐established, with many studies focused on vulnerable early life stages and immediate effects (e.g., mortality, developmental abnormalities). However, for organisms with complex life cycles, experiences at one life stage can have carry‐over effects on later life stages, such that sublethal effects may mediate later vulnerability to further stress. Here, we exposed embryos in benthic egg masses of the New Zealand intertidal gastropod Siphonaria australis to treatments of either periodic stress (e.g., elevated UVB, salinity, and water temperature mimicking tidepool conditions in which egg masses are commonly found during summer) or control conditions (low UVB, ambient salinity, and water temperatures). Although there was high mortality from stressed egg masses, 24% of larvae hatched successfully. We then exposed the hatching larvae from both egg mass treatments to different combinations of water temperature (15 or 20 °C) and light (high UVB or shade) 12 h per day for 10 days. The most stressful larval conditions of 20 °C/high UVB resulted in low survival and stunted growth. Carry‐over effects on survival were apparent for shaded larvae exposed to elevated temperature, where those from stressed egg masses had 1.8× higher mortality than those from control egg masses. Shaded larvae were also larger and had longer velar cilia if they were from control egg masses, independent of larval temperature. These results demonstrate that previous experience of environmental stress can influence vulnerability of later life stages to further stress, and that focus on a single life stage will underestimate cumulative effects of agents of global change.     

Effect of temperature on the development of the immature stages ofBembidion lampros [Coleoptera: Carabidae]

The effects of temperature on survival and development of immature stages ofBembidion lampros were examined under controlled conditions in the laboratory. The duration of development was examined at 5°C, 12°C, 17°C, 19°C, 22°C, 25°C, 30°C and 32°C and found to be inversely related to temperature. Between 12°C and 30°C there was a significant difference in duration of egg development, but no significant difference in percentage of eggs hatched. The upper and lower lethal limits for egg development were estimated (c 31°C and 4°C respectively). There are 3 larval instars and one pupal stage. Development of larva plus pupa required a minimum of 20.9 days at 30°C. Between 22°C and 30°C survival from larva to the adult stage was 80%.      

Biology and development of <Emphasis Type="Italic">Laricobius kangdingensis</Emphasis> Zilahi-Balogh and Jelínek,a newly discovered predator of <Emphasis Type="Italic">Adelges tsugae</Emphasis>

The biology and temperature-dependent development of Laricobius kangdingensis Zilahi-Balogh and Jelínek (Coleoptera: Derodontidae), a newly described predator of hemlock woolly adelgid (HWA), Adelges tsugae Annand (Hemiptera: Adelgidae) were investigated and compared with a related HWA predator, L. nigrinus Fender, that has already been released. As with other Laricobius species, there are four larval instars. The female to male sex ratio was 1:1.1. Mean lifetime fecundity per female was 196.4 eggs and 97.9 eggs for the parental generation (P₁) and first filial generation (F₁), respectively. Developmental rates at 6, 9, 12, 15, and 18°C were studied between fall 2002 and spring 2004 and used to determine low temperature development thresholds for the egg (2.8°C), and larval (1.6°C) stages. The egg and larval thresholds are lower than those observed for L. nigrinus. Laricobius kangdingensis individuals completed development only at 12 and 15°C; however, the adults did not emerge from aestivation after pupation. Our results suggest that L. kangdingensis may be a promising addition to the complex of predators currently being reared for control of HWA. Laricobius kangdingensis is long-lived, exhibits high fecundity, and can complete development on North American HWA. However, further studies will be necessary to secure its clearance for release, and the source of high mortality in the laboratory must be identified in order to improve its survival for mass-rearing. Handling editor: Eric Lucas     

Biology of Lysiphlebus fabarum following cold storage of larvae and pupae

Cold storage is one means of preserving parasitoids prior to release in augmentation biological control programs. This study examined the feasibility of storing larval and pupal stages of a sexual population of Lysiphlebus fabarum Marshall (Hymenoptera: Braconidae: Aphidiinae) at 6 ± 1 and 8 ± 1 °C, 50–60% r.h., and L14:D10 photoperiod. These life stages were stored for periods of 1, 2, and 3 weeks under fluctuating thermal regimes (2 h daily at 21 ± 1 °C). Generally, pupae gave better results than larvae, and 6 °C was better than 8 °C, considering wasp survival, wasp size (tibial and antennal lengths), egg load, and egg size. The best results were obtained with pupae stored for 2 weeks under a fluctuating temperature regime at 6 °C. Females emerging from this treatment did not differ from controls (developing directly at 21 °C) in body size, egg size, or progeny sex ratio, and suffered less than 20% mortality. Egg loads were reduced in these wasps, but the reductions were substantially less than occurred in other 2‐week‐storage treatments. Wasps stored in this manner successfully parasitized similar numbers of aphids as controls and produced similar progeny sex ratios. These results reveal a suitable set of low‐temperature conditions that can be used to delay the development of L. fabarum for 2 weeks with minimal impact on wasp fitness.     

Stage- and sex-specific heat tolerance in the yellow dung fly Scathophaga stercoraria

Thermal tolerance varies at all hierarchical levels of biological organization: among species, populations, individuals, and even within individuals. Age- or developmental stage- and sex-specific thermal effects have received relatively little attention in the literature, despite being crucial for understanding thermal adaptation in nature and responses to global warming. We document stage- and sex- specific heat tolerance in the yellow dung fly Scathophaga stercoraria (Diptera: Scathophagidae), a species common throughout the northern hemisphere that generally favours cool climates. Exposure of eggs to temperatures up to 32 °C did not affect larval hatching rate, but subsequent egg-to-adult survival at a benign temperature was reduced. Permanent transfer from benign (18 °C) to hot temperatures (up to 31 °C) at different larval and pupal stages strongly decreased egg-to-adult survival, though survival continuously improved the later the transfer occurred. Temporary transfer for only two days increased mortality more weakly, survival being lowest when temperature stress was imposed early during the larval or pupal stages. Adult flies provided with sugar and water tolerated 31 °C longer than previously thought (5 days in males to 9 days in females). Eggs were thus less susceptible to thermal stress than larvae, pupae or adults, in agreement with the hypothesis that more mobile stages require less physiological protection against heat because they can behaviourally thermoregulate. The probability of mating, of laying a clutch, and hatching success were generally independently reduced by exposure of females or males to warm temperatures (24 °C) during the juvenile or adult stages, with some interactions evident. High temperature stress thus affects survival differentially depending on when it occurs during the juvenile or the pre-reproductive adult life stage, and affects reproductive success via the mating behaviour of both sexes, female physiology in terms of oviposition, and fertility via sperm and/or egg quality. Our results illustrate that temperature stress, even when moderate and temporary, during early development can have profound lethal and non-lethal fitness-consequences later in life.     

Variation in early developmental stages in two populations of an intertidal crab, Neohelice (Chasmagnathus) granulata

Duration of embryonic development, egg size, larval size at hatching, and starvation tolerance of the first zoeal stage were studied in an intertidal crab from the southwestern Atlantic, Neohelice (formerly Chasmagnathus) granulata. These reproductive traits were quantified comparing (a) two populations living in ecologically contrasting coastal habitats in Argentina, a brackish lagoon, Mar Chiquita, MC vs. an open marine habitat near San Antonio, Patagonia, SA, (b) beginning vs. end of the reproductive season, and (c) two temperatures during egg development (18 vs. 27°C). Eggs in an early stage of embryonic development were in both populations larger at the beginning than at the end of the season, and were consistently larger in the SA population. These size differences persisted through larval hatching, independent of the temperature during embryogenesis. At 18°C, eggs produced at the beginning of the season developed in both populations more rapidly than those from the end of the reproductive season, while the opposite trend was observed at 27°C. The stage duration of the zoea I was in both populations shorter at the beginning as compared to the end of the season. The nutritional flexibility of the zoea I stage was compared using as indices the point-of-reserve-saturation (PRS₅₀) and the point-of-no-return (PNR₅₀). The PRS₅₀ was consistently lower in larvae from SA than in those from MC. In the MC population, this index was lower at the beginning than at the end of the season, while no significant seasonal difference was observed in larvae from SA. The PNR₅₀ varied between temperatures of embryonic development and populations, showing also significant interactions between all three factors. The PRS₅₀ was on average lower, and the PNR₅₀ was higher, than values previously reported for N. granulata, suggesting a stronger nutritional flexibility in the larvae used in the present study. Our results indicate significant intraspecific variability among separate populations, seasonal variation, and carry-over effects of environmental conditions prevailing during the embryonic phase, all of which may affect the performance of the larval phase.     

Stage-specific effects of temperature and dietary protein on growth and survival of Manduca sexta caterpillars

The effects of temperature and dietary protein concentration on growth and survival of Manduca sexta L. (Lepidoptera: Sphingidae) caterpillars during different larval stages were examined. Sets of caterpillars were raised from hatching at one of five constant temperatures (18, 22, 26, 30 or 34°C) and on one of two artificial diets (low or high protein concentration). Mass gain, duration (development time) and mean growth rate were measured for each caterpillar for the 1st to 3rd stadia, the 4th stadium, and the 5th stadium. Temperature significantly affected mass gain during each larval stage, resulting in smaller mass gains at higher temperatures at each stage. This effect was strongest at high temperatures during the 5th stadium. Temperature significantly affected durations of each larval stage, but the effect varied among stages: for example, the duration of stadia 1–3 decreased continuously with increasing temperature, whereas the duration of the 5th stadium was shortest at 26–30°C and increased at lower and higher temperatures. The effect of temperature on mean growth rate changed dramatically across larval stages: maximal growth rate occurred at 34°C during the 1st to 3rd stadia, at 30°C during the 4th stadium and at 26°C during the 5th stadium. Higher dietary protein concentration significantly decreased the duration of stadia 1–3 and of the 4th stadium, but had no significant effect on the duration of the 5th stadium. Temperature and dietary protein had little effect on mortality rates during any larval stadium, with one exception: mortality during the 5th stadium increased dramatically at temperatures of 30 and 34°C. These results demonstrate that the effects of temperature and dietary protein concentration on growth, development and survival in M. sexta vary markedly in different larval stadia during development; 5th instar caterpillars are particularly sensitive to higher temperatures.     

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.     

Effects of host stages and temperature on population parameters of Oomyzus sokolowskii, a larval-pupal parasitoid of Plutella xylostella

Oomyzus sokolowskii is alarval-pupal parasitoid of diamondback moth, Plutella xylostella. In a host stage preference test, the parasitoid parasitised all larval and pupal stages, but exhibited a strong preference for larvaeover prepupae or pupae, and did not show a preference among the larval instars. At 25°C, the developmental time, number and sex ratio of offspring per host pupa, and successful parasitism did not differ significantly among parasitoids reared from host larvae of different instars, indicating similar host suitability between larvae of different instars. Mean developmental times from egg to adult at 20, 22.5, 25, 30, 32.5, and 35°C were 26.5,21.0, 16.0, 12.7, 11.9 and 13.4 days, respectively. The favourable temperature range for development, survival, and reproduction of the parasitoid was 20--30°C. However, wasps that developed and emerged at a favourable temperature could parasitise effectively at 32--35°C for 24 hours. Life-fertility table studies at 20, 25, and 30°C showed that each female wasp on average parasitised 3.1, 13.2, 6.8 larvae of diamondback moth and produced 20.5, 92.1, 50.4 offspring, respectively, during her lifetime. The highest intrinsic rate of natural increase (r _m) of 0.263 female/day was reached at 30°C as a result of the short mean generation time at this temperature compared to that at 20 and 25°C, suggesting that the parasitoid had the highest potential for population growth at relatively high temperatures. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of Indian mustard on feeding,larval survival and development of Plutella xylostella at constant temperatures

Feeding behavior of Plutella xylostella under optional to non-optional conditions was studied at 10°C, 15°C, 20°C, and 25°C on Indian mustard, Brassica juncea. The study reveals that the variety Pusa Bahar was significantly less preferred by the larvae as compared with Pusa Bold and Varuna under optional to non-optional conditions. Larvae of P. xylostella consumed more food at 25°C than 20°C, 15°C and 10°C. Larval survival was found to be highest on cabbage (control) as compared with Indian mustard and was found to vary with host plants and temperature. The larval survival decreased to 11.29% on Pusa Bahar at 10°C. Increasing the temperature from 10°C to 20°C, larval mortality resulted more on Varuna than Pusa Bahar and Pusa Bold. Developmental period was prolonged on Pusa Bold at 10°C while it was shortest on cabbage at 25°C. A total of 536.47 degree days were required to complete the development by immature stages on Varuna at 25°C and 421.64 degree days on cabbage.     

Effects of temperature experienced during embryonic development on biomass and C and N composition at hatching in Palaemon serratus (Pennant, 1777)

In decapod crustaceans, the conditions experienced during embryonic development trigger phenotypic plasticity of the larvae at hatching. The objective of this study was to test the effects of temperature during embryonic development of Palaemon serratus on the phenotypic plasticity of hatching larvae. We incubated egg-bearing females from eggs laying to hatching at four temperatures (10, 15, 18 and 20°C). Weight, carbon and nitrogen contents were measured on newly laid eggs and on freshly hatched larvae. The duration of embryonic development was negatively correlated with incubation temperature. At 20°C, all females abandoned their eggs during development. Incubation temperature had no effect on the weight and the percentage of N of the larvae at hatching, while it did affect their percentage of C and their C/N ratio. Embryos incubated at 10°C seemed to produce larvae with fewer lipid reserves than those incubated at 15 and 18°C. They probably overconsumed their lipid reserves to compensate for the metabolic losses due to the low temperature. These results provide information on the link between maternal investment per egg and larval development in P. serratus.     

Development ofDiatraea Saccharalis [Lep.: Pyralidae] at constant temperatures

At constant temperatures between 15.6 and 32°C the incubation time of eggs ofDiatraea saccharalis (F.) was reduced by each increase in temperature. At 34°C the time decreased. Highest (98.6%) and lowest (9.9%) egg hatch occurred at 26 and 34°C, respectively. Larvae completed development at temperatures ranging from 22 to 34°C; however, only 4.4% of the larvae pupated at 34°C. Duration of the larval stage at 30°C (♂=18.1 days; ♀=19.1 days) was ca. 14 days shorter than at 22°C. Maximum rate of development in the pupal stage occurred at 28°C (ca. 6.8 days), and a higher temperature increased developmental time and mortality. Adult longevity and egg production generally were reduced with increasing temperatures and egg production was highest at 24°C (729.8 eggs/ moth). As many as 7 larval stages occurred; but most larvae completed development in 5 stages, and none completed development in less than 5 stages. The female larval stage was ca. 1 day longer than that of males, and this difference occurred primarily in the 5th stage.     

Effect of larval rearing temperature on adult female morphology of Anopheles (Nyssorhynchus) albimanus (Diptera: Culicidae)

Summary

Time to pupation, percent survival to pupation, and percent adult emergence of Anopheles albimanus Wiedemann decreased at higher larval rearing temperature. Mosquitoes reared at 30°C experienced higher mortality during the pupal stage than did mosquitoes reared at 22°C. Analysis of variance revealed that wing length and costal wing spot patterns of adult female A. albimanus were affected by larval rearing temperature. Female A. albimanus reared at 22°C had longer wings, and larger basal pale + prehumeral pale, prehumeral dark, and humeral pale costal wing spots than did female siblings reared at 30°C. Female A. albimanus reared at 30°C had larger subcostal pale spots than did female siblings reared at 22°C. Analyses of 2x2 contingency tables indicated that sex ratio was independent of larval rearing temperature, whereas survival to the adult stage and coalescence of wing spots were not independent of rearing temperature. The need to examine stability of morphological characters under differing environmental conditions is discussed.