Delayed mating reduces fecundity of blackheaded fireworm, Rhopobota naevana, on cranberry

This study examines the effects of delayed mating on two successive generations of blackheaded fireworm, Rhopobota naevana Hübner (Lepidoptera: Tortricidae), a pest of cranberry, Vaccinium macrocarpon Aiton (Ericaceae). The first (spring) generation produces eggs that hatch soon after oviposition, whereas the second (summer) generation produces mostly diapause eggs. Unmated female and male moths were placed together on the first, second, fourth, sixth, or eighth day after emergence. In the first generation, incidence of mating was greatest in the 1-, 2-, and 4-day treatments then declined as female survival decreased. In the second generation, incidence of mating was lowest in the 1-day treatment and greatest in the 2-, 4-, and 6-day treatments. Most second generation females in the 6- and 8-day treatments survived to mate. The mean oviposition period was 2.6 days for first generation females and 4.1 days for second generation females. Fecundity of singly mated females in both generations declined as age at mating advanced, but the pattern of decline differed between generations. First generation females that were mated on the first or second day laid more eggs than those mated on the fourth, sixth, or eighth day, and the number of infertile eggs increased as age at mating advanced. Fecundity of second generation females declined more gradually and the number of infertile eggs was greatest for females mated on the first, sixth, or eighth day. A consequence of the marked decline in fecundity due to mating delays in the first generation was that mean fecundity of the entire group of first generation females was ca. 13% less than that of the group of second generation females. On cranberry farms, pheromone-mediated mating disruption can prevent or delay mating of blackheaded fireworm. If the frequency of disrupted (prevented and delayed) matings is similar in the two generations, fewer eggs will be laid in the first generation than in the second.     

Importance of plant physical cues in host acceptance for oviposition by Busseola fusca

Plant and surrogate stems exhibiting specific combinations of physical cues were used to determine which plant‐related stimuli influence the oviposition of Busseola fusca (Fuller) (Lepidoptera: Noctuidae). The number of eggs and egg batches laid per female increased with an increase in diameter of both natural and artificial stems. Direct observations of the oviposition behaviour (walking, antennating, and sweeping with the ovipositor) indicated that the female moths preferred oviposition supports with a large diameter and non‐pubescent or smooth surfaces over pubescent or rough ones. Pubescence and rough surfaces significantly affected the behavioural steps leading to oviposition by interfering with the ovipositor sweep process necessary to find a suitable oviposition site. Furthermore, more eggs and egg batches were laid on soft than rigid supports. The rigidity of the support affected the proper insertion of the ovipositor for egg deposition. Our results underline the importance of physical stimuli in B. fusca's choice of an oviposition site, which may facilitate the identification of potential host plants or preferred oviposition sites on a plant for this species.     

Distribution of second generation European corn borer,Ostrinia nubilalis, egg masses in field corn and relationship to subsequent tunneling damage

The relationship between second generation European corn borer (Ostrinia nubilalis Hübner) egg mass numbers and subsequent field corn damage, as measured by stalk cavity numbers, was studied in 79 fields in northeastern North Carolina over three years. A mean of 0.028 egg masses per plant (645 egg masses/23400 plants) was found over the course of the study. Significant differences in oviposition rate were detected between fields and years. Ca. 85% of egg masses were deposited in a five leaf zone surrounding the primary ear; of these, 89% were found on the lower four leaves in this zone. Egg masses appeared to be distributed randomly within fields but at low rates of incidence, and oviposition was relatively uniform between sampling areas within individual fields. Under moderate to high oviposition pressure (mean number of egg masses per plant over the duration of the oviposition period >ca. 0.02), eggs laid during the early phases of the oviposition period account for more subsequent stalk damage than eggs laid during the later phases of the oviposition period. Variations in second generation egg mass numbers accounted for ca. 70% of variation in stalk cavity numbers.     

黄褐新圆蛛生物学以及对棉虫的控制作用

黄褐新圆蛛在湖北省以初孵幼虫在卵袋内越冬,一年可完成三个世代。雌蛛交配一次可终生产受精卵,一生最多可产9个卵袋。每个卵袋含卵粒数一般为80—90粒,单雌产卵量平均在450粒以上,最多可产869粒。卵的孵化率在90％以上。 成蛛的寿命较长,温度和食物对寿命有较大影响;有较强的耐饥能力。 在棉田内以结网捕食害虫,可捕食棉铃虫、红铃虫、棉小造桥虫、小地老虎、棉二点叶蝉、棉大卷叶螟和大青叶蝉等害虫。     

梨小食心虫蛹重对成虫繁殖力和寿命及下一代幼虫发育的影响

【目的】本文旨在明确营养状况不同造成的梨小食心虫Grapholitha molesta(Busck)雌、雄蛹重量差异对其羽化的成虫产卵量、产卵期、寿命及下一代(F1)幼虫发育的影响。【方法】室内条件下,通过不同的饲养方法,获得个体重量不同的梨小食心虫雌、雄蛹,待其羽化交配后,记录其产卵量、产卵时间和成虫寿命;卵孵化前后,分别测量卵和初孵幼虫大小,计算卵孵化率,统计幼虫发育历期。【结果】雌蛹重量对梨小食心虫的成虫产卵量影响显著,其重量与产卵量呈正相关(y=15.505x-59.292);同一条件下,雌蛹与雄蛹重量也呈正相关(y=0.823x-0.538)。同时,雌蛹重量对成虫产卵期影响也较大,蛹重大的个体羽化的雌虫比蛹重小的个体羽化的雌虫产卵高峰期提前1 d;较重、中等和较轻蛹羽化出的雌虫个体每天产卵量高于10粒/雌的时间分别为9~10,7和5~6 d;产卵量高于5粒/雌的时间分别为12~13,9和6~7 d。而雄蛹重量对产卵量、雄成虫寿命影响没有明显影响。较轻的蛹羽化的雌成虫寿命比较重蛹羽化的雌成虫短2~3 d;而雄蛹重量对其羽化的雄成虫寿命影响没有明显规律。雌、雄蛹重量对其羽化成虫的卵孵化率、卵和初孵幼虫的大小影响均不显著,对F_1幼虫发育历期影响也不显著。【结论】梨小食心虫雌蛹重对羽化成虫的产卵量和产卵期等影响显著,田间防治时应注意在不同条件下完成发育的个体,尤其是雌虫,由于营养差异引起的个体大小对随后种群增长的影响。     

条纹小斑蛾的生物学特性

条纹小斑蛾Thyrassia penangae(Moor)是乌蔹莓(Japanese cayratia)的重要害虫,在南昌1年发生4～5代,以老熟幼虫结茧越冬。由于该虫各世代总有极少部分个体进入滞育,少数进入越夏的个体1年只发生2代或3代。羽化时间多出现在上午7～10时,羽化后当日或次日下午交配,交配时间集中在下午3～6时,交配一般可持续12个h左右。成虫羽化后需取食花蜜做补充营养才能充分产卵。产配后次日即可产卵。第1代成虫常将卵数十粒聚产于幼嫩叶片的背面,以后各代主要聚产于花蕾上,平均每雌产卵量为43粒。幼虫为4龄。第1代主要取食叶芽、幼枝及嫩叶,以后各代主要取食花蕾。在自然条件下各虫态发育历期:卵为4～7d;幼虫为10～14d;非滞育的茧期(指幼虫结茧后的预蛹至成虫羽化的日期)为8～11d,越夏茧期为32～40d,越冬茧期为205～224d。成虫寿命为3～13d。     

Oviposition of potato tuber moth,Phthorimaea operculella zell. (Lepidoptera: Gelechiidae); fecundity in relation to mated state,age, and pupal weight

The fecundity of individually held potato tuber moths ranged from 0 to 236 eggs deposited over the total life span. The number of eggs laid was not correlated with pupal weight, but pupal weight and the number of mature eggs in the ovaries shortly after emergence from the pupa were positively correlated. This initial egg complement accounted for slightly more than half of the total number of eggs laid. Among moths held in groups at 25°c in the absence of host‐plant material, multiple‐mated females did not lay significantly more eggs (mean 98.4) than those mated only once (mean 91.0), but their life span was shorter (8.5 days cf. 14.4). Virgin females laid a small number of non‐viable eggs (mean 7.7), and lived about as long as single‐mated females. Males were significantly longer‐lived (23.6 days) than all groups of females. Peak oviposition of mated females occurred 2–5 days after emergence, and declined to low levels by age 7 days.     

Overwintering of the sycamore aphid, Drepanosiphum platanoidis

Spatial and temporal aspects of overwintering in the holocyclic sycamore aphid Drepanosiphum platanoidis (Schrank) (Homoptera: Callaphididae) were investigated. Eggs of D. platanoidis were principally laid on trunks and branches of Acer pseudoplatanusL., at considerable distances from the buds. Trunks with rough bark, followed by branches with moderate roughness supported more overwintering eggs than the relatively exposed smooth surfaces of twigs and terminal buds. Eggs were aggregated on rough bark. Aspect had no effect on the number of eggs laid. Experimental manipulations varying ovipara densities showed intra-specific competition among oviparae for optimal oviposition sites. Overwintering egg mortality was a function of time, with the greatest mortality rate occurring in late winter. Egg mortality varied from 80.4% to 76.9% on trunks and 83.0% to 65.9% on branches in 1996 and 1997.     

Density-dependent egg dispersion in flowers of Silene vulgaris by the seed predator Hadena confusa (Noctuidae)

Abstract.

• 1 Hadena moths drink nectar from, pollinate, and oviposit into the flowers of the genus Silene. In the gynodioecious Silene vulgaris (Moench) Garcke (Caryophyllaceae), eggs were laid by Hadena confusa (Hufn.) females both in male phase flowers, which could not be pollinated by the moth at the time of oviposition, and in female phase and female flowers that allowed pollination.
• 2 Flowers in which an egg had been laid had a lowered probability of receiving a second egg laid by another female during the same night.
• 3 The degree of flower discrimination by the moth with respect to the presence of eggs was positively correlated with the proportion of flowers containing eggs.
• 4 The oviposition behaviour of H.confusa is moulded by four factors: (1) a high probability of chosen male phase flowers later becoming pollinated by other moths, (2) the presence of conspecific eggs and risk for larval competition, (3) probability of presence of conspecific eggs also in neighbouring flowers, (4) capability of larvae to move to adjacent flowers.

     

Field oviposition rates and egg load dynamics of pollen beetles (Meligethes aeneus Fab.) (Colepotera: Nitidulidae)

Abstract 1 Egg loads from field collected pollen beetles (Meligethes aeneus Fab., Coleoptera: Nitidulidae) were determined by dissecting beetles caught at the beginning and end of the putative daily oviposition period. Field collected beetles were offered Brassica napus (L.) plants in cages for 8 (morning and early afternoon), 16 (overnight), and 24 h to ascertain the number of eggs laid during these time periods. 2 Most eggs were laid in the morning and early afternoon. The proportion of gravid females was higher at the beginning of the oviposition period than at the end. Most females in the morning carried two eggs, whereas one egg was more common in the afternoon. 3 We hypothesized that the number of eggs laid during the oviposition period would be equivalent to the difference between egg loads at the beginning and end of oviposition. This was not the case; differences in egg loads were significantly lower than number of eggs laid. However, the number of eggs laid was equivalent to the egg load at the beginning of the oviposition period, suggesting that eggs available in the morning are laid during the following day. 4 Population estimates of daily oviposition rates, approximately 0.7 eggs per beetle and day, were close to estimates from laboratory studies when the proportion of gravid females was taken into consideration.     

Pheromone-trap catch in relation to the phenology of codling moth (Cydia pomonella)

Relationships between a pheromone-trap catch, adult emergence and penetration of fruit by first-instar larvae of Cydia pomonella were investigated from 1975 to 1977 in an orchard in South West England. For the first generation the times of moth emergence and catch in the pheromone trap were not significantly different; nor were male and female emergence times. The catch of moths of the first generation in the pheromone trap anticipated the appearance of their larvae in the fruit by 140–169 day-degrees > 10 °C. Eggs hatched after 94 day-degrees in the laboratory but in the orchard, wind and sunshine modified the microclimate so that the number of day-degrees required for egg development, as measured by standard meteorological instruments, was affected by wind and sunshine but development lasted on average about 90 day-degrees. This indicated a lag of 50–80 day-degrees between the curves for trap catch and oviposition: the pre-oviposition period in the orchard was shorter than expected from laboratory studies. In 1975 and 1976, some larvae developed to produce a second generation of moths which gave rise to a second generation of eggs and larvae, after an interval of 161 day-degrees in 1975, but only 41 day-degrees in 1976, indicating that in 1976 some eggs were laid before moths of the second generation were trapped. These results indicate that the first insecticidal spray against first-generation larvae should be applied about 140 day-degrees after the start of the reference week in which five moths of the spring brood are caught per trap. A second spray, if required to maintain insecticidal cover, should be applied about 100 day-degrees later. A spray should be applied against second-generation larvae immediately after the reference week for second-generation moths.     

Yucca moth oviposition and pollination behavior is affected by past flower visitors: evidence for a host-marking pheromone

Insect larvae such as those of yucca moths that feed on small, patchily distributed food items often face an elevated risk of intraspecific competition or cannibalism. For this reason, ovipositing females may assess a potential oviposition site for prior conspecific eggs or larvae before deciding whether to oviposit. Selective abortion of yucca flowers with high egg numbers prevents competition among larvae of the yucca moth Tegeticula yuccasella, but the same mechanism should select for female detection of and fewer ovipositions in flowers that already contain eggs. Female yucca moths presented with either virgin or previously visited flowers laid significantly fewer eggs in the latter flowers and pollinated them less often. A significant negative association was found between number of previous oviposition attempts in a flower and number of additional attempts by a female, suggesting a quantitative assessment of prior egg load, but the correlation coefficient was low. Factors contributing to this low correlation may include variation in signal quality, poor detection capability, uncertainty contributed by a variable oviposition attempt to egg ratio, and a variable response criterion based on recent female experience and physiological status. Females rationed their pollen by pollinating at decreasing frequency during a bout within a flower, and by depositing smaller pollen loads during later pollinations within a flower. Females ovipositing into a previously visited flower pollinated as frequently as would a first female for a given oviposition attempt within a flower, i.e., the probability of pollination after the nth oviposition was independent of whether it was performed by a first or a later moth. Experimental presentation of virgin flowers marked with a homogenate from female abdomens induced the same oviposition and pollination behavior as seen on previously visited flowers, suggesting the presence of a host-marking pheromone. Given that all eggs within a selectively aborted flower die, there may be selection among some yucca moths for providing a strong signal of floral egg status to conspecific females. Received: 1 December 1998 / Accepted: 7 February 1999     

Egg size and composition in an ageing capital breeder – consequences for offspring performance

1. Egg size is often used as a proxy of egg quality although size and composition may vary, e.g. in insects egg size usually decreases as female ages. Whether this decrease in size reflects reduced concentrations of essential nutrients such as lipids and proteins of eggs laid by ageing females, or does reduced size per se explain often observed lower fitness of later laid eggs is poorly explored. 2. Egg properties were compared with fitness parameters of offspring laid on the first and fourth night during the oviposition period of a capital breeding moth, Cleorodes lichenaria (Hufnagel). The study aim was to explore whether decreased egg size is caused by decreased provisioning into later laid eggs measured as egg protein and lipid concentration, and whether it results in lower fitness of later laid offspring. 3. The fresh and dry weight of eggs decreased over the oviposition period, but the protein and lipid concentration remained constant. Survival of larvae was lower among the fourth night laid offspring on a low quality host Parmelia sulcata Taylor compared to a high quality host Ramalina fraxinea (L.) Ach. No differences were observed in egg fertility or hatchability, neonate survival without food and pupal mass between the offspring produced on different nights. 4. Decreased survival of offspring produced later was rather attributable to absolute provisioning (i.e. lower weight of eggs) than relative provisioning (i.e. decreased concentrations of nutrients in eggs). It is argued that lower survival of later laid smaller eggs on low quality diet is likely attributable to physical and chemical characteristics of host lichens and/or physical properties of tiny neonate larvae.     

The distribution and analysis of cabbage root fly egg populations

The distribution of the egg stage of the cabbage root fly around brassica plants was studied at Wellesbourne on 0.05–0.4 ha plots during 1970 and 1971. The three generations of flies occurred at similar times in both years and the numbers of eggs collected generally decreased from the first to the third generation. Differences between generations demonstrated that each generation should be treated separately. The number of plant samples required for a given level of precision increased from the first to the third generation, indicating that experiments relying on egg counts should be planned to coincide with the first generation whenever possible. A sampling plan for the range of oviposition normally encountered during the three generations is illustrated for both one- and five-plant samples. For the same level of precision, estimates of the populations from five-plant samples required only 50% to 80% of the time of those from one-plant samples. When aestivation occurs the peak of oviposition in the second generation is difficult to determine, and designed experiments should not be undertaken. The negative binomial distribution failed to describe the clumping of the eggs for a complete generation, since a common k could not be fitted to the data. The distribution of the eggs was best described by Taylor's power law which showed that although sampling factors changed with generation, the value of the power did not. A value of 1.4 appears to be the index of aggregation characteristic of the egg stage of this species.     

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.     

家蚕对马尾松毛虫质型多角体病毒的敏感性

用虫体克隆技术,对马尾松毛虫质型多角体病毒湖南株（DpCPV-HN）进行了分离纯化,鉴定为质型多角体病毒1型。以家蚕春蕾×镇珠杂种F₁代及自交的F₂代4或5日龄幼虫进行毒力测定,以纯化的家蚕质型多角体病毒对F₁代幼虫的毒力测定为对照。结果表明：家蚕品种春蕾×镇珠对家蚕质型多角体病毒敏感,马尾松毛虫质型多角体病毒湖南株能引起其感染发病;马尾松毛虫质型多角体病毒湖南株感染家蚕品种春蕾×镇珠F₁代幼虫和F₂代幼虫28天后的半致死剂量（LD₅₀）分别为885个和18个CPB(质多角体),前者为后者的49倍。马尾松毛虫质型多角体病毒湖南株感染后的家蚕,其结茧率、化蛹率、羽化率、全茧量、茧层量和单蛾产卵数均有所下降,全茧量、茧层量、茧层率和单蛾产卵数与病毒感染剂量之间无显著关联。     

Parasitoids of the African wild silkmoth,Gonometa postica (Lepidoptera: Lasiocampidae) in the Mwingi forests,Kenya

Gonometa postica Walker produces silk of high quality, but it is affected by parasitoids attack. A study on the parasitism of G. postica larvae and pupae on host and non‐host plants were undertaken for the first and second generations, corresponding to the long (March–May) and short (October–December) rainy seasons in 2006 at six field sites, three each in the Imba and Mumoni forests of Mwingi, eastern Kenya. All freshly spun cocoons of G. postica were sampled at each site from a total of 100 trees of host plants and other non‐host plants where they have migrated before pupation. The cocoons were kept individually in fine net‐sealed plastic vials to determine percentage parasitism. Two dipterans and four hymenopteran larval–pupal parasitoids were identified from the two forests. The most common parasitoids were Palexorista sp. (Diptera: Tachinidae) and Goryphus sp. (Hymenoptera: Ichneumonidae) with parasitism ranging from 1.8 to 32.7% and 2.2 to 7.5%, respectively. Parasitism varied significantly according to host or non‐host plants, seasons and sites. This study indicates that, of the six parasitoid species recovered, only two had a significant impact in reducing the quality of the cocoons.     

Effect of methanolic extracts of neem (Azadirachta indica A. Juss) and bakain (Melia azedarach L) seeds on oviposition and egg hatching of Earias vittella (Fab.) (Lep., Noctuidae)

Abstract: The effects of methanolic extracts of neem ( Azadirachta indica ) and bakain ( Melia azedarach ) seeds on the oviposition behaviour and hatchability of eggs of Earias vittella were investigated under laboratory conditions. Treatments included 2, 4, 6, 8 and 10% concentrations of both extracts to compare with nimbecidine and untreated control. When able to choose, the adults preferred to lay a greater number of eggs on the untreated portion of the oviposition substrate (muslin) compared with the extract-treated portion. However, under no-choice conditions, higher concentrations of extracts caused proportionate reductions in the number of eggs laid. The extracts also manifested repellent activity by reducing the number of eggs laid even when the ovipositing females were not in direct contact with the extracts. Eggs laid on extract-treated oviposition substrate exhibited reduced hatching and marked adverse effects on hatching were noticed when the eggs were dipped in different concentrations of extracts. Adults fed on an extract-containing sucrose diet laid significantly fewer eggs with poor hatching. There was no egg laying when the moths were fed on a sucrose diet containing 6, 8 and 10% neem and 10% bakain extracts.     

Oviposition of resistant and susceptible strains of Drosophila melanogaster in the presence of deltamethrin

Oviposition of three strains of Drosophila melanogaster in the presence of deltamethrin was observed. These strains had different levels of physiological susceptibility to deltamethrin. Two-choice tests were conducted with couples of flies in petri-dish arenas containing two oviposition dishes. On the first day of the experiment, females were given a choice between a treated oviposition dish and an untreated control dish. On the second day of the experiment, two control oviposition dishes were given to females. Although individual females showed a tendency to aggregate their eggs in one of the dishes, control experiments demonstrated an overall equal distribution of eggs between the dishes. When one of the two oviposition dishes in the arena was treated with deltamethrin, the percentage of females ovipositing and the mean number of eggs laid by females were reduced, compared with control arenas. Females avoided the treated oviposition dish and laid significantly more eggs on the control dish. Furthermore, when the deltamethrin concentration was increased on the first day, female flies postponed their oviposition and laid significantly more eggs on the second day. The resistant strain, SR, demonstrated the same capacity to select the untreated site for oviposition as the susceptible strain, but it showed a smaller oviposition reduction and egg retention. The relationship between physiological and behavioural susceptibility to deltamethrin is discussed.     

The egg parasitoid <Emphasis Type="Italic">Telenomus euproctidis</Emphasis> (Hymenoptera: Scelionidae) uses sex pheromone released by immobile female tussock moth <Emphasis Type="Italic">Orgyia postica</Emphasis> (Lepidoptera: Lymantriidae) as kairomone

Egg parasitoids Telenomus euproctidis Wilcox (Hymenoptera: Scelionidae) were attracted to egg masses laid by wingless immobile female Orgyia postica (Lepidoptera: Lymantriidae). Virgin females, a solvent extract of pheromone glands, and a synthetic sex pheromone, (6Z,9Z,11S,12S)-11,12-epoxyhenicosa-6,9-diene (posticlure), also attracted this parasitoid in the field, demonstrating that T. euproctidis uses the sex pheromone of female Org. postica as a kairomone to locate host eggs.