Population dynamics of the oriental fruit fly, Bactrocera dorsalis （Diptera： Tephritidae） in the Kunming area,southwestern China

Population dynamics of Bactrocera dorsalis Hendel （Diptera： Tephritidae） were studied through pheromone trapping over 4 years （1997, 1999, 2000, 2003） in the Kunming region, a high plateau area in southwestern China. B. dorsalis immigrates from southern Yunnan to Kunming each year, and occurs during early May through November. Annual trap captures recorded an increase in the B. dorsalis populations from May to July, when they peaked in abundance, and a decline until November. No flies were detected from November to April. The fruit flies had two generations. There was considerable overlapping due to the continuous arrival of immigrating flies during the summer months. Annual capture rates were significantly related to numbers of flies caught in July when peak captures were recorded; whereas the peak captures, in turn, positively depended on numbers of flies recorded in May, the first month of fly appearance in the current year. It suggested that the annual population abundance was mainly dependent on the size of the initial emigrating population. A daily average temperature of 18℃ was probably the threshold temperature required for the flies to undertake long-range dispersal, which partially explained the start of the fly in May each year on this high plateau. Under field conditions, the fruit flies can withstand 13℃ as a daily average temperature. No flies were recorded in any of the study years at a daily temperature colder than 10 ℃.     

Lake outlet blackflies - the dynamics of filter feeders at very high population densities

Larvae of the blackfly Simulium noelleri aggregated at very high population densities (up to 1.2 × 10⁶ individuals m⁻²) at a lake outlet in Kent, United Kingdom. During 1983 and 1984 their first appearance in these large numbers was in late-June and they completed three summer generations before the overwintering larval generation appeared in October. It is not known where the larvae overwinter but they recolonized the concrete steps of this outlet in May, together with larvae of the S. ornatum group which, however, were not found after completing one generation at this location.
Female flies from the overwintering generation oviposited en masse during late-June and the result was a well-synchronized growth of larvae in the first summer generation. Within this, and other generations, there was A wide range of emergence times for adults; they could emerge early and were then relatively small, or could emerge later and were then relatively large. Females were always larger than males and the emergence of flies was protandrous. A very similar pattern of growth and emergence times was found at a site in Finland.
In all generations, sex ratio was biased to males and the sex ratio in each generation was inversely correlated with population density. This ensured that there were sufficient males emerging, and surviving adult mortality, to guarantee fertilisation of the females which were more expensive to produce.     

一点拟灯蛾生活习性的初步观察

首次报道一点拟灯蛾AsotacaricaeBoisduval的生活习性 ,并描述其形态、寄主范围、成幼虫习性以及生活史。该虫在广州 1年发生 2代 ,以蛹在杂草、枯枝落叶以及其它缝隙等处越冬。翌年的 5月底至 6月成虫出现 ,第 1代发生在 5月底至 7月初 ,第 2代 (越冬代 )则从当年 6、7月到翌年 5月 ,幼虫 6或7龄 ,3龄前幼虫在叶背群集为害 ,4龄后分散取食。严重发生时 ,整叶被吃光 ,仅留主脉和侧脉。并提出了防治方法。     

玉米黄尾球跳甲的发生与防治

调查研究玉米黄尾球跳甲Sphaeroderma apicaleBaly的自然种群动态、自然种群生命表并对其药剂防治策略进行探讨。结果表明:玉米黄尾球跳甲在湖北宜昌1年发生1~2代,以成虫和蛹越冬。越冬代成虫4月中旬始现于田边的杂草,5月上旬迁入大田。百株成虫高峰出现在6月15日和8月7日;性比为0.491;卵始现于5月19日,产卵高峰出现在6月18日;平均卵量123.5粒,单雌最大卵量212粒;6月22日出现最高百株幼虫量。自然种群增长指数(I)为16.20。在发生盛期、高峰期、盛末期,玉米黄尾球跳甲被异角短胸姬小蜂Hemiptarsenus variconisGirault的寄生率分别为14.6,33.6和77.0%。马.辛硫磷1 000倍液和毒死蜱1 000倍液是防治玉米黄尾球跳甲比较理想的农药,校正防治效果分别为76.3%和66.5%;卵和1、2龄幼虫对化学药剂敏感性高,3龄幼虫对化学药剂敏感性低。结合以上的研究,提出玉米黄尾球跳甲的防治策略。     

滇西南稻区白背飞虱种群特征及其关键影响因子

为明确滇西南沧源县稻区白背飞虱Sogatella furcifera的种群发生特征及其影响因子,于2010-2019年通过灯诱监测和田间调查的方法,分析沧源县白背飞虱的越冬种群、灯诱种群及田间种群发生特征,并对白背飞虱种群数量的影响因素进行相关性分析.结果表明:(1)白背飞虱以成、若虫在再生稻、落粒稻上越冬,越冬虫量最...     

海北高寒草甸金露梅灌丛根田鼠种群生产力的研究Ⅰ.种群动态

1980—1982年在青海省海北高寒金露梅(Potentilla fruticosa)灌丛地区,用标志重捕法(CMR)对自然栖息地中的根田鼠(Microtus oeconomus)进行了野外调查。本文主要分析了根田鼠种群数量变动特点和繁殖、存活及年龄结构与种群动态的关系,并试图探讨根田鼠种群的稳定机制。     

江汉平原地区韭菜迟眼蕈蚊的发生特点

韭菜迟眼蕈蚊Bradysia odoriphaga Yang et Zhang在湖北江汉平原韭菜集中产区危害严重。在湖北荆州地区于2013-2014年对韭菜迟眼蕈蚊的田间种群动态进行了系统调查,发现该害虫一年发生春(3月中旬至5月上旬)、秋(9月中旬至翌年1月)2个危害高峰,但秋季危害高峰的危害期长且发生严重;夏季适温多雨导致韭蛆危害;幼虫最喜栖息和危害韭菜第一球茎,但秋季对白色茎的危害性增加;成虫可以在田间扩散,扩散时飞行高度主要在50 cm以上。因此,韭蛆在江汉平原地区韭菜的危害主要集中在秋季和冬初。     

Overwintering locations and hosts for onion thrips (Thysanoptera: Thripidae) in the onion cropping ecosystem in New York

Identifying locations where onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), overwinter and subsequently disperse is important for designing control strategies. In upstate New York from 2003 through 2006, potential overwintering sites in the commercial onion, Allium cepa L., cropping system were investigated early in the spring before onion seedling emergence and again late in the season after onions were harvested. Onion thrips adults were sampled directly from the soil and indirectly from the soil by using emergence cages. Sampling locations included onion field interiors and edges and areas outside of these fields, including woods. Host material sampled included onion culls; volunteer onions, which sprout from cull onions left behind after harvest; and weeds. Onion thrips adults were found in all sections of onion fields and in locations outside of onion fields, with the fewest emerging from woods. Emergence began in early May and extended into June. Peak emergence occurred during the last half of May, at which time 50-75% of the population had emerged. Adults colonized volunteer onions as early as late March and as late as mid-November. No adults were found overwintering in onion cull piles. Adults also colonized several weed species, especially pigweed, Amaranthus hybridis L., and lambsquarters, Chenopodium album L., late in the fall. Our results indicate that onion thrips adults overwinter in the soil within and near onion fields and that they probably colonize volunteer onion plants before subsequent generations infest the onion crop in the spring. Volunteer onions and weeds also provide onion thrips with a host after onions are harvested. Consequently, onion thrips management strategies should include tactics that reduce volunteer onion and weed abundance.     

Population density and seasonality effects on Sin Nombre virus transmission in North American deermice (Peromyscus maniculatus) in outdoor enclosures

Surveys of wildlife host-pathogen systems often document clear seasonal variation in transmission; conclusions concerning the relationship between host population density and transmission vary. In the field, effects of seasonality and population density on natural disease cycles are challenging to measure independently, but laboratory experiments may poorly reflect what happens in nature. Outdoor manipulative experiments are an alternative that controls for some variables in a relatively natural environment. Using outdoor enclosures, we tested effects of North American deermouse (Peromyscus maniculatus) population density and season on transmission dynamics of Sin Nombre hantavirus. In early summer, mid-summer, late summer, and fall 2007-2008, predetermined numbers of infected and uninfected adult wild deermice were released into enclosures and trapped weekly or bi-weekly. We documented 18 transmission events and observed significant seasonal effects on transmission, wounding frequency, and host breeding condition. Apparent differences in transmission incidence or wounding frequency between high- and low-density treatments were not statistically significant. However, high host density was associated with a lower proportion of males with scrotal testes. Seasonality may have a stronger influence on disease transmission dynamics than host population density, and density effects cannot be considered independent of seasonality.     

酢浆灰蝶生物学特性研究

通过野外观察、室内饲养等方法研究了酢浆灰蝶Pseudozizeeria maha(Kollar)的生活史及生物学特性。在南京地区,该蝶幼虫以酢浆草科Oxalidaceae的黄花酢浆草(Oxalis corniculataL.)为食,1年5代,世代交替发生。酢浆灰蝶在10月末以蛹在枯枝落叶或土壤表层浅洞中越冬,越冬代成虫次年5月始见、中旬为高峰期,5月中旬始见第1代卵及幼虫,6—10月间各月各虫态均同时发生,期间每月中下旬为成虫活动高峰期。幼虫共4龄,野外2～4龄幼虫具迁移、避热与适蚁行为。在室内饲养条件下,卵期为3～4d,幼虫期为22～26d,蛹期为6～7d。     

Seasonal Migration of Apolygus spinolae (Hemiptera: Miridae) between Grapevines and Herbaceous Plants

This study was conducted to verify the seasonal migration of Apolygus spinolae (Meyer-Dür) between grapevines and herbaceous plants. Overwintering eggs were hidden in the hair layer under grapevine bud scales. A. spinolae adults were captured on sticky traps in the grapevine yard from late spring to early summer, dwindled through the summer, and captured again in late fall. However, adults were observed from early summer in herbaceous plant fields. A. spinolae adults were abundant during the summer of July and August in the herbaceous field, and thereafter its density decreased through fall. A few or no A. spinolae was found on mesh-netted grapevines after the installation year of the mesh-net, which indicated that A. spinolae adults migrating to lay overwintering eggs during the autumn could not land at the grapevines because of the mesh-net. Damaged shoots by A. spinolae were concentrated near the edge of grapevine yards bordering the herbaceous plants. This distribution pattern of shoot damage was believed to be related to an oviposition behavior of A spinolae, reflecting that adults migrating from herbaceous plants lay eggs more frequently in grapevines adjacent to the summer host plants. Seasonal occurrence of A. spinolae in grapevine yards was suggested as follows: A. spinolae overwinter as eggs in dormant buds on grapevines and hatch in the spring. Nymphs feed on grapevines then develop to adults (spring population), and migrate to herbaceous plants. A. spimolae spends the summer on the herbaceous hosts (summer population). Then, adults migrate back to grapevines in late autumn and lay overwintering eggs.     

The Nematode Heterotylenchus autumnalis and Face Fly Musca autumnalis: A Field Study in Northern California

Helerolylenchus aulumnalis was found in six northern California counties surveyed, and the incitlence of nematode infection of face flies ranged from 4.7 to 43.8%. Intensive studies at a cattle ranch in Yuba County showed that population densities of the host and nematode infections were highest in flies from cow pats receiving full sun. Average host population density was 105.7 puparia per pat, and nematode infection averaged 38.6%. Pats in partial sun averaged 13.5 puparia and 13,1% nematode infection. No face fly was recovered from shaded pats. When data from pats first exposed during day or night were compared, no significant differences in host population density or nematode infection rates were apparent. Uninfected and superinfected flies were more frequent than predicted by a Poisson distribution.Infected and uninfected female flies of all ages captured on white sticky traps appeared to feed with similar frequency upon a creatny substance which was probably acquired from cattle, However, older infected females fed less on blood and more upon dung than older uninfected females. Percent nematode infection and host population densities were highest in spring and early summer, declined to a midsummer low, and then increased slightly. Both dung-reared flies and captured females showed similar trends in abundance anti infection rates. Regression analysis indicated that H. autumnalis may not be regulating face fly population density.     

The abundance cycle and influence factors on red tide phenomena of Noctiluca scintillans (Dinophyceae) in Dapeng Bay, the South China Sea

The seasonal occurrence of Noctiluca scintillans and the causativemechanisms of red tide phenomena were investigated in the northwesternpart of Dapeng Bay, the South China Sea, from March 1990 toJune 1992. It occurred in the plankton usually from Januarythrough May/June with peak abundance from March to early May.At least eight red tides of this organism, when the surfacewater was covered with the pink patches and slicks, were observedduring the investigation period, and all of them took placebetween March and early May. Noctiluca occurred at temperaturesfrom 15.8 to 2.8.6°C, and the population density was thehighest at temperatures between 19 and 25°C. It disappearedfrom the plankton in summer and fall when the temperature warmedto lethal level of     

铁杉球蚜的生物学及空间分布

通过对铁杉(Tusga chinensis Pritz)-云杉(Picea retroflexac Mast)、铁杉-华山松(Pinus armardi Franch)、云南铁杉(Tusga domosa Eichler)-槭树(Acer mono Maxim)-桦木(Betula platyphylla Suk)四川主要铁杉林类型中铁杉球蚜Adelges tsugae Annand林间定株、种群随机抽样、室内饲养研究表明,铁杉球蚜在四川1年发生2代(越冬代和第1代),世代重叠,成虫营孤雌生殖。越冬代从4月上旬至第2年的4月下旬,产卵盛期在5月下旬,平均产卵量为15.58粒,1龄若虫具有滞育越夏习性;第1代从12月下旬至8月中旬,产卵盛期在3月下旬,平均产卵量为67.37粒,并可产生有翅成虫,但无转主危害现象。种群的发育与温度有相关性,温度高林分种群发育进度快于温度低林分。该虫的危害与生境有一定相关性,铁杉针阔混交林危害重于铁杉针叶林;同一树冠不同层次之间、不同方位之间危害程度差异不显著;当年受害严重的树株第2年受害不严重。     

The population dynamics of the bushfly: the elucidation of population events in the field

At three well differentiated sites and over three seasons bushfly abundance at first increased rapidly, but then stabilized or fell slowly through the apparently favourable periods of summer and early autumn, before a rapid end of season decline. Analysis of the characteristics of flies taken regularly in a sampling programme allowed the sequence of population events involved to be elucidated. Adult flies immigrated in spring. They and their first progeny were comparatively large but in the subsequent locally bred generations a progressive decrease in fly size was associated with a gradual decline in the levels of natality and a gradual increase in the levels of mortality. Between site differences could be traced to variation in the balance of these changes. Climate may have a large role in the population dynamics of the bushfly but its effects are largely indirect. Fuller understanding of the bushfly life system requires some way of synthesizing the effects and interactions between the many factors involved.     

Gonad development of the sea anemone Anthopleura asiatica in clonal populations

Seasonal fluctuations in relative gonad volume and oocyte size of the sea anemone Anthopleura asiatica were examined in 3 unisexual (male) populations and one bisexual population in the Seto Inland Sea of Japan from December 1982 to December 1985. A distinct annual cycle of gonadal maturation with a peak in the summer was found in all of the populations, although they appeared to be sustained only by asexual reproduction. Spawning occured synchronously between the 2 sexes early in the fall in the bisexual population while it was one to one and a half months later in the unisexual populations.     

An introduction experiment of an herbivorous lady beetle: Characteristics of the adult population

In May 1971, 45 adults of an herbivorous lady beetleEpilachna niponica (Coleoptera: Coccinellidae) from Asiu Experimental Forest were introduced into a botanical garden of Kyoto University, where is 10 km south of the southern limits of its distribution with being 3–5°C warmer than the original site. The introduced population of the lady beetle was thus investigated from 1975 to 1981. Mark-release-recapture experiments were applied to individual adult beetles, to estimate population size and daily survival rate. Overwintering adults emerged from hibernation around early April, reaching peak numbers in late April to early May, then gradually declined to late June. No adults remained at the end of June. Adult survival was maintained at a high level to early May, and declined consistently until late in the reproductive season. New adults began to emerge in late June and quickly reached a peak in early July; thereafter they decreased in number and had entered hibernation by late October. In spite of seasonally deteriorating food resources and heat stress in summer, new adults showed moderately high survival during the inimical period. New adults which emerged later in the season tended to be smaller in body size than those that emerged early. The proportion of females in the new adult population gradually increased throughout the pre-hibernating period, suggesting that male-biased mortality occurred during this period. When compared to the source population, the introduced population had a higher rate of population growth. Coupled with the improved population growth, heavy leaf damage during the larval period suggested that intensive intraspecific competition was most likely to occur among larvae in the introduced population.     

The epidemiology of the metacercariae of Diplostomum baeri and D. spathaceum in perch (Perca fluviatilis) from the warm water effluent of a nuclear power station

Thermal effects on the dynamics of infection with metacercariae of Diplostomum baeri and D. spathaceum were monitored between May and September, in a year-class of perch Perca fluviatilis, in an artificial lake receiving warm water discharges from a nuclear power station and in an unheated reference site, for a two year period. In the heated area the prevalence of infection of the retinal form, D. baeri, was always 100%, whereas in the unheated site there was an increase from 93% in May to 100% in June 1986. The relative density of D. baeri was found to increase gradually during the first summer in both areas, although the accumulation rate of metacercariae was significantly increased in the heated area. In August of the first year the relative density of D. baeri peaked in the heated area, whereas it continued to increase in the unheated control. However, in September of the following year, the relative densities were at the same level in both thermal regimes. A concomitant decline in the degree of overdispersion of metacercariae within the host population was observed in the heated area as the population density of metacercariae decreased, whereas the index of dispersion remained at the same level throughout the study in the unheated area. However, it was not possible to sample perch in the unheated area between October 1986 and May 1987 and changes in the parasite population could have occurred during this period. The prevalence and relative density of D. spathaceum, the lens form, was on the contrary low, especially in the unheated site where it was recorded only occasionally. The infection of D. baeri exhibited a convex pattern in both thermal regimens, although the peak infection was noticed earlier in the heated area. Regulation of the parasite infrapopulation may have been achieved by the combined effects of a decreased transmission rate of cercariae with increasing age of the host, the mortality of metacercariae as a natural termination of the life span and to selective predation of heavily infected hosts. However, regardless of an increased accumulation rate of metacercariae in the heated area, the relative densities of D. baeri became equal in both thermal regimes at the end of the study. The mortality rate of metacercariae in the heated area was therefore presumably increased as compared with the unheated reference site.     

Two different strategies of host manipulation allow parasites to persist in intermediate–definitive host systems

Trophically transmitted parasites start their development in an intermediate host, before they finish the development in their definitive host when the definitive host preys on the intermediate host. In intermediate–definitive host systems, two strategies of host manipulation have been evolved: increasing the rate of transmission to the definitive host by increasing the chance that the definitive host will prey on the intermediate host, or increasing the lifespan of the parasite in the intermediate host by decreasing the predation chance when the intermediate host is not yet infectious. As the second strategy is less well studied than the first, it is unknown under what conditions each of these strategies is prevailed and evolved. We analysed the effect of both strategies on the presence of parasites in intermediate–definitive host systems with a structured population model. We show that the parasite can increase the parameter space where it can persist in the intermediate–definitive host system using one of these two strategies of host manipulation. We found that when the intermediate host or the definitive host has life‐history traits that allow the definitive host to reach large population densities, that is high reproduction rate of the intermediate host or high conversion efficiency of the definitive host (efficiency at which the uninfected definitive host converts caught intermediate hosts into offspring), respectively, evolving manipulation to decrease the predation chance of the intermediate host will be more beneficial than manipulation to increase the predation chance to enhance transmission. Furthermore, manipulation to decrease the predation chance of the intermediate host results in higher population densities of infected intermediate hosts than manipulation that increases the predation chance to enhance transmission. Our study shows that host manipulation in early stages of the parasite development to decrease predation might be a more frequently evolved way of host manipulation than is currently assumed.     

Sugar feeding in adult stable flies

Adult stable flies (Stomoxys calcitrans L.) are known to feed readily on sugars in the laboratory. However, little is known concerning the extent of stable fly sugar feeding in wild populations. We examined the frequency of sugar feeding in stable flies collected on Alsynite sticky traps in rural and urban environments. In addition, stable flies were visually examined to determine whether blood was present in the gut. In laboratory studies, sugars were detectable with the anthrone technique in stable flies for approximately 3 d after being imbibed, and blood could be visually detected in the gut for 24-48 h after feeding. Twelve percent of the field-collected flies had detectable sugar with a higher percentage of the urban flies having sugar fed than the rural flies, 21 and 8%, respectively. Female flies sugar fed at a slightly higher rate than males, 13 versus 11%, respectively. Less than 1% of the field-collected flies had blood in their guts. The frequency of observable blood was slightly higher in flies collected in an urban environment compared with those collected in a rural environment and did not differ between male and female flies. The number of flies with both blood and sugar was slightly higher than would be expected based on the frequencies of each alone. Seasonal patterns of both sugar feeding and blood feeding were similar in the rural and urban environments; both peaked in the early summer, May to mid-June, and dropped through the summer and fall. Sugar feeding in the urban environment increased again in October.