两近缘种烟草上棉铃虫种群适合度的比较研究

分别在室内和自然条件下,比较研究了普通烟草和黄花烟草两种不同寄主植物上棉铃虫生长发育、食物转化和利用及种群增长情况。结果表明： (1) 室内26±1℃、75%±5% RH和16L∶8D光周期条件下,与普通烟草相比,黄花烟草上幼虫的发育历期显著延长,1龄和2龄幼虫的存活率及雌蛾产卵量显著下降,种群净增殖率（R₀=30.5374）和内禀增长率（r_m=0.0951）减小;(2) 6龄幼虫对两种烟草的近似消化率及其相对生长率无显著差异,但对黄花烟草的利用率和转化率显著下降,相对取食量显著提高;(3) 第2代棉铃虫在普通烟田的种群增长（I=1.9922>1）比黄花烟田（I=1.1581>1）快,“烟草和其他”对种群起主要控制作用,特别是对低龄幼虫;第3代棉铃虫在普通烟田的种群增长有所减慢但仍呈上升趋势（I=1.5994>1）,而在黄花烟田则呈下降趋势（I=0.6434<1）,低龄幼虫受烟草抗性和雨水等的影响较大,高龄幼虫被病菌感染的数量增多。这些结果表明,与普通烟草相比,黄花烟草不适合棉铃虫种群的增长和繁殖。     

华北棉区棉田中棉铃虫的取食行为及为害特征的研究

在大量田间实验的基础上,本文揭示华北棉区棉铃虫Heliothis armigera(Hbner)在棉田中的取食行为及其咬食棉花不同发育阶段的繁殖器官的组成和数量.根据棉铃虫的取食行为与其寄主植物棉花生长发育的关系,分别列出第二、三、四代幼虫期内棉花全株上各发育阶段的繁殖器官的组成、各龄幼虫所在果枝上繁殖器官的组成、各龄幼虫咬食不同发育阶段繁殖器官的组成和数量以及其中脱落的数量.分析了不同世代幼虫取食行为的差异,及其对棉花生长发育和产量形成过程的影响.建立了用于棉田害虫管理系统的棉铃虫取食模型.     

寄主植物对乌桕黄毒蛾取食量及生长发育的影响

【目的】研究乌桕黄毒蛾Euproctis bipunctapex(Hampson)对5种不同科寄主植物(天仙果Ficus erecta var.beecheyana、拐枣Hovenia acerba、苦槠Castanopsis sclerophylla、杨梅Myrica rubra和杜英Elaeocarpus decipiens)叶片的取食量以及不同寄主植物对乌桕黄毒蛾生长发育和繁殖的影响。【方法】在恒定条件[温度(26±1)℃,相对湿度80%,光周期12L︰12D]下,设置5个处理组,每处理分别投喂不同寄主植物叶片,测定取食量、幼虫历期、存活率、繁殖力等指标。【结果】乌桕黄毒蛾对不同寄主植物的取食量差异显著,苦槠饲喂组最高(2 588.15 mg),杜英饲喂组最低(1 971.33 mg);但对不同植物的日取食量总体趋势相同,随时间呈指数增长,4龄起进入暴食期,4龄、5龄和6龄幼虫取食量占总取食量的80.68%~85.91%。取食不同寄主植物的乌桕黄毒蛾生长发育差异显著,天仙果饲喂组的个体幼虫历期(34.35 d)最短,存活率(60.20%)最高,产卵量(281.33粒/雌)最多,而杜英饲喂组的个体幼虫历期(41.36d)最长,存活率(38.78%)最低,产卵量(215.83粒/雌)较少。【结论】乌桕黄毒蛾虫害防治适期是4龄之前,苦槠和杨梅受乌桕黄毒蛾取食最多,天仙果是乌桕黄毒蛾生长发育的最适寄主植物。     

C3和C4植物寄主对华北地区棉铃虫越冬代和第一代的影响

确定华北越冬代棉铃虫虫源及其对第一代棉铃虫种群的影响是制定棉铃虫防治策略的基础。以越冬代棉铃虫蛾翅的稳定同位素δ¹³C为天然标记直接判定这些成虫的幼虫期寄主类型,并将雌虫接到春小麦植株上,调查其产卵、孵化、幼虫发育至化蛹、羽化等特征。结果表明,越冬代来自C₃植物(主要为棉花)的成虫个体数量占全部越冬羽化种群的53.1%,所产生的下一代老熟幼虫也较C₄来源的多(55.1%);雌蛾受精率都比较高;卵孵化率较高(52.9%>41.6%);幼虫发育在低龄阶段较比后者快,存活率低,但在高龄幼虫阶段相对后者慢,存活率高;与C₄植物(主要玉米)的来源个体后代的幼虫发育总历期接近,总存活率也相近。显示寄主植物小麦提供的营养条件在第一代棉铃虫的幼虫发育中具有决定性意义,即小麦只在特定阶段才适合幼虫的发育;而且不论是C₃还是C₄寄主来源的越冬代棉铃虫已经适应了这一限制。有效地评价了玉米和棉花等寄主植物对华北地区越冬代和次年第一代棉铃虫的影响,对于分析越冬代棉铃虫的虫源性质和第一代棉铃虫的防治及Bt抗性的治理有重要参考价值。     

寄主植物对亚洲玉米螟生长发育及雄蛾保护酶活性的影响

【目的】为了明确不同寄主植物对亚洲玉米螟Ostrinia furnacalis (Guenée)生长发育、繁殖及雄蛾保护酶活性的影响。【方法】在温度为(25±5)℃、湿度为75%±5%、光照周期为L∶D=16∶8的恒定条件下,研究了7科12种寄主植物对亚洲玉米螟发育历期、蛹期、成虫期、羽化率、雌蛾繁殖力及雄蛾体内超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活力的影响。【结果】亚洲玉米螟能够在12种寄主植物上完成生长发育。取食苍耳的幼虫历期较短(17.4 d),蛹期较短(5.9 d);成虫寿命较长(9.0 d),蛹重较大(50.7 mg);取食油菜的幼虫单雌产卵量较大(210粒/雌),取食油菜和油麦菜的幼虫成活率和蛹羽化率较高,均在80.0%以上。幼虫取食不同植物后,雄蛾体内保护酶的活性差异显著,幼虫取食酸模叶蓼后,雄蛾体内SOD活性较高,幼虫取食苍耳后,雄蛾体内POD和CAT活性较高。【结论】不同寄主植物对亚洲玉米螟生长发育、繁殖及雄蛾保护酶活性均有显著影响。取食苍耳和酸模叶蓼有利于亚洲玉米螟的生长发育。玉米螟在不同寄主植物上的生长发育和繁殖与保护酶活性呈现正相关性。亚洲玉米螟在取食不同寄主植物时,能调节自身保护酶的活性,来适应寄主,满足生长发育的需要。     

栎黄枯叶蛾生长发育与几种寄主内含物的关系

【目的】探讨饲喂不同寄主植物对栎黄枯叶蛾Trabala vishnou gigantina Yang生长发育及繁殖的影响,分析寄主植物内含物与其生长发育及繁殖的关系,为研究不同寄主植物对栎黄枯叶蛾种群动态的影响提供理论依据。【方法】在室内条件下,利用沙棘Hippophae rhamnoides、山杏Armeniaca sibirica、山杨Populus davidiana、旱柳Salix matsudana饲养该虫,观察幼虫发育历期、蛹历期、蛹重及产卵量等指标,同时测定寄主叶片中可溶性糖、可溶性蛋白质、水分、单宁及黄酮的含量,并进行线性回归分析。【结果】不同寄主植物饲喂栎黄枯叶蛾幼虫的发育历期、蛹历期、蛹重及产卵量均存在显著差异。取食沙棘的幼虫历期最短,仅为(74.50?1.76)d,而取食旱柳历期最长,达(106.00?1.51)d。取食山杨的蛹历期最长,为(44.00?1.41)d,最短的是取食旱柳的,仅为(32.70?3.13)d。饲喂沙棘和山杏的雌、雄蛹重和成虫产卵量显著高于饲喂山杨和旱柳的。对不同寄主的营养物质、次生物质和水分含量测定结果表明:不同寄主间营养物质、次生物质与水分的含量差异显著。回归相关分析表明:幼虫发育历期与寄主植物可溶性蛋白质含量呈显著负相关;雌蛹重和产卵量与寄主植物可溶性糖含量呈显著负相关;雌、雄蛹重与寄主植物含水量呈显著正相关;蛹历期与单宁含量呈显著正相关,但黄酮含量的高低与栎黄枯叶蛾生长发育等指标无相关性。【结论】沙棘是栎黄枯叶蛾生长发育及繁殖的最适寄主植物;并且寄主植物中可溶性糖、单宁的含量低、含水量和可溶性蛋白质含量高有利于栎黄枯叶蛾的生长发育和繁殖。     

寄主植物对松墨天牛幼虫体内酶系活性的影响

室内采用在马尾松、黑松、火炬松、湿地松和雪松皮下接入松墨天牛Monochamus alternatus Hope幼虫的方法,探明5种寄主植物对松墨天牛幼虫的存活、钻蛀取食及纤维素酶、酯酶、羧酸酯酶活性的影响。结果表明,5种寄主植物对松墨天牛幼虫存活和钻蛀取食有显著影响,接种于马尾松的天牛幼虫存活率100%;接种于雪松的松墨天牛幼虫存活率仅55.56%。松墨天牛取食不同寄主后,其体内纤维素酶、酯酶和羧酸酯酶活性存在显著差异。其中以取食火炬松的Cx酶活性最高,为(4.5754±0.1975)μmol·g-1(FW)·min-1,C1酶和β-l,4-葡萄糖苷酶活性以取食马尾松的松墨天牛幼虫消化道中最高,分别为(2.8199±0.0510)μmol·g-1(FW)·min-1与(3.0793±0.1733)μmol·g-1(FW)·min-1;而以取食黑松和马尾松的酯酶、羧酸酯酶活性最高,分别为1372.74mmoD/min·μg和744.82mmoD/min·μg。     

不同寄主植物上马铃薯甲虫种群生长发育的比较研究

马铃薯甲虫Leptinotarsa decemlineata (Say)是马铃薯Solanum tuberosum等茄科作物上的一种毁灭性害虫。为了探明寄主植物对新疆马铃薯甲虫种群生长发育的影响, 本研究通过非选择性试验测定了马铃薯、 茄子Solanum melongena和番茄Lycopersicon esculentum 3种栽培寄主及野生寄主中亚天仙子Hyoscyamus pusillus对马铃薯甲虫种群生长发育、 存活、 繁殖及生命表参数的影响。结果表明： 马铃薯甲虫幼虫虽然能够取食番茄, 但幼虫的发育历期长、 存活率低且蛹不能羽化, 表明番茄不是新疆马铃薯甲虫种群的适宜寄主。马铃薯、 茄子、 中亚天仙子3种寄主植物对该虫卵、 幼虫、 蛹的存活率和发育历期及成虫产卵前期没有显著影响, 但对蛹重和繁殖力影响显著。取食不同寄主植物后, 该虫蛹重和繁殖力从大到小的次序为： 马铃薯＞茄子＞中亚天仙子; 种群的净增殖率(R₀)、 内禀增长率(r_m)和种群趋势指数(I)从大到小依次为： 马铃薯＞茄子＞中亚天仙子。因此马铃薯为新疆马铃薯甲虫种群的最适宜寄主, 其次为茄子和中亚天仙子, 而番茄为不适宜寄主。     

园林害虫大袋蛾在四种寄主植物上的繁殖潜能评估(英文)

【目的】大袋蛾Clania variegata是一种严重危害多种植物的食叶性害虫。为了通过合理配植园林植物防治大袋蛾,本研究评估了在悬铃木、月桂、合欢及桃树4种寄主植物上大袋蛾的繁殖潜能。【方法】2018年7月15日至2019年6月21日,在室外纱网隔离环境中测定了大袋蛾分别在悬铃木、月桂、合欢和桃树上的卵期、幼虫期、蛹期、存活率、成虫寿命、雌成虫产卵期和每日单雌产卵量。采用年龄-龄期两性生命表程序TWOSEX-MSChart对大袋蛾发育历期、存活率、成虫寿命及雌虫繁殖力数据进行了分析。【结果】寄主植物种类可显著影响大袋蛾的发育历期和成虫寿命。取食月桂时,大袋蛾2, 3, 4和5龄幼虫的历期显著长于取食其他植物时的;取食桃树时,大袋蛾雌成虫寿命(11.47 d)显著长于取食月桂时的(10.26 d)。大袋蛾取食月桂时的产卵期(7.04 d)显著短于取食悬铃木(7.52 d)、合欢(7.59 d)及桃树(8.11 d)时的。大袋蛾取食悬铃木时的净繁殖力（R₀）(2 015.70粒卵)显著高于取食月桂(1 419.12粒卵)、桃树(1 289.66 粒卵)和合欢(976.67粒卵)时的。大袋蛾取食悬铃木时的内禀增长率(r)(0.02523/d)显著高于取食月桂(0.02377/d)、合欢(0.02304/d)及桃树(0.02194/d)时的。【结论】大袋蛾取食悬铃木时的繁殖潜能显著高于取食月桂、合欢及桃树时的,在园林设计中合理间隔种植月桂、合欢及桃树可能有利于减少大袋蛾对非嗜食植物的危害。     

棉铃虫营养生态学的研究:食物中糖含量的影响

用人工饲料研究了食物中不同含糖量对棉铃虫Heliothis armigera(Hfibner)生长、发育和繁殖的影响.基础饲料含粗蛋白质9.7%.饲料含糖12.5%对棉铃虫有最佳的营养效应.糖对蛋白质的比率在1.0—2.0对棉铃虫种群生长比较适宜.含糖量低于10%导致蛹的脂肪含量下降、成虫寿命缩短、产卵量显著减少.饲料含糖量超过28%使幼虫取食速率降低、代谢负担加重、发育历期延长、成虫繁殖力下降.因此,棉铃虫正常发育和繁殖所需的饲料碳水化合物含量应高于其蛋白质含量.这些结果与棉铃虫的食性特点是一致的.     

寄主植物对桃蛀螟生长发育及产卵选择行为的影响

为明确寄主植物对桃蛀螟生长发育及产卵选择行为的影响,利用实验种群生命表和二项产卵选择试验,研究了玉米、大豆、棉花和桃等4种寄主植物对桃蛀螟种群生长发育及产卵选择性的影响。结果表明:取食棉花的桃蛀螟幼虫存活率最低、幼虫历期最长,取食玉米的幼虫存活率最高、幼虫历期最短,取食桃和大豆的幼虫存活率和历期居于棉花处理组和玉米处理组之间;玉米处理组的桃蛀螟化蛹率、蛹重和蛹历期均为最高,棉花处理组为最低,大豆和桃处理组的这些参数均显著小于玉米处理组而大于棉花处理组;发育至成虫后,取食玉米的桃蛀螟羽化率显著高于其他3个处理组;取食桃的桃蛀螟成虫寿命(雌虫和雄虫)及个体发育历期均显著高于其他3种处理组;同时取食桃的桃蛀螟单雌产卵量最高,其次是玉米处理组,两者均显著高于大豆和棉花处理组。二项产卵选择试验结果显示,桃蛀螟雌蛾在棉花和玉米处理组、玉米和大豆处理组或棉花和大豆处理组间的落卵量差异不显著;但在包含桃的处理组中,桃蛀螟在棉花、玉米或大豆处理区的落卵量均显著高于桃处理区。上述结果表明,供试4种寄主植物中,桃蛀螟偏好在棉花、玉米和大豆上产卵,其中玉米对桃蛀螟的适合度相对较高,棉花对桃蛀螟的适合度相对较低。     

The effects of physiological factors and host plant experience on the ovipositional activity of the sweet potato whitefly, Bemisia tabaci

Both egg load and levels of vitellogenin and vitellin increased when Bemisia tabaci Gennadius (Homoptera: Aleyrodidae), were deprived of host plants. These increases resulted in significant increases in rates of oviposition. There was no difference in total fecundity between whiteflies temporarily deprived of hosts and a control treatment that had continuous access to hosts. The results of previous exposure to a preferred host, melon (Cucumis melo), and a non-preferred host, cotton (Gossypium hirsutum), were also examined. B. tabaci deposited significantly more eggs during a 6-h period on melon than on cotton, regardless of host species they were previously confined to. In addition, whiteflies previously exposed to cotton, deposited more eggs than females previously exposed to melon. This higher rate of oviposition resulted in a low egg load as well as lower levels of vitellogenin and vitellin. Conversely, a low rate of oviposition led to high egg load and high levels of vitellogenin and vitellin. Individuals from the same treatment exhibited variation in egg load, which was negatively and significantly correlated with previous oviposition activity. We conclude that the effects of previous host plant exposure on oviposition were, in part, due to behavioral differences that are not related to the reproductive physiology.     

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.     

Relative longevity of adult Nezara viridula in field cages of cotton,peanut, and soybean

Producers in the southeastern USA face significant crop losses from the stink bugs Nezara viridula (L.), Euschistus servus (Say), and Chinavia hilaris (Say) (all Hemiptera: Pentatomidae). Cotton, peanut, and soybean are major agronomic crops and host plants of stink bugs in the region. We conducted a field plot study to measure the relative longevity of adult, unmated N. viridula males and females caged on peanut, cotton, and soybean to test three hypotheses: (1) differences in mortality are associated with differences in host plant food suitability, (2) mortality rates increase with age, and (3) males have higher mortality than females. Using survival analysis, we found that the sex of the individual did not affect survival rates on any of the three host plants. Survival was significantly higher in cotton and soybean than in peanut. Mortality rates increased with age in peanut, but not in soybean or cotton. The frequency of canopy temperatures above 35 °C was higher in peanut than in soybean. Peanut appears to be a less than ideal habitat in terms of canopy temperature and/or food quality for N. viridula adults. Both, cotton and soybean were equally suitable food resources for N. viridula adults prior to maturation of the plants.     

Oviposition preference,larval performance and adaptation of Trichoplusia ni on cabbage and cotton

Most female herbivores ensure to lay eggs where their offspring can develop successfully. The oviposition preferences of females affect strategies in pest management. In this study, the performance of two cohorts of Trichoplusia ni larvae on cabbage and cotton (after they had been transferred from their original host plants) were investigated. The preferences of female moth ovipositing and larval feeding on these two host plants were observed. The results indicated that plants significantly affected oviposition preference of the female adults and development and survival of larvae of T. ni. All females preferred to lay eggs on cabbage than cotton regardless from which host they originated. The detrimental effects of cotton on the development and survival of T. ni larvae originated from cabbage (CaTn) increased with the increase of the larval age when they were transferred. In addition, the host plant change did not significantly affect the development and survival of larvae of T. ni originating from cotton (CoTn). Larvae of CaTn preferred cabbage plants as compared to cotton plants, whereas larvae of CoTn did not show a significant choice. Although the adult females preferred laying eggs on cabbage, they did not show preferences between cotton and cabbage in a Y‐tube olfactometer test. The hypothesis of oviposition preference and performance of larvae was supported by the results of CaTn, whereas they not supported by those from CoTn. Based on these results, the strategy to manage this serious pest was discussed.     

Differences in host selection and performance between B and Q putative species of Bemisia tabaci on three host plants

B and Q are two putative species of the Bemisia tabaci complex (Hemiptera: Aleyrodidae), and are among the most invasive and destructive pests of crops and horticultural plants worldwide. In China, Q predominates and is displacing B. Although researchers have proposed that the higher capacity of Q to utilize host plants plays an important role in its replacement of B, there are few relevant field surveys and experimental studies. The difference in host assessment between B and Q in multiple‐choice rather than in no‐choice situations may be essential to understanding the displacement. Here, we compared settling and oviposition preferences, and adult and nymph performance, for the putative species B and Q of the B. tabaci complex on three common host species: poinsettia [Euphorbia pulcherrima Wild. ex Klotsch (Euphorbiaceae)], cotton [Gossypium hirsutum L. (Malvaceae)], and cabbage [Brassica oleracea L. (Brassicaceae)]. Although the preferred hosts for settling and oviposition were the same as those that supported maximum fitness (adult longevity, fecundity, and nymph survivorship), these hosts differed between B and Q. When given a choice, B preferred to settle and oviposit on cabbage over poinsettia and cotton, whereas Q preferred to settle and oviposit on poinsettia and cotton over cabbage. In a no‐choice experiment, adult longevity, fecundity, and nymphal survival for B were greater on cabbage than on poinsettia and cotton, but the opposite was true for Q.     

外源基因导入对棉花烟粉虱种群的影响

以转基因棉花和对应的常规棉花亲本为材料,探讨外源基因导入对棉花烟粉虱Bemisia tabaci(Gennadius)种群的影响。结果表明,在转基因棉花GK12、33B、SGK上,烟粉虱从卵发育到成虫羽化的历期分别为15.56、15.35和15.25 d,较对应的常规棉亲本SM3(19.38 d)、33(20.81 d)、SY321(18.76 d)分别短24.55%、26.23%、18.71%;GK12和33B棉花上烟粉虱的存活率(69.16%)分别较对应的常规棉亲本SM3(54.76%)和33(64.91%)高26.29%和12.81%,而SGK(63.21%)上烟粉虱的存活率与对应的常规棉亲本SY321(62.61%)之间差异不显著;烟粉虱在GK12(84.00)和33B(77.25)上的产卵量分别较SM3(62.25)、33(70.00)高34.93%和10.35%,但SGK和SY321之间差异不显著;在转基因棉花GK12、33B、SGK上,烟粉虱的雌雄性比分别比对应的常规棉亲本高26.71%、46.23%和19.17%。结果表明,外源基因导入后,有助于烟粉虱的发育,提高了烟粉虱的产卵量和雌雄性比,从而促进了烟粉虱种群的上升。     

Nitrogen fertilization rate affects feeding, larval performance, and oviposition preference of the beet armyworm, Spodoptera exigua, on cotton

Nitrogen (N) is one of the most critical chemical elements for plant and animal growth, exerting a variety of bottom‐up effects. Development and oviposition of the beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), were studied in relation to varying N fertilization levels (42, 112, 196, and 280 p.p.m.) in cotton [Gossypium hirsutum L. (Malvaceae)]. Low N fertilization of cotton plants led to reduced plant biomass and a lower percentage of N in leaf blades and in leaf petioles. Development of S. exigua larvae fed with plants with reduced N applications (42 and 112 p.p.m.) was prolonged relative to treatments receiving higher N fertilization. Almost all larvae reared on artificial diets underwent only five instars before pupation. However, most larvae reared on cotton plants, irrespective of N levels, experienced a supernumerary sixth larval instar. Furthermore, significantly more larvae reared on lower N cotton plants underwent supernumerary development compared to larvae reared on higher N cotton plants. Life‐time feeding damage per larva ranged from 55 to 65 cm², depending on the nutritional quality of the food plant, although the differences were not statistically significant. Larvae distinguished between cotton plants with various nutritional qualities and fed preferentially on higher N plants. Female moth oviposition choice was also affected by host plant nutritional quality: cotton plants with higher N levels were preferentially chosen by S. exigua females for oviposition. The mechanisms of these effects are unclear, but they can have important implications for population dynamics and pest status of beet armyworms in the field.     

Effect of leaf nitrogen content of tomato plants on preference and performance of a leafmining fly

Summary In a study on intraspecific host plant acceptability, Liriomyza trifolii females that had previously been exposed to plants of high nitrogen content, showed a feeding and oviposition preference for plants of high nitrogen (Minkenberg and Fredrix 1989). Females showed a preference to feed and oviposit on the high middle leaves within plants. It was hypothesized that the preference between plants was related to a better performance of females and offspring on high nitrogen plants compared to low nitrogen plants. Different nitrogen dosages were applied to tomato plants, resulting in plants containing 3.4, 3.9, 4.6 or 4.9% leaf nitrogen. L. trifolii females responded to increased leaf nitrogen with significantly increased feeding and fecundity, longer oviposition periods, and higher feeding and oviposition rates. Their offspring on the same plants showed reduced developmental time, lower mortality and increased pupal size. Consequently, intrinsic rate of increase was positively linearly related to leaf nitrogen. Size of L. trifolii females appeared to be independent of fecundity, longevity and developmental time. Pupal length of males increased with increasing developmental time. These results indicate that L. trifolii is well adapted in its intraspecific host plant selection, because the ability to distinguish between plants with differences in leaf nitrogen content will directly lead to an increase in their fecundity, longevity and overall fitness. The implications of leaf nitrogen as a significant factor in the behavior and population dynamics of L. trifolii are discussed.     

Adaptation of Aedes aegypti (Diptera: Culicidae) oviposition behavior in response to humidity and diet

Effects of humidity and sugar concentration on the fecundity, temporal oviposition patterns and survival of a tropical strain of Aedes aegypti (L.) were investigated. Fecundity was significantly reduced by low humidity, but was not affected by sugar concentration. Low humidity caused a significant decrease in percentage survival after 19 days as compared to high humidity. Oviposition was inhibited by host availability for eight successive days. When access to a host was no longer provided, oviposition continued for 10 days in three to four distinct cycles without additional bloodmeals. Humidity stress and high sugar concentration caused oviposition to be delayed for one to four days, which is the typical duration of extreme low humidity periods in nature. These responses are hypothesized to protect the eggs of ovipositing females against the environmental hardships of periodic humidity stress and lack of hosts, thus enabling the perpetuation of the vector and the diseases it transmits in hot and dry seasons.