豚草生育期和被利用状态对广聚萤叶甲产卵选择的影响

【背景】植食性昆虫对产卵场所的选择行为受多种因素的影响,其中寄主植物的发育阶段和被同种其他个体利用程度是影响其产卵选择的重要因素之一。【方法】采用野外罩笼的选择性试验,观察了广聚萤叶甲成虫对不同生长发育阶段、不同被取食程度、不同落卵量的豚草植株的产卵选择行为,分析产卵选择频次,用Cox比例风险模型拟合识别期以估计产卵选择偏好性。【结果】开花期豚草被选择产卵的风险(瞬间概率)仅为生长期的16.5%,苗期豚草被选择产卵的风险为生长期的34.1%;成虫对3种被食程度豚草的产卵选择频次之间存在显著差异(n=20,P<0.01),在3级被食程度豚草上产卵次数最多(12次),而在5级被食豚草上产卵次数最少(2次),表明成虫明显偏好将卵产于已被中等程度取食的植株上;成虫对不同落卵量植株(0、4、8个.株-1)未表现出显著的产卵偏好,对不同密度(高、低)斑块的豚草的产卵选择亦无显著差异。【结论与意义】豚草生育期和被取食程度影响广聚萤叶甲雌虫的产卵选择,而植株上的落卵量和豚草密度对产卵选择没有影响。     

影响专食性广聚萤叶甲产卵选择的因素

【背景】广聚萤叶甲幼虫常群聚于部分豚草植株取食,可能与成虫产卵选择有关,因此,探究广聚萤叶甲产卵选择的影响因素具有重要意义。【方法】于2005年在广聚萤叶甲的主要分布区（江苏、江西、湖北、湖南）进行了1次随机抽样调查,并在南京城郊于2008年5月25日～9月1日进行了豚草的定点定期跟踪调查,用广义线性模型分析调查因子的影响。【结果】随机抽样调查结果表明,卵块数量随豚草植株冠层直径和健康程度的增大而显著增多,冠层直径每增大1cm,卵块数增多2%;健康程度每提高1级,卵块数增加近2.1倍;在豚草植株被利用程度增大的情况下,卵块数量随植株健康程度增大而增多,如果植株上增加1头幼虫或蛹,则植株健康程度每提高1级,卵块数增多2%,但植株冠层每增大1cm,卵块数减少0.6%。定点定期调查结果表明,豚草上的着卵块概率受豚草斑块大小、植株冠层直径、发育期和生境光照情况等因素的显著影响,豚草斑块每增加1株植物,产卵概率提高0.5%;植株冠层直径每增大1cm,产卵概率提高3%;在暴露生境中的豚草上产卵的概率比遮阴（树下）下的豚草提高近1倍。【结论与意义】豚草植株个体特性对着卵数量有显著影响,而豚草个体和群体特性以及小生境显著影响产卵发生。     

豚草条纹萤叶甲的交配和产卵行为

在我国大陆发现的豚草条纹萤叶甲Ophraella communaLeSage原产于北美洲,取食入侵生物豚草(Ambrosia artemisiifoliaL.)。通过观察该叶甲的交配和产卵行为以及两者之间的相关性,结果表明,豚草条纹萤叶甲一生多次交配,室内观察1次交配时间平均为38.2min,产卵历期平均13.2d,每雌平均产卵312.1粒;但野外产卵量高于室内,平均为553.8粒;卵多聚产在植株幼嫩叶片的背面。雌成虫平均寿命为16.0d。雌成虫随交配次数的增多,产卵量增大、产卵历期和成虫寿命延长,存在显著的直线相关性。     

广聚萤叶甲在豚草上的空间分布

广聚萤叶甲Ophraella communa LeSage是恶性入侵杂草豚草Ambrosia artemisiifolia L的一种重要天敌,为了了解广聚萤叶甲卵、幼虫、蛹、成虫在豚草上的分布情况,本文对各虫态广聚萤叶甲在豚草植株上的空间分布进行了调查。调查结果表明,各虫态广聚萤叶甲在豚草上的空间分布均为聚集分布;不同受害程度豚草植株上各虫态广聚萤叶甲主要分布于上部和中部。就不同受害程度豚草植株上同一虫态广聚萤叶甲而言,卵比例随受害程度的加重逐步递减,幼虫和蛹的比例则逐步增加。由此可见,广聚萤叶甲为了确保后代能获得更充足的食物,成虫倾向于在受害程度较轻的植株上产卵。     

广聚萤叶甲成虫取食经历对后续 产卵寄主选择的影响

【背景】取食经历对植食性昆虫的寄主选择行为具有较大影响,影响天敌昆虫寄主专一性测定的设计和结果解释。【方法】采用选择性试验,观察了入侵豚草的重要天敌——广聚萤叶甲成虫羽化后取食不同植物对其后续产卵寄主选择的影响。【结果】与取食豚草的试虫相比,有取食三裂叶豚草、苍耳或菊芋经历的成虫选择苍耳产卵的频次增加,不再对豚草表现出明显的选择偏好性。对产卵识别期的Cox模型分析结果表明,成虫早期取食不同植物,对后续产卵选择有显著影响,成虫羽化后如果先取食豚草或三裂叶豚草,则选择苍耳产卵的倾向显著低于豚草;但如果先取食苍耳、菊芋和农家向日葵,则选择苍耳产卵的倾向与豚草无显著差异。【结论与意义】由此推测,广聚萤叶甲初羽化成虫取食的植物对其后续产卵选择具有较大影响,因而在寄主专一性测定中应关注测试前饲喂的植物种类。     

永州广聚萤叶甲和豚草卷蛾的种群动态及对豚草的控制效果

【目的】豚草是一种重要的入侵杂草,严重危害农业生产和人类健康。广聚萤叶甲和豚草卷蛾是豚草的专一性天敌。研究这2种天敌在永州的种群动态及其对豚草的控制效果,可以为永州豚草的防控及这2种天敌的有效利用提供依据。【方法】在湖南省永州市江永县豚草大面积发生区域,人工释放广聚萤叶甲和豚草卷蛾,调查这2种天敌在释放区和扩散区的种群动态和对豚草的防治效果,以及这2种天敌在扩散区的越冬情况。【结果】广聚萤叶甲和豚草卷蛾的扩散能力强。释放1个月后,在释放区,广聚萤叶甲各虫态及豚草卷蛾虫瘿均被发现。整体上,随时间延长,广聚萤叶甲各虫态虫口密度先增后减,而豚草卷蛾虫瘿密度呈逐渐降低趋势。释放2个月后,在距释放区边缘10 km的豚草发生区,发现了广聚萤叶甲和豚草卷蛾,且成功建立了种群并顺利越冬。释放区豚草株高几乎没有增加,且叶片最终被取食精光,几乎全部死亡;扩散区豚草株高略有增加,最终近75%叶片被取食。【结论】广聚萤叶甲和豚草卷蛾可在永州成功建立种群并安全越冬,还能自行扩散,可持续控制野外豚草的发生。     

广聚萤叶甲成虫产卵行为及其产卵部位的选择性

【目的】明确广聚萤叶甲成虫产卵行为及其产卵部位的选择性。【方法】在室内条件下,对广聚萤叶甲成虫交配及产卵的系列行为、产卵场所选择、不同部位豚草植株叶片叶绿素b的含量进行了观察和测定:(1)将1对成虫放到养虫笼内的一株豚草上,观察交配时间,记录产卵数量、前后2粒卵之间的产卵时间间隔;(2)在均匀分为5部分(0～10、11～20、21～30、31～40和41～50 cm)的豚草植株上,随机放置10对成虫,观察雌虫对于产卵场所的选择。(3)将上述5个部位的豚草叶片通过丙酮匀浆法处理,用紫外分光光度计测定其在645和663 nm的吸光值,计算叶绿素b含量。【结果】广聚萤叶甲成虫完成一次成功交配平均需96.09 min。雌虫一般需45 min的时间来寻找其适应的产卵场所,在产卵过程中,成虫习惯将卵产于叶片背面,雌虫喜欢用口器来清理刚产下的卵粒。在一株50 cm高的豚草植株上,雌虫喜欢将卵产在植株中部21～30 cm和中上部31～40cm的叶片上(从下往上划分)。卵块数量和豚草不同部位叶片叶绿素b含量呈显著的正相关性。【结论】广聚萤叶甲成虫喜欢产卵在叶绿素b含量较高的叶片背面,可能以视觉识别叶片颜色来选择和定位产卵场所。     

豚草和苍耳上广聚萤叶甲的寄主选择和取食量比较

为探究豚草与苍耳上的广聚萤叶甲种群是否存在分化,对来自这两种植物上的叶甲(分别称为"豚草叶甲"和"苍耳叶甲")进行了选择性试验,并测定了其对5种近缘植物的取食量.选择性试验结果表明,两群来源不同的叶甲对豚草和苍耳的选择偏好存在显著差异,表现为豚草叶甲更偏好豚草,而苍耳叶甲相对更偏好苍耳.对广聚萤叶甲成虫取食量的测定结果表明,对不同测试植物的取食量随来源寄主植物不同而存在显著差异,两群叶甲对向日葵的取食量存在显著差异,但对其他植物的取食量均无显著差异.豚草叶甲对豚草的取食量显著大干对其他测试植物的取食,24h平均取食量达51.27 mm2,而对其他4种植物的取食量无显著差异,均低于40 m2;苍耳叶甲取食豚草的量为52.24mm2(24 h),与取食向日葵和三裂叶豚草量无显著差异,但显著大干取食苍耳和菊芋的量,取食后两种植物的量没有显著差异.研究结果说明,苍耳属植物可能是广聚萤叶甲除豚草外的另一潜在寄主植物.     

水椰八角铁甲和椰心叶甲对椰子和银海枣的寄主选择性

【目的】水椰八角铁甲和椰心叶甲均为棕榈科植物的重要入侵害虫,两者的外部形态、取食部位和危害特征相似。研究它们的寄主选择性有助于了解这2种害虫的扩散和成灾机制。【方法】在室内用椰子和银海枣2种寄主植物分别饲养水椰八角铁甲和椰心叶甲,研究在不同寄主植物上水椰八角铁甲和椰心叶甲的存活率、产卵率、发育历期等以及这2种害虫对不同寄主植物的选择性。【结果】水椰八角铁甲在2种寄主上的存活率差异显著,除了卵期和蛹期之外,幼虫期各虫态在银海枣上的存活率明显比在椰子上的存活率高;椰心叶甲在椰子上的存活率高于银海枣,各虫态平均存活率分别为95%和86%。取食银海枣的水椰八角铁甲达标准卵量概率为0.23,取食椰子不产卵,无法完成整个世代;取食椰子的椰心叶甲达标准卵量概率为0.86,取食银海枣不产卵,也无法完成整个世代;水椰八角铁甲取食银海枣完成世代的实验种群趋势指数为12.55,椰心叶甲取食椰子完成世代的实验种群趋势指数为66.55。【结论】水椰八角铁甲和椰心叶甲分别对银海枣和椰子这2种寄主植物具有明显的选择性。在海南椰子树的数量远远超过银海枣,该实验结果在一定程度上解释了椰心叶甲在海南岛广泛分布而水椰八角铁甲只是零星发生的原因。     

广聚萤叶甲对广东佛冈豚草的控制作用

广聚萤叶甲Ophraella communa是恶性入侵杂草豚草Ambrosia artemisiifolia的一种重要专一性天敌。为了评价其对广东省豚草的野外控制效果,2009和2010年分别在佛冈进行释放,试验调查了释放后的种群动态及其对豚草的控制效果。结果表明:广聚萤叶甲在广东省佛冈县可成功建立自然种群。广聚萤叶甲释放后,其虫口密度不断增加,豚草植株的死亡率也不断上升,2009年豚草死亡率低于20%,2010年叶甲对豚草的控制作用较好,豚草死亡率可达到95%以上,而大量豚草死亡后,广聚萤叶甲的虫口密度又急剧下降。广聚萤叶甲种群扩张与气象因子有密切关系,温度偏低是5～6月广聚萤叶甲的种群数量难以扩增的主要因素,大雨频繁和光照偏少也一定程度上限制了其种群增长,7～8月是广聚萤叶甲种群激增的关键时期,此时其种群数量急剧增加。     

Performance and host preference of Ascia monuste (Lepidoptera,Pieridae)

Experiments were conducted to determine the performance and host preference of Ascia monuste using kale (Brassica oleraceae, var. Acephala) and mustard (B. juncea). These plants differ significantly in water and nitrogen content, with mustard having larger amounts of water and kale larger amounts of nitrogen. The performance results confirmed that kale is a better food source than mustard for the species, even when eggs were collected on mustard leaves in the field. However, when eggs were collected on mustard, the kale nutritive value was lower than the nutritive value obtained when eggs were collected on kale leaves. Furthermore, the results of oviposition preference obtained in the field and in the laboratory have shown a preference for kale, indicating the presence of a positive correlation with performance. In contrast to the data about oviposition preference, there was no immature feeding preference. These results indicate that host selection occurs during the oviposition process. Furthermore, it is possible that the high abundance of kale cultivated in the region studied and the nutritional quality of this plant are two factors that influence the positive relationship between oviposition preference and performance for A. monuste.     

Oviposition site selection in Cactoblastis cactorum (Lepidoptera): constraints and compromises

Summary Oviposition by Cactoblastis cactorum on Opuntia ficus-indica and O. aurantiaca was assessed from the positioning of egg sticks on plants in the field. The number of egg sticks laid on O. ficus-indica plants was affected by: (1) plant size; (2) moth emergence near the plant; (3) cladode condition; and (4) plant conspicuousness. These factors contributed towards the clumping of egg sticks on plants. There was no apparent oviposition preference for one of the two host plant species despite the fact that egg predation was higher and fecundity lower on O. aurantiaca. The selection of a site for oviposition on the host plants was influenced by: (1) cladode condition; (2) height above ground; and (3) shelter from wind during oviposition. Succulent cladodes were the favoured sites for oviposition. The evidence suggests that in C. cactorum, oviposition site selection is largely the net result of a compromise between oviposition behaviour selected for increasing the probability of juvenile survival and oviposition behaviour selected for increasing the probability of laying the full complement of eggs. In addition, environmental and physiological factors such as wind and wing-loading, are thought to place constraints on the range of sites available for oviposition.     

Significance of a new field oviposition record for Graphium eurypylus (L.) (Lepidoptera: Papilionidae) on Michelia champaca (Magnoliaceae)

Abstract  Phytochemical similarities among ancient Angiosperms presumably played a role in the ecological and evolutionary diversification of the swallowtail butterflies (Papilionidae). Host family feeding specialisation is typical of most Papilionidae species, but field records of oviposition are rare for most swallowtail butterflies. It is even more uncommon to witness oviposition and larval feeding on new host plant species, especially in plant families not previously reported for the butterfly species. Oviposition by a female on a new host, or even on a toxic plant, may represent ancestral behaviour (with a loss of larval acceptance, detoxification or processing abilities) or novel behaviour (providing genetic variation for a potential expansion of host range, or host shift). We document the oviposition, larval use and pupation of the Annonaceae specialised and geographically widespread Graphium eurypylus on a Magnoliaceae species, all under field conditions in Queensland, Australia. This is the first time such field observations of oviposition and larval feeding on Michelia champaca (Magnoliaceae) have been documented anywhere for this species.     

Dynamics of oviposition in Danaus plexippus (Insecta: Lepidoptera) on milkweed, Asclepias spp

Where a butterfly chooses to lay an egg will influence the subsequent survival of her offspring. In this paper we report on the effect of a number of variables which influence the choice of oviposition site in Danaus plexippus L. Experiments were conducted under both flight cage and field conditions. The field observations consisted of recording the within and between plant egg dispersions across different patch sizes. Laboratory experiments looked at egg laying preferences as affected by plant species, age and condition. Butterflies were selective in their choice of oviposition site. Eggs were laid singly on the underside of medium sized leaves towards the top of a plant. More eggs were laid per plant on single isolated plants than on plants within a patch. The number of eggs per plant increases with plant height but decreases with plant age. Females preferred young plants or plants with fresh regrowth of leaves. These characteristics could override species preferences which were, in decreasing order, Asclepias curassavica. A. fruticosa and A. physocarpa. Species preferences varied between butterflies and with female age. Neither the presence of eggs nor larvae on a plant deterred oviposition. These results are compared with previous observations of egg laying in this species.     

How oilseed rape (Brassica napus) genotype influences pollen beetle (Meligethes aeneus) oviposition

Oviposition of phytophagous insects is determined either by adaptive behaviours allowing evaluation and response to host plant quality and/or by nutritional constraints occurring during oogenesis. Besides differences found among host plant species, plant intraspecific diversity can also affect insect oviposition. However, to date few studies have extensively investigated the factors accounting for the effect of this intraspecific variation. We addressed this question using oilseed rape (Brassica napus) and the pollen beetle (Meligethes aeneus), a phytophagous insect that uses the same plants and plant organs both for feeding and laying eggs. Our objectives were to test for a genotypic effect of oilseed rape on pollen beetle oviposition and identify the origin of the possible intergenotypic differences. We tested three hypotheses: oviposition is directly linked to (1) the amount of food eaten; (2) the nutritional quality of the food eaten; (3) a preference of females for certain plant genotypes. Results showed intergenotypic differences in both the number and the size of eggs laid. The factor that best accounted for most of these differences was the amount of food eaten. Nutritional quality of the pollen was of minor importance and females exhibited no preference among genotypes. These results reveal the importance of adult feeding on subsequent oviposition in phytophagous insects, an often neglected factor which partly determines the amount of energy available for oogenesis. Taking into account this factor may be of crucial importance in studies conducted on synovogenic insect species feeding on the same plant on which they lay eggs.     

Antibiosis resistance in soybean plant introductions to Dectes texanus (Coleoptera: Cerambycidae)

No soybean cultivars exhibit resistance to larval damage by the cerambycid, Dectes texanus LeConte, in the United States. Selected soybean varieties and plant introductions (PIs) in maturity groups VI to VIII from the U.S. Department of Agriculture National Soybean Germplasm Collection were evaluated for D. texanus resistance in a series of field and laboratory experiments from 2005 through 2008. In field cage experiments, the numbers of oviposition punctures (OPs) per plant were determined as indicators of oviposition antixenosis and the ratio of OPs per live D. texanus larvae (OP/Lv) served as an indicator of plant antibiosis to larvae. A D. texanus-susceptible variety treated with the systemic insecticide fipronil was used as a positive antibiosis control. Plant introduction PI165673 had the highest OP/Lv ratio, indicating that even if oviposition was successful, an antibiosis factor in PI165673 significantly reduced egg hatch and the resulting number of live D. texanus larvae. Factorial analyses indicated that maturity group is not a significant factor in the expression of resistance. Thus, PI165673 appears to be a potential source of resistance to D. texanus. In related field studies, the preferred D. texanus oviposition site was localized to leaf petioles in the upper four or five nodes of the plant canopy. Histomorphological analyses of petiole cross-sections of plant introductions PI171451, PI165676, and PI165673 indicated that leaf petiole morphology may be related to reduced D. texanus oviposition on petioles of PI171451 and PI165676, but that resistance in PI165673 is independent of petiole morphology.     

Distribution ofChilo partellus (Lepidoptera: Pyralidae) egg batches on maize

Distribution ofChilo partellus egg masses was studied in field, greenhouse, and laboratory experiments. The eggs were laid in batches mainly on the lower side and the lower leaves of the plant. The egg batch size ranged from 1 to 169 eggs, with a median of 33.5 eggs per batch (average, 40.5). Oviposition ofC. partellus is described at two levels. The first level, choice of oviposition plants, followed a random distribution. The second level, number of egg batches per plant, followed an aggregated distribution in the field, where more than one egg batch was deposited on the same plant by the same female, which was found on 25% of the oviposition plants. A mechanism for egg-layingC. partellus females to perceive preceding oviposition or injured plants could not be detected. Oviposition site choice seemed to be mediated by tactile stimuli.     

Possible Age-Dependent Variation in Egg-Loaded Host Selectivity of the Pierid Butterfly, Anthocharis scolymus (Lepidoptera: Pieridae): A Field Observation

To understand better the effects of age on host selection through conspecific egg detection by Anthocharis scolymus females, field observations were performed at a graveyard where the insect population was isolated and the host plant was limited to the cruciferous plant, Turritis glabra. We chased females and recorded their oviposition behaviors and the conditions of plants which females approached. Older females tended to avoid ovipositing on egg-loaded host plants and selectively laid eggs on nonloaded host plants. This result was not confounded by other factors such as seasonality, air temperature, plant height, plant phenological stage, surrounding vegetation, host plant density, and extent of plant damage. We discuss the possibility that females make an oviposition decision on how to lay their limited number of eggs during their remaining lifetime.     

Influence of Liriomyza species (Diptera: Agromyzidae) and their host plants, on oviposition by Opius dissitus females (Hymenoptera: Braconidae)

Two factors, among others, influence the oviposition of Opius dissitus Muesebeck. The first was the host species, the second the plant upon which the pest host larvae develop. O. dissitus females prefer Liriomyza trifolii (Burgess) larvae over those of L. huidobrensis (Blanchard). O. dissitus females were more attracted to the larvae of L. trifolii or L. huidobrensis when these were present on courgette rather than tomato or lettuce.