伞裙追寄蝇和双斑截尾寄蝇对草地螟的寄生特性

为认识寄生蝇对草地螟Loxostege sticticalis L.的寄生特性,调查了河北康保田间两种寄生蝇——伞裙追寄蝇Exorista civilis Rondani和双斑截尾寄蝇Nemorilla maculosa Meigen对草地螟各龄幼虫的寄生率、寄生部位及着卵量,并通过室内饲养对寄生蝇的存活率与寄主龄期、着卵部位及着卵量的关系进行了研究。结果表明： 两种寄生蝇在田间主要寄生草地螟5龄幼虫;寄生蝇可在每头寄主幼虫上着1～8粒卵不等,其中以1粒的居多（45.3%）,2粒的次之（33.6%）,但1头寄主幼虫中仅能羽化出1头寄生蝇;寄生蝇以寄生寄主幼虫头部和胸部较多,腹部较少,并且以寄生侧面居多,背面次之,腹面最少。寄生蝇的存活与寄主幼虫着卵量之间呈相关关系,在着卵量为1粒的寄主幼虫中,寄生蝇的存活率仅为66.7%,在着卵量为2粒及以上的寄主幼虫中,单头幼虫羽化出寄生蝇的比例为100%。     

双斑截尾寄蝇对寄主种类及草地螟幼虫龄期和寄生部位的选择性

双斑截尾寄蝇Nemorilla maculosa Meigen是草地螟和其他鳞翅类昆虫的重要寄生天敌,但国内外对其寄生行为知之甚少。为了明确双斑截尾寄蝇的寄生行为特征及其对草地螟种群动态的影响,在22℃,光照16 h的条件下就其对不同寄主种类及草地螟幼虫龄期、寄主部位的选择性进行了研究。结果显示：在草地螟、甜菜夜蛾和粘虫3种幼虫同时存在的条件下,双斑截尾寄蝇对草地螟的寄生率显著高于甜菜夜蛾和粘虫,而对甜菜夜蛾的寄生率又显著高于粘虫。另外,幼虫被寄生的平均次数也呈现相同的趋势,表明双斑截尾寄蝇喜选择草地螟。在3, 4, 5龄草地螟幼虫同时存在时,双斑截尾寄蝇对5龄幼虫的寄生率和平均寄生次数均显著高于4龄和3龄幼虫的,表明该寄蝇主要选择5龄幼虫为其寄主。在被寄生的草地螟幼虫中,胸部被寄生的比率（66.4%）和次数（4.2）显著高于头部（23.4%,1.0）和腹部（10.9%,1.1）,而腹部及头部被寄生的比例及卵粒数没有显著差异,表明双斑截尾寄蝇主要选择幼虫的胸部进行寄生。最后,就双斑截尾寄蝇对产卵寄主选择的原因和机理进行了讨论。     

草地螟的寄生蝇种类、寄生方式及其对寄主种群的调控作用

寄生蝇是草地螟的重要寄生天敌之一,其寄生率多数情况下高于寄生蜂,表现出很大的控害潜力。本文通过对文献资料的分析,结合多年来对草地螟寄生蝇的研究结果,对草地螟的寄生蝇种类、寄生方式、优势种及其控制作用,保护利用进行了总结和评述。草地螟寄生蝇种类丰富,目前已知有22个种,在草地螟的主要发生为害区都有分布,其寄生方式多样,寄主范围广,很多种类为多主寄生。优势种有4种：伞裙追寄蝇Exorista civilis Rondani,双斑截尾寄蝇Nemorilla maculosa Meigen,黑袍卷须寄蝇Clemelis pullata Meigen和草地追寄蝇Exorista pratensis Robincau Uesvoidy。这些优势种对控制当代草地螟的作用有限,而对控制下一代草地螟的发生为害起着重要的作用。本文最后讨论了草地螟寄生蝇的保护和利用前景。     

温湿度对伞裙追寄蝇飞行能力的影响

[目的]草地螟Loxostege sticticalis L.是我国北方天然草原和人工草原上的一种重要害虫,伞裙追寄蝇Exorista civilis Rondani,是草地螟优势性寄生天敌之一,是控制草地螟发生为害及种群动态的重要因素。研究不同温度和湿度对伞裙追寄蝇飞行能力的影响,探索其飞行规律,可为利用伞裙追寄蝇田间寄生防控草地螟提供依据。[方法]通过昆虫飞行磨系统测定了不同温湿度梯度下伞裙追寄蝇雌雄蝇的飞行距离、时间、速度等飞行能力指标。[结果]不同温度条件下,伞裙追寄蝇在21℃飞行能力最佳,飞行距离、飞行时间、平均飞行速度分别为:5.4543 km、2.7392h、2.2469km/h;不同湿度条件下,湿度为40%时寄蝇飞行能力最好,飞行距离、飞行时间、平均飞行速度分别为:5.7043km、2.6594h、1.8327km/h。[结论]在一定温度范围内,伞裙追寄蝇的飞行能力在21℃时较好,随后其飞行能力随温度的升高而下降。在一定湿度范围内,伞裙追寄蝇的飞行能力在湿度为40%时飞最好,不同性别的伞裙追寄蝇飞行能力无显著差异。     

伞裙追寄蝇的初步研究

近两年在广州郊区、肇庆、阳江、德庆等地调查,松毛虫害蝇主要有六种:伞裙追寄蝇(Exorista civilisRond.)、蚕饰腹寄蝇(Crossocosmia zebina Walk.)、家蚕追寄蝇(Exorista sorbillans Wied.)、松毛虫狭颊寄蝇(Carcelia bombylans rasella Bar.)、红尾追寄蝇(Exori-sta fallax Meig.)和棕尾别麻蝇(Boettcherisca peregrinaR.-D.)。前五种属寄蝇科,后一种属麻蝇科,主要寄生松毛虫的老龄幼虫。在低丘地带,十年生左右的松林中常以伞裙追寄蝇的寄生率为最高。 随着松毛虫生物防治的深入开展,我们对优势种伞裙追寄蝇进行了初步研究。     

峨山黄足毒蛾的生物学特性及防治

峨山黄足毒蛾是樟树的一种新害虫。该虫在福建一年发生3代,以幼虫越冬,翌年4月上旬开始化蛹,4月中旬末成虫开始羽化。幼虫7龄,少数6龄或8龄,老熟幼虫在樟叶面化蛹。主要天敌有日本追寄蝇、伞裙追寄蝇和瘤姬蜂等。敌敌畏、辛硫磷、敌百虫等农药喷雾防治效果较好。     

美国白蛾的天敌——日本追寄蝇

美国白蛾Hyphantria cunea Drury隶属鳞翅目灯蛾科,是一种世界性检疫对象,近年来在我国辽宁省丹东市发现。日本追寄蝇Exorista japonica Townsend经饲养,由美国白蛾幼虫中育出,现将该种寄蝇的生物学和利用途径介绍和探讨如下。 一、生物学特性 日本追寄蝇系大卵型寄蝇,雌蝇将尚未完成胚胎发育的卵,产于寄主体表,待幼虫孵化后,钻入寄主体腔。据北京地区初步观察,每年发生3—4代。7—9月饲养观察,完成一个世代需经16—17天。10月中旬最后一代脱蛆化蛹于土壤中越冬。卵期4—5天,幼虫期4—6天,蛹期7—8天。羽化后的成蝇能多次交配,每次所历时间长短不一,长的可达6小时,短的为2小时;雌蝇在自然界中较雄蝇迟数日出     

伞裙追寄蝇不同地理种群遗传多样性的ISSＲ分析

为从分子水平探索不同地区伞裙追寄蝇种群间的内在联系,本文利用ISSR分子标记技术对8个不同地区伞裙追寄蝇自然种群进行遗传多样性、种群间分化程度以及聚类分析等研究。结果表明:筛选出11对多态性稳定的ISSR引物,对8个地区伞裙追寄蝇群体的80个个体进行PCR扩增,共获得166个重复性好且清晰可辨的ISSR条带,平均每条引物扩增出15.0909个片段,且均为多态性条带,多态信息含量(PIC)为0.8441-0.8653;香农信息指数(I)为0.1240-0.3455;Nei's遗传多样性指数(H)为0.0841-0.2285;基因分化率(Gst)为28.78%,基因流(Nm)的均值为1.5702,即遗传变异主要存在于个体之间,不同种群间基因交流处于中等水平;8个地区伞裙追寄蝇种群被划分为4个类群,种群间的遗传分化与地理距离呈正相关关系。     

利用自然寄主玉米螟人工大量繁殖玉米螟厉寄蝇的研究

本文报道1983—1984年我国利用自然寄主亚洲玉米螟(Ostrinia furnacalis)幼虫人工大星繁殖玉米螟厉寄蝇(Lydella grisescens)的技术和方法。研究结果表明:在正常的玉米螟人工饲料配方中添加0.05克维生素E后,饲养和累代繁殖的供试玉米螟幼虫对提高寄蝇的生活和生殖力效果显著;温湿度、光照和风是影响寄蝇交尾的三因素,温度28～30℃,相对湿度70—80％,日光光照和微风吹拂为寄蝇交尾的适宜条件;掌握羽化1天以上的雄蝇与当天羽化的雌蝇这一有利时机,交尾率可达80—90％;受精雌蝇以5％稀蜂蜜液和牛奶喂饲后,寿命延长,胚胎发育良好;在温度25—30℃及相对湿度80—90％的条件下,子宫内的卵经9—11天全部成熟,采用人工剖腹取蛆,以蛆与寄主幼虫的密度比为3:1或4:1,使其充分接触的接蝇蛆方法,寄生率一般为80—90％,最高可达98％;根据同一寄主幼虫体内寄生1—4个蝇蛆的不同营养和发育情况,测定其蛹重,观察和比较成虫抱卵量、寿命和生殖力的强弱,证明1头玉米螟幼虫体内寄生1—2厉蝇蛆较为有利。 玉米螟厉寄蝇人工大量繁殖研究的成功,不仅有利于我国玉米螟防治工作,而且将为我国生防领域开辟出一条利用寄蝇的有效途径。     

饰额短须寄蝇的研究

饰额短须寄蝇是内蒙古西部地区小地老虎幼虫期的重要天敌。它对第一代和第二代小地老虎的寄生效率,分别为10.2%和34.7%。 该蝇在呼和浩特地区一年发生三代。第—代寄生期在5月下旬和6月间,第二代寄生期在7-8月,以第三代(越冬代)幼虫在警纹地老虎或黄地老虎末龄幼虫体内越冬。各世代历期,第一代大致为45天,第二代平均为51天,越冬代约长达8个半月余。 各世代的羽化率,常因蛹的坏死和重寄生等原因而有所减低,第一代羽化率为70.5%,第二代为81.2%:羽化时刻,雌雄两性均以上午6—8时最盛,而羽化期两性亦基本上一致。成虫羽化后,当天就能交配;一头雄蝇一般能交配10余次,一头雌蝇亦可受交2-3次。雌性比率,第一代为58.2%,第二代为56.6%。成虫大多活动在开花的作物上,取食紫花野豌豆、胡萝卜和荞麦等的花蜜。补充营养与成虫的寿命关系很大,用蜂蜜稀释液饲喂,第—代雌蝇平均寿命13.6天比不喂蜜的7.0天增加0.94倍,雄蝇平均寿命12.0天比不喂蜜的5.7天增加1.11倍:第二代在喂蜜的情况下,寿命的延长更为显著。补充营养的重要作用还明显表现在雌蝇的繁殖力上,没有饲喂蜂蜜只给清水的雌蝇概不产卵。本种寄蝇为卵胎生,卵的胚胎在母体内即已发育成熟,这种胚胎卵无卵壳似幼虫。胚胎卵陆续被产出,分散产于寄主活动的土表和寄主的食料植物上。产卵量很大,如能基本上产完,一雌可产1,000多粒。胚胎卵从母体产出后不久即脱下胎皮而成为真正的幼虫,自此开始至侵入寄主体腔这一自由生活阶段,称“闯蚴”。闯蚴寿命的长短与所在的处所有关,在植株上的比在土表上的要长,前者平均寿命为7.5天,后者为4.2天。闯蚴以蠕动方式爬行,活动范围一般在1—3厘米,最远可至8厘来。闯蚴从寄主体皮侵入,在寄主三龄以后侵入的才能寄生发育。侵入时寄主龄期愈大对寄蝇幼虫的发育愈有利,不仅发育期缩短,而且体长也随之增大。在—个寄主体内,只能完成一头寄蝇幼虫的发育。发育成熟后,即钻出寄主体皮,大多附于寄主残体上在土中化蛹。 本种寄蝇遭受一种锤角细蜂Trichopria sp.重寄生,第一代寄蝇的重寄生率为1.97%。该寄生蜂以蛹在第二代本种寄蝇蛹壳内越冬。     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.     

Composition and diversity of bird communities in Swedish farmland–forest mosaic landscapes

CapsuleThe amount of forest (at local and landscape scales) and occurrence of residual habitats at the local scale are shown to be the major factors influencing bird community composition in farmland–forest landscapes in central Sweden.

Aims To investigate the importance of local habitat and landscape structure for breeding birds in farmland–forest landscapes in central Sweden.

Methods Breeding birds were censused at 292 points. A detailed habitat mapping was made within 300 m of the points. Within a 300–600 m radius only two major habitats (forests and arable fields) were identified.

Results Cluster analyses of bird communities identified three site types that also differed in habitat composition: (i) partially forested sites in forested landscapes; (ii) heterogeneous sites with residual habitats in mosaic landscapes; and (iii) field-dominated farmland sites in open landscapes. A total of 19 of 25 farmland bird species (restricted to farmland or using both farmland and forest) had the highest abundance in farmland sites with mosaics of forest and farmland, while only six farmland species had the highest abundance in field-dominated sites. The bird community changed from being dominated by farmland species to being dominated by forest species (common in forest landscapes without farmland) at small proportions (10–20%) of forest at the local scale. A major difference in habitat composition between heterogeneous and field-dominated sites was the occurrence of different residual habitats (e.g. shrubby areas and seminatural grasslands). These habitats seemed to influence bird community composition more than land-use, despite covering <10% of the area. Seminatural grasslands were important for bird community composition and species-richness, but grazing seemed to be less important. Among different land-use types, cereal crops were the least preferred fields. Set-asides with tall vegetation and short rotation coppices were positively associated with species-richness of farmland birds.

Conclusion In general, the composition of the landscape was important for bird community composition, although amount and distribution of forests, occurrence of residual habitats and land-use of fields at the local scale had the strongest influence on bird community composition. The possible implications of these patterns for managing farmland–forest landscapes are discussed.     

Chemical constituents from the fruits of Rhus typhina L. and their chemotaxonomic significance

This work describes the isolation and characterization of twenty-nine compounds from the fruits of Rhus typhina L., including eleven flavonoids (1–11), eleven phenols (12–22), two pentacyclic triterpenes (23–24), two organic acids (25–26), one lumichrome (27), one courmarin (28) and one pyrimidine (29) on the basis of their spectroscopic data. Compounds apigenin (1), daidzein (4), orobol (5), 3′, 5, 5′, 7-tetrahydroxyflavanone (6), naringenin (7), butein (8), (-)-catechin (9), quercetin-3-O-α-L-(3″-O-galloyl)-rhamnoside (11), 2-hydroxybenzoic acid (13), 4-hydroxybenzaldehyde (14), vanillin (15), methyl 3,4-dihydroxybenzoate (16), 3,5-dihydroxybenzamide (18), tyrosol (19), caffeic acid (20), 3-(2,4,6-trihydroxyphenyl)-1-(4-hydroxyphenyl)-propan-1-one (21), phlorizin (22), friedelin (23), oleanolic acid (24), 4,4-dimethyl-heptanedioic acid (25), anthranilic acid (26), lumichrome (27), scoparone (28) and uracil (29) have not been recorded before in this plant. This is the first report on the occurrence of compounds 4–7, 9, 11, 13–14, 16, 18–21, 25–29 from the genus Rhus. Moreover, the chemotaxonomic significance of these isolated compounds was also summarized.