Adults Survived Research Articles

Effects of temperature on the survival of spotted lanternfly active life stages when held without food

Abstract Spotted lanternfly, Lycorma delicatula White (Hemiptera: Fulgoridae), is an invasive Southeast Asian planthopper that was recently introduced into the eastern United States and spreads along human transportation corridors by ‘hitch‐hiking’ on vehicles and cargo. To better understand the risk of establishment when mobile life stages are moved, it is critical to know how long spotted lanternfly mobile life stages will survive without food and water under different temperatures. This work reports on spotted lanternfly first, second, and third instar nymphal and adult survival without food over the 10–30°C temperature range. Survival time without food declined exponentially as temperature increased for all life stages of spotted lanternfly that were evaluated. At temperatures <30°C, first instar nymphs survived longer than second or third instar individuals. Female adults survived about 1 day longer than male adults at all but 10 and 25°C. Without food, 99% of all adults of both sexes are predicted to be dead in less than a week over the temperature range evaluated. First instars, which were the smallest, survived the longest and their survival exponentially decreased as temperature increased. This suggests that more attention to first instar movement may be warranted. The data presented here will provide a basis for assessing the risk of survival of transported spotted lanternfly active life stages along various pathways.

Discordant pattern between realised and fundamental saline niches in two supralittoral Ochthebius species (Coleoptera: Hydraenidae)

Abstract Determining the saline niche of the congeneric and co‐existing species that inhabit supralittoral rockpools subjected to extremely fluctuating saline conditions is a crucial concern to understand their spatial distributions and occurrence, and to predict their ability to face increasing environmental instability due to climate change. Therefore, we compared the realised and fundamental saline niches of Ochthebius quadricollis and Ochthebius lejolisii (Coleoptera: Hydraenidae) on the Mediterranean coast of the Iberian Peninsula. A realised niche was determined using field data on the abundance of the adults and larvae of both species. A fundamental niche was addressed with laboratory experiments by measuring the survival of the adults and larvae and the egg‐hatching success exposed to different salinity treatments (35, 60, 90, 110, 140 and 170 g L−1). Our study found a discordant pattern between realised and fundamental niches. Both species are euryhalines and support extreme salinity fluctuations from 1.80 to almost 140 g L−1, and O. quadricollis larvae in the field withstand up to 180 g L−1. However, physiological tolerance was greater in O. lejolisii than in O. quadricollis, and O. lejolissi adults survived in the laboratory at 170 g L−1 for more than 3 days with 30% egg‐hatching success, whereas O. quadricollis showed a maximum survival time of 2 days and no egg‐hatching success at that salinity. The larvae and eggs of both species were more tolerant than adults. The two studied species exhibited high physiological capacity to tolerate extremely fluctuating salinity, which will be exacerbated by climate change.

Migration and survival of Okanagan River Sockeye Salmon Oncorhynchus nerka, 2012\u20132019

BackgroundOkanagan River Sockeye Salmon Oncorhynchus nerka (Okanagan Sockeye) are one of two remaining self-sustaining Sockeye Salmon populations in the Columbia River Basin. We used detection histories of smolts implanted with passive integrated transponder (PIT) tags between 2012 and 2019 to estimate survival and behavioral metrics during reintroduction efforts and changing environmental conditions over the monitoring period.ResultsSmolts migrating to McNary Dam, whose route includes 130 km of the Okanagan River and 388 km of the Columbia River, generally had high survival (mean of 87.0% per 100 km) and fast migration speeds (up to 50 km/day) relative to other salmonids in the region. Smolt-to-adult returns (SARs) ranged from 0.4 to 6.1% and were greater for fish originating from Skaha Lake compared to cohorts tagged in Osoyoos Lake. Most adults returned after 2 years in the ocean (69%), followed by jacks (27%), and adults that spent 3 years at sea (4%), though Skaha Lake adults had a significantly younger age structure than cohorts from Osoyoos Lake. Survival of adults from Bonneville Dam (rkm 235) upstream to Wells Dam (rkm 830) was generally high (80–92%), and migration speed decreased in upstream reaches. Survival from Wells Dam to the Okanagan River was only estimable in 2018, where 64% of adults survived to the spawning grounds. The upstream migration of adult Okanagan Sockeye was significantly compromised during the drought of 2015 when less than 5% of Okanagan Sockeye that returned to the Columbia River reached spawning grounds.ConclusionsOur results indicate that Okanagan Sockeye have exceptional survival and migratory ability relative to other salmonids, though poor ocean conditions combined with warming water temperatures in freshwater habitats in recent years have the potential to devastate the population. The success of reintroduction efforts to increase spatial structure and diversity of Okanagan Sockeye is, therefore, critical to maintaining the population in years to come.

Impaired larval development at low salinities could limit the spread of the non-native crab Hemigrapsus takanoi in the Baltic Sea

The Asian shore crab Hemigrapsus takanoi, native to the northwest Pacific Ocean, was recently discovered in Kiel Fjord (southwestern Baltic Sea). In laboratory experiments, we tested the salinity tolerance of H. takanoi across 8 levels (0 to 35) and across 3 life history stages (larvae, juveniles and adults) to assess its potential to invade the brackish Baltic Sea. Larval development at different salinities was monitored from hatching to the megalopa stage, while survival and feeding of juveniles and adults were assessed over 17 d. Larvae of H. takanoi were able to complete their development to megalopa at salinities ≥ 20 and the time needed after hatch to reach this stage did not differ between salinities of 20, 25, 30 and 35. At a salinity of 15, larvae still reached the last zoea stage (zoea V), but development to the megalopa stage was not completed. All juveniles and adults survived at salinities from 5 to 35. Feeding rates of juveniles increased with increasing salinity across the entire salinity range. However, feeding rates of adults reached their maximum between salinities of 15 and 35. Our results indicate that both juveniles and adults of H. takanoi are euryhaline and can tolerate a wide range of salinities, at least for the time period tested (2 wk). However, larval development was impaired at salinities lower than 20, which may prevent the spread of H. takanoi into the Baltic Proper.

Tolerance to salinity and thermal stress by larvae and adults of the serpulid annelid Ficopomatus enigmaticus

AbstractThe serpulid annelid Ficopomatus enigmaticus is a widely distributed invader of shallow‐water, brackish habitats in subtropical and temperate regions, where it has numerous damaging ecological and economic effects. Its distributional pattern suggests that temperature and salinity play important roles in limiting its distribution, but because other factors often covary with these, drawing strong conclusions from these patterns is difficult. In an effort to more clearly identify the effects of these factors, we examined tolerance to acute thermal (16–28°C) and salinity (0–35 psu) stress by larvae (5‐day exposure, unfed) and adults (14‐day exposure, unfed) of F. enigmaticus in the laboratory experiments. Larvae showed higher mortality at the highest temperature tested 28°C; adult survival was unaffected by temperature. Neither larvae nor adults survived exposure to pure freshwater (0 psu), but survived well at salinities ranging 3.5–35 psu. In addition, high salinity did not slow tube growth in adults. These results suggest that salinity stress, in particular, does not directly limit the distribution of F. enigmaticus to low‐salinity habitats. Experimental work on the distribution of F. enigmaticus is uncommon in the literature, but is likely needed to identify the abiotic or biotic factors that limit the distribution of this frequently invasive species.

Laboratory rearing of Halyomorpha halys: methods to optimize survival and fitness of adults during and after diapause

Laboratory colonies are necessary to conduct year-round research on the invasive brown marmorated stink bug, Halyomorpha halys (Stal), a severe agricultural and nuisance pest in the USA. When adults are collected in the fall to either start or supplement colonies, they require a period of cold storage before they resume sexual development and egg production. There is a lack of understanding of how to collect and store diapause-triggered adults in the laboratory. A series of experiments in 2013–2015 assessed survival and fecundity of stink bugs collected from different locations and stored under different temperatures and durations. We found that a minimum of 7 weeks is necessary to break diapause and that a substantial proportion of adults can survive when stored at constant 9 °C, even for periods longer than needed to terminate diapause. Adults survived significantly better at 6 and 9 °C than at 3 °C in storage for 7 weeks. Longer durations up to 34 weeks in storage reduced adult survival and significantly affected survival rates, timing of first egg laying, and overall fecundity. Location where adults were collected at overwintering sites in the fall had a significant impact on survival in cold storage and colony performance. Adults collected from soybean fields in mid-September and fed in the laboratory for 2 weeks before storage had lower survival than adults collected in October at aggregation sites and stored immediately. The food sources available to H. halys adults at collection locations for nutrition and sequestration of sufficient energy reserves going into diapause are discussed.

Overwintering Survival of Drosophila suzukii (Diptera: Drosophilidae) and the Effect of Food on Adult Survival in California's San Joaquin Valley.

The overwintering survival and development of Drosophila suzukii Matsumura were investigated in California's San Joaquin Valley. Drosophila suzukii were exposed to overwintering conditions in cages hung in a citrus orchard, and the pupae were buried in the soil. Eggs exposed from late November to January did not survive; a low percentage (<3%) of larvae and pupae developed into adults. Survival of pupae was significantly higher when buried in the soil than on the citrus tree. From late January to March, all life stages developed into adults and overwintered adult female D. suzukii produced eggs when provided with 10% honey-water and sliced oranges. Adult survival varied among fruit juice provision treatments and overwintering exposure periods, ranging from 3.4 ± 0.9 d (water) to 44.1 ± 3.0 d (10% honey-water). Fruit juices of apple, cherry, grape, orange, and pomegranate were tested as adult food sources; results showed that adult female and male D. suzukii lived only 2 d with water only, whereas adults survived from 14.2 to 34.8 d with fruit juice treatments and the 10% honey-water control. An unexpected event was the oviposition and immature development of D. suzukii with the fruit juice. In a follow-up laboratory trial, when 10% honey-water or orange juice were provided along with an artificial diet for oviposition and immature development, female D. suzukii survived for 21.6 ± 2.4 or 21.6 ± 1.5 d, and produced 106.8 ± 14.1 or 98.5 ± 13.1 offspring, respectively. We discuss factors potentially influencing overwintering survival of D. suzukii.

Survival and Hsp70 Gene Expression in Plutella xylostella and Its Larval Parasitoid Diadegma insulare Varied between Slowly Ramping and Abrupt Extreme Temperature Regimes

BackgroundIn nature, insects have evolved behavioural and physiological adaptations to cope with short term exposure to extreme temperatures. Extreme heat events may increase as a result of climate change; this in turn will affect insect population dynamics. We examined the effect of abrupt and ecologically relevant gradual exposure to high temperatures on the survival and hsp70 gene expression in diamondback moth (DBM) adults and the parasitoid Diadegma insulare , as well as in parasitized and non-parasitized DBM larvae.Principal FindingsTolerance to high temperatures in DBM adults was higher than in D . insulare adults. There was no difference in the survival of DBM adults between abrupt and ramped increases from 25 to 38°C; however, at 40°C survival was higher when the temperature increased gradually. In contrast, more D . insulare adults survived when the temperature was ramped rather than shifted abruptly to both 38 and 40°C. There was no heat stress effect of up to 40°C on the survival of either parasitized or non-parasitized DBM larvae. In adults of both species, more hsp70 expression was observed when temperatures increased abruptly to 38°C compared to ramping. In contrast, at 40°C significantly more expression was found in insects exposed to the ramping rather than the abrupt regime. Hsp70 expression level was in agreement with adult survival data and appears to be a good indicator of stress levels. In parasitized and non-parasitized larvae, hsp70 expression was significantly higher after abrupt shifts compared to ramping at both temperatures.Conclusions/Significance Hsp70 gene expression was responsive to extreme temperatures in both DBM and D . insulare , which may underlie the ability of these insects to survive in extreme temperatures. Survival and hsp70 expression upon abrupt changes are distinctly different from those after ramping indicating that experimental protocol must be considered before extrapolating laboratory results to natural field situations.

Dosage rate, temperature, and food source provisioning affect susceptibility of Tribolium castaneum and Tribolium confusum to chlorfenapyr

A series of experiments were conducted to evaluate residual efficacy of the insecticidal pyrrolle chlorfenapyr (Phantom®) on treated concrete for control of Tribolium castaneum (Herbst), assess development of progeny from exposed parental adults, and to determine if starvation before exposure with or without a flour food source increased susceptibility of adult T. castaneum and adult Tribolium confusum Jacqueline du Val to chlorfenapyr. No adults survived exposure on concrete treated with chlorfenapyr at the maximum label rate of 1.1 g active ingredient (AI)/m2, and no progeny were produced in bioassays conducted at 0–8 weeks posttreatment. In the second test, application rates were reduced, and bioassays were conducted at 27 and 32 °C. Adult survival and progeny production decreased as the application rate increased from 28 to 225 mg AI/m2, and survival and progeny production were generally lower at 32 °C than at 27 °C, but at higher rates survival was <1 %, and no progeny were produced. In the final test, adult T. castaneum and adult T. confusum were starved for 1–7 days and then exposed either with or without flour on concrete treated with 3.9 and 27.5 mg AI chlorfenapyr/m2. Mortality generally increased with starvation time, the presence of a food source led to decreased mortality at both application rates, and T. confusum was the more susceptible of the two species. Results show that chlorfenapyr could effectively control both species, but precise dosage levels need to be determined. Also, the presence of a food source greatly compromises adult control.

Effects of different monoalgal diets on egg production, hatching success and apoptosis induction in a Mediterranean population of the calanoid copepod Acartia tonsa (Dana)

The influence of six monoalgal diets was tested on the reproductive success of the copepod Acartia tonsa over a 15-day period in order to define the most favorable diet for the optimization of this copepod species to be used in aquaculture and in ecotoxicology applications. The cryptophytes Rhinomonas reticulata and Rhodomonas baltica induced highest egg production rates (mean=24.4eggsfemale−1day−1and 21.9eggsfemale−1day−1) and hatching success (mean=76% and 86.1%) over the 15-day period, respectively. Lowest egg production rates were recorded with both diatoms Phaeodactylum tricornutum (mean=8.8eggsfemale−1day−1) and Skeletonema marinoi (mean=8.4eggsfemale−1day−1). These two diatoms also had detrimental effects on hatching success (mean=44.1% and 46.5%, respectively) and adult survival. No adults survived for longer than 13days with a diet of P. tricornutum. Moreover, nauplii produced by females that had fed on diatoms for >10 d, were positively stained for the apoptotic fluorescent marker TUNEL, indicating imminent death. The prasinophyta Tetraselmis suecica induced low fecundity (mean=13.4eggsfemale−1day−1) and hatching success (mean=62%), and after 15days only 37.5% of the adults survived. Isochrysis galbana induced low egg production per female (<10eggsfemale−1day−1) after 15days.

Sexual Differences in Life History Traits ofPhilornis seguyi(Diptera: Muscidae) Parasitizing House Wrens (Troglodytes aedon)

AbstractWe studied life history traits of Philornis seguyi García, 1952 (Diptera: Muscidae) parasitizing house wrens, Troglodytes aedon (Vieillot) (Passeriformes: Troglodytidae), and analyzed sexual differences in the size of larvae, pupae, and adults, as well as in the length of larval and pupal stages and in adult survival. Males were larger than females at the larval, pupal, and adult stages, but there were no sexual differences in the length of larval and pupal stages, or in the time adults survived. Larvae developed in 5–6 d and started the larval-pupal molt within 24 h after abandoning the host. Pupal stage lasted for 9 d and its length was positively associated with size of the pupa. The size of the pupa was positively associated with that of the larva and the size of the adult with that of the pupa. In laboratory conditions, 86% of the larvae pupated and 75% of the pupae emerged as adults. In natural conditions, the proportion of unsuccessful pupae increased by the end of host's breeding season. The proportion of males and females that survived until the adult stage did not differ from random. Our results show that P. seguyi has a relatively short generation time, which would allow it a rapid population growth during the host breeding season, and indicate that intrasexual selection may have selected for large body size in P. seguyi males.

Research Toward an Artificial Diet for Adult Asian Citrus Psyllid

Abstract Research progress is reported on an artificial diet for adult Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae). The primary objective was to develop a system for screening antimicrobial peptides and other potential toxic proteins for activity against adults. The base diet was a sterilized solution of sucrose (30%) and yellow-green food coloring (0.5%) in tap water. All of the studies presented were conducted at 25°C, 75% RH, and a photoperiod of 14:10 (L:D) h. Adult psyllids were &amp;lt;7 d old when they were transferred to diet. Addition of the food coloring was necessary to prompt adults to feed. Among the feeding trials discussed, a mean of 69.1 ± 3.2% adults survived for 14 d on the base sucrose diet. Survival rates of males and females were similar. Adults feeding on the sucrose diet may have ingested less food than adults feeding on citrus leaf disks based on differences in quantities of adult excrements deposited in feeding chambers. However, survival of adults feeding on leaf disks over a 2-wk period was only marginally better than survival of adults feeding on the base sucrose diet, and final rates of survival of adults fed these two food sources were not significantly different.

Influences of Temperature onHomalodisca vitripennis(Hemiptera: Cicadellidae) Survival Under Various Feeding Conditions

Survival of the glassy-winged sharpshooter, Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), was studied under various constant temperatures and feeding conditions. When provided a host plant (Citrus limon L. Burm. f.) to feed on during a 21-d trial, 100% mortality occurred at 0.1, 3.2, and 40.1 degrees C, whereas an average of 74-76% of adults survived in the 13.2-24.5 degrees C range. When individually confined with moist cotton, adult longevity was greatest (16.3 d) at 13.3 degrees C, but it was <3 d at -2.4 and 36.2 degrees C. In a companion study comparing the presence versus absence of a host plant, the presence of a host plant was not a significant factor influencing survival at temperatures < or =7.8 degrees C but was at temperatures > or =18.9 degrees C. The relationship between temperature and survival was described by a nonlinear function that estimated the optimum temperature in each feeding regimen: no host plant or moist cotton (5.5 degrees C), moist cotton (9.9 degrees C), and accessible host plant (25.1 degrees C). The model quantitatively predicted that H. vitripennis would survive longer periods at a wider temperature regimen when provided with a host plant than when provided with water alone (moist cotton) or when provided with neither plant host nor water. Our results suggest that continuous exposure to either low (<5 degrees C) or high (>30 degrees C) temperatures are detrimental for adult survival. Specifically, low temperatures caused early mortality because of inhibition of feeding activity and presumably this threshold lies between 7.8 and 13.2 degrees C. Furthermore, this study clearly shows that temperature may influence the survival of H. vitripennis adults regardless of feeding regimens, and its implications for population dynamics are discussed.

Influence of diet on long-term cold storage of the predator Podisus maculiventris (Say) (Heteroptera: Pentatomidae)

Abstract Long-term storage could aid in the cost-effective mass production of beneficial insects. Pre-conditioning, insect developmental stage and environmental conditions should be considered when selecting storage conditions in order to obtain the highest performance after storage. We evaluated the influence of nutrient quality on the response of eggs, nymphs and adults of Podisus maculiventris when exposed to two temperatures most likely to be used for long-term storage. Natural prey-fed insects were compared to artificial diet-fed insects. The results of our study showed that eggs survived storage at 10 °C better than 4 °C, and that eggs from diet-fed insects survived storage at 10 °C significantly better than eggs from prey-fed insects. Nymphal survival of cold storage treatment was slightly higher than for eggs, with a similar pattern of response to temperature, nutrient quality and time of storage. However, of the three developmental stages tested, the best survival was obtained with adults. Similar to eggs and nymphs, adults survival was higher at 10 °C. However, different from eggs and nymphs was that the prey-fed adults survived better than diet-fed adults. Our results show that prey-fed adults were able to withstand cold storage at 10 °C for 4 weeks with very little loss of survival, fecundity or viability of eggs oviposited by those adults. Longer periods of storage resulted in a decline in survival, fecundity and egg viability and that decline was greatest at 4 °C. For the longer intervals of storage at 10 °C, egg viability was highest for eggs from diet-fed adults. Collectively, these results demonstrate an influence of nutrient quality on the response to cold storage at different developmental stages, and that an optimal food source for continuous rearing is not necessarily an optimal food source for cold storage.

Specificity of Carvalhotingis visenda (Hemiptera: Tingidae) as a biological control agent for cat’s claw creeper Macfadyena unguis-cati (Bignoniaceae) in Australia

Biological control is considered the most suitable management option for cat's claw creeper, Macfadyena unguis-cati, a major environmental weed in coastal and sub-coastal areas of Queensland and New South Wales, Australia. The potential host range of the leaf-sucking bug, Carvalhotingis visenda (Hemiptera: Tingidae) was evaluated on the basis of nymphal survival and development, adult feeding and survival, and oviposition preference using choice and no-choice tests involving 38 plant species in 10 families. In no-choice tests, although adults survived on a few of the non-target plants, no eggs were laid on any of the non-target plants. In no-choice condition, the tingid oviposits and completes nymphal development only on M. unguis-cati. There was also no visible feeding damage on any of the non-target plants. In choice tests, adults showed distinct preference for M. unguis-cati, and the preference level increased over time as the tingids moved away from the non-target plants. At the end of the trial no adults were evident on any of the non-target plants. Host specificity tests confirm that the tingid is a highly host specific biocontrol agent, and does not pose risk to any non-target plants in Australia. This agent has been approved for field release by the relevant regulatory authorities in Australia.

Lethal and sublethal effects of different ecotypes of Melia azedarach against Plutella xylostella (Lepidoptera: Plutellidae)

Shade-dried, powdered drupes of Melia azedarach L. were selected from three states in India, each representing a different geographical region, viz. Rajasthan (arid), Punjab (open plains), and Himachal Pradesh (hilly). Drupes were extracted in chloroform: methanol (9:1) and evaluated against second instar larvae of Plutella xylostella (Linnaeus) using a ‘leaf-disc dip’ bioassay. The ecotype from the arid region of Rajasthan yielded the lowest LC50 (1.47%), followed by that from the open plains of Punjab (1.79%) and the hilly areas of Himachal Pradesh, which yielded the maximum LC50 (2.29%). The survivors demonstrated various types of sublethal effects such as prolongation of larval period (7.0–7.8 days compared to 6.3–6.5 days in the control), reduction in pupal weight (36.0–38.4mg/10 pupae in comparison to 54.4–56.0 mg in the control), deformation of pupae (up to 69.7%) and inhibition of adult emergence (up to 92%). A highly pronounced curtailment of fecundity (up to 10.4 against 73.2 in the control), significant reduction in oviposition period of the adults (up to 3.5 days compared to 7.4 days in the control) and longevity (5.5–7.8 days against 8.9–10.3 days in the control), were also recorded. The extracts produced from trees in the arid region of Rajasthan caused both lethal and sublethal effects following treatment of the second instar larvae of P. xylostella. Only 1.0% normal adults survived at the end of the study compared to 3.5 and 5.5% adult survival in the extracts from the open plains and hilly area ecotypes, respectively. An understanding of the bases of these variations in the toxicity of the crude extracts from the M. azedarach ecotypes growing in different climate conditions may open up the possibility of propagation and genetic improvement of the desired traits in the future.

Giant kelp (Macrocystis pyrifera) survival in deep water (25–40 m) during El Niño of 1997–1998 in Baja California, Mexico

During the 1997-1998 El Nino, we examined seasonally a giant kelp population in deep water (25-40 m) off the coast of Northern Baja California. Though most popula- tions in the region completely disappeared, large fertile adults survived the entire warming event at depth. At 25 m, there was no significant change in density or num- ber of fronds per individual during the warming period from spring 1997 to spring 1998, though the surface can- opy sloughed off (died) down to 15 m depth. By summer 1998, recruitment occurred at all depths at the site. Adult survival at depth was most likely important in post-dis- turbance recovery in surrounding populations by occu- pying substratum, providing vegetative growth, and producing spores. Survival in deep water during this extreme El Nino may have been due to local hydrogra- phy, such as internal waves bringing cool nitrate-rich water into the deeper regions of the shelf from below the thermocline, providing a refugium against the warm tem- peratures, low nutrients, and heavy wave action associ- ated with warming events. Deep-water populations may regularly survive El Nino warming in this region due to internal wave activity, and go undetected due to the depth at which they occur and the sloughing of the shal- low (-15 m) biomass.

Survival and fecundity of Bt‐susceptible Colorado potato beetle adults after consumption of transgenic potato containing Bacillus thuringiensis subsp. tenebrionis Cry3A toxin

AbstractSurvival and fecundity of Colorado potato beetle adults, Leptinotarsa decemlineata (Say), that had or had not fed previously on non‐transgenic potato before exposure to transgenic potato containing the Bacillus thuringiensis subsp. tenebrionis Cry3A toxin (Bt) was investigated. In the laboratory, &lt; 5% of first‐generation adults survived after two weeks when restricted to Bt foliage since eclosion, but over 85% of adults that had fed initially on non‐Bt potato survived exposure to Bt potato for two weeks. In field experiments, less than 0.5% of adults that were exclusively provided Bt potato plants survived overwinter, whereas 44% to 57% survived overwinter when fed non‐Bt potato plants for two weeks before being provided Bt potato as a final pre‐overwintering host. Survival through the winter increased as the duration of initial feeding on non‐Bt potato increased and was similar for beetles provided either tubers or Bt potato plants as a final pre‐overwintering host. Only overwintered beetles that fed initially on non‐Bt potato before encountering either tubers or Bt potato as a final pre‐overwintering host laid eggs the following spring. Survival and reproduction of potato beetle adults after colonizing Bt potato fields should not be adversely affected as long as they have had sufficient time to feed initially on non‐Bt potato. Implications for how potato production practices in the Mid‐Atlantic US may affect the utility of general resistance management plans for Bt potato are discussed.

Demographic attributes of an introduced herbivorous lady beetle

AbstractDemographic attributes of the adults of an introduced herbivorous lady beetle Epilachna niponica (Coleoptera: Coccinellidae) were investigated from 1975 to 1981 in the Botanical Garden of Kyoto University. Population growth rate varied from 4.8 to 16.8 throughout the study period. Fecundity and mortality in the late larval period contributed most to annual changes in the population growth rate. Population growth rate was negatively correlated with the density of overwintering adults. Adult survival from emergence to the reproductive season, which varied from 0.03 to 0.36 throughout the study, was almost completely determined by survival during the pre‐hibernation period. Adult survival to the preproductive season changed in a size‐ and sex‐dependent manner. Larger adults survived better than smaller individuals; male‐biased mortality occurred from adult emergence to the reproductive age. Severe intraspecific competition among late instar larvae due to host plant defoliation produced a higher proportion of small‐sized adults, resulting in lower adult survival to hibernation. The introduced population had a higher population growth rate and a lower adult survival to the reproductive season than the source population.

The life cycle and distribution of the wart-biter Decticus verrucivorus (L.) (Orthoptera: Tettigoniidae) in a chalk Grassland in Southern England

The Wart-biter Decticus verrucivorus (L.) (Orthoptera, Tettigoniidae) has only four populations in southern England and as such is one of Britain's most endangered insect species. This paper describes aspects of the species' ecology relevant to management recommendations for its conservation. The post-embryonic development and distribution, in relation to microclimate, within a chalk grassland are investigated for the largest population. Egg hatch occurred in mid-April, there were seven nymphal instars and adult emergence occurred in July, although its timing was strongly influenced by weather. From egg hatch to adult emergence, densities fell by 99·3% yet adult survival was high. The study population was estimated to contain at least 290 adults in 1987 and 190 in 1988. After emergence, adult females almost doubled in weight but did not reach their maximum weight (and potential fecundity) until September. No adults survived beyond mid-October. Realised fecundity may thus be severely curtailed by poor weather in September. Adults were smaller and maximum adult densities were 10 to 15 times lower than in typical continental populations. Within the study site, densities were influenced positively by mean temperatures and were highest on a south-facing slope. Mean temperatures were determined by interactions between weather, aspect and vegetation structure. A management policy must ensure that areas of short, open turf are available for the species to raise the body temperature by basking in direct sunlight. However, it is stressed that this is only one component of the species' habitat requirements (albeit crucial). Other studies demonstrate that a mosaic of vegetation structures is required.