Overwintering Of Eggs Research Articles

Takecallis nigroantennatus Wieczorek (Hemiptera: Aphididae) – implications of the ability to holocycle and overwintering of eggs on the spread of a potentially invasive bamboo aphid species

Takecallis nigroantennatus Wieczorek (Hemiptera: Aphididae) – implications of the ability to holocycle and overwintering of eggs on the spread of a potentially invasive bamboo aphid species

The effects of microclimatic winter conditions in urban areas on the risk of establishment for Aedes albopictus

The tiger mosquito, Aedes albopictus, has adjusted well to urban environments by adopting artificial water containers as oviposition sites. Its spread in temperate regions is favoured by the deposition of cold-tolerant diapausing eggs that survive winter temperatures to a certain degree. The probability of establishment in new geographical areas is estimated using predictive models usually based on meteorological data measured at coarse resolution. Here, we investigated if we could obtain more precise and realistic risk scenarios for the spread of Ae. albopictus when considering the winter microclimatic conditions of catch basins, one of the major sites of oviposition and egg overwintering in temperate urban areas. We monitored winter microclimatic conditions of catch basins in four Swiss cities and developed a regression model to predict the average microclimatic temperatures of catch basins, based on available meteorological parameters, accounting for the observed differences between cities. We then used the microclimatic model to correct the predictions of our previously developed risk model for the prediction of Ae. albopictus establishment. Comparison of the predictive model’s results based on local climate data and microclimate data indicated that the risk of establishment for Ae. albopictus in temperate urban areas increases when microhabitat temperatures are considered.

Assessment of habitat suitability for the cattle tick Rhipicephalus (Boophilus) microplus in temperate areas

The aim of this research was to analyze and model the aptitude of temperate areas to support permanent populations of the cattle tick Rhipicephalus microplus, which is principally distributed in tropical and subtropical areas. This work integrated field-derived data of tick development with temperature and land-based models of tick spread in Argentina. The integrated analysis of the results suggest that approximately 31°S is the southern limit where R. microplus finds appropriate climatic conditions to be established permanently. The establishment of permanent populations of R. microplus south of this latitudinal threshold is currently restricted because the low temperatures in autumn and winter inhibit the development of its eggs, but the introduction of cattle infested with R. microplus from early spring to late summer in temperate areas could produce engorged females laying eggs that would originate viable larvae from late spring to winter. The comparison of the temperature-based maps of habitat suitability with those obtained considering the lands suitable for livestock grazing, clearly shows that the models based only on climatic variables overestimate the potential dispersal of the cattle tick. The outcomes of this study suggest that an increase of temperature in the months of autumn and winter around 2°-2.75 °C should be necessary for the establishment of permanent populations of R. micoplus in the region belonging to temperate areas. This would allow that a tick generation emerged in early spring due to the overwintering of eggs and larvae originated from females detached from cattle during autumn or early winter.

On understanding and manipulating the hatching patterns of Diabrotica virgifera virgifera eggs to improve the design of experiments

AbstractDiabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae) is a well‐studied pest of maize (Zea mays L., Poaceae) in North America and Europe. Many studies on its biology, behaviour, or management rely on individuals reared from either field‐collected insects or laboratory colonies. Naturally, D. v. virgifera eggs require an obligate 8–10‐month diapause, which can cause technical challenges such as a deceleration of research activities. To allow better planning of experimentation, we have investigated the survival and temporal hatching patterns of the pest’s eggs depending on diapause length as well as post‐diapause incubation temperature. Laboratory assays revealed that the highest hatching rates and most synchronized hatching times in a wild diapausing population occurred when eggs were overwintered at the natural diapause length (8–10 months) or shorter (5–7 months) and then incubated at 20–24 °C. Eggs diapaused for only 2 months showed comparably good hatching rates, but hatching patterns appeared more variable. Diapause of <2 or >10 months reduced hatching success, as did low (16 °C) incubation temperatures. For comparison, a well‐studied non‐diapausing laboratory colony was assessed as well. Data matrices on egg overwintering survival, the start, peak, duration, and end of egg hatching, as well as hatching rates are provided for various diapause lengths and three incubation temperatures for both populations. This information will support scientists in choosing a D. v. virgifera colony that fits best their experimental set‐up and study conditions, as well as in optimally planning such studies.

Influence of cold temperature and exposure time on egg overwintering survival in the white-whiskered grasshopper (Orthoptera: Acrididae)

The effect of cold temperatures and exposure time on egg survival and hatching success were examined in the white-whiskered grasshopper, Ageneotettix deorum. Temperature treatments ranged from 4°C to -35°C, with treatment times ranging from 48 to 240 hours. Both decreasing temperatures and exposure time negatively affected egg survival, with a temperature below -25°C being lethal. Similar lethal temperatures are known for several North American grasshopper species. The relatively shallow location of A. deorum egg pods would result in increased vulnerability of eggs to cold temperatures in the absence of snow.

Habitat suitability modelling to assess the introductions of Aedes albopictus (Diptera: Culicidae) in the Netherlands

BackgroundIn the Netherlands, Aedes albopictus has been found each year since 2010 during routine exotic mosquito species surveillance at companies that import used tires. We developed habitat suitability models to investigate the potential risk of establishment and spread of this invasive species at these locations.MethodsWe used two methodologies: first, a species distribution model based on the maximum entropy modelling approach (MaxEnt) taking into consideration updated occurrence data of the species in Europe, and secondly, a spatial logic conditional model based on the temperature requirements of the species and using land surface temperature data (LST model).ResultsSuitability assessment obtained with the MaxEnt model at European level accurately reflect the current distribution of the species and these results also depict moderately low values in parts of the Netherlands, Belgium, Denmark, the British islands and southern parts of Scandinavia. Winter temperature was the variable that contributed most to the performance of the model (47.3%). The results of the LST model showed that: (i) coastal areas are suitable for overwintering of eggs; (ii) large areas in the northern part of the country have a low suitability for adult survival; and (iii) the entire country is suitable for successful completion of the life-cycle if the species is introduced after the winter months. Results of the LST model revealed that temperatures in 2012 and 2014 did not limit the overwintering of eggs or survival of adults at the locations where the species was found. By contrast, for the years 2010, 2011 and 2013, overwintering of eggs at these locations is considered unlikely.ConclusionsResults using two modelling methodologies show differences in predicted habitat suitability values. Based on the results of both models, the climatic conditions could hamper the successful overwintering of eggs of Ae. albopictus and their survival as adults in many areas of the country. However, during warm years with mild winters, many areas of the Netherlands offer climatic conditions suitable for developing populations. Regular updates of the models, using updated occurrence and climatic data, are recommended to study the areas at risk.

Population dynamics and seasonal variation in the embryonic dormancy of Pilophorus gallicus (Hemiptera: Miridae): ‘don't put all your eggs in one basket'

AbstractPilophorus gallicus Remane is a generalist predator in southern European pear orchards. Nymphs and adults are present in orchards from March to November; their winter absence suggests either migration to other hosts or embryonic dormancy on pear trees to overcome the adverse period. In addition, it has been hypothesized that aestivation takes place to cope with extreme summer conditions. The present study aimed to investigate the reproductive strategy of P. gallicus to overcome unfavourable periods. Accordingly, (i) its population dynamics were followed during several years and (ii) females were sampled in three different seasons to study the condition (diapausing or nondiapausing) of the laying. The results obtained show that nymphs were always the first mobile instar to show up in pear orchards and the presence of adults was delayed, indicating egg overwintering. Nondiapausing eggs prevailed in spring and summer, whereas the autumn eggs were mainly diapausing. Aestivation was rejected. Worthy of note are: (i) the presence of diapausing eggs under favourable conditions and (ii) the existence of females laying both diapausing and nondiapausing eggs; thus, ‘not laying all the eggs in one basket’. The reproductive strategy of P. gallicus is considered as bet‐hedging for the short‐ and long‐term survival of the species.

Development of an Emergence Model for Overwintering Eggs of Metcalfa pruinosa (Hemiptera: Flatidae)

The temperature-dependent development of Metcalfa pruinosa overwintering eggs was investigated at ten constant temperatures (12.5, 15, 17.5, 20, 22.5, 25, 27.5, 30, 32.5, and , Relative Humidity 20~30%). All individuals collected before April 13, 2012 failed to develop into first instar larvae. In contrast, some individuals that were collected on April 11, 2013 successfully developed when reared under temperature regimes. The developmental duration was shortest at (13.3 days) and longest at (49.6 days) in the fourth collected colony (April 26 2013). Developmental duration decreased with increasing temperature up to and development was retarded at high-temperature regimes (). The lower developmental threshold was and the thermal constant required to complete egg overwintering was 252DD. The Lactin 2 model provided the best statistical description of the relationship between temperature and the developmental rate of M. pruinosa overwintering eggs ($r^2

Fit for succession – community structure and life strategies of leafhoppers in urban brownfields

Abstract 1. Urban brownfields offer an excellent opportunity to study successional processes. Changes in the frequencies of biological traits during succession are of particular interest. They shed light on the general reasons why species emerge and vanish during the course of succession.2. Leafhopper (Hemiptera: Auchenorrhyncha) occurrence data (3763 species observations) of 194 species were studied. Data was collected on 246 brownfield plots, aged 0–40 years, in two cities in Northern Germany.3. Four categorical traits were studied: host‐plant type, phagy, dormancy, and voltinism. In these traits, two aspects were analysed: (1) changes in trait category frequencies during succession, and (2) distribution of trait categories (i) within the brownfield species pool versus the German species pool and (ii) within species observations.4. Trait categories showed clear successional trends. Young successional stages were related to feeding on herbs, polyphagy, egg overwintering, and two generations per year.5. By analysing combinations of two traits, species could be assigned to four functional groups: species associated with young, intermediate and old sites, and one group indifferent to site age. The pioneer group comprised the least number of species, but the highest number of observations.6. Categories associated with young site age were over‐represented in the brownfield species pool. Moreover, within this already biased species pool, species with pioneer trait categories occurred with higher frequency. For the slow colonisers among leafhoppers, brownfields seem to be habitats that are hard to exploit.

Phenology and prediction of pea aphid infestations on peas

Abstract This study was designed to investigate the possibility of predicting the timing and level of infestation of the pea aphid, Acyrthosiphon pisum (Harris), a pest of economic importance in peas. The source of infestation is perennial legumes. We followed the life cycle of the pea aphid from egg overwintering sites in leys of alfalfa, Medicago sativa (L.), and clover, Trifolium pratense (L.), to the infestations on peas, Pisum sativum (L.). Survival of overwintering eggs in the field was approximately 20%. Development of fundatrix to reproductive stage took 134 day‐degrees (DD) above a threshold of 5°C. Average total fundatrix fecundity was 52.04 nymphs. Because a considerable proportion of fundatrix offspring are alatae, these are probably an important source of first emigrants to the peas. Taking into account the low overall densities of these migrants, we found it impossible, using suction traps, to detect the timing or amount of migration to the peas early in the season. Catches in suction traps ...

The overwintering of eggs, intramolluscal stages and metacercariae of Fasciola hepatica under the temperatures of a Mediterranean area (Madrid, Spain)

The survival of embryonated and unembryonated eggs, of snails with mature or immature infection and of metacercariae over the winter of a Mediterranean area was analyzed. Embryonated eggs were more resistant than unembryonated eggs to cold weather, leaving a residual contamination which was responsible for earlier spring infection of the snail. Overwintering was similar in snail populations with both mature and immature infections although the lifespan was shorter in the former. Both snail populations survived in the mildest winter but not in the coldest. Only metacercariae from mid autumn were able to overwinter in an significant proportion (45%) but they were non-viable by mid spring. Our results suggest that in very cold winters no risk for grazing animals should be expected in spring.

The overwintering of Fasciola hepatica eggs under semi-arid and temperate Mediterranean climate (Madrid, Spain).

In this experimental work, conducted over two consecutive years (1988 and 1989), we have analyzed the overwintering possibilities of Fasciola hepatica eggs deposited in winter in a semi-arid and temperate Mediterranean area (Madrid, Spain). Eggs did not survive for more than a week in faeces at environmental moisture conditions. In contrast, over a 75% of the eggs maintained in permanently wet faeces survived winter temperatures, showing no high mortality until important thermic increment from June. The success of overwintering was higher in eggs arrested in wet faeces than included in water (55% "versus" 20% of hatching in spring), and it was unrelated to the deposition time (excretion in early or late winter). The hatching period of overwintered eggs started in May, at the same time as those excreted in early spring. Therefore, overwintering of eggs will have an effect on the level but not on the start of the spring contamination with miracidia. The dry winters of this semi-arid area greatly restrict the overwintering eggs contamination to soils next to streams, ponds or irrigation channels.

Viability and Developmental Rate of Overwintering Eggs of Trichosirocalus horridus (Coleoptera: Curculionidae)

The developmental rate of eggs of Trichosirocalus horridus (Panzer) in the laboratory was 0.0343 – (0.0071 × temp in °C). Egg hatch threshold was 4.8°C. Successful overwintering of eggs was affected by low temperatures at initial exposure. Eggs survived well when initially exposed to relatively high field temperatures between early November and mid-December, and from late February to March. However, eggs initially subjected to low temperatures between 15 December and 9 February suffered high mortality, although those surviving were not greatly affected by subsequent extended exposure to low temperatures. Most of the eggs initially exposed to field temperatures during this cold period hatched at about the same time. Eggs first exposed in November began hatching outside by mid-March.

Life-cycle variation ofMyzus persicae(Sulz.) (Hom., Aphididae) in different parts of the world, in relation to genotype and environment

AbstractLife-cycle variation, involving alternative methods of overwintering (holocycly and anholocycly), is found in many important pest aphids, and may have considerable ecological, genetic and economic significance. The occurrence of life-cycle variation in Myzus persicae (Sulz.) in different parts of the world is reviewed. The holocycle ofM. persicae, with sexual reproduction and overwintering of eggs on Prunus, occurs in the temperate regions of every continent, and although anholocycly is widespread in warm climates there are indications that the potential for sexual reproduction may be retained throughout the whole range of the species. The environmental factors involved in the determination of sexual morphs are considered. Photoperiodism provides the timing mechanism for sexual morph production, and the photoperiodic response is probably tuned to different regional conditions and buffered against other environmental variables within certain limits. The only other environmental factor clearly implicated in sexual morph production is temperature, and an attempt is made to correlate the global pattern of life-cycle variation inM. persicaewith temperature differences between regions, by dividing the world into six zones delimited by selected isotherms. The overall pattern of life-cycle variation can be explained largely on the basis of climatic differences between zones, and the effects of these differences on gene and genotype frequencies within the species. Clones of androcyclic character seem to be widespread and, although genetically isolated anholocyclic biotypes undoubtedly exist, androcyclic clones could be the principal source of parthenogenetic overwinterers in all parts of the world where life-cycle differences exist within populations.

Experiments on the artificial overwintering of eggs of the brown planthopper, Nilaparvata lugens Stål

Experiments on the artificial overwintering of eggs of the brown planthopper, Nilaparvata lugens Stål