牛粪和尿素对暗黑鳃金龟卵孵化及初孵幼虫存活的影响

为明确牛粪和尿素对暗黑鳃金龟的卵孵化和初孵幼虫存活的影响,在分别添加牛粪和尿素的土壤中接入暗黑鳃金龟的卵及初孵幼虫,并依据田间施肥量分别设置了5个处理剂量,检查暗黑鳃金龟的卵孵化率和初孵幼虫存活率,测量幼虫体长和体重。结果表明,添加牛粪的土壤中暗黑鳃金龟的卵孵化率和初孵幼虫存活率均显著高于对照,在牛粪添加量为15 g/kg时,幼虫的体长和体重均达到最大值。添加尿素的土壤中暗黑鳃金龟的卵孵化率及初孵幼虫存活率显著低于对照,且随着尿素用量的增加,卵孵化率和初孵幼虫存活率呈下降趋势。说明两种肥料对暗黑鳃金龟的卵孵化率和初孵幼虫存活率影响显著,在田间施肥应注意施肥种类及施用量对暗黑鳃金龟种群数量的影响,该结果为通过合理施肥保障农业生产,防治地下害虫提供了依据。     

不同龄期棉铃虫用氰戊菊酯汰选对其抗性发展的影响

利用中抗(15.06倍)品系,室内用氰戊菊酯对棉铃虫Helicoverpa armigera初孵至4龄幼虫分别进行连续汰选,选育9代后,以3龄幼虫汰选的抗性发展最快（31.5倍）, 其次是4龄、2龄幼虫汰选的品系（分别增加25.2倍和14.5倍）,用初孵幼虫汰选的抗性发展最慢（10.2倍）。抗性现实遗传力的测定表明,3龄幼虫汰选的抗性现实遗传力（0.4419）显著大于初孵幼虫的（0.2346）。代谢酶抑制剂的增效实验发现,磷酸三苯酯(TPP)对各品系棉铃虫均无明显增效作用。而增效醚(PBO)对高龄幼虫汰选的品系的增效作用比低龄幼虫汰选的品系增效作用强。测定初孵和3龄幼虫汰选品系试虫的击倒抗性发现,初孵幼虫汰选品系的抗性增加倍数（10.2）与击倒抗性增加的倍数（10.5）相似,而3龄幼虫汰选的抗性增加倍数（31.5）显著高于击倒抗性增加的倍数（19.9）。认为初孵幼虫期多功能氧化酶（MFO）表达不完全,用药主要是筛选击倒抗性,而高龄幼虫期用药则会同时筛选击倒抗性和MFO参与的代谢抗性。因而初孵幼虫期用药抗性发展缓慢。生产上不仅可以提高药剂的防效,同时可以延缓抗性的发展。     

三化螟自然种群生命表的研究

１９８４—１９８８年,在广东省四会县以生命表方法,进行了三化螟自然种群动态的研究,共获９个生命表．从生命表看出,各世代均以初孵幼虫入侵死亡率为最高,中后期幼以初孵幼虫入侵死亡率（ｋ５）为最大,冲后期幼虫转株死亡率（ｋ９）次之,但经图解法和回归法分析结果证实,中后期幼虫转株死亡率是影响三化螟种群数量变动的第１关键因素,而初孵幼虫入侵死亡率乃是第２关键因素．     

室内测定6种化学杀虫剂对草地贪夜蛾幼虫的毒力

2019年草地贪夜蛾Spodoptera frugiperda入侵我国多个省份和地区,对我国农业生产造成重大影响。化学防治是应对入侵害虫的主要措施,因此,本研究测定了6种不同作用机制杀虫剂对草地贪夜蛾初孵和3龄幼虫的生物活性。结果表明,对初孵幼虫具有较高毒力作用的为氯虫苯甲酰胺、多杀菌素、茚虫威、阿维菌素和甲氧虫酰肼;对3龄幼虫具有较高毒力作用的为氯虫苯甲酰胺、多杀菌素和茚虫威;与初孵幼虫相比,阿维菌素、茚虫威、多杀菌素和甲氧虫酰肼的LC 50分别提高了78.06、1.70、11.73和23.09倍。本研究筛选出了对草地贪夜蛾初孵幼虫和3龄幼虫杀虫效果较好的药剂,证明了低龄幼虫对部分农药抵抗力较弱,而3龄后的幼虫抵抗力显著增加,为田间草地贪夜蛾的化学防治提供了科学的用药指导。     

中黑盲蝽对小地老虎和甜菜夜蛾的捕食作用

中黑盲蝽Adelphocoris suturalis(Jakovlev)具有植食性和肉食性,但对其肉食性缺乏研究。作者在室内环境下研究了中黑盲蝽对小地老虎Agrotis ipsilon(Hufnagel)、甜菜夜蛾Spodoptera exigua(Hübner)卵和初孵幼虫的捕食作用。研究显示:(1)中黑盲蝽的捕食量随猎物密度的增加而上升,捕食功能反应符合HollingⅡ型方程;(2)捕食量随着若虫龄期的增加而增加,高龄若虫、雌性成虫与雄性成虫之间的捕食量没有明显差异,但均显著高于2龄若虫。雌成虫对小地老虎卵及初孵幼虫、甜菜夜蛾卵及初孵幼虫的最大日捕食量分别为38.60粒和6.80头、56.62粒和5.80头,表明中黑盲蝽对小地老虎和甜菜夜蛾卵和初孵幼虫具有较强的捕食能力。     

转Bt基因抗虫玉米对亚洲玉米螟幼虫取食行为的影响

室内研究了转cry1Ab杀虫蛋白基因的Bt抗虫玉米MON81 0和Bt1 1对亚洲玉米螟Ostriniafurnacalis初孵幼虫和3龄幼虫的取食行为、取食选择性和存活率的影响。在48h的非选择性试验中玉米螟初孵幼虫在MON81 0和Bt1 1玉米心叶组织上的幼虫取食率随时间的增加而下降,在对照玉米上的幼虫取食率随时间的增加而上升,两者间差异极显著。初孵幼虫接虫到MON81 0和Bt1 1玉米叶片48h的累计死亡率分别为67 .5 %和47 .5 % ,而在对照玉米上死亡率均为0. 3龄幼虫在Bt和非Bt玉米穗轴组织上的幼虫取食率随时间的增加呈上升趋势,第48h时在Bt和非Bt玉米上的幼虫取食率分别达到77 5 %和1 0 0 % ,差异极显著。选择性试验中,第4～48h内,初孵幼虫在Bt玉米上的幼虫取食率呈下降趋势,第48h时MON81 0和Bt1 1与各自非Bt对照的组合中初孵幼虫的累计死亡率分别为2 5 .0 %和1 7. 5 % ,二者差异不显著。3龄幼虫在Bt玉米和非Bt玉米上的幼虫取食率均随时间的延长而增加,但在非Bt玉米的幼虫取食率增加速度快,与Bt玉米差异极显著。Bt玉米对玉米螟幼虫取食有抑制和忌避作用。     

皮下接种松墨天牛卵及幼虫致死松树的研究

为了探明松墨天牛MonochamusalternatusHope直接致死松树的作用 ,作者采用在健康松树皮下接入松墨天牛卵或初孵幼虫方法做了试验和观察。结果表明 ,接入卵或初孵幼虫的松树平均枯死率为41 . 7%。松树枯死取决于松墨天牛幼虫取食时对松树韧皮部的破坏程度。每株接入 5个单位 (1单位指1粒卵或条初孵幼虫 ) ,松树枯死率达 85. 7% ;接入 1个单位 ,枯死率为 1 0 %。初步结论是 ,松墨天牛是引起松树枯死的主要原因之一 ;大力防治松墨天牛是保护我国松林的关键。     

转Bt基因玉米对甜菜夜蛾幼虫存活和发育的影响

在室内测定了2种转Cry1Ab基因的Bt玉米MON810和Bt11不同组织对甜菜夜蛾 Spodoptera exigua （Hübner）初孵幼虫以及心叶对4龄幼虫存活和发育的影响,在田间比较了甜菜夜蛾幼虫取食Bt 和非Bt玉米雌穗的存活和为害情况。结果表明,转Cry1Ab基因的Bt玉米的不同组织对甜菜夜蛾初孵幼虫都具有明显的杀虫活性,取食Bt玉米心叶、苞叶、籽粒时甜菜夜蛾均在幼虫期死亡; 取食MON810和Bt11雄穗的初孵幼虫化蛹率分别为5.2%和2.1%,羽化率为2.1%和1.0%;取食MON810和Bt11花丝的初孵幼虫化蛹率分别为1.0%和2.1%,但不能羽化。4龄幼虫取食MON810玉米心叶的化蛹率与对照差异不显著,而取食Bt11的化蛹率与对照差异显著; 取食两种Bt玉米心叶的４龄幼虫化蛹后的雌、雄蛹重和羽化率与对照组差异显著,但蛹期和平均单雌产卵量差异不显著,虽然对照组羽化的成虫平均产卵量高于Bt玉米组。田间接种初孵幼虫10 天后的调查结果表明,在MON810和Bt11玉米花丝上幼虫存活率分别为1.3%和0.3%, 而对照组分别为12.9%和16.2%;MON810和Bt11玉米雌穗被害率分别为18.3%和5.0%,而对照组分别为93.3%和95.0%,均显著低于对照组。     

果实种类及发育阶段对梨小食心虫幼虫钻蛀率和蛹重的影响

【目的】明确梨小食心虫Grapholitha molesta在寄主果实上的钻蛀率和蛹重与寄主种类和果实发育阶段的关系,为其田间预测预报和综合防控提供技术依据。【方法】在室内条件下测定了接卵后72 h梨小食心虫初孵幼虫在不同发育阶段的3个种共6个品种水果［苹果Malus pumila (嘎啦苹果), 桃Amygdalus persica (大久保毛桃、丰白毛桃和霞光油桃), 梨Pyrus bretschneideri (砀山酥梨和玉露香梨)］果实上的钻蛀率以及在不同果实状态的4个水果品种(大久保毛桃、丰白毛桃、砀山酥梨和玉露香梨)果实上72 h的钻蛀率;比较了接卵后24 h和72 h初孵幼虫在不同发育阶段的3个苹果品种(嘎啦苹果、富士苹果和金冠苹果)果实上的钻蛀率;并测定了不同发育阶段的金冠苹果、富士苹果、嘎啦苹果、砀山酥梨和丰白毛桃上的梨小食心虫蛹重。【结果】接卵后72 h梨小食心虫初孵幼虫在6个不同水果品种果实上的钻蛀率从高到低依次为：霞光油桃＞嘎啦苹果＞砀山酥梨＞玉露香梨＞大久保毛桃＞丰白毛桃;除霞光油桃外,其他5个水果品种果实的发育阶段显著影响初孵幼虫钻蛀率。对于嘎啦苹果,接卵后72 h初孵幼虫在其幼果上的钻蛀率最高(73.69%),在其着色期果实上钻蛀率最低(32.51%);在大久保毛桃、丰白毛桃、砀山酥梨和玉露香梨上,接卵后72 h初孵幼虫的钻蛀率均随果实生长发育而增加。初孵幼虫在3 个苹果品种着色期和成熟期果实上的钻蛀率随处理时间的增加而显著下降,而在其幼果上变化不显著。寄主种类及其发育阶段也显著影响梨小食心虫蛹重,成熟毛桃和梨饲养的雌、雄蛹重显著高于未成熟果实饲养的蛹重,着色期苹果不利于蛹重的增加。【结论】果实种类及发育阶段显著影响梨小食心虫初孵幼虫钻蛀率和蛹重,取食成熟期梨和桃的梨小食心虫初孵幼虫钻蛀率和蛹重显著高于取食未成熟果实的个体。     

沙雷氏杆菌S3菌株产几丁质酶对棉铃虫不同虫龄幼虫的后致死作用

研究了粘质沙雷氏杆菌（Serratia marcesens）S3菌株产几丁质酶（Chitinase）对棉铃虫(Helicoverpa armigera)的后致死作用。生物测定表明,沙雷氏杆菌S3菌株产几丁质酶对棉铃虫幼虫48h的毒力不高,其中几丁质酶浓度为50μg/mL对初孵幼虫的毒杀力仅为8.3%,对高龄幼虫48h不表现毒力。但几丁质酶对棉铃虫幼虫特别是低龄幼虫生长发育如10d龄虫重、蛹重、化蛹历期、蜕皮、羽化等影响较大,造成棉铃虫幼虫化蛹历期延长,死蛹率和不正常羽化率增加。其中经几丁质酶处理后的初孵、1d龄、2d龄、3d龄、4d龄幼虫蛹重分别是对照组的51.0%、77.1%、81.4%、86.0%、96.2%;化蛹率分别为74.5%、87.5%、93.7%、95.8%、95.8%,都低于对照组的97.9%;死蛹率分别为57.3%、18.8%、13.6%、7.8%、7.9%;初孵幼虫化蛹历期长达14d;初孵幼虫的正常羽化的蛹只有40.8%。几丁质酶对棉铃虫的后致死作用明显。     

核型多角体病毒感染对棉铃虫幼虫同类相残行为的影响

在室内研究核型多角体病毒（HaSNPV）感染对棉铃虫Helicoverpa armigera（Htibner）幼虫同类相残行为的影响。结果显示：感病棉铃虫随感病程度的加重,越容易被健康棉铃虫残食,而自然死亡的感病棉铃虫、冻死的感病棉铃虫和冻死的健康棉铃虫三者被健康棉铃虫残食的百分率无显著差异。表明感病棉铃虫和病虫尸体更易于被健康棉铃虫残食,是由于棉铃虫体力减弱而失去反击能力,不是由于病毒本身的影响。以健康棉铃虫、感病棉铃虫为残食者,冻死的病虫为被残食者,相残率无显著差异,表明病毒并未改变棉铃虫残食同类的天性。残食病虫的健康棉铃虫的化蛹率和羽化率均低于正常的健康棉铃虫,残食者为相残行为付出了很高的代价。     

二化螟滞育幼虫的蛋白和核酸含量以及保护酶活性的变化

为了阐明二化螟Chilo supprressalis滞育幼虫的分子特征及滞育期间保护酶活性的变化规律, 本研究应用Trizol法、 总量DNA提取法和蛋白定量试剂盒, 测定了在长光周期16L∶8D和25℃下发育的非滞育老熟幼虫、 在短光周期12L∶12D 和25℃下诱导滞育51 d的幼虫（称为滞育0个月）、 滞育1, 2和3个月幼虫的核酸含量和总蛋白含量; 同时应用试剂盒测定了老熟幼虫、 滞育0, 1和2个月的二化螟幼虫5种保护酶（POD, CAT, SOD, LDH和ATP酶）的活性。结果表明： 滞育幼虫的总RNA含量显著低于非滞育的老熟幼虫（P<0.05）, 而滞育1, 2和3个月的幼虫之间没有显著差异（P≥0.05）。老熟幼虫的总DNA含量显著高于滞育幼虫（P<0.05）。老熟幼虫的RNA/DNA比值较低, 滞育幼虫的RNA/DNA比值较高, RNA/DNA比值随着滞育时间的推移呈现出先上升后下降的趋势。滞育期大于1个月的幼虫中蛋白含量均显著高于非滞育的老熟幼虫（P<0.05）, 而滞育1, 2和3个月的幼虫之间没有显著差异（P≥0.05）。二化螟幼虫体内5种保护酶活性随发育阶段不同而存在差异。滞育幼虫中POD, CAT和SOD的活性随滞育时间延长而逐渐增强, 滞育2个月幼虫中的活性最高, 而非滞育老熟幼虫中的活性最低; LDH和ATP酶的活性则相反, 非滞育老熟幼虫中的活性最高, 滞育2个月幼虫中的活性最低。这些结果说明, 总RNA和DNA含量降低、 RNA/DNA比值先升后降、 总蛋白含量升高以及保护酶活性的变化是二化螟幼虫滞育过程中的主要生理特征。     

Effects of spatio-temporal intervals between newly-hatched larvae on larval survival and development inMonochamus alternatus (Coleoptera: Cerambycidae)

The effects of distance between hatching larvae on survival and development were investigated inMonochamus alternatus. Two newly-hatched larvae were inoculated intoPinus densiflora bolts at a distance of 2.5 cm or 10 cm, simultaneously or at an interval of 2 weeks. Some larvae were inoculated singly as a control. When larvae were inoculated simultaneously, mortality of the closely-inoculated larvae was significantly higher than that of distantly-inoculated larvae. Such high mortality was identified as due to conspecific bites. When the two larvae were inoculated asynchronously, the first-inoculated larvae killed some second-inoculated larvae but were never killed by them. Consequently, mortality was higher in second-inoculated larvae than in first-inoculated larvae. In particular, there was a significant difference in mortality between them when the larvae had been inoculated closely. The mortality of second-inoculated larvae was higher in the closely-inoculated group than in the distantly-inoculated group although there was no significant difference between them. In the case of two simultaneously-inoculated larvae, the initial distance between them had no significant effect on the development and growth in the early larval stage. When the larvae were inoculated asynchronously, the first-inoculated larvae grew more quickly than singly-inoculated control larvae.     

高效液相色谱法检测菜蛾绒茧蜂幼虫体内多杀菌素残留

应用高效液相色谱法检测施用于寄主幼虫的多杀菌素可否传递到在其体内发育的寄生蜂幼虫。以对多杀菌素高抗的小菜蛾Plutella xylostella幼虫作为菜蛾绒茧蜂Cotesia plutellae的寄主,待绒茧蜂发育到1龄幼虫时,将浓度为50 mg/L的多杀菌素点滴到寄主幼虫背板上,随后让寄主幼虫取食经50 mg/L多杀菌素处理过的甘蓝叶片,寄主幼虫和其体内的蜂幼虫再发育3天后,将寄主幼虫解剖取出蜂幼虫,用高效液相色谱法对经多杀菌素处理的小菜蛾幼虫体液以及绒茧蜂幼虫匀浆液进行检测,结果多杀菌素的2个活性成分spinosyn A和spinosyn D均被检测到,两者的多杀菌素残留浓度分别是2.79 mg/L和0.94 mg/L。这表明,通过寄主幼虫体壁接触和取食进入其体内的多杀菌素,可通过寄生蜂幼虫体壁浸透、蜂幼虫对寄主血淋巴的取食,或这两种途经一起进入蜂幼虫的体内,对蜂幼虫产生作用。     

越冬过程中桃小食心虫结茧和裸露幼虫体内耐寒性物质动态变化

为比较桃小食心虫Carposina niponensis Walsingham越冬过程中种群耐寒性的差异, 本文研究了其结茧和裸露幼虫自然种群的耐寒性,分别测定了不同时期桃小食心虫越冬幼虫过冷却点、体内含水量、总脂肪、总蛋白和总糖含量。结果表明：从10月至翌年2月份结茧和裸露越冬幼虫的过冷却点、结冰点、总蛋白含量、总糖和总脂肪含量及结茧幼虫的含水量均呈下降趋势。裸露幼虫含水量持续增加,在2月达到最高61.42%,在其存活的整个时期的含水量高于同时期结茧幼虫含水量。裸露幼虫的总糖含量持续降低,在2月份含量达到最低（0.65 μg/mg）,存活的整个时期显著低于同时期的结茧幼虫总糖含量。在裸露幼虫存活的整个时期总蛋白含量和总脂肪含量都和结茧幼虫没有显著差异(P>0.05)。在越冬过程中, 裸露幼虫体内高含水量和低含糖量可能是其不能正常越冬的原因。     

草地螟滞育幼虫的蛋白和核酸含量变化

为了阐明草地螟Loxostege sticticalis 滞育的分子调控基础, 本研究应用Trizol法、 DNA和蛋白质定量试剂盒、 SDS-PAGE电泳技术分别对进入滞育1, 2, 3和4个月、 解除滞育以及非滞育草地螟老熟幼虫中的核酸含量、 总蛋白含量和组分的变化进行了测定。结果表明： 滞育不同月份幼虫的总RNA含量显著低于非滞育幼虫的总RNA含量（P＜0.05）; 解除滞育幼虫的总RNA含量显著高于滞育2, 3和4个月的幼虫, 但仍显著低于非滞育的对照组。滞育不同月份、 非滞育以及解除滞育幼虫的总DNA含量没有显著差异（P＞0.05）。RNA/DNA比值随滞育的开始而显著下降, 随着滞育的结束而显著上升。滞育不同月份的幼虫总蛋白含量显著高于非滞育幼虫的总蛋白含量（P<0.05）, 但解除滞育与非滞育幼虫的总蛋白含量无显著差异。利用SDS-PAGE电泳分析发现滞育幼虫体内存在滞育关联蛋白, 蛋白条带在24 kDa左右, 但非滞育和已经解除滞育的幼虫则没有该蛋白条带。这些结果表明, 总RNA含量的降低、 RNA/DNA比值下降、 总蛋白含量的升高, 以及24 kDa蛋白的存在是草地螟幼虫滞育的主要生理特征。     

Ontogenetic- and condition-related effects of starvation on responsiveness in herring larvae (Clupea harengus L.) during repeated attacks by a model predator

The escape behaviour of fed and food-deprived herring larvae (20-30 mm SL) was studied during repeated attacks with a glass probe in order to investigate the causal mechanisms of starvation-induced changes in reaction to predators. Two experiments were set up: one where the fed and starved larvae were of the same age but of different sizes and one with groups of similar size but different ages. Biochemical and morphological condition measures described the condition of individual larvae. Starved larvae showed a lower responsiveness than fed larger larvae of the same age, and the responsiveness in this experiment decreased with decreasing nutritional status of the larvae. However, starved larvae that were of the same size but older than fed larvae showed a higher responsiveness, which could be explained by differences in development of sensory systems. A combination of condition and developmental factors thus explained the differences between starved and fed larvae. Both starved and fed larvae showed decreasing responsiveness over time with repeated attacks with no difference between starved and fed larvae in the relative change over time. The results emphasise the importance of taking into account individual age and/or development when the nutritional condition of wild-caught larvae is incorporated in survival models.     

Demersal schooling prior to settlement by larvae of the naked goby

Synopsis Field observations and collections indicate that the naked goby, Gobiosoma bosci, undergoes a near-bottom schooling phase prior to settlement. The size of these demersal larvae was intermediate between the sizes of larvae collected in plankton tows and of metamorphosed juveniles collected from the benthos. Two larvae that were captured unharmed quickly settled and metamorphosed. Otoliths of demersal larvae contained 20–41 daily increments. Most larvae were in schools made up of at least 25 individuals although single larvae were also seen. The dispersion pattern of demersal larvae was far more aggregated than that of recently settled juveniles indicating that larvae in schools probably do not settle to the benthos en masse.     

转cry1Ab/cry1Ac基因水稻对大螟幼虫体内三种保护酶活性的影响

为阐明转cry1Ab/cry1Ac基因水稻对大螟Sesamia inferens (Walker)作用的生理生化机制, 本研究用转cry1Ab/cry1Ac基因水稻茎秆饲喂大螟3龄和5龄幼虫, 采用酶活性测定方法研究了取食转Bt水稻对大螟幼虫体内3种保护酶SOD(superoxide dismutase)、 CAT(catalase)和POD(peroxidase)活性的影响。结果表明, 大螟3龄幼虫在取食转基因水稻24 h后SOD活性与对照相比提高了43.44%, 48 h后降至最低值; 在取食24 h后POD值达到最高值, 其酶活性比对照升高了29.22%, 最终在取食48 h后降至最低值, 并显著低于对照; 在取食转基因水稻4 h后, CAT活性升高了30.33%, 在取食48 h后, 与对照相比, CAT活性降低了27.01%; 5龄幼虫取食4 h后SOD活性显著高于对照水平, 36 h后降至最低值, 与对照相比, 活性下降了31.62%; 在取食8 h后POD活性达到最高值, 与对照相比, 升高了73.20%, 36 h后酶活性降至最低值; 在取食之初4 h CAT活性达到最高值, 与对照相比, 其值升高了75.73%, 在取食48 h后, 其活性与对照相比减少了7.55%。3龄幼虫与5龄幼虫相比, 对Bt的抗性水平较低, 自身防卫能力较差。结果说明, 在取食初期, 试虫体内保护酶活性升高, 以抵御Bt毒蛋白对虫体的伤害作用, 随着取食时间的延长, 保护酶活性迅速降低, 从而干扰虫体正常的代谢过程, 导致虫体出现中毒症状, 致使昆虫死亡。     

Larval competition for food between wild and hatchery-reared ayu, Plecoglossm altivelis Temminck et Schlegel, in culture ponds

To examine the larval competition between wild and hatchery ayu in the culture ponds, mixed rearing of 580 000 wild and 520 000 hatchery larvae was carried out in two 25-m³ ponds for 3 months, in contrast to the control in which 860 000 wild larvae were reared in another pond.
The number of wild larvae in the mixed-rearing treatments decreased rapidly 20 days after the start of mixed rearing, in contrast to hatchery larvae. Mortality of wild larvae was almost 100% at the end of the experiment (3 months), while the hatchery larvae showed the usual survival rate of 15–16%. In the control pond, however, 16% of the wild larvae survived. The wild larvae grew much slower (0.10mmday ^-1) than the hatchery larvae (0·26 mm day ^-1) in the mixed-rearing ponds, whereas the wild larvae in the control pond showed almost the same growth rate (0·24 mm day ^-1) as hatchery larvae. On day 6 the gut fullness of wild larvae was only 30% of that of the hatchery larvae in the mixed-rearing experiments. On day 46 the wild larvae occurred deeper in the mixed-rearing ponds than the hatchery larvae. This depth difference in vertical distribution appeared to cause a disadvantage for the wild larvae in the competition with hatchery larvae, since the food was supplied at the surface. Thus, the wild larvae starved and died.