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Insect development occurs within a specific temperature range. Constant temperature studies may produce misleading information on the eco-physiological impacts of temperature on the population dynamics of an insect species, as in most natural environments, temperature usually undergoes daily variation. In China, field surveys showed that the decline in the Agasicles hygrophila (Selman & Vogt) (Coleoptera: Chrysomelidae) population from early August to late September in summer resulted in difficulties in effectively controlling the population of Alternanthera philoxeroides (Mart.) Griseb (Amaranthaceae). Previous studies have largely ignored more natural, fluctuating conditions. In our study, we first investigated the impacts of different temperature conditions (25°C constant temperature for 20 h with a 4-h period of a high temperature of either 30°C, 33°C, 36°C, or 39°C) on adult reproduction and longevity, egg development time, egg hatch rate, female ovarian development, and oogenesis of A. hygrophila. Our results indicated that high temperatures of 30°C and 33°C did not affect the female ovarian development and oogenesis of A. hygrophila. Contrarily, high temperatures of 36°C and 39°C negatively affected the population development of A. hygrophila. At 36°C and 39°C, the egg hatch rates were very low, and the egg development times significantly lengthened. The frequency of abnormal ovaries significantly rose at 39°C. We concluded that the decline in the A. hygrophila population during August and September may be related to the extreme high temperatures that frequently occur in summer. These results help provide a better understanding of A. hygrophila population dynamics under natural conditions. [ABSTRACT FROM AUTHOR]

With increasing global climate change, analyses of stress-inducing conditions have important significance in ecological adaptation and the biological distribution of species. To reveal the difference in temperature-adaptive strategy between Turpan and Beijing populations of Bemisia tabaci (Gennadius) Middle East Asia Minor 1 (MEAM1) under high-temperature stress conditions, we compared thermal tolerance and life history traits between Beijing and Turpan populations of MEAM1 after exposure to different heat shock treatments for different times. The experimental design reflected the nature of heat stress conditions suffered by MEAM1. The results showed that eggs, red-eyed pupae, and adults of the Turpan population were more heat tolerant than those of the Beijing population under the same stress conditions. Additionally, it was found that longevity and F1 adult survival rate were significantly higher in the Turpan population than in the Beijing population after heat shock stress, but egg number and F1 female ratio were not significantly different between Turpan population and Beijing population. Overall, it was suggested that heat tolerance and longevity traits were the most relevant for climate characteristics and not reproductive traits, and improved heat tolerance and prolonged longevity were important adaptive strategies that helped MEAM1 to survive in harsh high-temperature conditions such as Turpan arid desert climate. The present results provided further insight into the modes of heat tolerance and the ways in which survival and longevity traits respond to environmental selection pressures. [ABSTRACT FROM AUTHOR]

The invasive Mediterranean Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) has emerged as one of the most common agricultural pests in the world. In the present study, we examined the cross-tolerance, fitness costs, and benefits of thermal tolerance and the variation in the responses of life history traits after heat-shock selection. The results showed that survival and longevity of Mediterranean B. tabaci were decreased significantly after direct or cross temperature stress and that the number of eggs per female was not reduced significantly. Furthermore, heat-shock selection dramatically increased the survival of Mediterranean B. tabaci within two generations, and it did not significantly affect the egg number per female within five generations. These results indicated that there was a trade-off between survival, longevity, and reproduction in Mediterranean B. tabaci after temperature stress. The improvement in reproduction was costly in terms of decreased survival and longevity, and there was a fitness consequence to temperature stress. In addition, heat tolerance in Mediterranean B. tabaci increased substantially after selection by heat shock, indicating a considerable variation for survival tolerance in this species. This information could help us better understand the thermal biology of Mediterranean B. tabaci within the context of climate change. [ABSTRACT FROM AUTHOR]

Use of plant secondary metabolic compounds is an important method for insect pest control. In this study, the survival, development, and reproduction of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) MEAM1 cryptic species were compared over two consecutive generations on three cotton cultivars of different gossypol levels. Both cotton cultivar and generation significantly affected the fitness of the whitefly. In both generations, the immature development times on the low-gossypol cultivar ZMS13 were significantly longer than those on the high-gossypol cultivar M9101 or medium-gossypol cultivar HZ401. The female fecundity and rate of population increase of the whitefly ranked in the following order: ZMS13 > HZ401 > M9101. On each cultivar, the immature development time was shorter and the immature survival rate was higher in the second generation than those in the first generation. Rate of increase was also higher in the second generation. These results demonstrated that the fitness of B. tabaci MEAM1 cryptic species on the low-gossypol cotton cultivar ZMS13 was higher than that on the medium- or high-gossypol cultivar. The comparison of the life histories of B. tabaci MEAM1 cryptic species on different cotton varieties is important for the development of an integrated pest management program of the whitefly by using plant secondary metabolic compounds. [ABSTRACT FROM AUTHOR]

Much attention has been focused on insects' ability to survive long-term high-temperatures stress and on their resulting population distributions under global warming. In this study, life tables of the whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) biotype B, were collected over five consecutive generations at 27, 31, and 35°C and for one generation at 37°C. At 37°C, the intrinsic rate of increase (r) and the net reproductive rate (R0) of the whitefly were 0.0383 d-1 and 2.8 offspring, respectively. These results demonstrate that the lethal high temperature for B. tabaci is >37°C. At 27°C, neither R0 nor r decreased over the generations studied. However, both of these values decreased over time at 31 and 35°C, and the decrease was more evident at 35°C. Our results on the ability of B. tabaci biotype B to survive long-term high-temperature stress are important for understanding its population distribution under global warming. [ABSTRACT FROM AUTHOR]

The article discusses a study concerning the effect of cotton gossypol cultivars on the growth, development and food utilization of successive generations of the beet armyworm, Spodoptera exigua. It is stated that individual and populations of larvae and pupae were examined to determine the effect of M9101, ZMS13 and HZ401 cotton gossypol cultivars on their growth. It further demonstrates the positive and negative effects of cultivars on insects' growth but no effect on its digestibility.

Ophraella communa (Coleoptera: Chrysomelidae) is a leafbeetle that is unintentionally introduced in China. It is a potential biological control agent against common ragweed, Ambrosia artemisiifolia (Asterales: Asteraceae). The effects of temperature on the development and fecundity of 0. communa were studied at eight constant temperature regimens (15, 20, 22, 25, 28, 30, 32, 36°C) in the laboratory. The results showed that the developmental periods for egg, larva, pupa, and entire immature stages decreased in response to the increasing temperature, with the exception of 30°C. The survival rates at different developmental stages were higher at 25 and 28°C than at other temperatures. Ovipositional period and longevity of female shortened with the increasing temperature. The highest fecundity of female was observed to be 2,712.3 eggs/female at 28°C. Life table of 0. communa was constructed based on the data at 20 -32°C. The innate capacity for increase (rm), the net reproductive rate (R0),and the finite rate of increase (λ) reached the maximum at 28°C, with values of 0.247, 1,773.0, and 1,280, respectively. The shortest period of a generation (T) was 24.6 d at 32°C, whereas the longest T value was recorded as 79.3 d at 20°C. These results offer valuable insight on the establishment potential of 0. communa in new environments with diverse temperature regimens and on its massrearing techniques in laboratory. [ABSTRACT FROM AUTHOR]

Transgenic Bt cotton, engineered to continuously produce activated 6-endotoxins of the soil bacteria Bacillus thuringiensis, holds great promise in controlling Helicoverpa armigera and other lepidopteran pests. However, it also may impact the invertebrate community, which needs to be clarified. The effects of Bt cotton on two nontarget in sects, Aphis gossypii and Onus sauteri, were assessed under semifield and laboratory conditions. Mean total duration of nymphal stages of A. gossypii was shorter (5.9 versus 6.3 d), and rm was higher (0.418 versus 0.394) on conventional Simian 3 (the most frequently planted non-Bt cotton in northern China) than on Bt transgenic NuCOTN 33B (the first Bt cotton commercially planted in China). Mean duration of fourth-instar 0. sauteri was significantly longer on transgenic GK-12 (3.7 d) than on NuCOTN 33B (3.2 d), but no different from Simian 3. Mean total mortality was significantly lower on Simian 3 (3.7%) than on GK-12 (14.8%). During the fourth in star, the predator consumed a significantly higher number of prey on Simian 3 (202.3 prey) than on NuCOTN 33B (159.0), whereas the mean total number of A. gossypii prey consumed during the nymphal stage was significantly higher on Simian 3 (336.8 prey) and GK-12 (330.3 prey) than on NuCOTN 33B (275.7). No detrimental effects were detected on development (nymphs, adults, and progeny eggs), fecundity, longevity, and egg viability of O. sauteri on Bt cotton aphids compared with non-Bt cotton aphids. These results suggest that Bt cotton cultivars GK-12 and NuCOTN 33B have no direct effect on nontargets A. gossypii and O. sauteni. Germplasm divergence may account for the negative effects observed on A. gossypii and O. sauteni when reared on NuCOTN 33B or NuCOTN 33B-fed aphids. The biological meanings of the small difference observed between GK-12 and Simian 3 on survival of O. sauteri will require close monitoring over longer time periods. [ABSTRACT FROM AUTHOR]

Laboratory feeding experiments using transgenic Bacillus thuringiensis (Bt) cotton plants were carried out to evaluate the transmission of Bt toxin among trophic levels and the effects of Bt-fed herbivorous prey on the coccinellid predator Propylaea japonica (Thunberg). The experimental host plants were transgenic Bt-expressing cotton cultivars, NuCOTN 33B and GK-12 and one corresponding untransformed isogenic (non-Bt) cultivar. The herbivorous prey, cotton aphid Aphis gossypii Glover, was not sensitive to Bt toxin. Trace amounts of Bt toxins (6.0 ng/g fresh mass [FM] in GK-12, 4.0 ng/g FM in NuCOTN 33B) were detected in A. gossypii feeding on Bt cotton cultivars. Bt toxin was detected in ladybirds preying on Bt-fed aphids, and its quantity increased as the predatory period extended (5-20 d). Small amounts of Bt toxin was also found in newly hatched, unfed coccinellid larvae when their parents fed on NuCOTN 33B-reared aphids (15.0 ng/g FM), but not when the parents were fed on GK-12-reared prey. In experiments assessing life history consequences, mortality was low (mean = 7.9%), confirming that the rearing methods were appropriate. There were no distinct differences in preimaginal mortality between predators reared on Bt-fed or Bt-free aphids. The preimaginal stages of the ladybird beetles developed faster when reared on prey fed on either Bt-cotton cultivar than those fed control prey. There was a trend of more adult malformations when the predator was fed with prey from one (GK-12) but not the other of the Bt cotton cultivars than on control prey. There were no significant differences in the preovipositing period or in fecundity. Ladybird beetles preying on Bt-reared aphids matured faster and mated more frequently than those fed on Bt-free aphids. These results indicate that Bt toxin expressed in transgenic cotton cultivars can be transmitted to a higher trophic level through a nontarget pest insect and may alter the biology and behavior of a predatory ladybird. Further work should evaluate the possible long-term, sublethal impacts on the agroenvironment under field conditions. [ABSTRACT FROM AUTHOR]