Induction of egg hatching by high humidity in the cicada Cryptotympana facialis

The timing of egg hatching in Cryptotympana facialis was examined in relation to short-term weather conditions. The brief underwater submergence, once a week, of dead twigs bearing cicada egg nests resulted in high hatching rates both at 25 degrees C and under outdoor conditions protected from rainfall. Under outdoor conditions with natural rainfall, most eggs hatched on rainy days. There was a significant positive correlation between the number of hatching eggs and daily relative humidity (RH). When eggs picked from twigs were exposed to various humidity levels, many eggs hatched quickly at higher humidity without direct contact with liquid water. Newly hatched nymphs showed a low tolerance to desiccation; at 81% RH at 25 degrees C, most of them died within 6 h. Under outdoor conditions, most nymphs died within 2 h on sunny days, whereas nymphs survived longer on rainy days. When newly hatched nymphs were released on dry ground, only 24% of them succeeded in burrowing into the soil, and many were killed by ants or desiccation. However, 92% of nymphs released onto wet ground successfully burrowed into it. The direct induction of hatching by high humidity ensures the survival and establishment in the soil of newly hatched nymphs in this species.     

Nymphal and adult performance of Apolygus lucorum (Hemiptera: Miridae) on a preferred host plant, mungbean Vigna radiata

Mungbean, Vigna radiata (L.) Wilczek, a preferred host plant of Apolygus lucorum (Meyer-Dür) (Hemiptera: Miridae), is used in China as a trap crop for this pest in cotton fields. Little is known, though, about the relationship between adult oviposition preference and offspring performance of A. lucorum on mungbean. In this study, we compared the oviposition preference of A. lucorum on mungbean versus cotton plants in both open-field plots and field cages. Field-plot experiments demonstrated that the population density of first instar nymphs of A. lucorum and the ratio of first instar nymphs to adults were significantly higher on mungbean than on cotton. Choice and no-choice cage experiments revealed that the number of eggs laid on mungbean was significantly higher than on cotton. We also compared adult longevity and fecundity, as well as offspring survival and development on these two host plants. We found that A. lucorum adult females survived longer and laid more eggs on mungbean than on cotton (P?<?0.05). Mungbean also promoted higher rates of development than did cotton (P?<?0.05), but did not affect nymphal survival (P?>?0.05). In summary, the preference of A. lucorum adults for mungbean is consistent with both adult and nymphal performance. This study furthers the understanding of the relationship between the polyphagous species A. lucorum and its host plants, which will help improve trap-cropping strategies for the control of A. lucorum that are based on the use of mungbean.     

Seasonal Alterations in Host Range and Fidelity in the Polyphagous Mirid Bug,Apolygus lucorum (Heteroptera: Miridae)

In herbivorous insects, host plant switching is commonly observed and plays an important role in their annual life cycle. However, much remains to be learned about seasonal host switching of various pestiferous arthropods under natural conditions. From 2006 until 2012, we assessed Apolygus lucorum (Meyer-Dür) host plant use in successive spring, summer and winter seasons at one single location (Langfang, China). Data were used to quantify changes in host plant breadth and host fidelity between seasons. Host fidelity of A. lucorum differed between seasons, with 87.9% of spring hosts also used in the summer and 36.1% of summer hosts used in winter. In contrast, as little as 25.6% host plant species were shared between winter and spring. Annual herbaceous plants are most often used for overwintering, while perennial woody plants are relatively important for initial population build-up in the spring. Our study contributes to an improved understanding of evolutionary interactions between A. lucorum and its host plants and lays the groundwork for the design of population management strategies for this important pest in myriad crops.     

新疆葡萄穴粉虱的形态学及生物学特性

【目的】葡萄穴粉虱是近年来入侵新疆吐鲁番地区的一种新害虫,明确其在新疆吐鲁番地区的生物学特性及发生危害情况,可为防治策略的制定提供科学依据。【方法】通过室内观察和田间调查,了解葡萄穴粉虱的形态学特征及生物学特性。【结果】葡萄穴粉虱属过渐变态。成虫复眼红棕色,翅膀表面覆盖白色蜡粉。卵倒锥形。若虫共4龄,扁椭圆形,体缘有蜡丝,末龄若虫在体壳内化蛹。4龄若虫(拟蛹)有半透明和黑色2型,越冬型4龄若虫(拟蛹)为黑色且有金属光泽。该虫在吐鲁番1年发生3~4代。越冬代成虫于4月上中旬破蛹羽化,开始在葡萄园危害,5月中旬第1代若虫孵化,5月下旬为孵化高峰;6月中旬2代若虫开始孵化,6月下旬—7月初为孵化高峰,世代重叠严重,10月中下旬之后以越冬代蛹在枯叶和枯枝上越冬。除为害葡萄外,葡萄穴粉虱还危害五叶地锦等葡萄科植物。【结论】在葡萄冬季埋土前或春季上架时,清除枯枝落叶可以大量减少越冬虫源,减轻防治压力。5月中旬第一代若虫孵化高峰期是化学防治的关键时期。在重点开展葡萄园防治的同时,应加强对五叶地锦等园林植物的防治。     

Influence of overwinteringDaphnia on spring zooplankton communities: An experimental study

To evaluate the influence of overwintering individuals of zooplankton on spring zooplankton communities, the dynamics of zooplankton communities with or without overwintering individuals were observed in experimental ponds from fall to spring. An insecticide, carbaryl, was used to regulate the overwintering individuals. In ponds which received insecticide applications in November or January, all cladoceran and rotiferan species were eliminated by the treatments and did not reappear until late March or early April, even when the chemical disappeared rapidly. The low water temperature may delayed the establishment of the populations from resting eggs. In these ponds, populations of various cladoceran and rotiferan species, which seemed to be originated from resting eggs, were built up in the spring. In control ponds,Daphnia ambigua orD. longispina overwintered as juveniles and adults and established a large spring population earlier than other cladocerans and rotifers overwintering as resting eggs. The latter zooplankters did not increase in the spring probably because their growth was suppressed by the precedingDaphnia species through competition. In nature, even if the number of overwintering individuals is small, they may have a potential to build up a large population earlier than the individuals hatching from resting eggs. As a result, the species which have overwintered as individuals seem to predominate in the spring and have a large influence on the spring zooplankton community.     

Relative contribution of biotic and abiotic factors to the population density of the cassava green mite, Mononychellus tanajoa (Acari: Tetranychidae)

The cassava green mite, Mononychellus tanajoa, is a key pest of cassava, Manihot esculenta Crantz (Euphorbiaceae), and it may be kept in check by naturally occurring predatory mites of the family Phytoseiidae. In addition to predatory mites, abiotic factors may also contribute to regulate pest mite populations in the field. Here, we evaluated the population densities of both M. tanajoa and the generalist predatory mite Euseius ho DeLeon (Acari: Phytoseiidae) over the cultivation cycle (11 months) of cassava in four study sites located around the city of Miranda do Norte, Maranhão, Brazil. The abiotic variables rainfall, temperature and relative humidity were also recorded throughout the cultivation cycle of cassava. We determined the relative importance of biotic (density of E. ho) and abiotic (rainfall, temperature and relative humidity) factors to the density of M. tanajoa. The density of M. tanajoa increased whereas the density of E. ho remained constant throughout time. A hierarchical partitioning analysis revealed that most of the variance for the density of M. tanajoa was explained by rainfall and relative humidity followed by E. ho density and temperature. We conclude that abiotic factors, especially rainfall, were the main mechanisms driving M. tanajoa densities.     

中华稻蝗长沙种群的生活史及其卵滞育的进化意义

中华稻蝗Oxya chinensis为重要的水稻害虫,在我国除青海、西藏、新疆、内蒙古等未见报道外,南起海南北至东北均有分布,在许多的分布区域1年发生1代。为探索中华稻蝗长沙种群的生活史及其季节适应特征,通过野外和实验室的研究,调查了其发生代数、孵化率和卵滞育率的季节变化及越冬卵的存活率。结果显示,中华稻蝗长沙种群为1年2代和1年1代混合发生:第1代卵产卵后大部分孵化为若虫而1年完成2代,但亦有19.4% -4.1%的卵不孵化而1年只能完成1世代。第1代成虫于6月上旬至8月上旬羽化,6月下旬至8月中旬产卵;第2代若虫于7月初开始孵化,9-10月羽化为成虫,10月上旬至11月下旬产卵。在室外自然条件下,中华稻蝗长沙种群6-8月(第1代)和10-11月(第2代)所产卵块均为部分滞育,滞育率为30%左右,皆无显著差异。然而,其卵滞育率在12月以后显著降低,仅为6.6%或以下,卵滞育快速地得以解除。因此,包括非滞育卵和滞育解除卵,中华稻蝗长沙种群的越冬卵皆以非滞育状态度过其后的寒冷季节。即使是遭遇长江流域2007年末至 2008年初异常寒冷的冬季,在长沙地区越冬后其卵的存活率亦在98%以上。非滞育状态的中华稻蝗长沙种群越冬卵完全能安全地越冬,其滞育的发生并非是为了提高其耐寒性而安全度过不适环境。并探讨了中华稻蝗长沙种群卵滞育的进化意义。     

Desiccation tolerance in fully developed embryos of two cicadas, Cryptotympana facialis and Graptopsaltria nigrofuscata

In two Japanese cicadas, Cryptotympana facialis and Graptopsaltria nigrofuscata , with different habitat distributions, fully developed embryos hatch in response to high humidity due to rainfall. Despite the advantage of hatching on rainy days, this trait burdens embryos with an extra period of desiccation until the unpredictable advent of rain. We compared the ability of the fully developed embryos of these cicadas to endure periods of low humidity. Eggs were exposed to a combination of different humidities (43% and 75% relative humidity, RH) and durations (0–15 days), and then transferred to an environment with 100% RH to stimulate hatching. In both species, total hatching rates decreased as duration increased, although there was no significant effect of humidity. In C. facialis , a considerable proportion of the eggs hatched during the desiccation period, and the hatching rate was higher at 75% RH than at 43% RH. After transfer to 100% RH, most hatching occurred within a day regardless of the desiccation level. In G. nigrofuscata , no nymphs hatched during the desiccation periods. However, more eggs required more than a day after transfer to 100% RH to hatch after desiccation at 43% RH than at 75% RH. Consequently, the overall proportion of timely hatching of eggs (eggs hatching within a day of moisture supply) was higher after desiccation at 43% RH in C. facialis , but it was higher after desiccation at 75% RH in G. nigrofuscata . These different physiological responses of the two species may reflect adaptation to habitat dryness.     

Embryonic stage of obligatory diapause and effects of abiotic conditions on egg hatching in the balsam twig aphid,Mindarus abietinus

Diapause‐mediated dormancy in overwintering insect eggs has rarely been studied with regard to the ecological factors controlling postdiapause development. In insects of temperate latitudes, water availability at the end of winter, in interaction with temperature, could control the resumption of development for insect stages in postdiapause quiescence. The balsam twig aphid, Mindarus abietinus Koch (Hemiptera: Aphididae), overwinters as eggs in southern Québec, Canada, on balsam fir, Abies balsamea (L.) Miller (Pinaceae), in Christmas tree plantations, where it is known as a pest. Previous work has shown that eggs of this aphid maintain low water content during winter, presumably to survive sub‐zero temperatures. Conversely, in late winter and early spring, they passively or actively absorb surrounding moisture, which is accompanied by notable changes in size, shape, and fresh mass. The primary objective here was to determine the embryonic stage at which winter diapause starts and is maintained in M. abietinus, a relatively primitive aphid. Secondly, we tested the hypothesis that free water availability to postdiapause eggs, in combination with temperatures above developmental threshold, is essential for embryonic development and hatching, by experimentally soaking field‐collected eggs in water at controlled frequencies. We observed that embryogenesis starts at the time of egg laying and stops after a few days, before the anatrepsis stage of blastokinesis is complete, when the germ band has not yet entirely immersed itself into the yolk. We also found that water surrounding overwintered eggs on fir shoots, in interaction with temperature regime, significantly increases M. abietinus egg hatching rates. Potential impacts of environmental factors such as precipitation are discussed in relation to M. abietinus egg hatching rates and potential for population growth in spring.     

Control of the flexible annual/biennial life cycle of the heather psyllid Strophingia ericae

Abstract. Strophingia ericae (Curtis) (Homoptera: Psylloidea) takes one or two years to complete its life cycle. In both cases eggs hatch over a prolonged period from midsummer, possibly extending into the following spring at high altitude, and instars overlap in time. Instar III is the predominant overwintering stage in the lowland, annual cycle, whereas in the upland, biennial cycle most first-year nymphs overwinter in instars I and II and most second-year nymphs in instar V. When moved to the laboratory, instars IV and V from a predominantly annual population showed accelerated development in response to elevated temperatures and to long days in both mid-winter and early spring. In the biennial life cycle, short autumn days retard instar V development but the response to photoperiod disappears by the end of winter. Exposure to LD 18 : 6 h retarded development of early instars in the annual population, resulting in an accumulation in instar III. The proportion of overwintering instars I and II rises with increase in altitude and moult to instar III becomes progressively delayed. Nymphs that reach instar III under long daylengths in the year following hatching are channelled towards the biennial cycle. Exposure of a predominantly biennial population to 15 °C and LD 18 : 6 h after midsummer, thus avoiding autumn conditions, promoted the rapid development of overwintered nymphs, switching the cycle from biennial to annual.     

Biology and population development ofAblattaria arenaria [Coleoptera: Silphidae], a snail predator

The biology ofAblattaria arenaria (Kraatz) was studied in the laboratory by using a helicid snail,Xeropicta derbentina (Kyrnicki) as prey. Population development ofA. arenaria in the field was studied in 1985 and 1986. The eggs ofA. arenaria were laid in the soil in lots of 5–45 at various intervals, and the total number of eggs per female varied from 144 to 193 during the oviposition period of 24–88 days.A. arenaria passed through the egg, 3 larval, prepupal, and pupal stages before reaching the adult stage. The mean duration of these stages was 9.8, 3.9, 2.5, 5.9, 3.8 and 5.7 days, respectively, with a total of 31.4 days. A. arenaria overwintered as an adult and became active and laid eggs during the spring. The start of spring activity seemed to be highly influenced by relative humidity. High humidity resulted in early emergence from overwintering sites. There was 1 generation in 1985, but 2 population peaks occurred in 1986. Immature stages of the 2nd generation became adult before the beginning of aestivation. Activity of the beetles was stopped by the beginning of hot weather in June, which synchronized well with the beginning of snail aestivation.      

Can overwintering versus diapausing strategy in <Emphasis Type="Italic">Daphnia</Emphasis> determine match–mismatch events in zooplankton–algae interactions?

Mismatches between predator and prey due to climate change have now been documented for a number of systems. Ultimately, a mismatch may have far-reaching consequences for ecosystem functioning as decoupling of trophic relationships results in trophic cascades. Here, we examine the potential for climate change induced mismatches between zooplankton and algae during spring succession, with a focus on Daphnia and its algal food. Whereas the development of an overwintering population of daphnids may parallel shifts in phytoplankton phenology due to climate warming, changes in the photoperiod–temperature interaction may cause the emerging population of daphnids to hatch too late and mismatch their phytoplankton prey. A decoupling of the trophic relationship between the keystone herbivore Daphnia and its algal prey can result in the absence of a spring clear water phase. We extended an existing minimal model of seasonal dynamics of Daphnia and algae and varied the way the Daphnia population is started in spring, i.e., from free swimming individuals or from hatching resting eggs. Our model results show that temperature affects the timing of peak abundance in Daphnia and algae, and subsequently the timing of the clear water phase. When a population is started from a small inoculum of hatching resting eggs, extreme climate warming (+6°C) results in a decoupling of trophic relationships and the clear water phase fails to occur. In the other scenarios, the trophic relationships between Daphnia and its algal food source remain intact. Analysis of 36 temperate lakes showed that shallow lakes have a higher potential for climate induced match–mismatches, as the probability of active overwintering daphnids decreases with lake depth. Future research should point out whether lake depth is a direct causal factor in determining the presence of active overwintering daphnids or merely indicative for underlying causal factors such as fish predation and macrophyte cover. Priority program of the German Research Foundation—contribution 5.     

The effect of overwintering temperature on the body energy reserves and phenoloxidase activity of bumblebee Bombus lucorum queens

Warming winters and changes in species composition related to the estimated global warming may cause a threat to bumblebees adapted to cold winters. During the overwintering period, their intermediary and respiratory metabolism decreases but metabolism remains responsive to temperature. The effect of temperature on diapause survival, phenoloxidase (PO) activity, and energy expenditure of the white-tailed bumblebee (Bombus lucorum) after a 4-month diapause were studied by manipulating the diapause temperature. Two overwintering temperatures were used, cold (1.8 °C) and warm (9 °C). Body fat content was used as an estimate of the remaining energy resources and PO activity as an immune function parameter of overwintering bumblebee queens. The baseline levels of PO activity were used to measure the differences in B. lucorum queen responses after overwintering in either temperature. We found a 0.4 g pre-diapause threshold weight of survival in B. lucorum. Large queens had more fat left and a higher PO activity compared to small ones after overwintering in warm conditions, but in the cold there was no effect of size on the remaining fat in the fat body of queens or their PO activity. The observed difference in energy usage appears to relate to normal size-dependent metabolism and variation in energy allocation between basic metabolism and immune functions.     

Cross-correlation analysis of invasive mango mealybug and its associated natural enemies in relation to meteorological factors: implications for biological control

Damage caused by invasive downey snow line mealybug, Rastrococcus iceryoides Green (Hemiptera: Pseudococcidae) has been reported to vary between 30% to complete crop loss where no control measure is applied. The current studies seek to determine factors influencing R. iceryoides population outbreaks, parasitoid – host and predator–prey relationships as well as predict optimal management strategies through weather modelling over a period of 28 months from 2008 to 2010 in Tanzania. The highest incidence of R. iceryoides was recorded during the dry season coinciding with the major mango fruiting season. The relationship between R. iceryoides and the parasitoid was positive but not significant, which implies the influence on outbreaks was negligible probably due to low percent parasitism (<12%). However, the predator abundance was directly and significantly related to that of R. iceryoides. Average temperature, average relative humidity, rainfall, and R. iceryoides abundance were autocorrelated to each other. Cross-correlation coef?cients vary significantly from ?0.286 to 0.589 for the pair-variable between R. iceryoides, temperature, relative humidity, rainfall, parasitism and predators. Our findings showed that temperature was the key climatic variable that significantly influenced R. iceryoides outbreaks while rainfall was significantly negatively associated with the pest. Time series analyses show R. iceryoides population increased 4 months after an increase in average temperature in all the sites, 11 months after rainfall and 11 months after relative humidity in Kibaha and Dar es Salaam, respectively. Our findings revealed that R. iceryoides is an excellent target for classical biological control. Thus, the importation of promising co-evolved parasitoid specific to R. iceryoides from the aboriginal home is crucial in formulating an efficient and sustainable management approaches against the invasive mealybug pest in mango agro-ecosystems.     

Effect of relative humidity on population growth of <Emphasis Type="Italic">Apolygus lucorum</Emphasis> (Heteroptera: Miridae)

Apolygus lucorum (Meyer-Dür) (Heteroptera: Miridae) is a significant insect pest of cotton, Chinese dates, grapes and many other crops in China, and its populations typically increase after heavy rains. However, the intrinsic mechanism of the rainfall-dependent outbreak is not yet fully understood. In our study, the effect of different relative humidity (RH), 40, 50, 60, 70, and 80% RH, on population growth of A. lucorum was evaluated in the laboratory. High humidity (e.g. 70 and 80% RH) was observed to significantly increase egg and nymph survival, prolong adult life longevity, and improve female fecundity. However, low humidity (e.g. 40 and 50% RH) led to unfavorable effects on survival and fecundity. As a result, the intrinsic capacity for increase (r _m), net production (R _o), and the finite rate of increase (λ) of A. lucorum population greatly increased with increasing relative humidity. Additionally, the relationships between r _m and R _o and relative humidity were good fits to the logistic models y = 36.82/(1 + Exp(10.76 − 0.19x)) (p < 0.001) and y = 0.10/(1 + Exp(9.26 − 0.19x)) (p = 0.003), respectively. This study provides insight into the phenology of A. lucorum, and may contribute to modeling of its population dynamics.     

印度查谟地区甜橙上柑桔潜叶蛾为害动态及其与重要气候因子的关系(英文)

本研究旨在揭示印度查谟柑桔潜叶蛾Phyllocnistis citrella Stainton为害甜橙Citrus sinensis的季节性变化,以及降雨量、相对湿度和温度等重要的气候因子对其种群的影响。本文对不同季节印度查谟的一个甜橙园里的柑桔潜叶蛾丰度进行了调查, 从2005年3月到2008年2月每两周调查一次。柑桔潜叶蛾在一年内有3个为害高峰,分别是4月中旬、7月中旬和9月中旬,这与甜橙新营养梢的生长期相吻合。相关分析表明,上午和下午的相对湿度和平均相对湿度与柑桔潜叶蛾的数量呈负相关;然而,平均降雨量、最高气温、最低气温和平均气温与柑桔潜叶蛾的数量呈正相关。降雨量和温度与柑桔潜叶蛾为害程度呈显著正相关。总之,柑桔潜叶蛾的数量不能简单地通过观察某一特殊地区的相对湿度来预测,而降雨量和温度在影响虫害方面均起着重要的作用。     

Abundance and seasonal activity of questing Ixodes ricinus ticks in their natural habitats in southern Germany in 2011

Questing ticks were sampled monthly over a period of 11 months from February, 2011 to December, 2011 at 13 sites in southern Germany using the flagging method. The ticks were identified to species, gender, and stadium. Although both I. ricinus and D. reticulatus were sampled, this study concentrated on I. ricinus, since it was the most abundant tick to be found. Additional weather data (air and soil temperature, relative air humidity, precipitation, sunshine duration) were recorded on each sampling site and the local vegetation described. A total of 14, 394 ticks was collected (7,862 larvae, 5,568 nymphs, 964 adults) and their activity was recorded in order to determine the seasonal activity pattern over different periods of the year. In contrast to the widely accepted pattern of a bimodal seasonal activity in moderate areas with a dominant peak in spring and a minor peak in autumn, a unimodal activity pattern was found for all development stages on six of the 12 sampling sites. Tick abundance was compared to weather variables. Tick host‐seeking activity was found to be significantly dependent on the temperature at ground level, precipitation, and sunshine duration as well as relative air humidity. Adult ticks showed a positive correlation with the duration of sunshine, whereas nymphs were mostly unaffected by this phenomenon.     

Quality assessment of Riptortus pedestris (Hemiptera: Alydidae) eggs cold-stored at different temperature and relative humidity regime

Supplementation of host resource can be more economical method for the biological control of insect pest compared to direct release of adult parasitoids. Periodical release of non-viable cold-stored eggs of Riptortus pedestris (Fabricius) (Hemiptera: Alydidae) has been found to enhance parasitism of this pest in soybean fields. To find the optimum environmental conditions for cold storage of these host eggs, we evaluated nine different combinations of temperature (2, 6, and 10 °C) and relative humidity (high 90–95%, medium 70–75%, and low 30–35%). After 30 d of cold-storage, eggs were weighed and held at 26.6 °C and 75% relative humidity for 8 d before testing. To test the eggs’ suitability as hosts following cold storage, females of Ooencyrtus nezarae Ishii (Hymenoptera: Encyrtidae) were released individually onto batches of eggs, and parasitization rates and the development, emergence, sex ratio, adult longevity, and size of parasitoid progeny were examined. Eggs stored at high relative humidity showed less weight loss than those stored at low relative humidity. The number of eggs parasitized was highest (5.9/15) on eggs stored at 6 °C and high relative humidity. Developmental times and adult emergence were optimal on host eggs stored at 2 °C and high relative humidity. A significantly lower proportion of eggs produced male parasitoids when eggs were stored at 2 or 6 °C. Adult longevity was not affected by egg storage conditions, but adult size of progeny decreased in eggs stored at 10 °C. In conclusion, eggs of R. pedestris stored below 6 °C and with a high relative humidity maintained the best quality for parasitization by O. nezarae.     

Factors affecting settlement rate of the hemlock woolly adelgid,Adelges tsugae,on eastern hemlock,Tsuga canadensis

1 We assessed the importance of several factors potentially affecting the settlement rate of the invasive hemlock woolly adelgid Adelges tsugae (Hemiptera: Adelgidae) on uninfested foliage of the eastern hemlock, Tsuga canadensis. We conducted our experiments in Massachusetts (U.S.A.) with overwintering sistens adelgids, and applied standard densities of infested foliage to uninfested branches in a planned multiple‐comparison design. 2 Settlement rates of progrediens crawlers produced by the overwintering sistens were highest when adelgid‐infested foliage was loosely attached to uninfested foliage and both branches were then enclosed in a mesh sleeve. 3 Early‐emerging crawlers settled at a higher rate than did late‐emerging crawlers. 4 Increasing the density of infested branches did not affect settlement rates. 5 We also tested whether less severe winter conditions improved settlement, and found that overwintering infested foliage in a refrigerator decreased settlement rate relative to foliage overwintered outdoors. 6 Our results suggest a protocol for adelgid inoculations that could substantially increase the success rate of experimental manipulations and encourage additional research on the population dynamics of this pest.     

Fecundity and fertility of ladybird beetle Harmonia axyridis after prolonged cold storage

Some species of ladybird beetles (Coleoptera: Coccinellidae) mate both before and after overwintering. The purpose of the pre-diapause mating was studied in the alien invasive ladybird Harmonia axyridis (Pallas 1773). Our study demonstrates the persistence of high fecundity (daily oviposition rate of 21 eggs per fertilized female during the first month of reproduction) and fertility (85 % of eggs hatching) of females of H. axyridis after long storage (up to eight months) at low temperature (6 °C). The females were not mated after activation in spring and had to rely on the sperm supply maintained from the pre-winter period (58 % of females were fertilized). Unfertilized females also laid eggs but in low numbers (an average of 345 eggs by virgin females during an individual’s lifetime, 1,174 eggs by females fertilized before winter) and after a longer pre-oviposition period (2–5 weeks in comparison to 7–8 days for fertilized females). We show that the unfertilised eggs were not trophic eggs. The high sperm survival ability observed questions the need for the high levels of sexual activity generally observed in Coccinellidae. Fertilized females of H. axyridis may found large colonies after dispersal to new areas even without males, which contributes to the striking invasive ability of this species.